SAFE SHIPPING ON THE BALTIC SEA - 23 September 2011

SAFE SHIPPING ON THE BALTIC SEA
23 September 2011
Gdańsk, Poland
Organising Committee:
Dr Jan Jankowski, Polish Register of Shipping – Chairman of the Committee
Dr Andrzej Królikowski, Maritime Office in Gdynia – Member
Mr Piotr Waszczenko, Short Sea Shipping in Szczecin – Member
Dr Adolf Wysocki, Polish Shipowners’ Association – Member
Honorary Committee:
Mr Willem De Ruiter, European Maritime Safety Agency (EMSA)
Ms Magdalena Jabłonowska, Shipping Safety Department, Ministry
of Infrastructure, Poland
Mr Paweł Szynkaruk, Polish Shipowners' Association
The Symposium is organized under the patronage of the Polish Presidency in the
European Union and the auspices of the Polish Ministry of Infrastructure with the
attendance of Ms Anna Wypych-Namiotko, Undersecretary of State.
5
CONTENTS
Overview by Jan Jankowski, Polish Register of Shipping .................................................. 5
Foreword by Anna Wypych-Namiotko, Undersecretary of State,
Ministry of Infrastructure, Poland ......................... 7
Foreword by Paweł Szynkaruk, President of Polish Shipowners’ Association .................... 9
Panel discussion and key points of Symposium presentations on 24.04.2010 ........... 11
Session I
Higher efficiency by working together in the EU framework, some examples
Willem de Ruiter, EMSA, EU .............................................................................................. 23
Implementing the risk approach to develop minimum
but sufficient safety standards
Jan Jankowski, Polish Register of Shipping, Poland ........................................................... 25
Session II
The shipping industry views on oil transport safety
Benoit Loicq, European Community Shipowners' Associations .......................................... 45
Safety of underwater pipeline systems
Magdalena Jabłonowska, Ministry of Infrastructure, Poland ............................................... 47
Formal LNG terminal design process from the navigational point of view
Prof. Lucjan Gucma, Maritime University in Szczecin, Poland ............................................ 57
Session III
Maritime surveillance for better maritime safety
Isto Mattila, European Commission Directorate-General for Maritime Affairs and Fisheries, EU ..... 69
Regional efforts for safer navigation, hydrographic re-surveys
and cleaner Baltic Shipping
Anne Christine Brusendorff, HELCOM ............................................................................... 75
Safety of small fishing vessels
Monika Warmowska, Polish Register of Shipping, Poland .................................................. 81
OVERVIEW
Shipping in the Baltic Sea Region is specific by nature. The Baltic Sea is a small and
enclosed water basin featuring characteristic, dangerous weather conditions, hazardous
particularly for some ship types. The specificity of shipping also includes heavy traffic of
people and goods between the well-developed countries around the Baltic.
The Szczecin 2010 Symposium SAFE SHIPPING ON THE BALTIC SEA confirmed
both the specifics and the needs, revealing several issues of general concern for
Baltic maritime stakeholders. The Gdańsk 2011 Symposium provides a continuation
of the discussion forum for maritime administrations and shipowners to identify and
discuss measures for progressing safe shipping on the Baltic.
Discussion will follow several introductory papers addressing three key issues
identified during the Szczecin 2010 Symposium.
I Seeking clarity in proliferated regulations for Baltic Sea shipping
•
Higher efficiency by working together in the EU framework, some examples;
•
Proliferation of regulations and controlling bodies;
•
Implementing the risk based approach to develop minimum but sufficient safety
regulation.
II Operational and technical safety on the Baltic
•
Oil transport;
•
Safety of underwater pipeline systems (Nord Stream);
•
Formal safety assessment of gas carriers.
III Gaps to be filled to ensure safe shipping on the Baltic
•
Developments in date collection, exchange around the Baltic;
•
Hydrographical re-surveys and safety of navigation in the Baltic Sea;
•
Statistics of sea states occurrence contributing to safer shipping on the Baltic.
The identification of hazards faced by the shipping sector and related discussions
cannot be expected to solve directly the practical problems but raising awareness
and better knowledge of necessary measures sets the first step in moving forward.
Jan Jankowski
Polish Register of Shipping
5
Ladies and Gentlemen,
It is a pleasure for me to welcome you for the third time to the Symposium dedicated
to safe shipping on the Baltic Sea.
The Maritime Administration in Poland, which I have the honour to represent, is fully
involved in the process of improving the safety conditions on the Baltic Sea.
On the national, non-conventional level, the Administration is working continuously
towards improving the safety of fishing boats, domestic passenger ships and
pleasure crafts.
On the European level, we are involved in executing European maritime safety legal
provisions and we follow closely the development of the new European maritime
safety law, having our services engaged in the process of its implementation. In July
2011, Poland took over the Presidency of the Council of the European Union.
My Administration is taking all necessary measures to continue work towards
ensuring shipping safety and environment protection.
On the global level, we are an active member of the International Maritime
Organization, engaged in the work of all its Committees and Subcommittees,
contributing to many initiatives dedicated to maritime safety and supporting
the initiatives of our colleagues from the fellow Member States of the European
Union.
In the recent months, a great load of legislative work has been done. We are
currently nearing the end of the process of transposition to the Polish legal system
of seven new European directives of the so-called Erika III Package. The new Act
on Maritime Safety introduces improvements to the functioning of the SafeSeaNet,
a new PSC inspection regime, harmonization of procedures of authorization
of recognized organizations and their supervision, ensuring compliance with flag
State requirements, and many other solutions aimed at enhancing maritime safety
and alignment with the European law.
Next to the ERIKA III transposition, the process of implementing the directive on shipsource pollution and on the introduction of penalties for infringements is coming
to a close, with the introduction of regulations imposing criminal sanctions for
polluting the sea. We strongly believe that the new law will ensure better compliance
with environment protection requirements, as criminal penalties are expected to be
more effective than administrative sanctions or civil liability for environmental
damage.
7
It should also be stressed that safety of navigation and environment protection
cannot be ensured without properly qualified ship crews. The Administration has
started the process of ratifying the 2010 amendments to the STCW Convention.
This will allow us to introduce changes to the Polish system of training and
certification of seafarers adopted at the Manila Conference.
Finally, I have to mention the Administration’s involvement in the matters concerning
LNG transportation. We are currently implementing our biggest hydrotechnical
investment, the construction of a three-kilometre long breakwater for the Outer Port
in Świnoujście, in order to adapt the existing port infrastructure to new requirements
resulting from locating an LNG terminal in this area. The innovative character of the
investment will ensure the highest safety standards.
Poland is also the leader of the flagship project 13.7 in the framework of the EU
Strategy for the Baltic Sea Region, concerning formal risk assessment for LNG
carriers in the Baltic Sea. The project will deal mostly with delivering knowledge
about possible risks of LNG transportation and use in the maritime sector, and will
set up safety requirements for LNG transportation and operation in port and coastal
areas. I would like to take this opportunity to invite representatives of other Baltic Sea
Region Administrations to cooperate with us in implementing this project.
Ladies and Gentlemen, I would like to warmly thank the Polish Register of Shipping,
and Dr Jan Jankowski in particular, for organizing this Symposium, their hard work
and commitment. Please accept my best wishes on the 75th anniversary of your
Society.
I am also grateful to the speakers who agreed to deliver presentations, and to all
the participants for their presence reflecting their dedication to matters related to safe
shipping and pollution prevention on the Baltic Sea. I wish everybody fruitful
discussions and new ideas. I believe that this Symposium will be very important for
further development of new maritime safety initiatives.
Anna Wypych Namiotko
Undersecretary of State, Ministry of Infrastructure, Poland
8
Ladies and Gentlemen,
On behalf of the Polish Shipowners Association I would like to welcome all participants
of the IV Symposium "Safe Shipping on the Baltic Sea."
Since our previous meeting, we have noted several significant events related to the safety
of navigation and protection of natural environment of the Baltic Sea. Russians are
expanding their Baltic ports in order to significantly increase oil transportation by sea.
For many months lively discussions continued on the impact of the Nord Stream pipeline
on the free movement of ships to the ports of Szczecin and Świnoujście. European
shipowners are increasingly concerned about the increasing pressure from the International
Maritime Organization and the European Commission as to the use of expensive fuels with
reduced sulphur content in the Baltic and other ECA (Emission Control Area) areas.
The Baltic Sea is closed and therefore very sensitive to changes in the environment.
Any such large scale disasters as the sinking of the tanker "Prestige" and "Erika", would
result in much more serious consequences to the Baltic countries than those that hit
the areas bordering the Atlantic. And yet, year after year, the Baltic sees more and more
ship traffic, including large tankers carrying east-west Russian oil. The current issue is the
construction of the Nord Stream pipeline, which longitudinally crosses the entire Baltic Sea.
A few years ago, some countries that have their economic zones in route of the Nord
Stream, loudly protested against this project, talking about the possibility of serious
environmental effects of the remnants of World War II, still littering the seabed. Currently,
these protests subsided, thanks to effective lobbying of authorities of Nord Stream, but they
are replaced with correct care for the future freedom of navigation on routes that cross
the Nord Stream. Although damage to the pipeline by passing ships and a large scale
ecological disaster as the Deepwater Horizont seems unlikely, but any lasting investment,
affecting the safety of Baltic shipping must be closely followed. Of course, both the increase
in oil transport in the Baltic, and the location of the pipeline on the bottom of the sea, inter
alia, serves to improve Europe's energy balance, but we cannot forget about the risks
related to the ecology of the Baltic Sea, and communities living in the Baltics.
Similarly, you can look at the problem of environmental pollution resulting from the operation
of ships. The establishment of the zone SECA (Sulphur Emission Control Area) or current
ECA in the Baltic was the ecologically right thing, but the increasing demands badly hit
the finances of shipowners, particularly companies involved in Baltic ferry shipping. Planned
for 2015, the requirement of the use of fuel with a content of 0.1 percent sulphur combined
with low economic situation in the transport market, for some of the Baltic ferry companies
maybe become a real disaster.
These matters are still subject to thorough analysis and evaluation by shipowners and the
MIF (Maritime Industries Forum) including: CESA, CLECAT, EMEC, ESPO, ECSA
(European Community Shipowners' Associations) and the various national associations of
shipowners. ECSA Sulphur Task Force, established in March this year, prepared a detailed
report. The results of this report were presented, on behalf of ECSA, by Task Force
9
Chairman Mr Peter Verstuyft during the EU Maritime Commission Stakeholder Event: “Clear
air at sea-Promoting solutions for sustainable and competitive shipping ", which was held
in Brussels on 1 June 2011.
The owners gathered in ZAP carefully follow all the IMO and the European Commission
initiatives concerning the future of European shipping. An important event was the adoption
of the strategy, "Transport 2050" by the EC. It consists of two documents: the so-called.
"White Paper" or the Roadmap to a Single European Transport Area, and detailed
guidelines – Commission Staff Working Document. The main elements of the Roadmap
to 2050 in the European transport list: the efforts to eliminate congestion, reduce emissions,
increase employment, increase income, increase reliability and service quality, increase
security and reduce dependency on the European transport system from the supply
of crude oil.
Particularly important for shipowners are the solutions proposed to environmental issues,
mainly concerning the reduction of emissions of sulphur, nitrogen and CO2. At the March
meeting of the EU Commissioner for Climate Action Ms. Connie Hedegaard and President
of ECSA Marnix van Overklift, Mr. Overklift confirmed the willingness to engage
the European shipowners to reduce CO2 emissions. He also said that ECSA supports
the adoption of EEDI (Energy Efficient Design Index), as one of the tools for reducing
energy consumption on vessels and thereby reducing greenhouse gases. Marnix van
Overklift also welcomed the idea of creating a special fund to reduce CO2 emissions, which
is to be made with funds contributed by industrialized countries.
ECSA and ZAP, as a member of the Association, also support other initiatives aimed
at improving the safety of navigation in the Baltic and more efficient operation of ships
in ports (the problem of congestion). One such activity is the project established by EMSA
(European Maritime Safety Agency) to select ships ready to assist with oil spills
off the coasts of EU countries. The same action was launched back in 2004, but this year
it has led to the strengthening of EMSA's fleet of "rescue", inter alia, in the Baltic Sea. So far,
EMSA has already signed contracts with fourteen private shipping companies. Their ships
hold a 24 hours day watch and can be quickly converted into a rescue unit to collect
oil spills.
Equally interesting and fully supported by the owners is "Maritime Blue Belt project" for
initiatives to remove restrictions and barriers of trade within the EU. This project,
implemented by EMSA, was launched in May this year and covers 180 ships that have
come forward to participate on a voluntary basis.
The owners also do not forget, this year's slogan for the European Maritime Day - "putting
people first" – considering that in 2011 - in addition to issues related to safety of navigation –
one should pay particular attention to social issues of seafarers. We must encourage all
local and international initiatives to improve the quality of work on board ships, as well as
those seeking to promote the profession of seaman.
Wishing you all a successful meeting I would like to ensure that both ZAP and other
shipowner associations in Europe, speak with one voice on the provision of adequate
security in the Baltic and respect for the environment of this sea. As representatives of
shipping companies, we fully support not only the actions relating to our ships and crews
sailing on them, but also those affecting the quality of life of residents of all Baltic countries’
coastal areas .
Paweł Szynkaruk
President of Polish Shipowners’ Association
10
PANEL DISCUSSION AND KEY POINTS OF SYMPOSIUM PRESENTATIONS
23.04.2010
Disclaimer
The opinions expressed during the panel discussion as collected do not necessarily present
the standing on particular issues of represented organisations or bodies but are individual
views, concerns and ideas as voiced by symposium participants during the open discussion.
Introduction
The issues covered by Session I on regional Baltic initiatives spread awareness
of successful safety monitoring projects on one hand and raised questions on the
other. It also gave evidence that problems relating to the human factor continue to
raise a stir. Session II devoted to rating the safety level focused on the philosophy
of safety, risk based approach and the required source data to progress safety
at sea. Session III addressing challenges of growing trade on the Baltic concentrated
on the practical side – the newly developed navigational safety management
for the Southern Baltic, controlling emissions and the system in place for regulating
marine operations on the Polish coastline as well as violations recorded. Discussion
covered several presentation related thesis, proposals and question marks.
Efficient monitoring is a successful project for the Baltic contributing to enhanced
navigational and environmental safety
“EMSA was given the task to “develop and operate any information system necessary
for attaining the objectives of Directive 2002/59/EC establishing a Community vessel
traffic monitoring and information system” reported Willem De Ruiter from EMSA in his
presentation. Accordingly, the Agency has set up and operates: SafeSeaNet, LRIT,
and CleanSeaNet. These 3 information systems constitute the core elements of the
EMSA integrated maritime surveillance platform aimed at improving response to
incidents, accidents or potentially dangerous situations at sea (incl. search and rescue
operations), contributing to improved prevention and detection of pollution by ships and
optimising logistic processes (ETA’s).
The EMSA concept, embracing SafeSeaNet based on Member States’ infrastructure
including 727 AIS coastal stations, VMS Coastal radar images, other AIS sources,
LRIT (LRIT = Long Range Identification and Tracking), CleanSeaNet images and SAIS, implements the Integrated Maritime Policy Common Information Sharing
Environment (CISE) with a mandate to establish, operate & maintain the EU LRIT
Data Centre. The latter (LRIT) is to provide information on: positions of EU flag ships
worldwide, non-EU flagged ships passing/coming to Europe and remains
complementary to “coastal” AIS information (SSN) of the 34 participating countries
(EU MS, EFTA, Overseas Territories).
11
The meeting participants raised the question regarding the ownership of the various
systems. Who is the owner of AIS – discussions have to start. Now there is an owner
of a satellite. How does the Global AIS Infrastructure fit into satellite-based
surveillance? There is a feeling of excess of information. All gathered information is
secured at present and available, but will AIS in future go commercial and what
consequences does that entail?
In reply to this question the example of Greenland was given where commercial
systems have been adopted. AIS was initially introduced as a collision avoidance
system now it has evolved into a monitoring system. We cannot say today whether
it will remain a public domain because the decision depends on adopted policies of
decision makers. In the case of the Long Range Identification and Tracking (LRIT)
we shall see the commercial aspect developing quickly. It would be nice if LRIT
followed the career of the Linux Advanced Radio Terminal (LART) a single-board
computer (SBC) designed by staff of the Delft University of Technology in the
Netherlands. The university released the software under the terms of the GNU
General Public License (GPL), and the hardware design under the MIT License. LRIT
is a further development to AIS operating on the VHF Radio range. While originally
designed AIS was designated for short range operation as a navigational aid, it has
now been shown to be possible to receive AIS signals by satellite. This is becoming
known as S-AIS and might replace LRIT. Satellite AIS is good in low traffic areas.
The European Space Agency (ESA) works with EMSA on data distribution
(SafetySea network). There are no regulations in this area.
Symposium participants voiced a concern that ESA cooperating with EMSA in
pollution monitoring established an ad hoc group to solve and not create problems
such as data ownership issues.
CleanSeaNet is the European satellite oil pollution monitoring system for detecting
deliberate and accidental spills linked with the national/regional response chain
strengthening operational pollution surveillance and response (penalties for
infringements). CleanSeaNet complements aerial/naval surveillance for illegal
discharges. Mr De Ruiter pointed out that 28% of CleanSeaNet images delivered
cover the Baltic Sea. The system ensures on site verification and follow-up actions,
as well as identification of potential polluters by combining CleanSeaNet and Vessel
traffic information available through SafeSeaNet and pinpointing offenders to
regulation enforcing bodies.
Usefulness of the data available from the monitoring systems was reflected, eg. in
statistical data presented in Session III by Ms Wesołowska, who in the session on
challenges of growing trade on the Baltic presented a study on violation
of regulations in the area of Maritime Office in Szczecin, which showed the recorded
offences during the last 5 years. Though the figures fluctuate the situation remains
stable with a slightly falling trend in 2009. Infringements regarding marine pollution
protection rated as more than half of the offences recorded. These were followed
by marine safety and security recorded offences and sanctions. The presentation
also familiarised Symposium participants with the organisational structure of maritime
administration in Poland, showed the Polish bodies involved in regulating, enforcing
and assuring safety at sea with a breakdown of competencies, scope of operation
and jurisdiction of marine chambers in Poland as well as types of accidents recorded.
The paper also included in-depth information on sanctions for violations.
12
The shipping community expressed concern that possible stricter emission
restrictions and sanctions with IMO declaring the Baltic a PSS (Particularly Sensitive
Sea Area) may move transport from sea back to land.
Nevertheless, though a burden to the shipping industry, transparency and precise
targeting of violations can ensure ample space for clean shipping on the Baltic. The
presentation by Mr Jalkanen from the Finnish Meteorological Institute shows how
ship emissions can be modelled to build a system, which is based on real ship
movements (AIS Data) and make emission calculations ship-specific and
transparent, useful for policymakers, authorities, shipowners, researchers.
The Ship Traffic Emission Assessment Model, STEAM, draws on AIS data
the registry number, location, heading and the speed of the vessel. AIS is a system
which keeps track of ship movements automatically, without the contribution
of the ships’ crew. The AIS system was originally built for collision avoidance. It helps
seafarers to observe the overall traffic situation, showing the speed and position
of every ship nearby. In the Baltic Sea area the coverage of the ground based AIS
network is complete. During the year 2007, over 210 million position reports were
sent by ships. If the ship cannot be found in the internal ship database, an automatic
query to Lloyds Register will be made to get such technical data of the ship as
physical dimensions, ship type, build year, design speed and especially: information
regarding the main and auxiliary engines. Their make, model, engine rpm, power
output, fuel type and so on. Shipowners provide information regarding their own
fleets: emission certificates, emission abatement techniques etc. From wave models
we get the significant wave height and direction in order to model the effects
of waves on ship’s ability to push through stormy waters. The Finnish Meteorological
Institute is investigating the possibility of including ice and sea current effects.
The principles on which STEAM is based on are ship-specific and come from the
basic rules of ship design. Each ship has different physical dimensions, engine
installations, design speed, hull structure etc. Once we know sufficient details of
every ship, we can compute the instantaneous power demand as a function of ship
speed.
The systems allows for visualisation of ship emissions summed up in a given grid cell
for a period of 15 minutes and tracking every ship, its emissions and fuel
consumption. We can produce inventories for NOx, SOx, CO2, PM and CO taking into
account abatement techniques and emission certificates.
The STEAM model can be used to study the effect of waves to fuel consumption
improving the accuracy of the predicted fuel consumption. Future further
developments are to embrace among others sea currents, effect of ice and health
effects e.g. in major cities close to shipping lanes providing an integrated assessment
tools for policymakers. The share of ship types vs. share of exhaust emissions and
proportion of each ship type compared to the total annual emission help us to identify
the kinds of ships that produce most emission. Further steps include the emission
divided by the distance travelled in each ship type and age group, comparison to fuel
consumption given by owner, the option to compare unit emission with other modes
of transport. In the Baltic the good news is that SOx emission decreased despite
the fact that overall traffic increased. This is the result of SOx Emission Control Area
rules of the IMO, which became effective on May 2006.
13
The STEAM model can be used to study the effect of waves to fuel consumption.
The inclusion of waves improved the accuracy of the predicted fuel consumption.
Future further developments are to embrace, among others; sea currents, effect
of ice and health effects e.g. in major cities close to shipping lanes providing
an integrated assessment tool for policymakers.
A report on HELCOM actions (1992 Helsinki Convention) focussing on prevention
and pollution elimination in order to promote the ecological restoration of the Baltic
Sea area and the preservation of its ecological balance prepared by Ms Brusendorff,
Helsinki, also draws on data collected by the monitoring systems and in databases.
Regional HELCOM activities have to take into account the international nature of
shipping, which stem from UN Convention on the Law of the Sea, requiring
elaboration of global rules and standards – and also stems from the fact that it is not
in the interest of the Baltic coastal countries to regulate only ships flying under their
flag but all crafts entering the water basin.
The nine Baltic Sea States within the International Maritime Organisation jointly
pursue initiatives of harmonising the implementation by the nine Baltic Sea States
of international regulations, where possible, with the strictest demands; and initiating
Baltic regional actions, either by making use of the possibility of HELCOM to act quicker
than what is typically possible in international organisations or by pursuing specific Baltic
interests that have not been taken into account in other international organisations.
An example is the use of pilots by ships posing a risk to the marine environment.
Already in the 1970s joint submissions by the Baltic Sea States led to the adoption
by IMO of a recommendation to ships to make use of local pilotage schemes when
navigating through the entrances to the Baltic. Another joint submission by the Baltic
coastal countries to IMO, proposed to designate the Baltic Sea Area as a special
area with regard to sewage. An initiative pursued within the International Maritime
Organization also includes promoting the use of Electronic Chart Display and
Information System (ECDIS), the use of which has been accepted by IMO as
equivalent to paper charts and recently made mandatory for certain classes of ships.
HELCOM has decided to cover major and secondary shipping routes by Electronic
Navigational Charts (ENC). Availability of ENC is a precondition to be able
to promote ECDIS, the use of which enables ships to display their own position
in real time. In one of the more recent initiatives by the Baltic coastal countries it is
proposed to cover the whole Baltic Sea with re-surveys in order to ensure up-to date
depth information and thus more safe sea areas for shipping.
These actions (initiated within HELCOM), are either building on or filling a vacuum
in international regulations, like the common Baltic AIS (Automatic Identification
System) monitoring system which has been operational since 1 July 2005. This
system builds on the IMO requirements for ships to be equipped with AIS, or the gap
filling measures addressing operational safety requirements for ships sailing in icy
conditions.
HELCOM has also adopted several regional measures, thus filling a gap in
international regulations to promote the harmonised and efficient implementation
of international rules and standards, including enforcement thereof. Regional
measures also make sense with regard to services to be provided by administration,
such as Vessel Traffic Services, hydrographical and pilotage services. This is also
true for response activities in case of a pollution incident.
14
Prof. Gucma from the Maritime University of Szczecin presented the concept and
development of a navigational safety management method for Baltic and other coastal
areas where ship traffic monitoring, e.g. AIS is implemented. A mathematical model
of navigational safety is needed to predict how the changes made in traffic or
navigational markings will influence the safety of navigation. Traffic monitoring delivers
all necessary data about incidents (near misses), which could be the circumstances of
accidents. Usually, the number of accidents is not sufficient to assess the risk on its
basis, especially when it is necessary to consider spatial distribution.
A novel method of navigational incidents analysis, based on AIS monitoring is
proposed to overcome problems of insufficient statistical accuracy.
The knowledge of incidents (near miss), defined as an event or series of events,
which could lead to an accident, but due to preventing action no losses occurs, and
their causes, could come from their observation and analysis and remain crucial for
the system safety determination.
The second important part of the safety management system is the stochastic model
of navigational safety based on microscopic simulation principle, which means that
each ship is modelled as an individual object with several functions and attributes
with various models of navigational accidents applied. The model of navigational
safety management system (NavSMS) is a multistage iterative algorithm that could be
used for risk assessment and in cases when risk reduction measures are necessary.
Navigational risk and its acceptability criteria involve risk based safety indicators
related with risk acceptability (tolerability) and are usually based on: individual risk
criteria, societal risk criteria, economical risk and acceptable losses level criteria.
The navigational incident management model of incidents (NavSMS) is completely
independent from the ship and is based on external monitoring by AIS. Two separate
models of navigational accidents are created: grounding and collision. Places
of possible incidents are presented according to severity (distance between ships
passing each other).
This model of navigational safety could be, according to Prof. Gucma, applied in any
coastal area where AIS monitoring exists. The model requires monitoring and that
reduces its usability to coastal regions. The incident model is quite novel but requires
stable accident to incident ratio functions in given areas. Research conducted in this
field reveals interesting dependencies between navigational accidents and incidents.
The presented concept of safety management on coastal sea areas is under validation on
the Polish coast and southern Baltic area. The results are very promising and the presented
navigational safety management system will be applied as recommended in this area.
The introduction of AIS can be, according to one of the Symposium participants,
compared to the invention of the telephone, i.e. the inventor did not foresee the use
of letters in phone-transmitted messages. AIS did not initially project that land-based
stations would have more and more data and could intervene on board a ship.
Shipping vessels are not as independent as they used to be in the past.
A question was put forward to EMSA whether the merging of systems at user
interface level is projected. This would allow input of data to and from national
networks. The question of harmonising the reporting system was subsequently raised
and the questions of potential benefits and barriers such as different requirements
for mariners for example.
15
Some steps have already been made, as reported by EMSA, towards DR 3 system
merging like AIS + Safernet (combined help detect polluters). Harmonisation in importing
data is projected with the first legislation measures, then technical issues
at the operational level will be addressed. The project aims at integrating all data
sources.
The relative low number of ship accidents seen in the Baltic Sea could be further
reduced according to Per Sonderstrup of the Danish Maritime Authority by adopting
a risk-based approach and by building a philosophy to decide what measures are
feasible and to evaluate their long-term effects in line with one of the tasks outlined
in the EU Baltic Sea Strategy.
The last decade of new safety and environmental measures provides a very broad
and genuine framework to ensure that shipping can be operated on safe basis
in the Baltic Sea area. Although we haven’t seen the long term effects coming from
some of the recently introduced safety measures, there seems to be tendency
towards a fewer number of accidents.
Risks from accidents in general can be assessed by the common Risk model: Risk =
Frequency x Consequence which seems simple, but can be very difficult in terms
of estimating the frequency and consequence of a future scenario.
The experience of the Danish Maritime Authority shows that risk structure in a Risk
Based Approach to Safety of Navigation can be divided into “defence lines” i.e.
factors where incentives would have the highest impact on preventing an accident.
The 1st line is the quality of ships and crews and the handling of the ships like route
planning, proper bridge team including the use of pilot. The 2nd defence line is
the external factors like providing the ship with proper sea charts, traffic routes, land
and sea marks or, in general, aids to navigation. The 3rd defence line is the external
control of the ship i.e. monitoring ship navigation.
During the last decade there have been several 2nd and 3rd line initiatives to manage
risks from maritime traffic like: the monitoring of ship traffic and Vessel Traffic
Services; extensively covered by Mr De Ruiter and Mr Jalkenen in their
presentations. Future projects are in place: new traffic routes are analysed
by Helcom; inspection of ships are carried out in Baltic ports (Port State Control);
the phasing out of single hull oil tankers is progressing; higher compensation rates
for oil spills are in force; insurance for maritime claims (Bunkers and HNS
convention); new regulations for transfer of oil at sea (STS operations); increased
capacity for oil spill response and EU 3rd maritime safety package have been
introduced.
To effectively target the 1st line of defence it is necessary to focus on the human factor.
The problem was more widely described by Mr R. Sirol from Estonia and found
repercussion in the proposed project outlined below.
Ship owners need to address human factors by establishing a proper safety culture and
to have thorough understanding of the impacts the shipping affects the environment
with. Therefore there is a need, in the shipping community and amongst stakeholders,
to maintain a high level of awareness of the risks that are prevailing in shipping.
16
Human related factors regionally and globally
With the significant attention given to the safe ship equipped with relevant equipment
and systems as well as more and more intensified safety rules it is alarming that
the crew, and particularly the watch crew, are at risk and somewhat forgotten,
reminds Mr R. Sirol from the Estonian Administration.
Shipping rules are getting tougher with a constant flow of new obligations to consider,
to legalize and adopt as regulations for shipping companies to follow and
administrations to inspect. Today, there are often only two navigators (the master
and the mate) who keep watch 6 hrs over 6 hrs in short-sea shipping, with a few
sailors and an engineer. Short crossings and cargo handling time often is limited to
a few hours. Nevertheless, there is a need for cleaning the hold deck, managing
the paperwork and for meeting various other demands. And there might be a little
time for navigation and rest. Questions arise as to an urgent need to increase
the number of minimal crew. Flag State have the right authority to introduce such
requirements but face the risk of losing shipowners.
The bridge is equipped with sophisticated systems and devices providing extensive
data. But a question arises: is it all necessary and is time provided to the crew to
acquire relevant information and skills?
Crew fatigue poses a serious problem also for shipmasters. The Council of the Baltic
Shipmasters recognises the problem where various rules bring about additional
duties and ships with limited crew may, on the contrary, diminish the shipping safety.
When working out and establishing new criteria all the for and against arguments
should be considered carefully including the feasibility of the already minimised crew
to take on accruing duties and their questionable impact on actual safety
of navigation at risk. Especially in the Baltic Sea conditions where the sea is quite
small, shallow, with many narrow sections where ships traffic is dense, where
the weather conditions are variable and the sea is partly covered with ice
in the wintertime. When adding additional responsibilities to the crew, should we not
also revise and regulate in a cohesive manner the requirements for minimum
manning?
Suggestions were put forward to take under consideration the above in the process
of implementing the EU Strategy for the Baltic Sea Region.
Remarks were voiced that casualty statistics showed a falling trend in the number
of casualties (often related with groundings, insufficient training of engine room staff)
up to 2004 and a growing trend after that year. The casualties are often of human
error related incidents. A multinational crew is a mistake in the opinion of some
symposium participants, as the crew has no feeling of solidarity, commonness.
The human element issue is not covered by certificates or IMO Rules but remains
the responsibility of the owner.
Pilotage services are linked with the human factor of safe shipping on the Baltic.
The problem of multinational crews and communication obstacles, as viewed from
an owner’s perspective, are vivid in pilotage (some accidents are caused by pilots
and masters who remain in service of shipowners) and tug boat cooperation,
the problem requires investigation.
17
The need for improvement of communication between pilot and tugboats is clear.
Maritime law is too flexible. Poland for example requires a review of exemptions, new
regulations on manoeuvrability of vessels (in view of old port regulations). Such
revised solutions could be introduced first nationally, enforced by coastal states and
then put forward to IMO.
In Denmark, almost all vessels use pilots in the Danish Straights as recommended
without mandatory regulations, though in ports there may be areas that require
consideration of introducing pilotage for safety reasons.
The question remains open as to what can be done to reduce human error.
Danish Administration discussed these issues analysing accidents to improve safety
issues. The right relations on board are difficult to specify but they must be identified.
It was pointed out that the minimum safe manning procedures/requirements are
difficult to change because they are directly related to economic/profit issues for
the owner. At the same time it was indicated that STCW will be discussed during
an oncoming MSC meeting where owners will have to find a balanced solution.
The number of hours per crewmember depends on vessel kind and size.
The EU has no defined policy on seafarers. National legislations in particular
countries in EU give a green light on a bit of multilateral cooperation (taxes, rules).
EU intends to establish a taskforce to study to see if seafaring is endangered with
extinction but there remains another issue relevant for seafarers’ – their safety and
educational matters.
A proposal was put forward by Capt. Byczyński to establish a European Fund for
Social Security and Education of Seafarers justified by the following arguments.
During the recent years a significant shortage of number of qualified ship officers
on the world labour market has been noted. This problem regards also the ships
registered under the flag of the European Union Member States. The effective
method to reverse this trend and to increase the number of cadets (new entrants to
the profession) would be the increase of attractiveness of seafarers’ profession
in the EU Member States. Seafarers all over the world are employed under various
flags on the free global labour market. They are subject to different labour legal
systems, different regulations regarding the social security and as the matter of fact
quite often they are unable to execute their due, legal rights and privileges, resulting
from the flag state law and international conventions. Due to international character
of shipping and seafarers’ labour market, even in EU Member States the status
of seafarers (in respect to social security) is significantly different than the status
of employees working in other sectors of economy. The EU shipping companies have
to compete on the open international free market, including the competition on terms
of employment, where they cannot offer better (and more expensive) working
conditions to their crew, than those offered by other world shipping companies.
This puts the EU seafarers in a seriously disadvantageous position in comparison to
other EU employees. Any attempt made towards forcing the EU shipping companies
into adopting national social security regulations for their crew may, (and inevitably
will) cause the escape of EU shipping from EU jurisdiction, by reflagging the ships
to the flags of states where such regulations are not applicable (Panama, Liberia,
Mongolia, Honduras, etc.). The shipping companies will move also their land based
operation there, causing the loss of a number of land-based (office) jobs within
the EU territory.
18
It is also worth to bear on mind, that seafarers’ profession has been fully
internationalized by the International IMO STCW Convention on education,
certification and watchkeeping, which sets the common and internationally accepted
minimum standards of education to the all world seafarers community. That is why
each seafarer, regardless of his nationality, may work under every ship in the world
regardless of its flag (State of registry).
The Proposal for action involves creation of the “European, Fund for Social
Security and Education of Seafarers” on the Community level of European Union.
Such “Fund” could be financed directly from the EU budget – within the framework
of support to the EU maritime policy. Seafarers originating from the States associated
with EU (within EEA) and employed on ships registered under EU flags or under
the flags of States associated with EU within EEA would be eligible to participate
in the “FUND” as well as their families. The European Commission could develop
the detailed rules for governing the “FUND” and could later on supervise its activities.
The “FUND” could serve seafarers from Member States and States associated with
EU within EEA, establishing the social security support for seafarers, at least
on minimum standards level. The relevant States could create the supplementary
“FUND” to increase the level of security support to their national standards, if they
wished to do so. The seafarers eligible to the social security support from the “FUND”
would be also eligible to the educational financial support, e.g. . financed the first set
of trainings, enabling them entry into the profession with the Certificate of
Competency, to serve as an officer on ship (nautical or engineering). The total
number of candidates to be awarded by the financial educational support from
the “FUND” would be proposed each year by the Commission and approved
by Member States. The financial educational support, should have a form
of educational “bonus” (assigned sum of financial resources on separate bank
account) giving the right to the future seafarer to select the European Training Centre
from among those recognized by the Commission.
This solution should significantly improve the attractiveness of seafarers’ profession
in EU Member States, possibility regulate (at least in part) the seafarers’ labour market
within EU and along the lines of EU overall maritime policy as well as integrate
European seafarers as a professional group within EU forging a European seafarers’
identity. Resultant increase of training standards of EU seafarers would contribute to
growing safety at sea, including the increased level of marine environment protection,
to increase the attractiveness of EU shipping market and significant increase
the attractiveness of European flags for shipowners as well as create perspectives
for further future quick development of maritime education in Europe.
The question of future attractiveness of the seafaring profession is also related to
the development and adoption of measures assuring a technically safe working
environment, i.e. a technically safe ship.
Establishment of new regulations for stability, the impact of new standards of roPax
construction (probabilities methods) have been discussed since 2004. When there is
a quest designers will find a way. Dr A. Jasionowski proposes 0% tolerance. There
are big obstacles like tonnage tax, value of the ship drops with changing regulations
– the economic impact is a problem. In the case of aviation, which we should follow,
there is a 0 tolerance.
19
The example of Estonia casualty with loss of 853 human lives in 1994 on the Baltic
Sea and underlying technical causes of the casualty state clearly why tragedies such
as that of MV Estonia will happen again, said in his presentation Mr A. Jasionowski from
the University of Strathclyde, unless firm actions are taken to develop the overall
philosophy of ship safety, not limited to discussing shortcomings.
An accident is a conjunction (sequence) of undesirable events occurring despite
measures taken to prevent each of these events from materialising and causing
a loss. Some events (phenomena) can recur for many permutations of initiations, and
as such can be considered as “critical” or “root” cause of a loss. In a holistic view,
each of these events may be considered as the cause of the loss.
Historically summaries of the consequences in terms of loss of life attributable to
flooding and loss of stability accidents show that at least one serious ship flooding
accident has taken place every year on average, for the past 20 years.
Therefore, the historical average rate of catastrophic loss of life on ships in case
of a serious flooding accident seems to be of the order of 35%.
Although the principle of mean recurrence interval of 100 years as ship design target
seems rather conservative when compared to current SOLAS regulations, it is still
rather relaxed (accident occurrence in 100 years with 63% probability) when
compared to design basis of e.g. hurricane shelters, or adopted by the aviation
industry.
The root cause of the loss derives from the fundamental flaw in the philosophy
of maritime safety provision underlying current regulatory instruments of IMO, and
pertaining to inadequate requirements on ship stability to mitigate consequences
of very often recurring phenomenon of ship flooding.
Therefore, it is recommended that the level of damage ship stability is raised
substantially to meaningfully increase the safety standard of passenger ships. It is
proposed that a goal to reduce the rate of catastrophic fatal flooding accidents from
a 35% historical average to not more than 1% is adopted by all passenger ships
without delay and with clear targets for achieving this goal within the foreseeable
future.
Holistic survey of the Baltic
The interest in holistic surveying of the Baltic to enhance safety was not only
expressed by HELCOM but also by Prof. M. Pawłowski, a naval architect from
the Gdańsk University of Technology, who in his presentation strongly advocated
for the Baltic Sea spectrum in his presentation of similar format as JONSWAP
spectrum for the North Sea, based on three parameters, with the bandwidth parameter
ε less than 1. So far, despite the heavy shipping there is no reliable spectrum
available for the Baltic Sea.
The paper demonstrated that the ITTC and JONSWAP spectra can be reduced through
affinity transformation to a common unit-area nondimensional spectrum that can be
precisely approximated by the log-normal distribution. Such spectra, contrary to
the original ones, are narrow-banded, with the bandwidth parameter ε less than 1,
and have moments of any order.
20
A wave spectrum for the Baltic Sea could be developed, either through the law
of similarity, described in the presentation, or through establishing a Joint Baltic Sea
Wave Project (JOBSWAP). In addition, scatter diagrams with probability
of occurrence of various sea states around the Baltic Sea could be delivered through
this project. The knowledge of the two deliverables is essential for better prediction
of ship motions while operating in the Baltic Sea, both for short - and long-term
predictions.
The proposal was seconded by Dr J. Jankowski from Polish Register of Shipping
who as a representative of the classification sector views safe shipping in terms
of necessary and sufficient conditions. The necessary condition is the technically
safe ship, whereas the sufficient condition is safe ship operation.
The 2009 Gdańsk Symposium identified several areas of concern voiced during the
Panel Discussion, which were later presented in the Panel Discussion Key points and
roundup. One of the issues related to the technically safe ship is the need to develop
a Wave Spectrum for the Baltic Sea and a scatter diagram representing the
probabilities of occurring sea states. The Baltic wave spectrum enables us to develop
the Baltic irregular wave, then to simulate ship motions in waves and any response of
the ship and its structure (including stresses) to that wave. Scatter diagrams enables
us to make long-term prediction of ship response to waves.
During this year’s Symposium we have a follow up on the subject with the proposal of
developing a wave spectrum for the Baltic.
The conclusions of the paper on assuring stability of damaged passenger vessels
indicate an urgent need to increase their safety level. For the Baltic area this is
of major importance as the number of ferries crossing the Baltic continues to grow.
Prof. Pawłowski has developed a criterion for ro-ro passenger vessels in damage
conditions. This criterion is based on wave parameters.
Calling to mind again the Estonia catastrophe it is clear that a sequence of events led
to the vessel sinking. However, it was the wave impact loads on the visor that caused
the first event. The wave impact loads destroyed the visor securing devices and then
the visor opened down the ramp, which served as collision bulkhead. Seawater
washed onto the vessel and water on deck caused the capsizing of the vessel.
Therefore, there is an urgent need to have the wave spectrum and scatter diagram –
it will provide grounds for further development of technical requirements to make
progress in assuring technical safety of ships operating on the Baltic according to
Dr J. Jankowski.
Round up
The initial anti-collision system AIS has evolved far beyond the original concept giving
access to data used for various safety and environmental protection projects and
enforcement measures to the benefit of shipping safety. Further developments in this
area remain an open question.
Developing holistic monitoring of shipping, however, does go in line with filling the gaps
in geological and hydrological surveys of the Baltic Sea, which are indispensable to
improve safe shipping in the water basin. This gap needs to be eliminated and joint
efforts of Baltic oriented countries and organisations made to conduct relevant research
projects as proposed by HELCOM and PRS.
21
To operate safely at sea ships need well educated, satisfied and not overburdened
crews that have a feeling of common interests and understanding – an issue that could
be addressed by the EU in the Baltic strategy or the seafarer’s workforce. Proposals put
forward in this respect may help to cure the present complex and problematic situation.
Excessive regulatory measures may be detrimental to further development of shipping
not only in terms of the economic and human factor but also in terms of overall safety
at sea. This problem together with issues on further Baltic surveys and ship technical
safety require extensive discussions on the Baltic forum.
Therefore, Symposium organisers suggest to deliberate on the following issues during
the IV Symposium on Safe Shipping on the Baltic Sea, which shall take place on 23
September 2011 in Gdańsk, Poland:
I
Overregulation of Baltic Sea shipping
1)
Higher efficiency of EU measures over those nationally undertaken
2)
Implementing/adopting the risk based approach to develop minimum but
sufficient safety regulation.
3)
Polish initiatives and contributions to safe shipping on the Baltic or EU trends
in instrumental development of safety on the Baltic
II
Operational and technical safety on the Baltic
1) Oil transport
2) Safety of small of vessels
3) The human factor contributing to safety of shipping
III
22
Gaps to be filled to ensure safe shipping on the Baltic
1)
Developments in date collection, exchange around the Baltic
2)
Statistics of sea states occurrence contributing to safer shipping on the Baltic
3)
Hydrographical survey of the Baltic
Higher Efficiency by Working Together, Some Examples
Willem de Ruiter, Executive
EMSA
selena.matic@emsa.europa.eu
Summary of the presentation to be made at the Symposium on Safe Shipping in the
Baltic Sea - 23 September 2011, GDANSK.
1.
Achieving higher efficiency by working together is one of most central
objectives behind the concept of building a European Union.
This general objective is certainly also applicable to the sectoral policy of maritime
safety and protection of the marine environment.
2.
EMSA was legally created in 2002 and started its first activities in 2003.
Looking back, it is not difficult to identify a number of EMSA projects that were
designed to achieve higher efficiency by working together.
3.
Working together in the field of oil pollution response could be mentioned as
a first example. Here two elements should be distinguished: pollution detection and
pollution response.
The first point refers to the CleanSeaNet service which uses satellite radar images to
detect oil spills at sea. Several Member States, including Baltic States, were already
experimenting with this technology before EMSA got involved. However, when it was
decided that EMSA would negotiate centrally with the satellite image providers,
acting on behalf of the whole group of EU Member States, it was possible to
negotiate from a position of strength. It resulted in a system with the highest technical
specifications possible at a substantially reduced price per satellite image and better
operational conditions than those that could have been obtained by Member States
individually.
4.
The fleet of oil pollution response ships (presently 16 ships operational) that
EMSA has mobilised through so-called “stand-by contracts” with private operators, is
another example of how a robust response system was built, with limited financial
means, that covers all the different sea areas of the EU coast line. This could not
have been created by acting in a national context only. In addition, by working
together with the experts of the various Member States and by involving specialised
private parties, best practices can be identified and shared.
5.
A completely different area where working together leads to higher efficiency
is Port State Control. The development of “Rule Check”, the electronic rule finder
currently used by all European PSCO’s, was a first example. The common PSC
trainings organized by EMSA in cooperation with the PMOU and the further
development of Distant Learning Packages for the benefit of all participating States
23
is a second example. In a way, the whole concept of the New Inspection Regime
(NIR) as supported by the New Information System (NIS), is based on the principle
that by working together closely in the framework of EU and PMOU the Port State
Control activities can be organised more efficiently than previously, when “the 25%
per State” rule lead to substantial duplication of effort.
6.
Another obvious example of efficiency gains was the set-up of a joint EU-LRIT
datacenter. The alternative would have been that all EU and EEA Flag States would
have set up their own national LRIT datacenter. The benefits for the Member States
in terms of reduced costs for development and operation are certainly substantial.
In addition the daily exchange of LRIT data between datacenters globally benefits
from the fact that Europe has created one single centralised DC instead of 29 small
DCs.
7.
The inspection work conducted by EMSA to check the quality of maritime
training colleges in the labour-providing countries should also be mentioned in this
context. Previously inspection teams of labour-receiving Flag States were travelling
to the labour-providing third countries to verify compliance with the STCW
requirements. Since it was decided that EMSA shall perform these inspections
for the EU flags, duplication of effort has been substantially reduced. Some claim that
there is also a gain in quality since a single combined inspection can examine
matters in greater depth, than a multitude of national inspections.
8.
I do not want to make the list of examples too long, but SafeSeaNet should
here be mentioned as a unique project of the EU coastal States and the Commission.
This system allows to have a full real time overview of all ship movements around
the EU coastline. Initially designed for safety and protection of the marine
environment only, it now becomes clear that the system also has potential for other
user communities, e.g. customs (Blue Belt), border guards, fisheries control, etc.
9.
Working together in a regional framework appears to be essential for a great
variety of topics in our sector. The development of a distribution system for LNG as
a future green fuel for shipping in the ports around the Baltic Sea and the North Sea
is another – and completely different – topic that requires such regional cooperation.
10.
As a last point I would like to mention the development of mathematical
models to calculate ship emissions, in terms of CO2, SOx, NOx, and PM on the basis
of data on ships actual movements (AIS data). The Baltic region took the lead in this
field within Helcom. EMSA will be instrumental in ‘exporting’ this approach to
the wider European region in order to achieve a better understanding
of the environmental impact of shipping.
24
Implementing the Risk Approach to Develop Minimum
but Sufficient Safety Standards
Jan Jankowski
Polish Register of Shipping
j.jankowski@prs.pl
Introduction
The trend to optimize fleets has led to new ship types adjusted to the diversity
of carried cargo and loading and unloading means. New improved materials have
been introduced in building ships. Bigger and faster ships, new loading technologies,
improved propulsion systems and computerised deck control systems revolutionised
shipping. However, these innovations were not followed by appropriately developed
safety regulations.
Following a series of catastrophes, classification societies and International Maritime
Organisation (IMO) developed new requirements, often retroactive in nature, which
in case of ferries and bulk carriers required rebuilding/conversion of ships
in operation – in effect creating a maze of regulations, which few manage
to embrace. At the same time the number of controlling and auditing bodies has
proliferated complicating operators’ life and frequently resulting in an adverse attitude
to safety considerations.
Casualty statistics show that ”during a period of 25 years between 1982 and 2007,
there were 419 bulk carriers lost, along with nearly 2000 lives'” [1]. The next few
years showed a falling trend in bulk carrier casualties, however these figures leaped
in 2009 [2],[3]. INTERCARGO statistics indicate that about 30% of bulk carrier total
losses were caused by failure of ship structure or her equipment [4].
As early as in 1989, following the catastrophe of the tanker ''Exxon Valdez'' and
heavy pollution of Alaska's coast, the US Senate resolved that tankers entering
American waters must have double shell plating. This requirement was later
introduced to MARPOL Convention to provide a second line of defence against
polluting the environment.
In 1999, the tanker ''Erika'' broke in half and foundered along the French coast.
The incident resulted from the bad technical condition of the ship hull. It caused
an ecological catastrophe in the region. Similar consequences met the coast of Spain
following the catastrophe of the tanker ''Prestige''.
After the disaster, the European Union issued the so-called ''Erika packages''
to improve the safety of European waters. The ''Prestige'' case induced International
Maritime Organisation (IMO) to develop, for the first time, structural ship safety
standards, starting with requirements for bulk carrier and tanker hull structure (so
called Goal-Based Standards) and the International Association of Classification
Societies (IACS) developed ''Common Structural Rules for Tankers''. Up to date
the safety assurance of ship structures remains the domain of classification societies.
1994 witnessed the sinking of the passenger car ferry ''Estonia'' on route from Tallinn
to Stockholm with loss of 852 lives [5]. In reaction to this catastrophe:
25
•
IACS enhanced requirements on impact wave loads acting on the bow and
formulated new requirements for the second line of defence against water ingress
as well as other requirements improving ferry safety, e.g. monitoring bow visors
to detect potential tightness failure;
•
Swedish government organised a conference, in result of which some states, not
only those of the Baltic region, signed the so-called Stockholm Agreement,
referring to safety of ferries in damage condition [6].
Recent statistical data show that general cargo ships lead in the number
of foundered vessels. The general cargo fleet is ageing and its replacement will
follow tanker and bulk carriers replacement trend. In terms of life loss, however, small
vessels, particularly fishing vessels are most vulnerable. They are often incapable
of surviving extreme weather conditions in which they operate.
The biggest catastrophes in recent decades resulted in loss of life and environmental
disasters. The reasons of the catastrophes were often technically related. A major
problem in enhancing ship safety is the time lag between shipping industry innovations
and development of class rules and other safety regulations, which are traditionally
developed in reaction to specific casualties, thus following an inductive approach
(reasoning from specific to general). Logic says that when the inductive approach is
applied exemptions can occur and modification of the existing state is required. Bulk
carriers, tankers and Ro-Ro vessels, their casualties, and the reaction to casualties,
are good examples of this approach. The occurring exemptions (casualties) are
information that the safety regulations developed basing on the inductive approach are
not fully harmonized with the sea environment and ship operation, as the sea
environment and ship operation underlie the majority of casualties.
A technically safe vessel is a necessary condition for safe shipping, whereas the
sufficient condition to be met is safe ship operations, which involves improved
performance of the so-called human factor. The paper presents, on the example
of construction of bulk carriers, the novel trend in the rules development process.
History of class rules development
Up to the nineteen fifties, classification assessment of ship's strength was mainly
based on past experience as the natural forces and behaviour of the sea waving
were deemed at the time to be entirely unpredictable. Rules and minimum standards
framework, developed under the approach, ensured safety for existing ship types but
was more difficult to apply to new types of ships. Furthermore, the requirements
referring to the ship's structure scantlings had a tabular form and were dependent
on ship's main dimensions. These requirements in general fail to satisfy the principles
of physics, in particular structure mechanics. At the time ship structure was appraised
in terms of separate structure members. It was conservatively assumed that if each
structure member satisfied the minimum requirements then the whole hull structure
would be safe. On larger ships, the verification of deck cross section was additionally
required.
Nevertheless, the trend to optimize the fleet led to new ship types adjusted to
the diversity of carried cargo and loading and unloading means. The safety standards
applied at the time appeared to be inadequate for the new types of ships.
Classification societies started to develop new safety standards in response to the
new situation.
26
Safety standards in the present rules correspond to division of the hull structure
strength into 3 problems: longitudinal, zone (hold) and local problem. Theoretically 4
criteria, namely; yielding of the structure material, buckling of the structure, fatigue
of structure details and ultimate strength, have to be applied to each problem,
resulting in 12 problems in total. In practice, the ultimate strength criterion, in current
rules, is only applied to certain structures (e.g. bulkheads), and the fatigue strength
criterion is applied only in the design requirements for some structure connections
(e.g. for connections of longitudinals), thus reducing the number of problems.
In the yield check the allowable stress is divided into components, i.e. the criterion
for longitudinal, zone and local strength components.
However, the division of allowable stress into components is not simple. This results
mainly from the fact that class rules require application of different wave loads,
in the form of formulae, which are likely to occur once in a ship's life. These loads do not
appear ''simultaneously'' – there is a phase shift between them. Therefore, the summing
of the stresses resulting from the application of the rule load components (for example,
wave bending moments, wave pressure and ship's accelerations), in a particular
structure member (e.g. bottom longitudinal), yields a different value than in the case
of loads superposition taking into account their phase shift. The proper combination
of the stress components is important for deriving the total stress value, giving rise to
the question: How to combine the dynamic load components determined by the rule
formulae to obtain the stresses in the structure approximating the actual values?
Finally, the allowable stresses for each strength level (longitudinal, zone and local)
are adopted mainly basing on experience, setting different probability levels
for required loads (for example, 10-8 for wave vertical bending moment and 10-4 for
wave pressure). To verify the buckling of structure members, knowledge of wave
loads is required for which the probability of exceeding thereof is less than 10-8.
Decades of applying such rules and past ship structure casualties linked with
uncertainties in wave load determination, notably affecting structures of bulk carriers
and tankers, gave rise to the development and implementation of new requirements
in direct reaction to these casualties. For example, the analysis of different class rule
requirements referring to wave pressures on shipside and section modulus (strength)
of side frames show how these criteria have changed in time.
This unsatisfactory state of regulations on ships' structure triggered both:
•
The development of Common Structural Rules for Bulk Carriers and Double Hull
Oil Tankers by IACS (CSR) [7], and
•
The development of the Goal Based New Ship Construction Standards (GBS) [8].
The proposed Common Rules are intended to embrace more aspects of safety, such
as ultimate strength, fatigue strength and the strength in damage conditions, than
the presently binding rules. Design loads - the most uncertain aspect affecting safety
at present - are in the form of a combination of static and dynamic, local and global
loads and they ''consider the most unfavourable combination of load effects''.
The requirements referring to the dynamic load components (wave bending moments
and shear forces, external sea pressures, internal dynamic pressures, ship motion
and accelerations) are given in the form of formulae. The loads for scantling
requirements and strength assessment are given at a 10-8 probability level (10-4 for
fatigue strength). The load combination factors are given as tabulated values and are
calculated by application of the equivalent design wave approach.
27
A method for practical estimation of the design loads, which is based on the following
definitions [9], [10]:
•
design sea state is the sea state that generates response value equivalent to
the long-term prediction of stress,
•
design regular wave is the regular wave that generates response values
equivalent to the response values generated in design irregular wave (sea state),
and
•
design loads are the loads generated by design regular wave and adopted
in designing the hull structure,
was developed. The values of stresses estimated with the use of the proposed
design loads are claimed to be equivalent to the long-term predictions of stresses
for typical load cases.
In the design regular wave approach, the dominant load is determined for such waveheading angle, wave period and height values which produce a maximum response.
The dominant load is determined for each load case. Then the load combination
factors, representing the relationship between the response to dominant load and
response to secondary load, are determined. This regular wave approach has been
widely used in local scantling and finite element analysis of ship structure (zone
strength analysis).
Direct methods of determining the loads acting on a ship and its structure response
to the loads are based on hydrodynamics, structure mechanics and probability
theories. The actual shape of the ship, mass distribution, randomness of the sea and
loading conditions are taken into account in these theories. Theoretically, an infinite
number of loads acting on the ship should be considered; in practical calculations,
however, a sufficient number of finite representative cases are implemented.
Most important of all, the actual phase shifts between loads are determined in the
evaluation of the stresses in the structure.
Goal – Based Standards
The IMO Maritime Safety Committee has started the development of Goal Based
Standards, which was initiated in 2002. It is the first time in its history that IMO is
setting standards for ship construction. So far the Committee has developed
the following five-tier system of GBS:
•
Tier I: goals – high – level objectives to be met;
•
Tier II: functional requirements (criteria to be satisfied in order to conform to the
goals),
•
Tier III: process of verifying rules and regulations for ship design and construction
against functional requirements;
•
Tier IV: rules and regulations for ship design and construction;
•
Tier V: industry practices and standards.
The five-tier system introduces a hierarchy to the regulatory system. The MSC
decided to develop GBS along two parallel tracks: applying the prescriptive approach
and developing the safety level approach.
28
GBS as adopted by IMO, are based on the prescriptive (referred also as traditional)
approach. The goal assumes that ''ships shall be designed and constructed for
a specified design life to be safe and environmentally friendly, when properly
operated and maintained under the specified operating and environmental
conditions, in intact and specified damage conditions, throughout their life'', while
the functional requirements refer, among others, to the design life, environmental
conditions, structural strength, fatigue life, and residual strength.
The problem of quantification of the functional requirements has led to the concept
of GBS – safety level approach (GBS SLA), which was clarified in [11]. It was
assumed in this approach that goals of Tier I take the form of safety objectives
(for ship, cargo, passengers, crew, environment, etc.), defined by risk level
(eg. probability of failure and fatality); and that these safety objectives are achieved
when each ship function (Tier II) such as manoeuvrability, seakeeping performance,
stability and floatability, ship strength and fire protection, satisfies the risk level set
for each function. Verified class rules (Tier IV) are assumed to meet the functional
requirements and consequently meet the goals. The aim of the rules of classification
societies is to transpose the required set safety level to the safety level of ships.
The safety level (probability of failure) for each ship function, assumed as
a requirement, can be determined with use of a risk model – a fault tree with
mathematical models used to describe basic events [12].
The fault tree technique postulates some specific states of a system with sequential
and parallel basic events (failure modes) contributing to the undesired event built in
systematically. This is not a model of all possible causes of system failure but only
those faults that contribute to the undesired event – it describes the logical
interrelations of the key events that lead to the undesired event. The risk model is
a quantitative model that can be evaluated quantitatively [13].
Under the hazard identification process all casualties of the considered ship function
and the potential scenarios which lead to the undesired event should be identified.
Therefore, GBS SLA and risk model, used for developing criteria for each ship
function, follows a deductive approach (reasoning from general to specific) and thus,
if correctly applied, no exemptions should occur and modification of the existing state
will not be required.
Taking this approach to GBS, IMO Maritime Safety Committee started to identify:
•
all possible types of ships (general approach), and
•
the current safety level (probability of failure) for vessels, basing on the available
statistical data.
Current safety level
The approximation of the current safety level for bulk carriers has been performed as
an example in [14], Annex 5, based on the Bulk Carrier Casualty Report
of INTERCARGO [4]. The results of the assessment are presented in Table 1 and 2.
29
Table 1. Current safety level of safety objectives
Safety objective
Current risk, pOB, per year
-3
Safety of the ship
≈2.1 10
Safety of the cargo
> 2 10
-3
Safety of passengers
Protection of the environment
Safety of third parties
Safety of seafarers
-4
> 3.2 10
The current safety level was assessed, in form of quantitative values, only for these
safety objectives and bulk carriers function for which the data was available. It can be
used for verification of the actual level. However, it is assumed that a safety level
in GBS-SLA will be set by applying systematic computations using the risk models
and by accounting for the current safety level.
Table 2. Current safety level of ship functions
Ship’s feature/capability
Current risk, pf, per year
Manoeuvrability
Power generation
Propulsion
-5
> 8.6 10
Habitability
Seakeeping performance
-5
> 4.3 10
Stability and floatability
Ship’s strength
-4
> 6.2 10
Watertight integrity
-4
Safety of navigation
≈9.4 10
Fire protection
≈2.8 10
-4
Emergency protection
Life – saving possibilities
Other
-5
> 8.6 10
The example of application of the risk model to evaluate the safety level of panamax bulk
carrier’s structure strength (function of Tier II), which sank in 2000, is presented below.
Risk models
The sea, the ship response to waves and ship operation are of a random character
and therefore appropriate deterministic and probabilistic models need to be
developed and used to make a quantitative evaluation of basic events leading to
the undesired event – the ship’s sinking. In case of ship’s structure strength:
•
the failures of its structure strength as the basic events, described by
a mathematical models, and
•
the loss its strength leading to the sinking of the ship as a undesired event;
constitute the system called the risk model of a ship function (ship strength, Tier II).
30
The risk model enables identification of the risk (probability) of ship function failure
and appraisal of its conformity with the risk level set as the criterion. The risk model
can also be used to make an analysis in order to set safety level as a criterion. In this
paper the risk model of the structure strength of the panamax bulk carrier (Fig.1)
mentioned above, is used as an example of safety level evaluation of this function.
Fig.1. Panamax bulk carrier covered by the analysis; built in 1977 and sank in 2000
The bulk carrier casualties studied have led to identify the following scenarios of bulk
carrier losses due to structure failures [13]:
• failure of the side and progressive collapse of bulkheads due to sloshing in
flooded holds (analyzed for each hold);
• collapse of the first hatch cover due to green seas and progressive
collapse of the bulkheads;
• loss of ultimate strength of hull girder; and
• failure of Capesize bulk carriers structures due to the high loading rate,
which failure originates in still port waters with wave loads generated
at sea causing further failure of the structure and the sinking of the ship.
Identified scenarios give the basis for building the risk model of bulk carrier
structure, which comprises:
• a fault tree, which is a graphical model of various sequential and parallel
combinations of faults (events) that result in the sinking of the ship; and
• mathematical models, based on physical theories, enabling simulations of
particular events of the fault tree, conversion of the results to probability
distributions and calculation of the of ship sinking probability due to
structure failure.
The simple fault tree leading to terminal event SL is presented in Fig. 2, where
the terminal event SL is the sinking of the ship due to the loss of structural strength.
HS – is the loss of hull girder strength, SiB, (i=1,2,3,4 is the number of the hold) – is
the side structure failure and corrugated bulkheads collapse due to hold flooding, C1B
– is the No 1 hold hatch cover collapse caused by green water and corrugated
bulkhead collapse due to hold flooding.
However, the fourth scenario, which starts with the high loading rate, is not as yet fully
identified. The impact of loading at high rates remains an area of concern. PRS has
developed a hypothesis, however, it requires verification. Therefore, a full-scale
experiment (measurements on an existing ship) of the double bottom structure response
to the impact load caused by falling cargo hitting the ship bottom should be carried out.
31
Fig. 2. Simple fault tree of bulk carrier structure failure
Breach of the side (S4)
© 2003 PRS S.A.
Break of the hull (HS)
Wave loads on the hatch
cover (C1)
The destroyed bulkhead
single corrugation (B4/3)
32
Prediction of ship structure response to the waves
Seas and oceans are normally divided into distinct areas Al, l = 1,2,...,n, (Hogben et
al, 1986), characterized by the spectral density function. Wave spectrum
representing the steady state sea conditions (short-term sea state) depends on
the significant wave height Hs and average zero up-crossing period To (Ochi, 1998).
The short-term response of the ship to waves (e.g. wave bending moment MW ) is
a set of probability distributions (e.g. probability density functions) of the given
random variables for one sea state in a given area Ai, for various ship courses etc.
Long-term statistics of the given ship response is the accumulation of response
statistics referring to: sea areas Al, l=1,...n, short-term sea states, ship courses
in relation to waves and ship’s loading conditions, taking into account the frequencies
of their occurrence.
The long-term probability density function f(y) of the ship response y (e.g. wave
bending moment Mv as the random variable) can be expressed as:
∞ ∞

f ( y ) = ∑∑∑  ∫ ∫ f klm ( y | (H s , T0 ))g (H s , T0 )dH s dT0  p kl p l p m


m l k  −∞ −∞

(1)
where f(y(Hs,T0)) = probability density function of the random variable y in the sea
state condition (HS,To) and g(Hs,T0) is the probability density function of sea state
occurrence.
Taking into account the formula determining the conditional distribution, and by
approximating (by the relevant sums) the integral occurring in (1), the following
formula is obtained:
f ( y ) = ∑∑∑∑∑ f
m
l
k
j
i
ijklm
( y | (H s , To )) p ijl p kl p l p m
(2)
where fijklm = the short term probability density function of random variable y; pm = the
probability of the ship’s loading condition occurrence (different drafts for different
loading conditions); pl = the probability of ship presence in sea area Al; pkl =
the probability of ship course in relation to waves in sea area Al (uniform distribution
in the interval [0,2π] is used); pijl = the probability of the short-term sea state,
determined by (Hs, To), occurrence in the sea area Al, l=1,...,n.
The probability distributions of the sea states occurrence are given in the form
of a matrix – called scatter diagram, which presents the probabilities pijl of sea state
occurrence in the interval [Hsi, Hsi+1]l x [Toj, Toj+1]l, i = 1,...,r, j = 1,...,s, l=1,...,n,
(Hogben et al, 1986).
The numerical long-term probability density functions (2) of random variable y,
representing different ship structure response to waves, is computed, basing on
simulations of ship motion and the structure’s behaviour in irregular waves.
The shipmaster’s decisions exercising good seamanship like e.g. speed reduction in
high seas and change of course in relation to the waves, are projected in the longterm procedure.
33
Simulation of ship motion in irregular waves
The simulation of vessel motions in waves is based on numerical solutions of nonlinear equations of motion. This method assumes that:
•
Froude-Krylov forces are obtained by integrating the pressure caused
by irregular waves, undisturbed by the presence of the ship, over
the actual wetted ship surface;
•
the diffraction forces are determined as a superposition of diffraction
forces caused by the harmonic components of the irregular wave;
•
the radiation forces are determined by added masses for infinite
frequency and by the so-called memory functions given in the form
of convolution.
The non-linear equations of motion are solved numerically. The comparison
of the computations results using non-linear and linear models is presented
on Fig. 3. This comparison shows that the linear method can be used in
the long-term process determining the ship’ structure response to waves,
however, such a comparison is not sufficient to make final conclusion and
further investigations are necessary.
Figure 3 Time history of heave, pitch and vertical bending moment Mv
The next example showing the time history of the bulk carrier considered and its
structure response to waves, computed using the non-linear model, is presented in
Fig.4 to 8.
34
4.0E+6
Mv [kNm]
4.5E+6
Mh [kNm]
3.0E+6
Mv [kNm]
Mh [kNm]
2.0E+6
1.5E+6
0.0E+0
0.0E+0
-1.5E+6
-2.0E+6
t[s]
2960
2990
3020
2960
3050
Figure 4 Time history of vertical Mv and
horizontal Mh bending moments in the cross
section at midship, generated by irregular
wave determined by: Hs = 6.5 m, To = 7.5 s
and β =120º.
250
p [kPa]
200
t[s]
-3.0E+6
2990
3020
3050
Figure 5 Time history of vertical Mv and
horizontal Mh bending moments in the cross
section at midship, generated by irregular
wave determined by: Hs = 15.5 m, To = 11.5
s and β =180º.
at bottom
1.5
at side
1.0
av [m/s2]
0.5
150
0.0
100
-0.5
50
-1.0
t[s]
0
t[s]
-1.5
6900
6900 6920 6940 6960 6980 7000
Figure 6 Time history of wave generated
pressure p at the bottom and at the side
(bold line), generated by irregular wave
determined by: Hs= 15.5 m, To = 15.5 s and
β =180º.
6920
6940
6960
6980
7000
Figure 7 Time history of acceleration av in
loaded aft hold, generated by irregular
wave determined by: Hs = 15.5 m, To=15.5
s and β =180º.
σ [MPa]
0
-100
-200
-300
t[s]
-400
6900
6920
6940
6960
6980
7000
Figure 8 Time history of stresses σz in lower part of frame in the midship hold, generated
by irregular wave determined by: Hs = 15.5 m, To = 15.5 s and β =180º .
35
Probability distributions of load effect
The numerical long-term probability density functions of the random variable
considered were computed according to formula (2) taking into account the following
assumptions:
pm = , as only the three loading conditions of the ship were considered: alternate;
pl = 1, as according to the IMO Goal-Based Standards the areas Al. l=1, should
cover only the North Atlantic area;
pk = uniform probability distribution in the interval [0,2π], representing the ship course
in relation to waves in the sea area Al was used in the computation of the long-term
probability density functions;
pij = the probability of sea state occurrence in the North Atlantic; IACS Rec. 34 was
used in the computations of the long-term probability density functions;
fijk = the short term probability density function of random variable σ, occurring in (2),
is approximated by a step function obtained by dividing the number of extremes
(separately one minimum and one maximum in a stress cycle) belonging to the set
interval of stress ∆σ by the total number of extremes occurring in a sea state
(represented by one its realizations – an irregular wave) and by the length
of the interval ∆σ .
f ij (∆σ ) =
n
N ∆σ
(3)
where n = number of maximums or minimums in the stress interval ∆σ; N = total
number of maximums or minimums in the time of simulations of one realization
of stresses in a chosen structure member in a given sea state; one stress maximum
or minimum is per one stress cycle.
The examples of numerical long-term probability density function, computed
according to (2), are presented in Fig. 9, Fig. 9 and Fig. 10.
The probability density function of stress σ in the considered structure member
enables the computation of its characteristic values, for example, the stress value for
the given probability (e.g. 10-8) of exceeding this stress value. The process
of computation also enables the selection of:
•
the sea state defined by (Hs, To), and
•
the angle between ship course and wave propagation;
from all sea states and ship courses accounted for in the simulations that
demonstrate the extreme value of stress σ in the considered structure member.
They are called the “extreme load cases”. All together 640 cases (sea states and
ship courses) were used in the computation process.
36
f( σ )
0.08
f( τ )
0.08
0.04
0.04
σz
τ
0.00
0.00
0
20
40
60
80
100
0
Figure 9 Probability density function of
stresses σz in frame (hold No.4),
shown in Fig. 11.
20
40
60
80
100
Figure 10 Probability density function of
stresses τ in side plating of hold No. 4
The events occurring in the first three scenarios of the bulk carriers sinking was
described using the deterministic and probabilistic mathematical models, which
enabled computations of the probabilities of ship sinking in particular scenarios.
Limit states functions
On the basis of the assumptions made in building the fault tree, the probability
of ship sinking is determined by the following sum of probabilities:
4
Pr ( SL) = Pr ( HS ) + Pr (C1 B ) + ∑ Pr ( S i B ).
(4)
i =1
The random variables assigned to the events occurring in formula (1) are as follows:
•
M H = M U − (M S + M W ) ,
•
•
for hull girder strength HS
∑ C = ∑ Y − ∑ LC ,
FB = FU − FL ,
(5)
•
for hatch cover strength C1
(6)
for corrugated bulkhead strength Bi/i-1 i =
2,3,4
(7)
or collapse of the side frames Si, i =
1,2,3,4
∑
F
= ∑ FY − ∑ LF .
(8)
The degree of safety depends on the margin between the actual value of load
effect and value of the load effect that the structure can ultimately sustain –
formulae (5) to (8). The margins MH, Σ C , FB , Σ F are called the limit states
functions. The failure will occur when the limit state is less than zero.
In the case of hull girder strength, the failure will occur when the ultimate vertical
bending moment MU for the hull girder structure is less than the sum of still water
bending moment MS and wave bending moment MW. The situation is similar for
corrugated bulkheads. The failure will occur when sloshing forces FL in the flooded
hold acting on a single corrugation of the bulkhead exceed the ultimate force value FU.
The side is assumed to have lost integrity when the stress ΣLF in the frame faceplate is
greater than the yield point ΣFY of the frame faceplate material. Whereas the hatch
cover is deemed to have lost integrity when the ultimate strength of the cover
compressed upper plating or of its stiffeners is breached by the green seas effect.
37
Loss of side and hatch cover integrity result in flooding of the hold. The method
applied to determine hull girder, bulkhead, side and hatch cover strength is presented
in Chapter 4.2.
All load effects MS, MW, ΣLC, FL, ΣLF, and the ultimate, for the structure, values MU, ΣY,
FU, ΣY are random variables so the limit state functions MH, ΣC, FU, ΣF are also
random variables. They have their own distributions and the probability density
function of their sum (difference) is obtained as the convolution of the particular
probability density functions [13]. For example, the probability distribution of the sum
of random variables Ms and Mw, representing the vertical bending moments in still
water and in waves respectively, is obtained from the following formula:
h ( m) =
∞
∫f
s
( m s ) f w ( m − m s ) dm s .
(9)
−∞
Taking into account the limit state function random variables (formulae (5) to (8)):
The probability of hull girder strength loss is determined by the formula:
0
Pr ( HS ) = P( M H < 0) = ∫ f (mH )dmH ,
(10)
−∞
where f is the probability density function of random variable MH.
The probability that the sequence of events C1 and B1/2 occurs (see Fig. 1) is equal to:
Pr (C1 B ) = Pr (B1/ 2 | C1 )Pr (C1 )
where
Pr (C1 ) = P(∑ C < 0 ) = ∫ g (σ C )dσ C ,
0
(11)
−∞
Pr (B1 / 2 | C1 ) = P(FB < 0 | C1 ) =
0
(12))
∫ g B (f B | C1 )df B .
−∞
The probability that the sequence Si and Bi/i-1, i = 2,3,4, or S1 and B1/2 (scenarios) occurs
is equal to:
Pr (S i B ) = P(Bi / i −1 | S i )Pr (S i ),
i = 2,3,4,
(13)
(for S1B similarly), where
Pr (S i ) = P(∑ Fi < 0 ) = ∫ h i (σ F )dσ F ,
0
(14)
−∞
(
)
Pr (Bi / i −1 | Si ) = P FBi / i −1i | Si =
0
∫ g Bi (f B | σ F )df B , i = 2,3,4
−∞
38
(15)
Fig. 11. The point in which the stresses were computed
Fig. 12. The probability distributions of frame stresses (in way of hold No. 4)
4.0E-6
0.0E+0
-4.0E+6
0.0E+0
4.0E+6
8.0E+6
1.2E+7
-4.0E+6
0.0E+0
4.0E+6
8.0E+6
1.2E+7
0.0E+0
4.0E+6
8.0E+6
1.2E+7
2.0E-6
0.0E+0
2.0E-7
0.0E+0
-4.0E+6
Fig. 13. The probability distributions of hull girder strength
Fig. 11 and 13 show the process of computations determining the probability of hull
girder strength loss and the collapse of the side frames. These figures show that
the probability of hull girder strength loss and the collapse of the side frames is equal
to the area under the probability density functions for the random variables MH or ΣF
less than zero (see Fig. 12).
39
Probability of structure failure - quantitative assessment of ship loss
The computations of probability of ship loss (event SL), according to the fault
tree presented in Fig.2, taking into account the probability of a given loading
condition and ship’s corrosion state, are presented in Tables 3.
Table 3. Probability of loss of the as built ship
Table 4. Probability of strengthened ship loss
40
The computations of failure probability show that:
•
the weakest structure is the ship side frames installed between rigid tanks, and
its probability of collapse is at the level of 10-1,
•
the most probable scenario of ship sinking is the loss of the side integrity, and
then, collapse of the bulkhead due to the sloshing and progressive ship flooding
leading to its sinking; this bulk carrier sank according with this scenario,
•
the calculated probability of ship loss due to its structure failure Pr(SL)/23 = 2.6
10-3/year (the ship sank after 23 years of operation), which is high,
•
the current safety level of ship’s strength evaluated in Table 2 is: Pr(SL)/10 > 6.2
10-4/year; in the evaluation of the current safety level takes into account
the population of almost 5000 dry bulk carriers,
•
to evaluate the current safety level of bulk carriers strength using the risk model
all subclasses of their structures and the number of ships in the subclasses
should be taken into account, however, this is tremendous work which requires
cooperation of all players involved in safety insurance at sea.
The catastrophes at sea and public pressure to improve safety indicate that
the safety level at sea should be “raised”. This is a political decision undertaken
following in-depth of current and other possible states. This can be done using
the risk models. For example, the risk model applied to a bulk carrier that sank
showed that if the weakest structures were strengthened the safety level of that ship
function (its strength) would increase. Strengthening of the weakest structures – by
increasing: the frame section modulus (Fig 11) two times, and the corrugated
bulkhead strength by 33% (to the level presently required), increases the ship safety
(Table 4) to the level Pr(SL)/25 = 1.2 10-4, which could be acceptable.
Most important, the risk model, understood as a fault tree of various
sequential and parallel combinations of faults (events) leading to the sinking
of the ship and the physical theory based mathematical models describing
the basic events, enables derivation of the safety criteria corresponding to
these events. For example, the following strict form of criterion for ultimate
hull girder strength has been derived in [15]:
___
M s+
(
)
ln N
ln p 

δ u 2 + δ s 2 + 1 −
M W , N ≤ M u ,
2M W , N
 ln N 
(14)
where Mw,N is the characteristic value defined by the equation F(Mw,N) = 1/N,
F is the cumulative distribution function of the wave bending moment MW, N
___
(≈ 108) is the number of wave cycles met by the ship in its lifetime, M s and
___
M u are mean values of still water and ultimate moments respectively, δs2 and
δu2 are their variances, and p is the target probability of hull girder failure.
The fault tree imposes events for which the criteria should be derived.
Formula (14) (criterion), presented as an example, includes parameters
representing:
• the ship life-time expressed by N – the number of vertical moment cycles
in ship life, which can be determined by owner as a design parameter;
• the characteristic value of wave moment Mw,N, determined by class rules
or direct computations;
41
•
•
still water load distributions: Ms and δs2, determined by loading conditions
and ship designers;
the ultimate hull girder strength distribution: MU and δU2 (which also
describe the actual regime of ship designing and construction),
determined by ship designers and the technology of ship designing and
construction.
As mentioned above the goals of Tier I of the GBS – SLA system will take
the form of safety objectives defined by risk level (eg. probability of failure
and fatality) and that these safety objectives will be achieved when each ship
function (Tier II) satisfy the risk level (probability) set for that function.
The safety levels of the objectives and ship functions will be set, after
thorough risk analysis. Next, the rules of classification societies to be
an element of GBS – SLA system will have to include, among others,
the criteria in form of formula (14) corresponding to the basic events
of the ship function fault tree. The target probabilities of the key events
of the risk model corresponding to one ship function (see Table 2) should
result in identifying the target probability for determining the safety level set
for the function considered (e.g. structure of the ship).
As the criteria include probabilistic parameters, which should be determined
for individual ship designs, it will be necessary to use sophisticated computer
programs in the process of ship designing to determine these parameters.
The five-tier system of GBS and risk model for each ship’s function reflects
the deductive approach to the ship’s safety regulations development
(reasoning from general to specific) and therefore, if correctly applied.
Conclusions
Series of catastrophes at sea show that the innovations introduced in shipbuilding
and shipping industry are not covered by appropriately developed safety regulations,
which are traditionally developed in reaction to casualties. Such regulations are not
fully harmonized with the sea environment and ship operation.
Development of ship’s safety regulations in reaction to casualties follows
the inductive approach (reasoning from specific to general), which lead to
the proliferation of regulations and the number of control bodies.
The five-tier system of GBS and risk model for each ship’s function reflects
the deductive approach to the ship’s safety regulations development (reasoning
from general to specific) and therefore, it is a proactive approach.
The safety regulations developed under GBS–SLA and risk models (fault trees and
mathematical theories used to describe basic events) will be harmonized with
the sea environment and ship operation.
The fault tree determines events for which safety criteria should be derived.
The arguments of such criteria will be the probability parameters. This implies that
sophisticated computer programs will need to be used in the process of ship
designing to determine these parameters.
GBS – SLA will be developed by MSC as a high priority issue under the current
agenda item on GBS. It is a huge project and, therefore, requires cooperation
of maritime players. The GBS – SLA, if successful, could heal the ailing safety
system and like the Okham razor”shave away" the superfluous regulations.
42
References
[1]
Lloyd’s List, 10 of March, 2008
[2]
Benchmarking Bulk Carriers 2009 – 10, INTERCARGO, 2010
[3]
Lloyd’s List, May 17, 2010
[4]
Bulk Carrier Casualty Report, INTERCARGO, 2005
[5]
The Joint Accident Investigation Commission of Estonia, Finland and Sweden, Final
report on the capsizing on 28 September1994 in the Baltic Sea of the Ro-Ro
passenger vessel m/v Estonia, 1997
[6]
IMO, Agreement concerning stability requirements for ro-ro passenger ships
undertaking regular scheduled international voyages between or from designated
ports in North West Europe and the Baltic Sea, SLF40/INF.14, 1996
[7]
IACS Common Rules for Bulk Carriers and for Double Hull Oil Tankers , Draft for
Comments, 2004
[8]
IMO Document MSC 78/26, Report of Maritime Safety Committee on its seventy
eight’s session, item 6, 2004
[9]
Shigemi T., Zhu T., Practical Methods of the design loads for primary structural
members of tankers, Marine Structures 16 (2003), pp 275-321
[10]
Zhu T., Shigemi T., Practical Estimation Method of the Design Loads for Primary
Structural Members of Bulk Carriers, Marine Structures, 16, 2003, pp. 489 – 515
[11]
Document MSC 81/6/14 submitted by Germany, IMO, 2006
[12]
Jankowski J., Bogdaniuk M., Risk Model Used to Develop Goal – Based Standards
for Ship Structures of Single Bulk Carrier, The Royal Institution of Naval Architects,
London, 2007
[13]
Vesely W.E, Golberg F.F., Roberts N.H., Haasl D.F., Fault tree handbook, US
Nuclear Regulatory Commission, 1981
[14]
IMO, Maritime Safety Committee, Goal-Based New Ship Construction Standards,
Report of the Correspondence Group on Safety Level Approach, MSC 83/5/3, 2007
[15]
Boitsov G. V. Partial safety factors for still water and wave loads, Ship Technology
Research, Vol. 47, 2000
43
The Shipping Industry Views on Oil Transport Safety
Benoit LOICQ
ECSA, European Community Shipowners' Associations, BELGIUM
Loicq@ecsa.eu
The Maritime Safety Package III was part of different measures agreed upon
in the EU following the accidents of the Erika and the Prestige, respectively in 1999
and 2002.
Whereas the first measures taken following the Erika accident were often purely
political as a reaction to the accident and the oil spill, the 2005 Maritime Safety
Package III was not reactive but proactive. The ECSA overall assessment was that
the new directives acknowledge the realities of shipping, aim at more safety and
promote quality shipping. At the same time the importance and the authority of IMO
was recognized.
Moreover, industry and Member States were consulted prior to issuing the Package.
In addition, the technical advice from the European Maritime Safety Agency (EMSA),
contributed significantly to delivering a workable package with direct added value.
On Flag State Compliance – which is largely based on the relevant IMO instruments
– one should observe an improvement in Flag State compliance and a steady shifting
of different registers to the White List of the Paris MoU.
The key point of the Directive on Port State Control i.e. targeting substandard ships is
fully supported by the shipping industry, as it keeps improving the efficiency of Port
State Control in terms of their resource allocation through targeting and rewarding
quality shipping with fewer controls.
With regard to Traffic Monitoring and Reporting processes, the establishment
of SafeSeaNet constitutes a very practical result of this Directive creating direct
added value – together with other action fields of EMSA such as CleanSeaNet,
the EU LRIT Data Centre and the EMSA Oil Spill Response constitute a package
of maritime surveillance now in place.
Another key point is the action taken on places of refuge. Pre-establishment
of possible places of refuge, a clear decision making structure with an independent
authority and a clear chain of command in maritime emergencies are at the basis
of the places of refuge policy.
In recent years, the number of accidents and pollution in EU waters has sharply
decreased. Nevertheless, a decent accident investigation with well-trained
investigators remains essential. In this respect, the technical expertise with EMSA is
a key element.
In conclusion, the Maritime Safety Package III concluding the EU regulation
development on safety at sea that is also directly linked to the IMO legislation offers
a decent EU maritime safety framework, which should be enforced by every EU
Member State and its application properly monitored by the European Commission.
45
Safety of Underwater Pipeline System
Magdalena Jabłonowska
Ministry of Infrastructure, Poland
mjablonowska@mi.gov.pl
The most important international public act on seas and oceans is the United Nations
Convention on the Law of the Sea of 1982. (UNCLOS)1 – gives coastal states
the right to build and use installations and constructions in their exclusive economic
zones (Article 56). Benefiting from this right ensues the obligation to respect
the provisions of the Convention guaranteeing the rights of other states, including
the right to “freedom of navigation” for sea going ships (Article 58).
Restricting the freedom of navigation involves not only the closing of a selected water
basin for navigation of foreign ships by a coastal state but also changes in the nature
of the water basin under its jurisdiction resulting from erection of constructions or
laying installations which inhibit safe navigation of ships from other countries.
Pipelines are a method for transporting substances from the producer to a wide
range of recipients. In some cases they may seem to be the only practical transport
means of large volumes which could not be transported by road or rail. They are also
believed to be one of the safest and economically viable methods for transporting
hazardous substances2. Nevertheless, they may pose a serious risk. Releasing
of flammable and toxic materials may trigger emergencies with catastrophic effects.
The frequency and type of emergency and resultant consequences depend on
the substance transported, type of pipeline, etc.3.
Underwater pipelines for transporting crude oil and natural gas always put the safety
of people and the natural environment at risk. History shows that emergencies and
damage to a pipeline lying on the sea bottom do take place, not in fact so
infrequently4. Failures in gas pipeline operation may originate from the following:
corrosion (internal and external), material and mechanical defects, natural hazards
(e.g. sea currents and storm waves), other risks (e.g. sabotage, accidently
transported mines) and external interruptions such as fishing, navy and commercial
shipping. 5.
The dominating risk is believed to come from external factors. These include damage
caused by cast or trawled anchors, dredge nets trawled by fishing vessels as well as
abrasion or hitting of the pipeline by a ship sailing over the pipeline without sufficient
clearance. Pipelines can also suffer damage caused by a heavy container lost in
heavy weather overboard a vessel navigating over the pipeline. In areas of heavy
traffic a collision resulting in ship sinking and resting on the pipeline cannot be
excluded.
1
2
3
4
5
United Nations Convention on the Law of the Sea, 1982 (Journal of Laws of 2002 No 59, item. 543, Appendix).
Cullen, J., The competent PIG, Pipes & Pipelines International, Nov.-Dec. 1996.
M. Borysewicz, S. Potempski, Ryzyko powaŜnych awarii systemów przesyłowych substancji niebezpiecznych.
Metody oceny, 2002, p. 24.
According to the US Department of the Interior, Minerals Management Service, in the years 1996-2006 80
emergencies in gas pipeline systems were recorded. Five involved catastrophic bursts of the pipeline, in four
cases leading to fire and/or explosions.
Nord Stream Espoo Report, Chapter 5 “Risk Assessment”, p. 241.
47
Damage to a pipeline by anchoring vessels is possible only in the case of emergency
anchorage in the area of the pipeline due to technical problems such as failure
of the main engine, auxiliary engine, steering gear as well as drifting of vessels
in unfavourable hydrometeorological conditions6.
The risk of damaging the pipeline by operating fishing vessels is connected with
various factors among them: type of vessel, fishing techniques used, type of fishing
gear, frequency of operations and navigational equipment of the vessel. The greatest
risk is generated by vessels using bottom trawl, as the passage of the trawl over
the pipeline may result in the trawl catching the pipeline by the otter board, and lead
to damage7.
The probability of ship sinking resulting in damage to the offshore pipeline is small8,
nevertheless, it significantly increases in regions of heavy traffic, particularly in traffic
delimitation zones and in roadways to ports.
This paper refers only to a wider study on safety of offshore pipelines for transporting
oil and gas laid on the sea bottom in water bodies of limited depth, and the freedom
of navigation of deep draught ships.
IDENTIFYING PARAMETERS ALLOWING FOR SAFE NAVIGATION OF SHIPS
ON WATER BODIES OF LIMITED DEPTH
A safe passage of ships on water basins of constrained depth requires compliance
with the basic conditions of safe navigation that can be formulated as follows:
h≥T+∆
where:
h – depth of water body,
T – ship draught,
∆ – keel clearance.
It is the keel clearance that remains decisive in safe passage of a ship over the sea
bottom or navigational obstacle on the sea bed. Safe clearance depends on various,
further presented factors
Identifying keel clearance.
Clearance can be divided into two constituents: static clearance ∆ and dynamic
s
clearance ∆ . Total keel clearance thus reads:
d
∆ = ∆ +∆
s
6
7
8
d
Analiza oddziaływania Ŝeglugi i rybołówstwa na rurociąg podmorski Balticpipe w polskiej strefie Morza
Bałtyckiego opracowana w oparciu o metody szacowania ryzyka”, study directed by S. Gucma, WyŜsza Szkoła
Morska Szczecin, Instytut InŜynierii Ruchu Morskiego, Szczecin 2002.
Ditto. Breaking load of the finest (14 mm) trawling line used by fishing vessels is 75-85 kN, which usually
exceeds the sustainability of the bedded pipeline.
See for details: Analiza oddziaływania Ŝeglugi …, Chapter 3.
48
Static clearance does not depend on the ship motion and remains fixed for the given
water body, comprising the following:
∆
∆
∆
∆
∆
1
2
3
4
5
water margin for sounding error dependent on water body depth;
navigational margin due to lack of sounding continuity;
mud margin dependent on navigational water basin;
water margin for tide estimation error dependent on navigational water body ;
margin for stating water state caused by water level oscillation
with reference to map zero;
∆
∆
6
7
error margin for ship draught dependent on ship type;
error margin for ship heel dependent on ship parameters.
Dynamic margin ∆ depends on ship motion and weather conditions. The margin
d
components are:
∆
∆
8
9
margin for squat due to ship’s motion;
margin for sea waving, dependent on wave and ship parameters.
Water margin for sounding error (∆ )
1
Water margin for sounding error depends on water body’s depth and is assumed for
quick reference from the table given below.
Depth of water body (H) [m]
Water margin (∆1) [m]
up to 4
4 – 10
10 – 20
20 – 100
0.10
0.15
0.20
0.01 H
For the needs of this study waters of limited depth refer to 20 m isobaths, therefore
the sounding error should read:
∆ = 0.2 m
1
Navigational water margin (∆2)
Navigational water margin9 results from insufficient knowledge of depth, bottom
cleanliness, interpolation errors between particular soundings and effects of hull
bottom potentially touching the sea bed. The margin depends on the frequency and
type of sounding and kind of sea bottom. The navigational margins on limited waters
are given in the table below10.
9
10
Not all authors take into account the correction called “navigational water margin” connected with ship squat.
For example M. Jurdziński does not mention it in planning keel clearance in the study Nawigacyjne
planowanie podróŜy, Wydawnictwo Morskie, Gdańsk, 1989.
Data given according to S. Gucma, InŜynieria Ruchu Morskiego, Okrętownictwo i śegluga 2001, p. 47,
Gdańsk 2001.
49
No.
Type of water basin and sounding
Type of sea bottom
Water margin (∆ ) [m]
1.
Trawled fairway
irrelevant
0.0
2.
Fairway and port basins Continuous
sounding – other sounding
soft
hard
0.2 – 0.3
0.3 – 0.4
3.
Access fairways to port (scope
dependent on sounding frequency)
soft
hard
0.5 – 0.8
0.7 – 1.0
2
Navigational margin expresses tentative estimations of other margins and errors.
In extreme cases, when other margins and errors are estimated precisely,
the navigational margin is the one that protects the ship from touching the sea
bottom.
Therefore, the navigational margin should be specified as the last, following
identification of other margins and errors and their probability level. In terms of safety,
adoption of a navigational margin of 0.5 m seems fully justified in conditions under
study, i.e.:
∆ = 0.5 m
2
Water margin for mud (∆3)
The value of this factor depends on the water body type and frequency of sounding.
It reads 0.1 – 0.3 m with bigger values adopted at river mouths. Taking into account
the fact that the study scope is limited to open sea waters this value should be
assumed to read:
∆ = 0.0 m
3
Water margin for tide estimation error (∆ )
4
As there are no significant tides in the area covered by this study the value of this
correction reads:
∆ = 0.0 m
4
Water margin for identifying the water state (∆ )
5
The reference level to map zero may oscillate mainly in conditions of changing
hydrometeorological conditions. This value varies from 0.1 to 1.0 m.
Years of observations by the Institute of Meteorology and Maritime Economy in
Gdynia of the Polish section of the Baltic coast11 indicate the option of considerable
oscillation of the sea level compared to the average water level. These changes are
particularly clear in autumn and winter12. In regions of significant deviation from
the average water level, an error may appear in forecasting and current data though
ships request information on the present sea level in a given region. Thus, the error
in identifying the state of water is adopted at least:
11
12
50
P. Instytut Meteorologii i Gospodarki Wodnej, „Warunki środowiskowe Polskiej Strefy Południowego Bałtyku
w 2001 roku”, Gdynia 2004.
Grzegorz Rutkowski, Ocena głębokości Północnego toru podejściowego do portu Świnoujście od pozycji
gazociągu Nord Stream do terminalu LNG w aspekcie obsługi jednostek o maksymalnych gabarytach –
Metody uproszczone. Instytut Nawigacji Akademii Morskiej Gdynia
∆ = 0.1 m
5
Water margin for identifying ship draught (∆ )
6
The draught of a ship at sea is calculated on the basis of load change resulting from
fuel and provisions consumption, ballast operations, changing salinity and hull
deflections. These calculations are performed with a specified degree of accuracy
(familiarity with ships plays a certain role). The error margin for ship draught is 0.1 –
0.3 m and is adopted proportionally to the ship’s size. Taking into account
the parameters of the ship in question the draught margin error is assumed to be:
∆ = 01 m
6
Margin for ship heeling (∆ )
7
The margin for ship heeling is adopted due to the error resulting from difficulties in
maintaining the ship upright and heeling connected with change of course. The error
referring to keeping the ship upright in practice does not exceed 1o, whereas heeling
due to change of ship course is one of the components of the margin and depends
on the speed. For ships moving approximately at 5 knots it is in practice negligible,
but for ship speed of approximately 20 knots this value may read even 5o.
The ship heeling margin is calculated according to the following formula:
∆ = 0.00875 · B · α [m]
7
where:
B
ship breadth [m];
α:
ship heel angle
Assuming that the ship heel angle is equal to: α = 0.50o and the ship breadth does
not exceed 40-50 m, the margin for ship heel amounts to respectively:
∆ (B = 40-50 m) = 0.183-0.218 m ≈ 0.2 m
7
The total value of static margin ∆ = ∆ + ∆ + ∆ + ∆ + ∆ + ∆ + ∆ and in the given
S
1
2
3
4
5
6
7
case reads ∆ = 0.2m + 0.5m + 0m + 0m + 0.1m + 0.1m + 0.2m = 1.1 m
S
In order to proceed to calculating the dynamic margin the ship type must be known.
Parameters of sea going ships under analysis13
Three types of ships presently operating worldwide have been chosen for
the analysis: bulk carriers, gas carriers and container vessels of the following shapes
and sizes:
13
The bulk carrier and container vessel parameters adopted from the study by Instytut InŜynierii Ruchu Morskiego
Akademii Morskie in Szczecin „Określenie minimalnych głębokości podejściowych torów wodnych do portu
Świnoujście zapewniających bezpieczną Ŝeglugę planowanych do eksploatacji statków” – scientific study,
Szczecin 2010. (…). Gas carriers parameters according to MAN in “Propulsion Trends in LNG Carriers”.
51
Ship type
LOA
L
PP
B
T
c
Speed [kt]
b
[m]
[m]
[m]
[m]
bulk carrier
270
255
43
13.5
0.82
15.,0
10.0
gas carrier
315
298
50.0
12.0
0.75
20.0
16.0
container
vessel
274
260
41.5
13.5
0.62
18.5
15.0
operational
reduced
Some of the ship parameters have been limited due to the water body’s parameters
(up to 20 m) chosen for the study. For the bulk carrier the depth of 13.5 m is not
the maximum draught, however in the case of the container vessel, the operational
speed of 18,5 knots is much lower than the maximum speed, which can reach even
25-26 knots. Squat for all ship types has been identified for two speeds: operational
for limited water bodies and reduced.
Water margin for squat of ship in motion (∆ )
8
There are several methods of determining ship squat value. For the needs of this
study a simple and common method C.B. Barrass method (recommended by, e.g.
popular the Brown’s Nautical Almanac) giving indirect results as compared to
the Huusk or Romish method is applied.
The formulas for squat of ship in motion on open waters reads as follows:
S
max
=c x V²
b
k
where:
c
b
V
k
block coefficient;
ship speed [kt].
The scope of applying the method limits the interrelation:
1.1 ≥ h/T ≤1.4
which means in short that the keel clearance does not exceed 25% of the ship
draught.
Following the calculation of squat for each of the three ship types sailing at assumed
speed over the pipeline, the squat margin in motion reads:
–
bulk carrier (speed 15 knots):
∆ = 1.8 m
–
bulk carrier (speed 10 knots):
∆ = 0.8 m
–
gas carrier (speed 20 knots):
∆ = 3.0 m
–
gas carrier (speed 16 knots):
∆ = 1.9 m
–
container vessel (speed 18.5 knots ): ∆ = 2,1 m
–
container vessel (speed 15 knots):
52
8
8
8
8
8
∆ = 1.4 m
8
Water margin for sea waving (∆ )
9
Water margin for sea waving depends on a number of factors, such as: wave height
and length, breadth and length of the ship. her speed, angle between ship course
and wave propagation, and many others, thus, it is the most difficult to calculate.
The margin for a still ship can be calculated by the following formula:
∆ = k · h [m]
9
f
where:
k
h
adopted coefficient of 0.33 – 0.66;
f
wave height [m].
Coefficient k depends on the ship’s breadth and length to wave length and wave
propagation angle The biggest values are adopted in the case of ships side facing
heading wave, where the ship side is less than half of the wave length. For ships that
are big as compared to wave dimensions this coefficient assumes a minimum
value14. For wave height corresponding to 15 m/s (7°B) win ds the water margin for
waving may read:
∆ = 0.4 m
9
The value of dynamic margin ∆d = ∆ +∆ for particular ships amount to:
8
9
–
bulk carrier (speed 15 knots):
∆ = 1.8 m + 0.4 m = 2.2 m
–
bulk carrier (speed 10 knots):
∆ = 0.8 m + 0.4 m = 1.2 m
–
gas carrier (speed 20 knots):
∆ = 3.0 m + 0.4 m = 3.4 m
–
gas carrier (speed 16 knots):
∆ = 1.9 m + 0.4 m = 2.3 m
–
container vessel (speed 18.5 knots ): ∆ = 2.1 m + 0.4 m = 2.5 m
–
container vessel (speed 15 knots):
d
d
d
d
d
∆ = 1.4 m + 0.4 m = 1.8 m
d
Calculating total keel clearance
The value of total keel clearance ∆ = ∆ +∆ for particular ships amount to:
s
d
–
bulk carrier (v = 15 knots):
∆ = 1.1 m + 2.2 m = 3.2 m
–
bulk carrier (v = 10 knots):
∆ = 1.1 m + 1.2 m = 2.2 m
–
gas carrier (v = 20 knots):
∆ = 1.1 m + 3.4 m = 4.5 m
14
A ship is considered to be big when her length exceeds the wave length at angle between ship course and
o
wave propagation equal 0 or 180 degrees or her breadth exceeds half of the wave length at 90 angle
between ship course and wave propagation.
53
–
gas carrier(v = 16 knots):
∆ = 1.1 m + 2.3 m = 3.3 m
–
container vessel (v = 18.5 knots):
∆ = 1.1 m + 2.5 m = 3.6 m
–
container vessel (v = 15 knots):
∆ = 1.1 m + 1.8 m = 2.9 m
Identifying conditions for safe navigation of large draught ships
The calculations above indicate that safe operation of ships with parameters adopted
for the analysis on water bodies of limited depth (20 meters) in varied weather
conditions amount to 15:
–
for bulk carriers with draught of 13.5 m. 16.7 m
–
for gas carriers with draught of 12 m.
–
for bulk carriers with draught of 13.5 m. - 17.2 m.
16.7 m
Therefore, to satisfy both criteria for safe passage of all ship types covered by
the analysis, the minimum safe depth should not be less than 17.2 m (or 16.7 m
in case of neglecting correction ∆ ).
2
In the case of pipelines laid on the sea bottom or embedded underwater structures
these values should be increased by the pipeline diameter or the height
of the structure over the seabed. In the case of 1.5 m gas pipeline diameter
the minimum safe depth for passage of all ship types should read 18.7 m (or 18.2 m
when neglecting correction ∆ ) over the sea bed.
2
In all cases the safety zone adopted by the gas pipeline owner should be accounted
for (if bigger than the value given in this study).
Pipeline damage consequences
Damage to a pipeline transporting hazardous substances may generate various
consequences, as a rule negative for people, the environment and technical
structures, depending on the extent of damage. Damage may be partial or
a complete bursting with catastrophic effects. Damage to a pipeline may additionally
lead to fire or even an explosion if a source of ignition is nearby, e.g. lightening,
operating machinery or operations on board ships.
Possible consequences of pipeline damage also depend on whether the dangerous
substance is retained by the water environment or released to the atmosphere.
Releasing of gas in water results in its free dispersion16. In the atmosphere, the gas
meeting no ignitions vanishes, or early ignition takes place followed by stream fire, or
free dispersion of the gas air mixture, which results in delayed ignition and in effect
immediate ignition or gas explosion. Gas pipeline emergencies may result in heat
radiation during a fire or overpressure during the explosion.
15
The values next given may be reduced by 0.5 m provided the discrepancies in studies referring to application
of correction ∆ are accounted for.
16
54
2
According to DONG Naturgas, A/S Risk Assessment of anchor Damage, October 2001, local gas leakage will
not pollute the environment or cause any changes.
Analysis of physical consequences of natural gas released by underwater pipelines
conducted in recent years confirms the risk of fires and explosions of varied
characteristics. The kind and area of adverse impact of emergencies depend on
the location, process parameters, presence of ignition sources and weather
conditions. The consequences of fire and explosions caused by failures may pose
a serious risk for man, sea going ships and other technical objects in the vicinity
of their adverse effects. A study conducted for the crossing of a gas pipeline and
fairway confirmed the risk of damage or even sinking of floating units in case
of damage, if in the vicinity of heat radiation or overpressure17.
An effective and common method for protecting offshore pipelines (similarly to shore
pipelines) is their mounting below the sea bottom. The correct depth of embedding
the gas pipeline in the seabed minimises the risk of damage and failures.
Though many studies have been performed relating to underwater installations,
including oil and gas pipeline systems, there are no relevant international regulations
in force, which invites various interpretations of these analyses and in effect does not
contribute to improving their safety.
17
Study of Biuro Studiów i Projektów Gazownictwa „Gazoprojekt”, PGNiG Gruop: „Potencjalne skutki awarii
gazociągów podmorskich”.
55
LNG Terminal Design Process from the Navigational Point of View
L. Gucma & M. Gucma
Maritime University of Szczecin, Poland
P. Vidmar & M. Perkovic
University of Ljubljana, Slovenia
l.gucma@am.szczecin.pl
Abstract
Localization of sea terminals, especially when designed to handle potentially dangerous
cargo like LNG gas, requires extremely demanding and complete studies. Although
appropriate tools exist, each study demands special adaptations of risk models. This article
presents risk calculation methods with determination of all stages’ parameters and variables
used in formal assessment and special respect to simulation methods. This article copes with
localization of LNG (Liquefied Natural Gas) terminal in terms of navigational advantages.
Full mission simulations describe very well the environment of vessels and provide full
interactions, while limited task simulations along with Monte Carlo methods can in certain
aspects speed up the development process. The authors present below the issue
of designing a new terminal and case studies for Slovenia and Poland.
1
1.1
Introduction
The LNG projects in Poland and Slovenia
Liquefied Natural Gas is of interest to many countries as an alternative, clean and
efficient fuel. European countries are looking for reliable and diversified solutions, not
based on a single fuel source - mainly pipe. In Poland there is a project of building
an LNG terminal in north western Poland (Port of Swinoujscie), whilst in Slovenia
an LNG port will be constructed outside of Koper Port. Although these are different
types of localizations many similarities can be outlined. In both ports, the concept
of a detailed study on navigation risk has been prepared. Currently there are no
coherent and complex methods of LNG port and infrastructure design from
the navigational risk point of view. Vessels that will be operating in ports are in
ranges of capacities from 75000 to 216000 m3 of LNG cargo.
1.2
Mathematical model
Hydrodynamic models of two classes are run on limited tasks simulators at
the Maritime University of Szczecin and the University of Ljubljana. One class models
are exploited only when limited parameters are known (usually when non-existing
ships or general class ships are modelled). Other class models are used when
precise characteristics of hulls, propellers and steering devices are known.
Additionally, real manoeuvring characteristics are used for model validation.
In the present study the latter model is used.
The model used in this study is based on modular methodology where all influences
such as hull hydrodynamic forces, propeller drag and steering gear forces as well as
certain external influences are modelled as separate forces and at the end summed
as longitudinal, transverse and rotational forces.
57
The model operates in the loop where, for given input variables (settings and
disturbances), the system instantly calculates the forces and moments acting on
the hull, from which instantaneous accelerations and speeds of surge, sway and yaw
are evaluated. The most important forces acting on the model are (Gucma S. et.al.
2009):
− thrust of propellers;
− side force of propellers;
− sway and resistant force of propellers;
− bow and stern thruster forces;
− current, wind and ice effects;
− moment and force of bank effect;
− shallow water forces;
− mooring and anchor forces;
− reaction of the fenders and friction between fender and ship’s hull;
− tugs’ forces;
− other forces depending on the characteristics of ship’s propulsion and steering units.
The functional diagram of the ship manoeuvring simulation model is presented in
Figure 1.1.
Fig. 1.1 Functional diagram of ship manoeuvring simulation model
The model interface is a typical 2D chart interface (Fig. 1.2) and 3D world as seen
on an actual vessel (Fig.1.3) The interface delivers information on the ships state
(position, course, speed, yaw etc.), quay and shoreline location, navigational marks,
soundings, external conditions, tug and line control and control elements
of the model. The model is implemented in Object Pascal using Delphi™
environment and in Visual C™ using C++ language.
58
Fig 1.2 Chart view during manoeuvring in designed port model
Fig. 1.3 3D full mission simulator view of LNG port
1.3
Example solution of a full mission simulator model
A typical example of a full mission simulator is a Kongsberg Polaris™ simulator
located at the Marine Traffic Engineering Centre (MTEC), Maritime University
of Szczecin (Fig. 1.4). Its basic components are:
− one full mission navigation bridge simulator with 270° visual projection and live
marine ship equipment (DNV class A);
− two part task navigation bridges with 120° visual p rojection and mix of real and
screen-simulated ship-like equipment including one Voith-Schneider tug console
(DNV class B);
− two desktop PC simulators with one monitor visual projection and one monitor
screen;
− simulated ship-like equipment.
59
Fig 1.4 Full mission simulator in MTEC
For performing simulations, the University of Ljubljana Faculty of Maritime Studies
and Transport (FPP UoL) utilizes similar tools – a simulation facility developed
by Transas™
Fig 1.5 Full mission simulator in FPP UoL (by Transas)
All hardware and software forming ship manoeuvring simulators (both in MTEC
& FPP UoL) were granted a DNV certificate of compliance and meet the training
requirements set forth in STCW’95 (Section A-I/12, Section B-I/12, Table A-II/1,
Table A-II/2 and Table A-II/3). The simulator has a hydrodynamic ship-modelling tool
for the creation of own ship models. This tool enables creating of almost any type
of ship (controls for two main engines and for controllable or 10 fixed-pitch propeller,
azimuth thrusters, rudder controls for simulating various types of conventional
rudders, active rudders, Z-drive/azimuth and thrusters) with very high fidelity
hydrodynamics in six DOF (surge, sway, heave, yaw, roll, pitch). The hydrodynamics
comprise all known to date external effects like squat, bank and channel effects.
60
2.
Design of an experimental system in simulation research
Based on the studies of the theory of modelling and simulation (Zeigler, 1984),
simulation-based research can be summarized as the following procedure:
− formulation of the problem,
− modelling of the object to be examined,
− development of computer programs,
− model validation,
− design of an experimental system,
− experiment,
− analysis of the results.
In designing an experimental system we have to define the scope of research that in
our considerations depends on the following (Gucma & Gucma, 1998):
− examined variants of the area infrastructure,
− examined types of ship (their maximum parameters),
− hydrometeorological conditions under which operations in the examined area will
be performed (manoeuvres, types and number of tugs in manoeuvres, etc.).
Having defined the data specifying the experiment range, we can establish specific
research conditions (Gucma & Gucma, 1998):
− number of series of planned manoeuvres,
− conditions prevailing in particular manoeuvre series.
3
Verification of simulation models
The acceptable level of model conformity with reality in marine traffic engineering
studies aimed at the determination of waterway parameters is assumed at 90%
(Gucma S., 1990). Model 11 verification is a routine applied before each experiment.
The repeated verification of optimum results in simulation tests was positive, which
proves that the human-technology-environment system was well represented
(Gucma S. 2001). There are three levels of simulated model verification:
1
verification of the mathematical model,
2
verification of pilot’s/navigator’s behaviour,
3
verification of the simulated system.
To verify the model, we have to answer three questions:
1
Will the ship proceed along the same or similar route during an identical
manoeuvre in the same waters and under the same conditions?
2
Will the pilot perform the same manoeuvre(s) in the same time length?
3
Will the simulated system fit reality?
61
The first answer is given after the mathematical model verification. To answer
the second question seems to be more difficult due to various ways and outcomes
of manoeuvring, even with the same pilot. This may result from the fact that
the navigator, while planning a manoeuvre, predicts future positions of the ship.
Predictions are often burdened with errors, and in addition, there exist various ways
of making the same manoeuvre. On the other hand, complete adequacy of the model
to reality does not have to be greater than the designed tolerance of fairways, i.e.
approximately three meters (Webster, 1992). Striving for higher accuracy
of simulators for waterway designs would be of academic rather than practical
nature. The model can be verified on the basis of:
− data from real tests,
− physical model tests,
− theoretical relationships – analytical calculations (extrapolation or interpolation
by theoretical models),
− expert opinions.
3.1
Verification of mathematical models
The verification of a mathematical model, i.e. quantitative assessment of its
adequacy, is always carried out after the model is built and is based on conformity
indicators of ship’s manoeuvring characteristics (Gucma S., 1990). The verification
makes use of comparative parameters to compare ship’s manoeuvres:
− acceleration − distance and time for various operating modes of the main engine;
− stopping − distance, time, deviation from the original course for various ME working
modes;
− turning ability (turning circle tests) − diameter, linear velocity and rate of turn in
turning;
− course stability (zigzag tests) − time of rudder response, maximum angle of deviation,
yaw time, non-dimensional yaw period;
− turning ability with thrusters or engines − time to alter course by a specific value.
Verification is a lengthy and usually iterative process. The verification
of a mathematical model and pilot’s behaviour involves teams of pilots and
professionals in the field of ship movement computer simulations. To eliminate
systematic errors, at least two groups working independently are arranged.
Then the results are compared. The verification by pilot experts is a subjective
process, so the results should be treated with reserve.
4
Monte Carlo Simulation Methods
The safety assessment of complex marine systems calls for models of a number
of parameters, such as: vessel traffic, hydrometeorological conditions, area
parameters and others. These parameters are mostly random, therefore analytical
methods are not suitable for constructing their models, particularly if these models
are to include the human factor (probability of operator’s error). Such systems can be
modelled by simulations methods, Monte Carlo (MC) methods in particular.
62
These consist in generating random numbers aimed at estimating their distributions.
The generation of numbers is mainly done by computers. The method is really helpful
when relations between distributions are described by sophisticated functions and
depend on random elements. The MC method offers several advantages, (Vose,
2000) (Brandt, 1998) enabling:
− examination of a large number of scenarios,
− modelling of correlations and internal relations,
− application of a simplified mathematical level,
− application of a computer for calculations,
− fast introduction of active changes in the model,
− sensitivity analysis by changing distributions and their parameters,
− incorporation of a large quantity of data from a long time interval,
− evaluation of the method error.
The disadvantages of the MC methods are as follows:
− weak convergence of the method, which can be compensated by a large number
of iterations.
− only approximate solutions can be obtained.
− high computing power demand (some very complex problems require long
simulation time).
This subchapter presents the methodology of creating MC models for
the determination of marine structures safety in view of their possible damage by
passing vessels. These models often have to take into account possible human
errors and feature human behaviour (e.g. decision to execute emergency anchor
dropping). Incorporation of these aspects in models other than simulation is not
usually possible. The presented models can be used for assessing the probability
of ship’s collision with marine structures, such as: wind turbines, drilling rigs and
other objects that may be considered dangerous for surface navigation, or
the probability of indirect damage to submarine pipelines or cables by a ship’s
anchor. The essential advantage of the MC method is the possibility of projection.
In such cases we have to know the function of probability distribution changes or
their parameters in time. Principally there are four groups of problems solved
by marine traffic engineering using MC simulation methods:
1
stochastic models of vessel traffic streams with elements of MC simulation
(Gucma L. 2003), (Hansen & B.C., 2000);
2
MC methods based on generalized simulation and real models (Iribarren, 1999);
3
simulation models of ship movement in fast time with random external excitations
(Hutchison, Gray, & Mathai, 2003);
4
methods of measurement error analysis and uncertainties using MC simulation
(Sand, Nielsen, & Jakobsen, 1994).
63
The first group of methods comprises simulations of large marine traffic engineering
systems found mostly in offshore areas. The vessel traffic streams are the subject
of simulation, but the objective of simulation is the determination of system safety.
Microscopic methods of simulating vessel traffic streams are used, i.e. single ship
movement is simulated. These methods utilize much-simplified models
of the navigator, while the ship is regarded as a material point. The models contain
analytical or empirical modules for defining probabilities of some modelled events.
In these models time is deliberately accelerated in order to create an adequately
large number of scenarios, as simulated events are rare (collisions, groundings,
indirect damage). Projected magnitudes of random variables can be introduced in
the models. External conditions are simulated as random variables.
The second group of methods encompasses MC tests, using distributions of random
variables and their parameters obtained from previously conducted real or simulation
tests. These methods are generally aimed at getting a larger number of accident
scenarios that may be obtained by simulation methods. The models are often
combined with analytical or empirical models.
The third group of methods consists in modifying simulation models of ship
movement operating in fast time with a navigator’s model. Random disturbances,
often dependent on time, are introduced. Also, random models of navigator’s
behaviour can be implemented. Methods of this type are mostly used for port areas,
basically in the designing and optimization of waterway parameters.
Finally, the fourth group of methods is helpful in the determination of measurement
errors in complex measurement systems, i.e. where this cannot be done by analytical
methods. These models can be combined with analytical or empirical models in
conjunction with uncertainty analysis. The probabilistic method of underkeel
clearance determination is an example of such a method. Accidents generally
happen due to navigator’s errors, often enhanced by ship’s technical failure and
random conditions. The discussed models are based on an assumption that
parameters of vessel traffic stream are the most important factor affecting safety.
These models can also include empirical or analytical algorithms of ship’s behaviour
in various conditions, such as models of drift, leeway, dragging anchor, etc.
The applicability of these methods is wide enough to include probability assessment
of direct accidents, such as ship’s collisions with marine structures or indirect
accidents caused by, e.g. dragging anchor.
The above methods can be used for determining the probability of ship’s collision with:
− open sea drilling rigs and oil platforms,
− offshore wind farms,
− fixed aids to navigation,
− submarine pipelines or cables,
− bridges and their supports,
− other stationary marine structures.
64
4.1
Model for the assessment of LNG carrier safety – case study
The assessment and comparison of the navigational safety of two proposed locations
of an LNG terminal in Poland with several approach routes will be presented.
Safety assessment is based on the original probabilistic model created at
the Maritime University of Szczecin. The model is capable of assessing the risk
of a large complex system with consideration of human (navigator) behaviour
models, ship dynamics model, real traffic stream parameters and external conditions
such as wind, current, visibility, etc. The model works in fast time and can simulate
a large number of scenarios. The output from the model such as a place of collision,
ships involved, and navigational conditions can be useful for risk assessment
of the proposed LNG terminal locations. The results were used for the determination
of the optimal location of the LNG terminal based on the navigational risk criterion.
Of the several simplifications assumed, one of the most important was considering
an LNG carrier as a conventional ship.
The developed model, presented in Figure 4.21, can be used for assessing almost all
navigational accidents, such as collisions, groundings, collision with a fixed object
[Gucma 2003], indirect accidents involving anchors or accidents caused by ship
generated waves [Gucma & Zalewski 2003]. The model can comprise several
modules responsible for different navigational accidents. This methodology has
already been used by several authors with various effect [Friis-Hansen & Simonsen
2000, Merrick et al. 2001, Otay & Tan 1998]. In these studies the model is used to
assess the safety of different variants of LNG terminal location.
Fig. 5.1 Diagram of a fully developed stochastic model of navigation safety assessment
5
Conclusions
Many possible sources of threats, though important like fire hazard, loss of stability
etc. have been intentionally omitted in this article. Neither individual nor social risk
models were presented in full scale, due to the fact, of keeping the subject of the
article at some general assumptions level.
65
The article presents several aspects of safety with special respect to port operations i.e.:
− manoeuvring,
− mooring,
− alongside,
− unloading of LNGC inside port area.
Results from manoeuvring simulations proved the optimal shape of designed terminal
in Swinouśjcie with use of statistical tools for comparison. An energy induction
analysis in the first point of contact led to evolution of mooring facilities especially
the fendering system.
The paper also presents results of analysis for safety of stay of LNGC alongside
the terminal and for performing unloading operations. In terms of terminal operation
processes these are most important and must be described thoroughly in port
procedures booklets.
Safety assessment has been conducted for typical LNG vessels for the designing
of outer port in Swinoujście, where the largest analyzed vessel was Q-Flex type,
within range of prospected operations inside the port.
References
Gucma S. 2001 Marine Traffic Engineering, Gdańsk: śegluga i Okrętownictwo Publish House.
Gucma S. (ed.) 2008. Simulation methods in marine traffic engineering, Szczecin: Maritime
University of Szczecin.
Gucma S. (ed.) 2009. LNG terminals design and operation.
Navigational safety aspects. Maritime University of Szczecin Publish House, 2009.
Gucma, L. 2005. Risk factors modeling of vessels collisions with port and sea constructions.
Studies 44. Szczecin: Maritime University in Szczecin Publish House.
Gucma M. Gucma S. 2008. Safety of manuvering, mooring and unloading of LNG carriers in
outer port of Swinoujscie, Proceedings of the XVI-th International Scientific and Technical
Conference, Proc. intern. conf.,“The Role of Navigation in Support of Human Activity on the
Sea” October 22-24, 2008. Gdynia, Poland
Gucma M. Gucma S. Slaczka W. 2007 determination of the optimal shape and parameters
of the LNG terminal in Świnoujście with use of the simulation-expert method, Transport XXI,
Proc. intern. conf. 18-20.09.2007, Warsaw: Technical University of Warsaw.
Gucma M. 2007 Navigational risk assessment in optimization of LNG terminal parameters.
In C.G. Soares, P Kolev (eds), Maritime Industry, Ocean Engineering and Coastal Resources
(vol. 2); Proc. intern. symp., IMAM 2007 Rotterdam: Balkema.
Gucma M. Gucma S. 2007. Simulation method of navigational risk assessment in
optimization of LNG terminal parameters. In T. Aven, J.E. Vinnem (eds), Risk, Reliability and
Societal Safety (vol. 3). Proc. intern. symp., ESREL 2007 Rotterdam: Balkema.
IMO, 2007. Guidelines for Formal Safety Assessment (FSA) for use in the IMO rule-making
process. MSC83/INF.2 (Consolidated version). London: International Maritime Organization.
66
IMO, 1993. International Code for Construction and Equipment of Ships Carrying Liquefied
Gases in Bulk (IGC) (third ed.). London: International Maritime Organization,.
IACS, 2004. Experience with Formal Safety Assessment at IMO. MSC 78/19/1, London:
International Maritime Organization.
C.G. Soares and A.P. Teixeira, Risk assessment in maritime transportation, Reliab Eng Syst
Saf 74 (3) (2001), pp. 299–309
Vanem E., Antao P., Ostvik I., Castillo de Comas F. de, Analysing the risk of LNG carrier
operations, Reliability Engineering & System Safety, Volume 93, Issue 9, Safety in Maritime
Transportation, September 2008, Pages 1328-1344,
Pitblado R. 2007. Potential for BLEVE associated with marine LNG vessel fires, Journal of
Hazardous Materials, Volume 140, Issue 3, 20 February 2007, New York: Elsevier
Fang Q, Yang Z, Hu S, Wang J. 2005 Formal safety assessment and application of the
navigation simulators for preventing human error in ship operations. Journal of Maritime
Science Applied 2005;4(3), Rotterdam: Balkema
67
Maritime Surveillance for Better Maritime Safety
Isto Matilla
European Commission Directorate-General for Maritime Affairs
and Fisheries, EU
Isto.MATTILA@ec.europa.eu
Policy background
The overall objective of Maritime Surveillance is to develop mechanisms
for improving maritime awareness by sharing operational information between
government departments and agencies. The Commitment of Member States and
stakeholders to this project shows that they fully understand the benefits that
cooperation and the creation of a network across ALL surveillance authorities may
bring: Search and rescue authorities will swiftly avail of better information when
people's lives are in danger at sea. Coast Guards, police and navies may share
information to combat all kinds of illegal activities at sea or to protect merchant ships
and fishing boats from all kinds of threats. Increased safety, security and cleaner
seas are ultimate objectives for all. Therefore, surveillance policy initiative is
an enabler for those authorities to respond adequately to the challenges and risks
in the waters under their jurisdiction and in the High Seas.
The political process, which is admittedly the most crucial, comprises three main
components: coordination, trust-building and sense of ownership. All are progressing
very well. The Commission provided the necessary guidance and working tools
by means of two consecutive and complementary Communications; October 2009
setting the guiding principles and October 2010 outlining 'A Roadmap towards
the Common Information Sharing Environment'. After the first (2009) Communication,
all institutions unanimously asked for a Roadmap towards the Common Information
Sharing Environment. After the second (2010) Communication, the Council strongly
requested to ensure coherence and coordination through the Member States Experts
Sub-group.
69
The paradigm of information exchange is gradually changing from the more
restrictive "need to know" to the more open "need and responsibility to share". Even
more importantly, authorities across the EU have embraced the Common Information
Sharing Environment as their own project and the proponents are increasing day
by day. This is the prerequisite for success. As mandated by the Council – again
– coordination will be effected through the Member States' Experts Sub-Group.
Challenges for maritime surveillance
The following challenges are currently being faced with regard to the development of
a common information-sharing environment for the EU maritime domain:
Diverse user and operator communities: Both at national level and at EU level,
national authorities responsible for defence, border control, customs, marine
pollution, fisheries control, maritime safety and security, vessel traffic management,
accident and disaster response, search and rescue as well as law enforcement are
collecting information for their own purposes. While the technological means exist to
share this information in a meaningful manner, most of the information needed to
build up this maritime situational awareness is still being collected by numerous
sectoral systems at national, EU and international level.
While in some cases the involved authorities are unaware that similar information is
collected by other authorities and systems, in other cases they are aware but unable
to share this information with one another because information sharing standards,
agreements, policies regarding information exchange processes currently exist only
in certain user communities.
Diverse legal frameworks: The different maritime surveillance activities fall under
different articles of the Lisbon Treaty. Surveillance systems have been developed
on the basis of sector-specific, international and EU legislation. Regardless
of the given EU framework, nothing should prevent the Member States to integrate
their maritime surveillance activities.
Cross border threats: Threats faced by Member States in the EU maritime domain
often require an improved trans-national and sometimes even a trans-sectoral
approach, in particular with regard to the high seas.
Specific legal provisions: International and EU legislation frame on maritime
surveillance activities on the high seas and with regard to the processing of personal,
confidential or classified data.
A Common Information Sharing Environment (CISE) for all EU sea basins is
the vision.
This cross-sectoral surveillance tool will interconnect different national authorities
with a mission at sea on a "responsibility to share data" logic, across sectors and
borders. It will thus enable coordinated actions through increased data flows.
The first tangible result will be better tactical patrolling and increased response
capability in case of maritime incidents (being they of law enforcement/border control
nature or search and rescue, response to natural disaster, tracking illegal fishing or
polluters of the marine environment etc). At a second level, better knowledge
of the processes and interactions in the EU maritime domain has a strong potential to
contribute to improved governance and thus create a favourable environment for
maritime economic activities to flourish.
70
The Common Information Sharing Environment Roadmap is being carried out by the
Technical Advisory Group (TAG). It was a strategic option of the Directorate General
for Maritime Affairs and Fisheries to work with the User Communities, the Member
States and the real experts instead of going directly to the industry. This presents the
most modest possible allocation of resources in such times of tight budgets.
The Technical Advisory Group brings together the seven user communities experts
and agencies including military component. It makes proposals and suggests
solutions on how to put the data exchange into practice. The work of the Technical
Advisory Group continues until end of 2012.
In parallel, based on the results of the carried out within MARSUNO and
BlueMassMed Pilot projects, which will show the way forward, implementing studies
will focus on the cost-benefit ratio of Common Information Sharing Environment,
legal challenges and IT-needs, with a view to delivering an impact assessment.
In the Commission's view the most appropriate way to address the legal, technical
and financial aspects of the Common Information Sharing Environment would be
by continuing the close collaboration with the Member States and the EU Agencies.
Expertise available therein is nowhere else available.
User communities
The CISE brings together the following communities in an unprecedented way.
These communities meet regularly in the framework of the Technical Advisory Group
which reports to the Member State Expert sub Group on Integrated Maritime
Surveillance.
(1)
Maritime Safety (including Search and Rescue), Maritime Security and
prevention of pollution caused by ships. Under leadership of DG MOVE
within the Commission, this user community is for now the biggest and
best developed with an efficient and productive Agency: EMSA.
The transport layer within CISE will be of high value added to all other user
communities.
(2)
Fisheries control, under the leadership of DG MARE within the Commission,
and its Agency the EFCA, has a number of data sharing issues and experience
to share with the environmental, the transport and the law enforcement user
communities.
(3)
Marine pollution preparedness and response; Marine environment under
the leadership of DG ECHO and DG ENV within the Commission with
the European Environmental Agency (EEA) are crucial element as
environmental crime related issues do not only touch upon law enforcement but
also on security matters due to ecological threats (see tsunami now in Japan).
(4)
Customs under the leadership of DG TAXUD within the Commission is
an essential actor as regards economic safeguard of the EU. It cooperates
closely with transport, law enforcement and the border control user communities
with which it needs to enhance regular data exchange.
(5)
Border control under the leadership of DG HOME is creating EUROSUR
with its agency Frontex. Border Control user community requires transport
related data as well as data gathered by the militay community as regards
human trafficking through the Mediterranean Sea in view first of all to save as
71
many lives at sea as possible. In the present Mediterranean context this
becomes an even more relevant task. HOME is also in charge of the Internal
Security Strategy of the Commission.
(6)
General law enforcement18 under the responsibility of DG JUST, the
Maritime Analysis and Operation Centre–Narcotics (MAOC-N) is representing
this community in the TAG. Maoc's deep cross-sectoral experience in data
exchange is of very high value to the CISE process.
(7)
Defence is represented directly by Member States as for military matters
the Council is only responsible for Common Security and Defence Policy
(CSDP) matters. The defence TAG member and substitute has thus been
selected directly from Member States applications.
Conclusions
An integrated approach to maritime surveillance should improve the effectiveness of
the authorities responsible for maritime activities by making available more tools and
more information necessary for the performance of their duties. This should result
in more efficient operations and reduced operating costs.
Therefore the establishment of the common information sharing environment should
ensure:
Interoperability: Ways and means have to be found to enable the exchange
of information between sectoral systems both operational and those currently being
developed by the European Union and its Member States supported by EU agencies
such as EMSA, EFCA, FRONTEX and EDA. This requires that existing and future
standards, interconnections, non-technical processes and procedures are developed
and established enabling information sharing and the protection of information
shared on the basis of agreed access rights. This should also lead to improved
interoperability between sectoral systems within a Member State.
Improving situational awareness: The information obtained in this environment
should considerably improve the situational awareness within the EU and
the Member States.
Efficiency: Furthermore, this environment should also contribute to a unity of effort
across entities with maritime interests by avoiding duplications in the collection
of information and thereby considerably reducing the financial costs for all actors
involved. In time, a multi purpose approach could be envisaged when using
surveillance tools and assets from different user communities.
Subsidiarity: The vast majority of monitoring and surveillance activities at sea are
carried out under the responsibility of Member States. Following the principle
of subsidiarity, Member States are responsible for coordinating the collection and
verification of information from all their agencies, administrations and national
operators, preferably via a single national coordination mechanism. Member States
will also, where applicable, manage third party access rights, qualify the information
and data security levels, and approve and control the selective dissemination and
data security mechanisms.
18
With focus on the prevention of any criminal / illegal activity and on police administrative activities in the EU
maritime domain.
72
INTEGRATED MARITIME SURVEILLANCE
INTO ACTIONS
Integration
-VISION
Full-scale
CISE
FP7
Pilot
projects
TAG
Implementation
Etc.
Legislation
Conclusions
Roadmap
Non-paper
2008-2009
20010-2013
2014
2015
2016
2017
73
Regional Efforts for Safer Navigation, Hydrographic
Re-surveys and Cleaner Baltic Shipping
Anne Christine Brusendorff, Monika Stankiewicz
HELCOM, Finland
anne.christine.brusendorff@helcom.fi, monika.stankiewicz@helcom.fi
Abstract
HELCOM, an inter-governmental organization of the nine coastal countries and
the European Union, has for more than three decades shown how the regional co-operation
in the Baltic Sea Region has remarkably improved the safety of navigation and reduced
the environmental impacts of the dense maritime traffic as well as ensured a standing
national and trans-national response to accidents at sea. Among the latest initiatives is
the approval by IMO/MEPC 61 in 2010 of the Baltic Sea Area as the first Special Area under
Annex IV (sewage) of MARPOL, expected to be adopted by MEPC 62, as well as the
preparation of a joint submission to IMO asking for the designation of the Baltic Sea Area as
a NOx Emission Control Area (NECA) under Annex VI of MARPOL. Under the EU Strategy
for the Baltic Sea Region, and more specifically the flag ship project BRISK (Sub-regional
risk of spill of oil and hazardous substances in the Baltic Sea) and its like-minded BRISK-RU
project, a risk analysis of oil spills has been carried out, both for the use in the planning
of response operations and for further considerations of needed additional maritime safety
measures. Another EU Strategy’s flag ship project on speeding up hydrographic re-surveys
of the Baltic Sea, led jointly by HELCOM and the Baltic Sea Hydrographic Commission, has
been politically backed-up by the HELCOM Moscow Ministerial Meeting in 2010, including
setting a timetable for its implementation, and has already led to initiation of a new EU
Motorways of the Sea project – MONALISA, focusing on quality assured hydrographic
surveys in Sweden and Finland as well as on application of IMO’s e-navigation concept.
Keywords
HELCOM, Baltic Sea Action Plan, maritime safety, Baltic Sea Special Area, risk of spills,
hydrographic re-surveys.
1.
Overview of the maritime transportation in the Baltic Sea Area
HELCOM has, as one of the first international organizations, been able to regularly
survey and estimate the maritime transport in the Baltic Sea Area, since 1 July 2005.
This is due to a decision taken at ministerial level, involving both transport and
environment ministers, whereby national land-based monitoring systems, based on
Automatic Identification System (AIS) signals makes up the basis for the common
Baltic Sea monitoring system.
The data derived from this monitoring system provides for annual reports and statistics
on ships’ traffic in the Baltic Sea area as well as trends compared to earlier years.
In 2010, vessels entered or left the Baltic Sea via Skav 56,564 times (figure
representing the number of crossings through a pre-defined AIS line in Skav).
This figure has increased by more than 10% since 2006 (51,628 crossings).
Approximately, 19% of those ships were tankers, 44% other cargo ships and 4%
passenger ships. Additionally, 31,933 ships passed through the 98-kilometer long
Kiel Canal (in 2010).
75
The task of the shore-based AIS network is to provide the competent authorities with
a monitoring tool for supervision, risk analyses, designing new routeing measures,
search and rescue operations, port state control, security and other safety-related
tasks to ensure safe navigation in the Baltic Sea. An example of such AIS application
is a system to detect single hull tankers carrying heavy grade oil entering the Baltic
Sea, developed jointly by HELCOM and the European Maritime Safety Agency
(EMSA) and put into operation in October 2007.
But there are also other uses of AIS which go beyond the “traditional” safety aspects,
monitoring of ship emissions being one of them. The AIS data are used, for instance,
for calculating nitrogen oxides (NOx) emissions from Baltic Sea shipping, which
reached 357,000 tonnes in 2009, giving the most precise estimate of this kind.
This information is particularly important for the region as atmospheric nitrogen
deposition is one of the main contributors to the high nutrient concentrations that
stimulate massive algae blooms in the Baltic.
To allow fully benefiting from AIS, HELCOM has undertaken a revision
of the Agreement on Access to AIS Information in the Baltic Sea in order to broaden
the eligible uses of AIS data to activities and projects aiming at the protection
of the marine environment and consistent with the goals of the Helsinki Convention
on the protection of the marine environment of the Baltic Sea Area.
2.
Promotion of international regulations and their harmonized implementation
As shipping is international, it is necessary to promote regulations that are applied to
all ships sailing in the Baltic Sea Area, whether in territorial seas or in the exclusive
economic zones and whether under the flag of a Baltic Sea State or another flag.
For this reason HELCOM works for the promotion of rules within the International
Maritime Organization.
At the same time, HELCOM works for the advancement of rules that takes into
account the character of the maritime traffic and the specific sensitivity of marine
environment, and thus are tailored to the specific conditions in the Baltic Sea Area.
This has been recognized since the establishment of the Convention on
the Protection of the Marine Environment of the Baltic Sea Area in 1974, through
Resolutions adopted at the Diplomatic Conference requesting ships other than those
flying the flag of a Contracting Party to observe the same special rules when
operating in the Baltic Sea Area. This was followed up by four IMO Resolutions
recommending the application of the special provisions of Annex I, II, IV and V
of MARPOL prior to their global entry into force.
Another issue of importance in the HELCOM cooperation is the implementation, in
a harmonized way, of adopted regulations. And, where possible and necessary,
HELCOM works for the implementation of rules with the strictest content as well as
for an earlier implementation in the Baltic than the global entry into force.
3.
The Krakow and Moscow Ministerial Meetings – specifically with regard
to maritime transportation
When ministers met in 2007 in Krakow, under HELCOM Polish presidency, they
adopted the HELCOM Baltic Sea Action Plan (BSAP), which alongside other
segments, contains one specific section on “Maritime Activities”.
76
The section on “Maritime Activities” deal with both improved safety of navigation:
−
through the promotion of enhanced use of the information in the Automatic
Identification System and introduction of a general requirement for carriage
by ships of an Electronic Chart Display and Information System (ECDIS),
as well as the prevention of pollution from ships:
−
through the proposal for an amendment to Annex IV to MARPOL on requirements
for the nutrient discharges in sewage from passenger ships, including
the designation of the Baltic Sea as Special Area, and through a proposal for
the designation of the Baltic Sea as a NOx Emission Control Area (NECA) under
Annex VI to MARPOL.
Based on the support of also Baltic Sea countries, IMO adopted in 2009
the amendment to Chapter 5 of SOLAS regarding carriage requirements for
shipborne navigational systems and equipment under which, cargo ships, tankers
and passenger ships engaged in international voyages shall be fitted with an ECDIS
according to the specific timetable. The new regulations mean that a majority
of the ships in the Baltic Sea will be carrying ECDIS onboard by 2018 at the latest.
Work continues in the Baltic Sea to test and further develop non-mandatory AIS
application-specific messages to enhance communication between ships and shore
authorities, according to the recently adopted IMO circulars (SN.1/Circ.289 and
SN.1/Circ.290). The IMO circulars were developed utilizing the experience of, e.g.,
the Baltic Sea region and the results of the HELCOM supported Baltic AIS Trial Project.
In 2009 the HELCOM countries submitted a proposal to IMO (IMO documents MEPC
60/6/2, 60/6/3, 60/INF.4), aiming at establishing the Baltic Sea as a Special Area for
sewage under Annex IV of MARPOL, whereby passenger ships will be banned to
discharge sewage in the Baltic Sea unless it has been treated to remove phosphorus
and nitrogen to certain levels. Alternatively, sewage can be delivered to a port
reception facility (PRF). The proposal for new sewage regulations was approved
by the 61th session of the IMO Marine Environment Protection Committee (MEPC)
in 2010 and is expected to be adopted by MEPC 62 on 11-15 July 2011.
As agreed in the BSAP, HELCOM countries supported efforts within IMO under the then
ongoing review process of MARPOL Annex VI by submitting a joint document to MEPC 57
in 2008 (IMO document MEPC 57/INF.14) calling for tighter international regulations to
prevent a predicted sharp increase in NOx emissions from Baltic shipping. The paper
indicated that with the projected annual 5.2% growth of maritime traffic in the Baltic Sea,
the 19% reductions in emissions from diesel engines would not change the situation but
would even lead to further increases in emissions in the region. Only the most challenging
requirement – an 80% reduction in emissions from marine diesel engines - would reverse
the increasing trend of NOx emissions in a long term.
The Krakow decisions were followed-up in 2010, when ministers met in Moscow
under Russian HELCOM presidency.
Based on a Moscow decision, a joint proposal by the Baltic Sea countries to IMO
applying for a NO x Emission Control Area (NECA) status for the Baltic Sea
is close to completion. Comprehensive analyses were finalised to estimate the NOx
emissions from ships operating in the Baltic Sea area, and the impact of the
emissions on air quality, ecosystems and human health, as well as economic impact.
77
The studies have confirmed that NOx emissions from Baltic shipping contribute
significantly to air pollution, have adverse effects on human health, especially in big
coastal cities, and contribute to the eutrophication of the Baltic Sea.
Regarding the Baltic Sea Special Area under Annex IV of MARPOL, practical work
and investments at port level have been initiated to enhance reception facilities for
sewage in the prioritized ports (listed in the Roadmap for upgrading Port Reception
Facilities (PRF) adopted by the Moscow Ministerial Meeting). A Co-operation
Platform on PRF has been established under the HELCOM umbrella, consisting
of national administrations, ports, water and wastewater associations and passenger
shipping industry to facilitate this work.
In order to meet the risks related to increasing maritime transportation in the Baltic
Sea, the ministers decided to enhance regional cooperation on maritime safety,
taking into account the IMO work, which resulted in the arrangement in 2011
of the First Meeting of the Experts on Maritime Safety in the Baltic Sea.
HELCOM Recommendation 31E/5 on mutual plan for places of refuge, adopted
at the 2010 ministerial session, is the first of its kind agreement providing the basis to
accommodate a ship in need of assistance in the Baltic Sea in the safest shelter
irrespective of national borders.
The ongoing BRISK project, implementing HELCOM Recommendation 28E/12
on strengthening of sub-regional cooperation in the response field, is finalizing
the overall risk assessment of shipping accidents covering the whole Baltic Sea Area.
A corresponding project in Russia (BRISK-RU) provides a vital expertise to the risk
assessment and secures Russian participation in the joint activities.
Based on the outcome of the risk assessment, missing response resources in each
sub-region of the Baltic Sea will be identified. The gap identification needs to be
followed by the necessary investments in the response equipment as well as
optimization of the emergency response. The risk assessment will also enable
identification of hot spot areas with the highest risks and will provide the basis for
development of further risk control measures.
The scope of the 2001 HELCOM Copenhagen Declaration regarding hydrograhic resurveys has been extended to cover more routes and other areas, and all Baltic Sea
countries are to present their national re-survey plans, including the time schedule for
the implementation, by 2015 at the latest.
4.
Overall risk assessment of shipping accidents
The main aim of the Project “Sub-regional risk of spill of oil and hazardous
substances in the Baltic Sea” (BRISK in short) as well as BRISK-RU project
(www.brisk.helcom.fi) is to optimize response capacities in the Baltic Sea based on
the results of the risk assessment of shipping accidents and pollution. All HELCOM
countries participate in the risk assessment, eight EU members through EU cofinancing (2.5 mln from the European Regional Development Fund within the Baltic
Sea Region Programme 2007-2013) and Russia through the funding by the Nordic
Council of Ministers. The project is led by the Admiral Danish Fleet.
The project is being conducted within the framework of HELCOM to implement
the national commitments under the HELCOM Baltic Sea Action Plan, and is also
a flagship project under the EU Strategy for the Baltic Sea Region.
78
The risk assessment modelling provides a unique and detailed picture of the risks
associated with spills of oil and hazardous substances in the Baltic Sea. Its findings
are based on some of the most advanced tools available for modelling shipping traffic
flows, the risks of accidents at sea and their consequences. It models the events
leading to spills (ship accidents, etc.), the frequency, size, type and location of spills,
the spreading and fate of the spilt substances and the vulnerability of the marine
environment. Moreover, it models the effect of emergency response measures and
the effect of various existing and decided risk control measures that are affecting
navigational safety.
Based on the results of the risk assessment, the coastal countries are investigating
whether the existing emergency and response capacities are sufficient to tackle
medium-size and the largest spills of oil or hazardous substances, and will jointly
plan their investments in the response equipment so as to make sure that each subregion of the Baltic is capable of efficiently responding to the spills. The risk
assessment can also be utilized to develop new risk control measures to improve the
safety of navigation.
5.
Speeding up hydrographic re-surveys in the Baltic Sea
The 2011 Copenhagen Declaration requested the HELCOM members “to develop
a scheme for systematic re-surveying of major shipping routes and ports in order to
ensure that safety of navigation is not endangered by inadequate source
information.” The IHO Baltic Sea Hydrographic Commission (BSHC) developed and
approved in 2002 the Harmonised Hydrographic Re-Survey Scheme and established
a Monitoring Working Group to monitor its implementation. During eight years
of implementing the re-surveys according to this scheme it has been found out that
a major revision of the scheme is needed. The reasons for this are changed traffic
patterns and densities, new shipping routes, more accurate information on actually
used routes, and other needs for accurate and update hydrographic information (e.g.
for environmental purposes).
BSHC adopted a new Vision for the re-surveys in 2009 which states that the whole
Baltic Sea area should be covered by a harmonised re-survey scheme. The revised
re-survey scheme will be based on national re-survey schemes (and generalized,
if needed). The re-survey areas should be specified in three Categories:
CAT I – includes the current Scheme, re-surveys specified by the 2001 HELCOM
Copenhagen Declaration;
CAT II – for extended routes and areas according to national re-survey schemes as
specified for safety of navigation; and
CAT III – for extensions for other purposes than the above (e.g. for environmental
protection).
The speeding up of hydrographic re-surveys has been included as a flagship project
of the EU Strategy for the Baltic Sea Region, jointly led by HELCOM and the Baltic
Sea Hydrographic Commission.
HELCOM ministers in Moscow gave their full political support for the revision
of the Baltic Sea Re-survey Scheme according to the BSHC Vision, to consist
of national re-survey plans to be developed and presented preferably by 2013, and
by 2015 at the latest.
79
The Baltic Sea countries also agreed to undertake necessary measures to ensure
that sufficient funding, including external funding, will be available for re-surveys and
to improve mariners’ abilities to assess and interpret hydrographic content in nautical
charts and publications either in printed or digital form, especially in ECDIS.
To speed-up re-surveys in Finnish and Swedish waters – two countries having
the largest maritime area in the Baltic Sea to be re-surveyed, a new project has been
initiated within the Motorways of the Sea, financed by the EU TEN-T. Re-surveying
of HELCOM fairways and Baltic Sea port areas is to be conducted using modern
quality-assured methods to ensure accuracy of hydrographic data presented
in existing nautical charts and other nautical publications. Additionally, common
technical standards for depth data models, vertical references and depth
presentations in nautical publications will be elaborated to enhance harmonization
of data presentation among the countries. The MONALISA project, involving
Denmark in addition to the two countries mentioned above, will also deal with
dynamic and pro-active route planning as a practical application of e-navigation,
verification system for officers’ certifications and sharing of maritime information.
Conclusions
While it is recognized that IMO is the global regulator of shipping, regional
cooperation on maritime safety and environmental impact of shipping provides
a platform for coastal countries to deal with the specific needs of their regional seas
and jointly pursue harmonized implementation, and influence the adoption of stricter
international regulations. Thanks to the HELCOM efforts, the sensitivity of the marine
environment of the Baltic Sea has been widely recognized, and the issues
of maritime safety and clean shipping remain high on political agenda of the coastal
countries, followed by concrete actions and projects. Through HELCOM
Observership, non-governmental stakeholders have a possibility to influence and
contribute to developing new measures.
One important development supporting the enhanced regional cooperation on
maritime matters is the HELCOM map and data service, which has been initiated to
make environmental information publicly accessible for stakeholders and interested
users. The service enables viewing, searching and downloading of various data
related to the Baltic Sea. This data includes e.g. shipping traffic, accident risk areas,
emergency response capacity, marine protected areas and environmental status
indicators. The purpose of the service is to act as a regional information hub.
The advantage of a centralized data hub is the possibility of combining different
thematic datasets into a single map presentation. The development of this interactive
data portal is in line with the EU’s INSPIRE Directive’s goal of making spatial
information publicly accessible in a standardized format to support environmental
policies or activities having an impact on the environment.
The next HELCOM ministerial meeting in 2013 will review the progress
in implementing the Baltic Sea Action Plan, including regarding the enhanced
maritime safety, speeded up hydrographic re-surveys, improved emergency and
response capabilities, and reduced environmental impact of shipping.
80
Safety of Fishing Vessels
Monika Warmowska, Jan Jankowski
Polish Register of Shipping
m.warmowska@prs.pl
Abstract
PRS started a long-term project for the development of stability criteria and standards for
smaller vessels which covers:
− Theoretical analyses of physical phenomena;
− Development of mathematical models and computer software;
− Carrying out the model tests verifying the theories and software;
− Performing systematic numerical simulations;
− Statistical analyses of real accidents vs. “safe” ships;
− Development of rational criteria preventing capsize;
− Development of safety standard.
This paper presents the results of theoretical analyses of the studied phenomena,
mathematical models and results of computations. It comprises presentations of modelling
of irregular waves, modelling of ship motion on irregular wave and inflow and outflow of water
on the vessel’s deck. The behaviour of water on deck was modelled by the shallow water
flow. Verification of the theories and software is also presented in the paper. The conclusions
summarize the results obtained and present further necessary steps to develop safety
criteria referring to the stability of smaller vessels moving in waves.
Keywords: motion of small vessel, modelling of water flow over vessel’s deck, the shallow
water problem
1.
Introduction
Figures reported by the International Maritime Organization (IMO) show that
the annual loss of life on world’s small vessels is huge. There are many reasons for
this situation – among them the capsizing of vessels moving in waves. Therefore,
there is a strong and urgent need for significant increase of survivability of smaller
vessels. PRS believes this can be achieved by, inter alia, the development of new
survivability standards based on ship dynamics in extreme weather conditions –
a significant element missing in the safety assurance system. Particularly alarming is
the safety of fishing vessels, which is the most acute problem.
The main reasons underlying stability problems and safety standardization of smaller
involve:
− generally unfavourable relation between stability capability/capacity and
the magnitude of external heeling moments (waves, wind);
− water trapped on deck;
− shift of weight on smaller ships result in significant change of centre of gravity,
often causing dramatic change of stability;
− inadequate stability criteria and standards – based on static stability in calm
water, and not on real dynamic behaviour in waves.
81
Additionally, small vessels, in particular fishing vessels, often lack technical
documentation, may be in poor technical condition, often undergo alterations to hull
and equipment without appropriate supervision; and are sometimes operated
by insufficiently skilled crew. Small vessels also face insufficient financial resources
to make technical improvement.
Therefore, the project focused on improving the safety of smaller vessels should aim
at: developing a set of rational stability criteria and standards, and operational
guidelines and training courses for crews.
PRS decided to start a long-term project developing stability criteria. As the first step
a computer program were developed to simulate the motion of smaller vessels taking
into account effects of water flowing on deck. The stage of developing mathematical
modelling of these phenomena is nearly completed.
2.
Modelling of small vessel’s motion with effects of water trapped on deck
The simulation model of smaller vessel’s motion consists of models describing:
− irregular wave rounding the vessel,
− forces and moments acting on the vessel and determining equations of vessel
motion,
− phenomena of water inflow and outflow on vessel deck,
− motion of water over the deck,
− forces and moments caused by water trapped on deck.
2.1 Modelling of irregular wave
Accurate values of velocity field, pressure of water around ship and free wave
surface are very important for determining a small vessel’s motion in waves.
The attained accuracy enabled the computation of wave forces and moments acting
on the vessel and the computation of forces generated by water trapped on vessel
deck. Both linear and non-linear models have been developed. Irregular waves,
defined by probabilistic parameters: significant wave height Hs and zero up-crossing
mean period T0, is composed of harmonic waves.
Fig. 1 Velocity field and free surface determined by linear method
Fig. 1 presents the velocity field and free surface obtained using a linear model.
In this method the velocity potential φ of one harmonic component of irregular wave is
well know and it is defined as follows:
φ (t ) =
82
r0 kz
e sin (kx − ωt ) ,
ω
where r0 is an amplitude of harmonic wave, ω is a frequency of harmonic wave, k is
a wave number, (x, z) is a position of water’s particle, t is a time’s parameter.
In the linear method, the pressure and velocity are well estimated when a small
elevation of free surface is assumed. However, in the case of small vessels’ motion
the dimension of vessel is of similar size range as the wave height. Therefore,
the non-linear method for wave description has to be applied. In the method
developed the motion of water’s particle is defined as motion around an average
value of water’s particle position, Fig. 2.
Fig. 2 Position of free surface’s particle during simulation of irregular wave
The position (x, y, z) of water’s particle for one harmonic component or irregular wave
is defined by equations:
x(t ) = x0 − r0e
kz
0
sin (kx0 − ωt ),
y (t ) = y0 ,
z (t ) = z0 + r0e
(1)
kz
0
cos(kx0 − ωt ).
where (x0, y0, z0) the average position of water’s particle. Fig. 3 presents the velocity
field and free surface determined by the non linear method.
Fig. 3 Velocity field and free surface determined by non-linear method
The position of free surface results directly from equation (1). This approach gives
the possibility to find the proper value of pressure and velocity in close proximity
of the free surface Warmowska [6].
83
2.2 Modelling of vessel’s motion in irregular wave
The simulation of vessel motions in waves is based on numerical solutions of nonlinear equations of motion. The non-linear model used is presented in Jankowski [3].
It is assumed that the hydrodynamic forces acting on the ship and defining
the equations of its motions can be split into Froude-Krylov forces, diffraction and
radiation forces as well as other forces, such as rudder forces, non linear damping
and generated by water moving on deck.
− The Froude-Krylov forces are obtained by integrating the pressure caused by
irregular waves, undisturbed by the presence of the ship, over the actual wetted
ship surface.
− The diffraction forces are determined as a superposition of diffraction forces
caused by the harmonic components of the irregular wave. The irregular wave is
assumed to be a superposition of harmonic waves. It is assumed that the vessel
diffracting the waves is in its mean position. This is possible under
the assumption that the diffraction phenomenon is described by a linear
hydrodynamic problem. Such an approach significantly simplifies calculations
because bulky computations can be performed at the beginning
of the simulations and the ready solutions can be applied to determine
the diffraction forces during the simulation.
− The radiation forces are determined by added masses for infinite frequency and
by the so-called memory functions given in the form of convolution. The memory
functions take into account the disturbance of water, caused by the preceding
vessel motions, affecting the motion of the vessel in the time instant considered.
The dynamics of water trapped on deck, caused by water motion over the deck in
the vessel’s actual position and vessel’s acceleration, are also taken into account
in the equations of vessel motions. The forces and moments caused by water-ondeck are obtained by integrating the pressure generated by moving water in relation
to deck.
The ways of solving 3D hydrodynamic problems and determining forces appearing
in the equation of motion are presented by Jankowski&Laskowski [2]. The non-linear
equations of motion are solved numerically, Fig. 4.
Fig. 4 Simulation of fishing vessel’s motion in waves obtained using simplified method
84
2.3 Modelling of water flow on small vessel’s deck
The phenomenon of water flow on small vessel’s deck can be divided into
the following stages (Fig. 5):
− the inflow of water over upper edge of bulwark,
− the inflow and outflow of water from deck through openings in the bulwark,
− the flow of sea water over the submerged vessel deck,
− the dynamic water motion on deck.
Fig. 5 Inflow and outflow of water over vessel bulwark
In the model developed it is assumed that the volume of water on deck, varying
in time, depends on the difference in heights between the wave surface and
the following edges: the upper edge of the bulwark, and the lower edges of openings
in the bulwark. To determine the amount of water on the deck it was assumed in
the first approach that the vessel presence and its motion do not disturb the velocity
field around the vessel. The amount of water on deck depends on the wave velocity
field.
Further, it was assumed that the dynamic water motion over the deck is directed
along the deck, that the vertical acceleration a3 and that viscosity forces can be
neglected. These assumptions allow for the motion of water to be described with
Euler equations. The assumption enables to model the problem of dynamic water
motion on deck by the shallow water flow Warmowska [5].
This model enables to determine:
− the shape of free surface elevation,
− the velocity field of water particles over the deck,
− the pressure, forces and moments acting on the deck caused by water moving
over the deck.
The forces and moments generated on deck are built-in to the vessel equations
of motions and, therefore, affect the vessel motions.
2.3.1 Inflow and outflow of water over the bulwark and through the openings
It is assumed that the flow rate of water volume over the bulwark can be calculated
as the flow over a weir, whereas the flow through the openings in the bulwark is
modeled as a flow through a submerged orifice in a dam. The general formula for
the flow rate is:

q = ( sign(H ))cb 2 g  23 H

3
2
1

+d H 2

(2)
85
where
q – changing mass of water,
c – correction coefficient for non-stationary flow, established experimentally,
b – the width of the orifice or the fragment of bulwark above which the deck is
flooded,
H – vertical distance between the wave profile and the water free surface on the deck
at a point considered (positive if the wave exceeds the water level on the deck),
d – the depth of water at the orifice or the instantaneous elevation of wave profile
above the deck edge at the orifice.
Formula (2) assumes various forms depending on relative water levels inside and
outside the deck flow and on the position of the opening in the bulwark
(Pawłowski, [4]), and was applied separately for the upper edge of bulwark (Fig. 6)
and the openings in the bulwark (Fig. 7).
Fig. 6 Flow of water through the openings in the bulwark
Fig. 7 Water flow on the vessel deck through the bulwark
Correction coefficient c for non-stationary flow occurring in (2) is established
experimentally for the needs of hydraulics. However, it is questionable whether this
coefficient can be used to model the inflow and outflow of water on the vessel’s deck
in wave conditions where there is the velocity field in the irregular wave, disturbed by
the presence of the vessel. Therefore, it is the next problem, which is on the agenda
for solving.
86
2.3.2 Deck submerged in water
As it was mentioned, it is assumed that the velocity field around the vessel is
the velocity of the undisturbed sea wave. In the case of deck submerged in a wave
(Fig. 8), the water particle velocity over the deck, near vessel’s bulwark, is
determined by velocity filed being the average of the deck water velocity field and
the wave velocity field.
Fig. 8 Deck submerged in water
2.3.3 The flow of water on deck
The flow of water on deck was modelled by the so-called shallow water flow
described by differential equation problem, presented by Warmowska [5].
This problem was solved in the following four steps determining:
− the domain Ω occupied by water,
− the pressure field,
− the horizontal components u1 , u2 of velocity u,
− the vertical component u3 of velocity u,
− the forces and moments generated by moving water over the deck.
The motion of the free surface SF is described by the following equations:
dx
(t ) = u1 (t , x,y,z ),
dt
dy
(t ) = u 2 (t , x,y,z ),
dt
dz
(t ) = u 3 (t , x,y,z ).
dt
(x(t ),y(t ),z (t )) ∈ S F (t )
(3)
Equations (3) are integrated using the Runge-Kutta method. The nodes of the net
determining the free surface moving in time are updated in each time step
by interpolating the function describing free surface over the nodes (xAi, yAi, zAi)
of constant Euler grid of deck.
87
It is assumed that the vertical acceleration can be neglected. The pressure field on
deck pA is obtained integrating third Euler equation defining water motion. As a result
we obtain:
p A (t , x,y,z A ) ≅ p a + ρ
zA
∫ f (t , x,y,s )ds, (x(t ),y(t ),z (t )) ∈ Ω(t ) ,
3
z A + h (t , x , y , z A )
A
(4)
where
pa – pressure on the free surface SF corresponding to atmospheric pressure,
f3 – vertical component of the force acting on the water in point (x,y,zA).
Horizontal components of the velocity field in the domain Ω are determined from
the two first Euler equations:
du1
(t , x,y,z ) = f 1 (t , x, y, z ) − 1 ∂p (x,y,z ),
ρ ∂x
dt
du 2
(t , x,y,z ) = f 2 (t , x, y, z ) − 1 ∂p (x,y,z ),
dt
ρ ∂y
(x(t ),y(t ),z (t )) ∈ Ω,
(5)
where pressure is determined by formula (4), and f1, f2 –horizontal components
of the force acting on the water in point (x,y,zA).
The vertical component u3 of the velocity field in the domain Ω is determined from
the equation of mass conservation. Additionally, in the shallow water model it is
assumed that horizontal velocities u1 and u2 do not depend on the vertical coordinate
z. Basing on this assumption, the equation determining vertical component u3 takes
the form:
∂u
 ∂u

u 3 (t , x, y, z ) =  − 1 (t , x, y ) − 2 (t , x, y ) + q ( z − z A ) .
∂y
 ∂x

(6)
Fig. 9 Free surface of water over the vessel deck and distribution of velocity
in the flow over the deck
The shallow water method is three dimensional. The solution of this method depends
on such parameters as mass of water q and value of water velocity trapped on deck
and inertial forces (f1, f2, f3) acting on the vessel. While, the accuracy of this method
depends significantly on the accuracy of free surface determination and on
88
the proper accounting of the boundary conditions. Fig. 9 shows the free surface and
velocity field in water over the vessel deck.
The velocity field and pressure can be obtained for all particles of water domain.
The pressure field enables us to determine the force F=(F1,F2,F3) and movement
M=(F4,F5,F6) generated by moving water on deck:
Fi = − ∫ ni p AdS ,
i = 1,2,3
S
Fi + 3 = − ∫ (n × R )i p AdS , i = 1,2,3
(7)
S
where :
S – the wetted part of surface of the deck and bulwark,
R – the position vector of points belonging to S,
n – normal vector.
3.
Verification of the theories and software
The program simulating shallow water flow on deck has been developed in PRS.
The results of the program depend on such parameters as:
− parameters of sea wave (height, period of oscillation, wave direction),
− shape of the deck and bulwark, level of water on deck,
− parameters of ship motion on sea waves.
In effect the shape of free surface elevation, velocity field of water particles, pressure,
forces and moments acting on the deck are obtained.
3.1
Deck moving with constant acceleration
To verify the method applied, the simulation of water motion on the rectangular deck,
moving with constant acceleration a =(1m/s2, 0m/s2,0m/s2) has been carried out.
The result shows the flat free surface finally inclined at the angle 5.82o to the deck
(Fig. 10). The velocity field, responsible for the inclination of the free surface, appears
during the simulation. After reaching the angle 5.82o the velocity field starts to
disappear.
Fig. 10 The form of free surface of water on deck moving with constant acceleration
a1=1m/s2
89
3.2
Inflow and outflow on non-moving deck
The inflow of wave on deck affects the water flow on deck. The upshot effect is
accounted for in the relevant boundary conditions. Numerical procedures describing
this phenomenon were worked out. Fig. 11 and Fig. 12 show the regular wave
affecting the water on deck.
Fig.11 Wave running on the deck being at rest
Fig.12 Wave running backward from the deck being at rest
The height of sea wave is equal to 1m and the period of wave oscillation equals 6s.
The length of deck is equal to 20m. The deck is on the level of the sea surface.
The changing in time mass of water on deck, motion of water on deck and
superposition of incoming and reflected wave can be observed.
3.3
Water motion on oscillating deck
The simulation of water motion on deck, moving with a harmonic acceleration has
also been carried out and verified with numerical results obtained
by Huang & Hsiung [1].
The original O of the reference system OXYZ is fixed in the geometric centre
of the deck. The mass of water on the deck is constant. The parameters applied to
make the simulation are given in Table 1.
90
Table 1. Parameters of the simulation
Length
Wide
Water depth
Frequency
Pitch
Roll
amplitude amplitude
Case No. 1
1.0m
0.91m
7.62 cm
1.57rad/s
−
9.5°
Case No. 2
1.0m
0.91m
5.08 cm
2.07rad/s
−
5°
Case No. 3
1.0m
0.91m
5.08 cm
3.644rad/s
−
7.5°
Case No. 4
1.0m
0.91m
5.08 cm
4.71rad/s
−
7.5°
Case No. 5
1.0m
0.8m
10 cm
4 rad/s
5°
5°
Case No. 6
1.0m
0.8m
10 cm
7.8 rad/s
5°
5°
In Case 1, the frequency of deck oscillation is close to one half of the first natural
frequency. Case 2 corresponds to the first natural frequency, in Case 3 frequency
of deck motion is equal to one and half of the primary resonant frequency. In case 2
and 3 the bore can be clearly observed. In Case 4, the frequency is equal to second
resonant frequency. This case presents a wave that is composed of two waves:
coming and reflected. Case 5 and Case 6 represent the superposition of two waves
generated by coupled sway and pitch excitation.
Verification of the presented results against those obtained in the experiment and
from calculations by Huang and Hsiung [1], are presented in Table 2. The verification
shows correctness of the model applied.
Table 2 Wave profile – verification with experiment and numerical calculations
Wave profile
Wave profile
Case No. 1
Case No. 2
0.30
0.30
0.25
0.25
0.20
0.20
0.15
0.15
0.10
0.10
0.05
0.05
0.00
-0.50
-0.25
0.00
0.25
0.50
0.00
-0.50
Case No. 3
-0.25
0.00
0.25
0.50
Case No. 4
0.30
0.30
0.25
0.25
0.20
0.20
experiment
Huang - Hsiung
numerical calculation
0.15
0.15
0.10
0.10
0.05
0.05
0.00
-0.50
-0.25
0.00
0.25
0.50
0.00
-0.50
-0.25
0.00
0.25
0.50
91
3.4
Comparison of simplified method and shallow water method
For the reason of comparison the forces Fd and moments Md caused by water on
deck are calculated by two different models (Warmowska [7]):
− the simplified method – the model used in Ro-Ro ferries damage stability
calculations;
− the shallow water model.
In the simplified method, the position of water trapped on deck is determined by
the horizontal plane and the actual position of the vessel deck in the given time
instant. The dynamics of water caused by the motion of water particles in relation to
the deck is neglected. The forces and moments caused by water-on-deck are
obtained by integrating the hydrostatic pressure determined by (Jankowski &
Laskowski [2]):
− water horizontal plane above the deck in the vessel’s actual position, and by
− the vessel’s acceleration and the changing heights of the horizontal plane above
the deck have been added to the model to better describe the phenomenon.
Taking into account the assumptions, the pressure pA in point A on the deck is equal
to:
dh
p A = ρ v A + ρ( g + a A ) h
(8)
dt
where: h – changing distance of the horizontal plane from the point A in the inertial
system, vA, aA – velocity and acceleration of the deck point A, determined in the
inertial system.
Fig. 13 shows the simulation of the frame of water flow on the vessel deck, moving in
waves, obtained using shallow water model.
Fig. 13 Simulation of the water flow on the moving vessel’s deck, 262s
The irregular wave, determined by significant wave height Hs=6m and mean period
Tz=8s, followed the vessel moving with the forward speed u=6m/s. The angle
between the vector of forward vessel velocity and the wave vector was 30 degree.
92
Fig. 14 presents force Fd3 generated by water on deck, which increases the vessel
draught, and Fig. 15 – the rolling moment Fd4, responsible for vessel capsizing.
Fd3 [kN]
shallow water method
200
simplified method
0
-200
-400
-600
220
240
260
280
t [s]
Fig 14 Time history of vertical force Fd3 (increasing the draught)
When the vessel is in a relatively calm wave trough and the water surface on deck is
almost a horizontal plane both methods match well, (in period (240s, 248s)). There
are some differences in period (248s, 260s). In the shallow water model the mass of
water on deck does not change as rapidly as in the simplified method − Fig. 14. In the
simplified method the volume of water on deck depends only on the difference
between the wave surface and deck water surface and does not depend on the
velocity field on the deck. In periods (260s, 265s) the water surface in the simplified
method drops immediately, while in the shallow water method the velocity field in the
water on deck falls down slower − Fig. 14.
The rolling moment matches very well for both methods (Fig. 15); this is probably
because the following wave is considered, which does not generate significant water
motion across the deck.
Fd4 [kNm]
800
shallow water method
simplified method
400
0
-400
-800
220
240
260
280
t [s]
Fig. 15 Time history of rolling moment Fd4
93
3.5
Comparison of results obtained for vessels with open and closed stern
Water flow on deck with open and closed stern was also considered. For an open
stern vessel the mass of seawater inflow on deck and its outflow is faster than in
the case of closed stern, which was reflected in the computations using the shallow
water model (Fig. 16).
0
Closed stern
F3 [kN]
Open stern
-100
-200
-300
-400
time [s]
28
29
30
31
32
33
34
35
36
Fig. 16 The vertical forces caused by water on deck
In the case of closed stern vessels the water stays longer on the deck. It increases
the heave of the vessel and it changes the GM value. A similar situation is observed
when the orifices are small or closed. The closed bulwark around small vessels’ deck
may cause vessel capsizing.
4.
Conclusions
Survivability standards based on ship dynamics in extreme
a missing element in the safety assurance system
The development of such standards is, as mentioned in the
problem and should be perceived as a long-term project. In
modelling of:
− irregular waves,
− ship motion in irregular wave,
− inflow and outflow of water on the vessel’s deck,
− water flow on the vessel’s deck.
weather conditions are
for smaller vessels.
introduction, a complex
the first step it requires
These problems have been solved but still require improvement. First of all, the free
surface around the moving vessel in waves should be more accurately determined –
the diffraction of the free surface shape should be taken into account.
The second problem which should be improved is the modelling of the inflow and
outflow of water on the vessel’s deck – the velocity field in water around the vessel
moving in waves should be taken into account to determin more accurately the flow
of water through openings in and over the bulwark.
The validated models of vessels with water trapped on deck moving in irregular
waves and computer programs based on these models, enabling the simulation
of this phenomenon, are necessary elements of the project for developing vessel
dynamic stability criteria. The validation should also include model tests verifying
the theories and software. Then, using the software, it will be possible to perform
systematic numerical simulations to identify the essential elements affecting
the vessel’s dynamic stability such as the extreme waves for a given vessel.
94
References
1.
Huang Z.-J., Hsiung C. – C., ‘Nonlinear shallow-water flow on deck coupled with
vessel motion’, Proceedings of the Twenty – First Symposium of Naval
Hydrodynamics, National Academy Press, Washington, D.C., 1997.
2.
Jankowski J., Laskowski A., ‘Capsizing of small vessel due to waves and water
trapped on deck’, Proceedings of the 9th International Conference STAB 2006, Brasil,
2006.
3.
Jankowski J., ‘Statek wobec działania fali’, Raport Techniczny Nr 52, PRS, Gdańsk,
2007.
4.
Pawłowski M., ‘Subdivision and Damage Stability of Vessel’, Euro-MTEC series,
pp.217-220, 2004.
5.
Warmowska M., ‘Problem of water flow on deck’, Archives of civil and mechanical
engineering, Wrocław, Poland, vol. VII, No. 4, 2007.
6.
Warmowska M ‘Fala biegnąca’, Raport Techniczny Nr 56, Polski Rejestr Statków,
Gdańsk, Poland, 2010.
7.
Warmowska M., Jankowski J., ‘Problem of water flow on deck of small vessel’,
Proceeding of 18 th International Conference on Hydrodynamics in Vessel Design,
Safety and operation, Hydronav’10, Gdańsk, Poland, 2010.
95