model of an oil tanker

Transcription

Model Of An Oil Tanker
MODEL OF AN OIL TANKER
A PROJECT REPORT
Submitted by
DARSHAN SHAJI
DIBIN JOSEPH
JITHIN K.P
JITHIN R
MAHBOOB ALAM
MAHESH P DAMODARAN
In partial fulfillment for the award of the degree
of
BACHELOR OF TECHNOLOGY
In
MARINE ENGINEERING
K M SCHOOL OF MARINE ENGINEERING
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY
COCHIN-682 022
JULY 2011
CERTIFICATE
This is to certify that that this is a bonafide record of the project entitled “MODEL
OF AN OIL TANKER” submitted by DARSHAN SHAJI, DIBIN JOSEPH,
JITHIN K.P, JITHIN R, MAHBOOB ALAM, MAHESH P DAMODARAN to the
department of Kunjali Marakkar School of Marine Engineering towards the partial
fulfillment of the requirements for the VIII semester of the B.Tech Degree course in
Marine Engineering of Cochin University of Science and Technology.
Head of the Department
K M School of Marine Engineering
Cochin University of Science and Technology
Project guide
Asst. Prof. K. Vidhyadharan
ACKNOWLEDGEMENT
First of all we bow our heads in all humbleness to the lord almighty who has given us the
strength to prepare this project well above the level of simplicity and into something
concrete.
We would also like to express our deep sense of gratitude to Director Prof K.A Simon for
providing us the necessary facilities.
We are very thankful to our project guide Asst. Prof. K. Vidhyadharan who was always
been there to show us the right track when the team needed the help and guided us
through the different stages of our project work. We are also very thankful to Prof.
(Dr.) P. V. Sasikumar gave us moral support and helped us in the matters regarding to
project report outline and its presentation.
We are equally thankful to our project coordinator Prof. N.G. Nair for his valuable help.
We would also like to thank the course coordinator Associate Prof. Roy.V.Paul for his
valuable suggestions
Last but not least, we would like to thank our parents and friends and all others who
helped us a lot in gathering different information, collecting data and guided us from time
to time in making the project despite of their busy schedule.
ABSTRACT
The oil tanker model is a replica of a very large crude carrier (VLCC). The design of a ship
of vlcc deadweight range was done up to the stage of calculation of main dimension which
was then scaled down to obtain the model‘s main dimensions. The scale used for the model
is 1:180. Two real ships of vlcc deadweight range were used to study the features of oil
tankers and to check the correctness of the calculated main dimensions.
The model exhibits key features including hull markings, cargo manifolds, ship
superstructure, survival crafts, mooring arrangement, protection for crew on deck, propeller
and rudder.
TABLE OF CONTENTS
Page No
CERTIFICATE
ii
ACKNOLEDGEMENT
iii
ABSTRACT
iv
TABLE OF CONTENTS
v
LIST OF FIGURES
vii
LIST OF TABLES
x
CHAPTER 1 INTRODUCTION
1
1.1 OIL TANKERS
1
1.2 OIL TANKER CATEGORIES
2
1.3 DOUBLE HULL TANKERS
7
1.4 STANDARDS FOR THE DOUBLE HULL CONSTRUCTION
OF OIL TANKER
CHAPTER 2 MODEL FAMILIARISATION
7
9
2.1 MODEL DIMENSIONS
9
2.2 OTHER FEATURES
10
CHAPTER 3 DESIGN
3.1 MISSION ANALYSIS
19
3.2 PARENT SHIP DATA AND ANALYSIS
23
3.3 FIRST ESTIMATE OF THE MAIN DIMENSIONS AND
COEFFICIENTS
25
3.4 FIRST ITERATION
27
3.5 PRILIMINERY GENERAL ARRANGEMENT
28
CHAPTER 4 FBRICATION
32
CHAPTER 5 DECK ARRANGEMENTS
49
5.1 MOORING ARRANGEMENTS AND LAYOUTS
49
5.2 SCUPPERS AND BULWARK
50
5.3 ANCHORS AND CABLES
50
5.4 WINDLASS
50
5.5 HOSE HANDLING CRANES
51
5.6 DAVITS
52
5.7 LIFEBOATS
52
5.8 FUNNEL
53
5.9 ENGINE CASING
54
5.10 FIRE MAIN
54
CHAPTER 6 SHIP CONSTRUCTION
55
6.1 BOTTOM STRUCTURE
55
6.2 SIDE FRAMING
55
6.3 DECK
57
6.4 BULKHEADS
57
6.5 SUPERSTRUCTURE
57
6.6 WEATHERTIGHT DOORS
58
6.7 FORE END STRUCTURE
58
6.8 RUDDERS
59
6.9 PROPELLERS
60
CHAPTER 7 TANKER SYSTEM
62
7.1 CARGO TANK VENTILATORS
62
7.2 INERT GAS SYSTEM
63
CHAPTER 8 – CONCLUSION
66
REFERENCES
67
LIST OF FIGURES
Figure No
Title
Page No
1.1
Cargo tank boundary lines
4
1.2
Cargo tank boundary lines within the bilge for oil tankers
4
1.3
Cargo tank boundary lines for double bottom space
6
2.1
Model of Oil Tanker
10
2.2
General Arrangement
11
2.3
Fore End Structure
12
2.4
Ship Side
13
2.5
Weather Deck
14
2.6
Forecastle Deck
15
2.7
Amid Ship
16
2.8
Superstructure
17
2.9
Aft End Structure
18
3.1
Principal Ship Dimensions
21
3.2
Oil Tanker Marbat
30
3.3
Cap Victor
31
4.1
Wood was Selected as the Material
32
4.2
Dimensions were Marked on the Wood Before Cutting
33
4.3
The Wood is Cut Accordingly
33
4.4
Forward Portion is Shaped
34
4.5
Aft End is Shaped
34
4.6
Wooden planks of 4cm Thick are Marked on the Block
35
4.7
Wooden Planks of 4cm Thick are Cut from the Block
35
4.8
The Planks are Arranged to the Shape of an Open Box
36
4.9
The Joints are made by Hammering in Adhesive Applied
Wooden Nails
37
4.10
Wooden Planks are Inserted at Equal Intervals
38
4.11
The Parallel Middle Body after Inserting Planks
38
4.12
Three Parts are Joined by Wooden Nails and Adhesives
39
4.13
The Parallel Middle Body is Closed
39
4.14
The Lower Edge of the Parallel Middle Body is Shaped
Using a Plane
40
4.15
Fully Assembled Hull
41
4.16
Coating of Filler and Adhesive is Applied
41
4.17
Inverted and Painted Crimson Red Using a Spray Gun
41
4.18
Painting of Crimson Red Completed
42
4.19
Masking Tape is Applied at Summer Load Line
42
4.20
Deep Blue is Applied on the Freeboard
43
4.21
Stages in Fabrication of Superstructure
44
4.22
Using Knitting Wire the Railings were Made
45
4.23
Anchor
45
4.24
Files used for Fabrication
46
4.25
Lifeboat and Life raft
46
4.26
Propeller Hub
47
4.27
Overall View of Model from Stern
48
5.1
Windlass
51
5.2
Hose Handling Crane
51
5.3
Davit
52
5.4
Funnel
53
6.1
Longitudinally Framed Double Bottom Structure
55
6.2
Side Frame
56
6.3
Deck Plating
57
6.4
Weather tight Door
58
6.5
Fore End Construction
59
6.6
Rudder
60
7.1
High Velocity Vent
62
7.2
Simple High Velocity Vents
63
7.3
Inert Gas System
65
LIST OF TABLES
Table No
Title
Page No
3.1
Parent Ship Analysis
23
3.2
Analysis of Ratios
24
3.3
Ratio of Main Dimensions
26
3.4
Result of Iteration
27
3.5.
Model Dimensions
28
CHAPTER 1 - INTRODUCTION
1.1 OIL TANKERS
An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk
transport of oil. There are two basic types of oil tankers: the crude tanker and the product
tanker. Crude tankers move large quantities of unrefined crude oil from its point of
extraction to refineries. Product tankers, generally much smaller, are designed to
move petrochemicals from refineries to points near consuming markets.
Figure 1.1 Oil Tanker Ab Qaiq
Source: Internet
Oil tankers are often classified by their size as well as their occupation. The size
classes range from inland or coastal tankers of a few thousand metric tons
of deadweight (DWT)
to
the
mammoth ultra
large
crude
carriers (ULCCs)
of
550,000 DWT.
Tankers have grown significantly in size since World War II. A typical T2 tanker of
the World War II era was 532 feet (162 m) long and had a capacity of 16,500 DWT. A
modern ultra-large crude carrier (ULCC) can be 1,300 feet (400 m) long and have a
capacity of 500,000 DWT. Several factors encouraged this growth. Hostilities in the Middle
East which interrupted traffic through the Suez Canal contributed, as did nationalization of
Middle East oil refineries.[28] Fierce competition among ship owners also played a part. But
apart from these considerations is a simple economic advantage: the larger an oil tanker is,
the more cheaply it can move crude oil, and the better it can help meet growing demands for
oil.
In 1958, United States shipping magnate Daniel K. Ludwig broke the barrier of
100,000 long tons of heavy displacement. His Universe Apollo displaced 104,500 long tons,
a 23% increase from the previous record-holder, Universe Leader which also belonged to
Ludwig. The world's largest super tanker was built in 1979 at the Oppama shipyard
by Sumitomo Heavy Industries, Ltd. as the Sea wise Giant. This ship was built with a
capacity of 564,763 DWT, a length overall of 458.45 metres (1,504.1 ft) and a draft of
24.611 metres (80.74 ft). She had 46 tanks, 31,541 square metres (339,500 sq ft) of deck,
and at her full load draft, could not navigate the English Channel. Sea wise Giant was
renamed Happy Giant in 1989, Jahre Viking in 1991, and Knock Nevis in 1999 (when she
was converted into a permanently moored storage tanker). In 2009 she was sold for the last
time, renamed Mont, and scrapped. As of 2011, the world's two largest working super
tankers are the TI class super tankers TI Europe and TI Oceania. These ships were built in
2002 and 2003 as the Hellespont Alhambra and Hellespont Tara for the Greek Hellespont
Steamship
Corporation. Hellespont
sold
these
ships
to Overseas
Ship
holding
Group and Euronav in 2004. Each of the sister ships has a capacity of over 441,500 DWT, a
length overall of 380.0 metres (1,246.7 ft) and a cargo capacity of 3,166,353 barrels
(503,409,900 l). They were the first ULCCs to be double-hulled.[37] To differentiate them
from smaller ULCCs, these ships are sometimes given the V-Plus size designation.
With the exception of the pipeline, the tanker is the most cost-effective way to move
oil today. Worldwide, tankers carry some 2 billion barrels (3.2×1011 l) annually and the cost
of transportation by tanker amounts to only US$0.02 per gallon at the pump
1.2 OIL TANKER CATEGORIES
IMO distinguishes three categories of tankers that are:

Category 1 - oil tankers of 20,000 tonnes deadweight and above carrying crude
oil, fuel oil, heavy diesel oil or lubricating oil as cargo, and of 30,000 tonnes
deadweight and above carrying other oils, which do not comply with the
requirements for protectively located segregated ballast tanks (commonly known
as Pre-MARPOL tankers)

Category 2 - as category 1, but complying with protectively located segregated
ballast tank requirements (MARPOL tankers), and

Category 3 - oil tankers of 5,000 tonnes deadweight and above but less than the
tonnage specified for Category 1 and 2 tankers
In 1954 Shell Oil developed the average freight rate assessment (AFRA) system
which classifies tankers of different sizes. To make it an independent instrument, Shell
consulted the London Tanker Brokers‘ Panel (LTBP). At first, they divided the groups as
General Purpose for tankers under 25,000 tons deadweight(DWT); Medium Range for
ships between 25,000 and 45,000 DWT and Large Range for the then-enormous ships that
were larger than 45,000 DWT. The ships became larger during the 1970s, which prompted
rescaling.
The system was developed for tax reasons as the tax authorities wanted evidence that
the internal billing records were correct. Before the New York Mercantile Exchange started
trading crude oil futures in 1983, it was difficult to determine the exact price of oil, which
could change with every contract. Shell and BP, the first companies to use the system,
abandoned the AFRA system in 1983, later followed by the US oil companies. However,
the system is still used today. Besides that, there is the flexible market scale, which takes
typical routes and lots of 500,000 barrels. Merchant oil tankers carry a wide range of
hydrocarbon liquids ranging from crude oil to refined petroleum products. [3] Their size is
measured in deadweight metric tons (DWT). Crude carriers are among the largest, ranging
from 55,000 DWT panamax-sized vessels to ultra-large crude carriers (ULCCs) of over
440,000 DWT.
1.2.1 Suezmax
Suezmax is a naval architecture term for the largest ship measurements capable of transiting
the Suez Canal, and is almost exclusively used in reference to tankers. Since the canal has
no locks, the only serious limiting factors are draft (maximum depth below waterline), and
height due to the Suez Canal Bridge. The current channel depth of the canal allows for a
maximum of 20.1 m (66 ft) of draft, meaning a few fully laden super tankers are too deep to
fit through, and either have to unload part of their cargo to other ships ("transhipment") or to
a pipeline terminal before passing through, or alternatively avoid the Suez Canal and travel
around Cape Agulhas instead. The canal has been deepened in 2009 from 18 to 20 m (60 to
66 ft).The typical deadweight of a suezmax ship is about 240,000 tons and typically has a
beam (width) of 50 m (164.0 ft). Also of note is the maximum head room—"air draft"—
limitation of 68 m (223.1 ft), resulting from the 70 m (230 ft) height above water of the
Suez Canal Bridge. Suez Canal Authority produces tables of width and acceptable draft,
which are subject to change. Currently the wetted surface cross sectional area of the ship is
limited by 945 m2, which means 20.1 m (66 ft) of draught for ships with the beam no wider
than 50.0 m (164.0 ft) or 12.2 m (40 ft) of draught for ships with maximum allowed beam
of 77.5 m (254 ft 3 in).
Figure 1.2 Oil Tanker Stena Vision
Source: Internet
1.2.2 Panamax
Panamax and New Panamax are popular terms for the size limits for ships travelling
through the Panama Canal. Formally, the limits and requirements are published by
the Panama Canal Authority (ACP) titled "Vessel Requirements". These requirements also
describe topics like exceptional dry seasonal limits, propulsion, communications and
detailed ships design. The allowable size is limited by the width and length of the
available lock chambers, by the depth of the water in the canal and by the height of
the Bridge of the Americas. Consequently, ships that do not fall within the Panamax-sizes
are called Post Panamax. The limits have influenced those constructing cargo ships, giving
clear parameters for ships destined to traverse the Panama Canal.
Figure 1.3 Panama Canal Miraflores Locks
Source: Internet
1.2.3 Aframax
An Aframax ship is an oil tanker smaller than 120,000 metric tons deadweight (DWT) and
with a breadth above 32.31 m. The term is based on the Average Freight Rate
Assessment (AFRA) tanker rate system. Aframax class tankers are largely used in the
basins of the Black Sea, the North Sea, the Caribbean Sea, the China Sea and
the Mediterranean. Non-OPEC exporting countries may require the use of Aframax tankers
because the harbours and canals through which these countries export their oil are too small
to accommodate very-large crude carriers (VLCC) and ultra-large crude carriers (ULCCs).
Figure 1.4 The Aframax Tankers Gerd Knutsen
Source: Internet
"Super tanker" is an informal term used to describe the largest tankers. Today it is
applied to very-large crude carriers (VLCC) and ULCCs with capacity over 250,000 DWT.
These ships can transport 2,000,000 barrels of oil/318 000 metric tons. By way of
comparison, the combined oil consumption of Spain and the United Kingdom in 2005 was
about 3.4 million barrels (540,000 m3) of oil a day. Because of their great size, super tankers
often can not enter port fully loaded. These ships can take on their cargo at off-shore
platforms and single-point moorings. On the other end of the journey, they often pump their
cargo off to smaller tankers at designated lightering points off-coast. A super tanker‘s routes
are generally long, requiring it to stay at sea for extended periods, up to and beyond seventy
days at a time.
Smaller tankers, ranging from well under 10,000 DWT to 80,000 DWT panamax
vessels, generally carry refined petroleum products, and are known as product tankers. The
smallest tankers, with capacities under 10,000 DWT generally work near-coastal and inland
waterways.
1.3 DOUBLE HULL TANKERS
Double hulls' ability to prevent or reduce oil spills led to their being standardized for other
types of ships including oil tankers by the International Convention for the Prevention of
Pollution from Ships or MARPOL Convention.
A double hull does not protect against major, high-energy collisions or groundings which
cause the majority of oil pollution, despite this being the reason that the double hull was
mandated by United States legislation.
After the Exxon Valdez oil spill disaster, when that ship grounded on Bligh
Reef outside the port of Valdez, Alaska, the US Government required all new oil tankers
built for use between US ports to be equipped with a full double hull. However, the damage
to the Exxon Valdez penetrated sections of the hull (the slops oil tanks) that were protected
by a partial double hull. The double hull required by the new regulations would not have
prevented extensive loss of oil from the Exxon Valdez, though it might have somewhat
limited the losses. Furthermore, a double-hulled tanker does not need longitudinal
bulkheads for longitudinal strength, as the inner hull already provides this. Eliminating
longitudinal bulkheads would result in much wider tanks, significantly increasing the free
surface effect. However, this problem is easily corrected with the addition of anti-slosh
baffles and partial bulkheads.
1.4 STANDARDS FOR THE DOUBLE HULL CONSTRUCTION OF OIL TANKER
―MARPOL‖ means the International Convention for the Prevention of Pollution by Ships,
1973, and the Protocols of 1978 and 1997 relating to the Convention, as amended from time
to time;
―Oil tanker‖ means a self-propelled vessel that is constructed or adapted primarily to
carry oil in bulk in its cargo spaces, and includes a combination carrier, an NLS tanker as
defined in Annex II of MARPOL or a gas carrier that is carrying a cargo or part cargo of oil
in bulk (note that in the Regulations an oil tanker includes both self-propelled and non-selfpropelled vessels);
―Oil tanker delivered after 1 June 1982‖ has the same meaning as in regulation 1.28.4
of Annex I where it is defined to mean an oil tanker:
1. For which the building contract is placed after 1 June 1979; or
2. In the absence of a building contract, the keel of which is laid or which is at a similar
stager of construction after 1 January 1980; or
3. The delivery of which is after 1 June 1982; or
4. Which has undergone a major conversion:

for which the contract is placed after 1 June 1979; or

in the absence of a contract, the construction work of which is begun after 1 January
1980; or

which is completed after 1 June 1982;
―Oil tanker delivered before 6 July 1996‖ means an oil tanker which is not an oil
tanker delivered on or after 6 July 1996, as defined in regulation 1.28.5 of Annex I of
MARPOL;
―Oil tanker delivered on or after 6 July 1996‖ refers to an oil tanker mentioned in
subsection 54(1) of the Regulations and has the same meaning as in regulation 1.28.6 of
Annex I of MARPOL were it is defined to mean an oil tanker:
1. For which the building contract is placed on or after 6 July 1993, or
2. In the absence of a building contract, the keel of which is laid or which is at a similar
stage
Of construction on or after 6 January 1994, or
3. The delivery of which is on or after 6 July 1996, or
4. Which has undergone a major conversion:

for which the contract is placed on or after 6 July 1993; or

in the absence of a contract, the construction work of which is begun on or after 6
January 1994; or

which is completed on or after 6 July 1996;
CHAPTER 2 - MODEL FAMILIARISATION
2.1 MODEL DIMENSIONS
Length overall
:
183cm
Breadth
:
30cm
Depth
:
15.8cm
Draught
:
10.6cm
Freeboard
:
5.2cm
2.2 OTHER FEATURES
The ship has been given the name ―KMSME‖ by our team. The oil tanker belongs to
Category 2 (MARPOL tanker) of IMO‘s oil tanker classification.
Deadweight
:
215000t (Very Large Crude Carrier)
Bulbous bow
:
provided
Machinery space location
:
Aft
Stern
:
Transom
Propulsion
:
Single screw
Propeller
:
4 blade skewed propeller
Rudder
:
Semi balanced
Figure 2.1 Model of the Oil Tanker
Source: Team
Figure 2.2 General Arrangements
Source: Team
1. Poop Deck
2. Engine Casing
3. Superstructure
4. Pipe Lines
5. Bunker Manifold
6. Weather Deck
7. Fore Castle
Figure 2.3 Fore-End Structure
Source: Team
1. Name of the ship
2. Freeing Ports
3. Bulbous bow marking
4. Anchor
5. Chafing ring
6. Forward draught marking
7. Bulbous bow
Figure 2.4 Hull Markings
Source: Team
1. Freeboard
2. Summer Load Line
3. Name of the Ship
4. Bunker Manifold Markings
5. Plimsoll Marking
6. Tug Marking
7. Bulbous Bow Marking
8. Forward Draught Marking
Figure 2.5 Weather Deck
Source: Team
1. Side Railings
2. Gangway
3. Walkway
4. Cross Over
5. Catwalk
6. Bulwark Stay
Figure 2.6 Forecastle Deck
Source: Team
1. Railing
2. Bulwark stay
3. Bulwark
4. Bollard
5. Anchor chain
6. Windlass
7. Forecastle space entry
8. Forward mast
Figure 2.7 Amid ship
Source: Team
1. Walkway
2. Cargo hose handling crane
3. Drip tray
4. Bunker manifold
5. Catwalk
Figure 2.8 Superstructure
Source: Team
1. Main mast
2. Monkey island
3. Bridge
4. Lifeboat
5. Gravity davit
6. Life raft
7. Weather tight door
8. Engine casing
9. Funnel
10. Mushroom shaped blower suction
Figure 2.9 Aft End Structure
Source: Team
1. Aft end draught marking
2. Transom stern
3. Propeller blade
4. Rudder stock
5. Propeller hub
6. Rudder
CHAPTER 3 - DESIGN
3.1 MISSION ANALYSIS
The main dimensions have a decisive effect on many of the ship characteristics. It affects
 Stability
 Hold capacity
 Hydro dynamic qualities such as resistance, manoeuvring,sea keeping
 Economic efficiency
Determining the main dimensions,proportions and form coeffient is one of the most
important phases of overall design.
Crude oil tankers are essentially slow speed ships carrying imperishable cargo. The
shipment of crude oil over the last two decades has increased tremendously. Hence the need
for eceonomic optimallity in design,capacity etc is necessiated.
The double skin tankers have a slightly reduced L/D ratio as compared to single skin
tankers. But both have similar B/T and L/T ratios.
Type of ship
:
Double skin crude oil tanker
Type of cargo
:
Crude oil
Speed
:
15 knots
Shape of hull
:
B.S.R.A
Shape of stern
:
Transom stern
Shape of stem
:
Bulbous bow is provided
Figure 3.1 Principal Ship Dimensions
Source: Ship Construction
After Perpendicular (AP): A perpendicular drawn to the waterline at the point where the
side of the rudder post meets the summer load line. Where no
rudder post is fitted it is taken as the centre line of the rudder
stock.
Forward Perpendicular (FP): A perpendicular drawn to the waterline at the point where the
fore side of the stem meets the summer load line.
Length Between Perpendiculars (LBP): The length between the forward and aft
perpendiculars measured along the summer load line.
Amidships: A point midway between the after and forward perpendiculars.
Length Overall (LOA): Length of vessel taken over all extremities.
Base Line: A horizontal line drawn at the top of the keel plate. All vertical moulded
dimensions are measured relative to this line.
Moulded Beam: Measured at the midship section is the maximum moulded breadth of the
ship.
Moulded Draft: Measured from the base line to the summer load line at the midship section.
Moulded Depth: Measured from the base line to the heel of the upper deck beam at the
ship‘s side amidships.
Extreme Beam: The maximum beam taken over all extremities.
Extreme Draft: Taken from the lowest point of keel to the summer load line. Draft marks
represent extreme drafts.
Extreme Depth: Depth of vessel at ship‘s side from upper deck to lowest point of keel.
Half Breadth: Since a ship‘s hull is symmetrical about the longitudinal centre line, often
only the half beam or half breadth at any section is given.
Freeboard: The vertical distance measured at the ship‘s side between the summer load line
(or service draft) and the freeboard deck. The freeboard deck is
normally the uppermost complete deck exposed to weather and
sea which has permanent means of closing all openings, and
below which all openings in the ship‘s side have watertight
closings.
Sheer: Curvature of decks in the longitudinal direction. Measured as the height of deck at
side at any point above the height of deck at side amidships.
Camber (or Round of Beam): Curvature of decks in the transverse direction. Measured as
the height of deck at centre above the height of deck at side.
Rise of Floor (or Dead rise): The rise of the bottom shell plating line above the base line.
This rise is measured at the line of moulded beam.
Half Siding of Keel: The horizontal flat portion of the bottom shell measured to port or
starboard of the ship‘s longitudinal centre line. This is a useful
dimension to know when dry-docking.
Tumblehome: The inward curvature of the side shell above the summer load line.
Flare: The outward curvature of the side shell above the waterline. It promotes dryness and
is therefore associated with the fore end of ship.
Stem Rake: Inclination of the stem line from the vertical.
Keel Rake: Inclination of the keel line from the horizontal. Trawlers and tugs often have
keels raked aft to give greater depth aft where the propeller
diameter is proportionately larger in this type of vessel. Small
crafts occasionally have forward rake of keel to bring propellers
above the line of keel.
Parallel Middle Body: The length over which the midship section remains constant in area
and shape.
Entrance: The immersed body of the vessel forward of the parallel middle body.
Run: The immersed body of the vessel aft of the parallel middle body.
Tonnage: This is often referred to when the size of the vessel is discussed, and the gross
tonnage is quoted from Lloyds Register. Tonnage is a measure of
the enclosed internal volume of the vessel.
3.2 PARENT SHIP DATA AND ANALYSIS
The relevant data of double skin tankers in the dead weight range of 1,45,000t to 1,55,000t
were analysed and ratios calculated. They are expressed in the tabular form below.
Table 3.1 Parent Ship Analysis
NAME
Dwt
LBP
B
D
T
Vkm
L/B
B/T
T/D
L/D
Fn=v/√(gxl)
African ruby
150173
260
45.0
24.3
16.0
15.5
5.78
2.81
.658
10.7
0.149
Atauilo Alves
152980
258
46.0
24.4
17.2
14.5
5.61
2.81
.705
10.5
0.140
British hunter
151459
264
47.8
23.6
17.0
15.5
5.73
2.62
.72
11.9
0.157
Cap georges
148500
264
45.0
22.8
16.1
15.5
5.52
2.71
.707
11.5
0.152
Chilinh
150500
277
48.0
25.4
17.0
15.0
6.15
2.97
.669
10.9
0.148
Cosmic
150284
263
51.9
22.4
15.3
15.7
5.48
2.64
.676
11.7
0.140
Cossak Pioneer
151892
268
48.0
25.6
16.2
15.4
5.17
3.14
.633
10.7
0.141
Eliomar
150709
263
46.3
22.4
15.3
15.4
5.48
3.19
.683
11.7
0.142
Fair Way
149748
259
46.0
23.9
16.9
15.0
5.60
3.14
.683
10.8
0.143
Front Glory
149300
258
46.0
23.9
16.8
14.9
5.61
2.75
.705
10.7
0.153
Front Pride
149686
258
46.0
23.9
16.8
15.0
5.61
2.73
.704
10.7
0.143
GenmarArinston
151910
256
46.2
23.8
16.8
14.0
5.61
2.96
.704
10.7
0.144
Genmar Sky
151910
256
44.5
23.8
16.8
14.0
5.54
2.44
.671
10.7
0.143
Genmar Travler
149996
260
46.2
24.2
15.6
14.0
5.84
2.68
.686
10.7
0.144
Hudson
149999
264
48.0
23.1
15.9
14.0
5.50
2.81
.738
11.4
0.142
Table 3.2 Analysis of Ratios
RATIO
RANGE
AVERAGE
L/B
5.17-6.15
5.76
L/D
10.47-11.58
11.03
T/D
0.63-0.74
0.69
B/T
2.44-3.19
2.83
3.3 FIRST ESTIMATE OF THE MAIN DIMENSIONS AND COEFFICIENTS
3.3.1 Symbols List and Their Units
Dwt
-
Dead weight (t)
∆
-
Displacement(t)
LBP
-
Length between perpendiculars (m)
V
-
Velocity (kn)
g
-
Accelaration due to gravity (m/s2)
B
-
Moulded breadth of the ship (m)
D
-
Moulded deph of the ship (m)
T
-
Draft of the ship (m)
CB
-
Block coefficient of the ship
Fn
-
Froude number
3.3.2 Iterative Procedure for Determining Main Dimensions
1. Estimate the weight of the loaded ship
2. [using the typical value of cd=(Dwt/displacement)]
3. ChooseLBP (Using empirical formulae)
4. Determine B,T,D
3.3.2.1 Estimation of loaded displacement
Displacement is estimated using the deadwight to displacement ratio, cD.
CD
= 0.8to 0.86 for tankerss (from existing parent ship data)
CD is taken as 0.85 owing to more steel weight
∆
=
250000/0.85
=
294100 t
3.3.2.2 Estimation of length
a) Schneekluth formula:
LBP
=
∆0.3 x V0.3 x C
Where,
∆ in tones, V in knots
C
=
3.2 if CB is with in the range of 0.48 to 0.85
Assume C
=
3.2
LBP
=
315m
b) Ashik’s formula:
LBP
=
(5.35+0.4) x ∆1/3
=
382.3m
3.3.2.3 Range of length selected
From the length obtained by the above formula a range of length is selected.The rage is
from 315 to 382m
3.3.2.4 Estimation of block coefficient (CB)
CB
=
0.975-(0.9xFn)+0.02
Dankwart Formula
Fn
=
V/√(gL)
schneekluth
CB corresponding to length found above is thus calculated.
3.3.2.5 Determination of B, T, D
B,T and D are calculated from the ratios (L/B, B/T, L/D) obtained from parent ships.
Table 3.3 Ratio of Main Dimensions
Ratio
Range
Average
L/B
5.17-6.15
5.76
L/D
10.47-11.58
11.03
T/D
0.63-0.74
0.69
B/T
2.44-3.19
2.83
3.4 ITERATION
Selected length is L = 315m
Breadth
We have the mean value of L/B= 5.76
B=54m
Draught
We have the mean value of B/T=2.83
T =19.18m
Depth
We have the mean value of L/D=11.03
D= 28.5m
CB =0.75
Displacement
∆ = L.B.T.CB x 1.025 x 1.006
= 253000 t
Table 3.4. Result of Iteration
LBP
315m
B
54m
D
28.5m
T
19.18m
CB
0.75
𝝙
253000t
DWT
215050t
Scale used for the model is 1:180
Table 3.5. Model Dimensions
Ship
Model
LOA
33Om
183cm
LBP
315m
175cm
B
54m
30cm
D
28.5m
15.8cm
T
19.2m
10.6cm
3.5 PRILIMINERY GENERAL ARRANGEMENT
The allocation and dimension of main spaces like length of cargo tanks, width of double
skin and height of double bottom etc of double hull tankers are determined by the regulation
13 F MARPOL 73/78 for the construction of new tankers. All new tankers of dead weight
above 5000 t are to have either a double hull or damage to the hull due to collision or
grounding.
The mid deck arrangement makes use of a horizontal subdivision (mid deck) of the
cargo spaces so that the oil pressure is reduced to level less than the hydrostatic pressure. As
a result of even if hull is damaged there oil out flow will be considerably reduced.
Double hull construction makes use of wing tanks and double bottom spaces through
the cargo region, so that even if the outer is damaged oil out flow will not occur. Double
hull construction is the modern trend.
3.5.1 Ballast Tank or Spaces
According to regulations 13F AND 13G OF MARPOL 73/78 the entire cargo length should
be protected by ballast tanks or spaces other than cargo and fuel oil tanks.
a) Wing Tank or Spaces
Wing tank or spaces should extend the hull length of ship side, from the top of the
double bottom to the upper most deck, disregarding a rounded guwale where fitted.
They should be arranged such that the cargo tanks are located in board of section is
measured at right angles to the side shell as specified below.
W
OR
W
=
0.5+Dwt/20000 m
=
0.5+1500000/20000
=
8m
= 2m, whichever is the lesser
The minimum value of W is 1m.
b) Double Bottom Tanks or Spaces
At any cross section the depth of each double bottom tank or space is such that the
distance h between the bottom of the cargo tanks and moulded line of the bottom shell
plating measured at right angles to the bottom shell plating is not less than specified
below:
h=B/15= 3.13m
OR
h= 2m, whichever is lesser
The minimum value of h is 1.0m
3.5.2 Size and Arrangement of Cargo Tanks
The length of each cargo tank shall not exceed 10cm or nor of the following values,
whichever is the greatest
When two or more longitudinal bulkheads are provided inside the cargo tanks
i)
For wing cargo tanks
ii)
For centre cargo tanks
0.2LBP
-if bi/B>1/5
0.2LBP
-if bi/B<1/5
0.2LBP
(0.5 bi/B + 0.1) LBP m, where no centreline bulkhead is provided
(0.25 bi/B + 0.15) LBP m, where a centreline bulkhead is provided
The following are the photos of two oil tankers which have been refered to check the
correctness of our main dimension calculation and also for information on deck
arrangement.
Figure 3.2 Oil Tanker Marbat
Source:Team
Length
: 333m
Breadth
: 60m
DWT
: 315000t
Speed ( Max/Avg )
: 19.6 / 19.6
Flag
: Malta
Figure 3.3 Cap Victor
Source: Team
Length
: 274m
Breadth
: 48m
DWT
: 157700t
Speed ( Max/Avg )
: 16.5 / 15.1
Flag
: Greece
CHAPTER 4 - FABRICATION
After completing the design selection and analysis the fabrication was done in steps.
The hull of the model is fabricated from wood. Due to the difference in technique of
fabrication the hull was made in three pieces and joined. The fore and aft portion of the ship
is shaped from solid block of wood using chisel and mallet. The parallel middle body of the
ship is made by joining planed wooden planks from all four sides. The joint is accomplished
by nailing. The parallel middle body is also provided internally with planks placed
transverse similar to the bulkheads of ship. The lower edge o the parallel middle body is
given a radius using plane along full length. The fore and aft portions have been joined with
the parallel middle body using nailed stiffening pieces from inside along with wood
adhesives. After completing the hull form the hull is finished by applying two coatings of
wood protector followed by a fine layer of filler and adhesive which completely eliminates
the joints. The surface is now rubbed gently with emery paper to give a good surface finish.
Now paint is applied over this finished surface.
Figure 4.1 Wood was Selected as the Material
Source: Team
Figure 4.2 Dimensions were Marked on the Wood Before Cutting
Source: Team
Figure 4.3 The Wood is Cut Accordingly
Source: Team
Figure 4.4 Forward Portion is Shaped
Source: Team
Figure 4.5 Aft End is Shaped
Source: Team
Figure 4.6 Wooden planks of 4cm Thick are Marked on the Block
Source: Team
Figure 4.7 Wooden Planks of 4cm Thick are Cut from the Block
Source: Team
Figure 4.8 The Planks are Arranged to the Shape of an Open Box
Source: Team
Figure 4.9 The Joints are made by Hammering in Adhesive Applied Wooden Nails
Source: Team
Figure 4.10 Wooden Planks are Inserted at Equal Intervals
Source: Team
Figure 4.11 The Parallel Middle Body after Inserting Planks
Source: Team
Figure 4.12 Three Parts are Joined by Wooden Nails and Adhesives
Source: Team
Figure 4.13 The Parallel Middle Body is Closed
Source: Team
Figure 4.14 The Lower Edge of the Parallel Middle Body is Shaped Using a Plane
Source: Team
Figure 4.15 Fully Assembled Hull
Source: Team
Figure 4.16 Coating of Filler and Adhesive is Applied
Source: Team
Figure 4.17 Inverted and Painted Crimson Red Using a Spray Gun
Source: Team
Figure 4.18 Painting of Crimson Red Completed
Source: Team
Figure 4.19 Masking Tape is Applied at Summer Load Line
Source: Team
Figure 4.20 Deep Blue is Applied on the Freeboard
Source: Team
The super structure of the model is made according to the drawings made. Copies of
the plan were made and required stencils cut out from it for each member required. These
are then used to get the profiles of all the required pieces marked on the fourex board and
duplex board. It is then cut precisely. Then corresponding fourex and duplex pieces are
joined. The pieces are then joined in order using adhesives to get the shape of
superstructure. Markings are then done on it for completion.
Figure 4.21 Stages in Fabrication of Superstructure
Source: Team
The railing for the whole superstructure and deck has been made by cutting and
joining fibre threads.
Figure 4.22 Using Knitting Wire the Railings were Made
Source: Team
The ships anchors are shaped from insulating boards using files.
Figure 4.23 Anchor
Source: Team
Figure 4.24 Files used for Fabrication
Source: Team
The lifeboats and life rafts have been shaped from insulating boards using files.
Figure 4.25 Lifeboat and Life raft
Source: Team
The pipelines on the deck have been made by joining fibre tubes and bents made by
heating.
The propeller the ship has been made according to the plan. The profile of the skewed
propeller blades are carefully transferred on to the GI sheet and cut using metal strip. The
propeller hub is made from insulating board using files and the blades are attached to it at
required angle.
Figure 4.26 Propeller Hub
Source: Team
Figure 4.27 Overall View of Model from Stern
Source: Team
CHAPTER 5- DECK ARRANGEMENTS
5.1 MOORING ARRANGEMENTS AND LAYOUTS
The objective of a good shipboard mooring arrangement is to provide and arrange
equipment to accomplish the following:
a.
Provide for an efficient mooring pattern at conventional piers and Sea Islands
b.
Facilitate safe and quick mooring, unmooring and line- tending operations with
minimum demand on manpower.
c.
Facilitate safe and efficient handling of tugs.
d.
Permit safe and efficient conduct of other customary tanker operations such as hosehandling and mooring alongside of fuel barges.
e.
Allow safe and efficient specific anticipated operations such as ship-to-ship transfers
or canal transits.
f.
Provide for emergency situations such as excessive winds requiring doubling of
lines, emergency towing of disabled ships, or shipboard fires requiring the ship to be
towed off the berth quickly without shipboard assistance.
The primary concern in the shipboard mooring arrangement is suitability for mooring
at conventional piers and Sea Islands, since this is the requirement most commonly
encountered. The principles for an efficient and safe mooring operation at these terminals
are covered in Section 1. These principles apply to ships of all sizes and may be
summarized as follows:
a.
Mooring arrangements should be symmetrical.
b.
Breast lines should be as perpendicular as possible to the longitudinal centre line of
the ship.
c.
Spring lines should be as parallel as possible to the longitudinal centre line of the
ship.
d.
Mooring lines in the same service should have about the same length between the
vessel's winch and the jetty mooring points.
In addition to the foregoing principles, the following general guidelines should be kept in
mind in laying out the mooring equipment:
a.
Keep mooring areas as clear as possible.
b.
Locate mooring operations as far forward and aft as possible.
5.2 SCUPPERS AND BULWARK
Scuppers are normally in close proximity to the super structure to ensure that there is
adequate drainage of any water to prevent corrosion where freeing ports are designed to
remove large volumes of water quickly that have been shipped due to weather. Scuppers
and freeing port in bulwarks not functioning satisfactorily could greatly reduce stability,
endangering the ship due to the large raising the centre of gravity and the large ―free surface
effect‖. Oil tankers have guard rails fitted instead of normal bulwarks as they have very low
freeboard and large open deck areas, thus require that a minimum of 30 percentage freeing
port area would have to be cut in bulwarks to ensure the rapid drainage of water off the
deck, also retention of water on deck would greatly increase the longitudinal bending
moment and possibly cause cracking. By fitting open rails green seas are not retained on
deck and there is no danger of cracks in the rails spreading into the hull.
A bulwark is an extension of the side shell plating above the upper deck and is a
safety barrier for personnel to preventing falling overboard.
5.3 ANCHORS AND CABLES
The forecastle deck houses the windlass or windlasses which raise and lower the anchor and
cable. Various items of mooring equipment, such as bollards, fairleads, etc., are also
arranged around the deck edge. The anchors are housed against the forward side shell,
sometimes in specially recessed pockets. The anchor cable passes through the shell via the
hawse pipe on to the forecastle deck. It travels over the cable stopper and on to the windlass
cable lifter drum. From the cable lifter it drops vertically down into the chain locker below.
5.4 WINDLASS
An anchor windlass is a machine that restrains and manipulates the anchor chain and/or
rope on a boat, allowing the anchor to be raised and lowered. A notched wheel engages the
links of the chain or the rope.
F i gu r e 5 . 1 W i n d l a s s
Source: Team
5.5 HOSE HANDLING CRANES
During tanker loading and unloading operations large hoses have to be lift from the shore to
the ship deck to connect to the cargo manifolds. For this purpose tankers are provided with
hose handling cranes near to the cargo manifolds.
Figure 5.2 Hose Handling Crane
Source: Team
5.6 DAVITS
Gravity davit is one the most common arrangement for lifeboat launching on merchant
ships.
Figure 5.3 Davit
Source: Team
5.7 LIFEBOATS
Open and partially enclosed lifeboats are no longer allowed on new constructions.
In addition all lifeboats must use buoyancy material, fire retardant resins and an engine
approved by IMO's SOLAS requirements and U.S. Lifeboats must also follow additional
USCG requirements. In tanker vessel fully enclosed life boats are used and it is mandatory
as per the regulations because of the dangers like fire, toxic vapours and in bulk carrier
vessels these dangers are very less. In tanker vessels when accidents happen there is a great
possibility of the cargo oil to spill in the sea and catches fire. In that situation with open
lifeboats no one can steer thru the water safely without getting roasted. So in tanker vessels
Fire retarded life boats with water sprinkler system are mandatory.
5.8 FUNNEL
The funnel is a surround and support for the various uptakes which ensure the dispersion of
exhaust gases into the atmosphere and away from the ship. The shape of the funnel is
sometimes determined by the ship owner‘s requirements but more often by smoke –clearing
arrangements and the need for streamlining to reduce resistant. The owner‘s housemark or
trademark is often carried on the outside of the funnel structure.
In the funnel ventilation louvers are fitted on the after end below the upper rainflat.
These louvers disperse the exhaust from the various ventilators led up the funnel. Fire flaps
are fitted in the air tight flat beneath these ventilators and are used to shut off the air outlet
from the engine room in the event of a fire. A hinged watertight door is fitted in the funnel
leading out on to the deck upon which the funnel stands. Holes or grilles are cut into the
forward face of the funnel towards the top, and the whistle is fitted on a small seat just aft of
the opening.
Figure 5.4 Funnel
Source: Team
Ladders and platforms are also provided inside the funnel for access purposes. Hugs
are fitted around the outside top shell plating to permit paining of the funnel.
5.9 ENGINE CASING
The accommodation or upper deck spaces are separated from the engine room or machinery
spaces by the engine casing. Access doors are provided at suitable levels between the engine
casing and the accommodation. The volume enclosed by the casing is made as small as
possible but of sufficient dimensions to allow maintenance and machinery removal from the
engine room. The casing leads up to the upper decks, finishing below the funnel, fresh air is
drawn in through jalousies or jouvers in small fan room off the casing and passes down
trunking into the engine room. The hot air rises up the engine room into the casing and out
of the funnel at the top.
5.10 FIRE MAIN
All cargo ship in excess of 1000 gross tones must have at least two independently driven
fire pumps. Where these two pumps are located in one area an emergency fire pump must
be provided and located remote from the machinery space. The emergency fire pump must
be independently driven by a compression ignition engine or other approved means. Water
mains of sufficient diameter to provide an adequate water supply for the simultaneous
operation of two fire hoses must be connected to the fire pumps. An isolating valve is fitted
to the machinery space fire main.
CHAPTER 6- SHIP CONSTRUCTION
6.1 BOTTOM STRUCTURE
At the centre line of the bottom structure is located the keel, which is often said to form the
backbone of the ship. This contributes substantially to the longitudinal strength and
effectively distributes local loading caused when docking the ship. The commonest form of
keel is that known as the ‗flat plate‘ keel, and this is fitted in the majority of ocean-going
and other vessels. If a double bottom is fitted the keel is almost inevitably of the flat plate
type. The double bottom of larger ships are usually longitudinally framed.
Figure 6.1 Longitudinally Framed Double Bottom Structure
6.2 SIDE FRAMING
The ship‘s side framing consists of hold frames at every frame space and web frames at
equal intervals along with longitudinal stiffeners. The plates are welded over this side
framing.
Figure 6.2 Side Frame
6.3 DECK
Figure 6.3 Deck Plating
6.4 BULKHEADS
The principal bulkheads subdivide the ship hull into a number of large watertight
compartments.
6.5 SUPERSTRUCTURE
Superstructures might be defined as those erections above the freeboard deck which extend
to the ship‘s side or almost to the side. Deckhouses are those erections on deck which are
well within the line of the ship‘s side. Both structures are of importance in the assignment
of the load line as they provide protection for the openings through the freeboard deck. Of
particular importance in this respect are the end bulkheads of the superstructures,
particularly the bridge front which is to withstand the force of any seas shipped. The bridge
structure amidships or the poop aft are, in accordance with statutory regulations, provided as
protection for the machinery openings. It is possible however to dispense with these houses
or superstructures and increase considerably the scantlings of the exposed machinery
casing. Unless an excessive sheer is provided on the uppermost deck it is necessary to fit a
forecastle forward to give added protection in a seaway. Each structure is utilized to the full,
the after structure carrying virtually all the accommodation in modern ships. The crew may
be located all aft in the poop structure or partly housed in any bridge structure with the
navigating spaces.
Of great structural importance is the strength of the vessel where superstructures and
deckhouses terminate and are non-continuous. At these discontinuities, large stresses may
arise and additional strengthening will be required locally as indicated in the following
notes on the construction.
6.6 WEATHERTIGHT DOORS
The integrity of houses on the freeboard and other decks which protect the openings in these
decks must be maintained. Access openings must be provided to the houses and
weathertight doors are fitted to these openings. These must comply with the requirements of
the Load Line Convention and are steel doors which may be secured and made watertight
from either side. Weathertightness is maintained by a rubber gasket at the frame of the door.
Figure 6.4 Weather tight Door
6.7 FORE END STRUCTURE
An overall view of the fore end structure, and the panting stiffening arrangements are of
particular importance. These have already been dealt with in detail earlier as they are
closely associated with the shell plating.
On the forecastle deck the heavy windlass seating is securely fastened, and given
considerable support. The deck plating thickness is increased locally and smaller pillars
with heavier beams and local fore and aft intercostals, or a centre line pillar bulkhead, may
be fitted below the windlass.
Figure 6.5 Fore End Construction
6.7.1 Bulbous Bows
A greater degree of plate curvature is involved, unless a rather convenient cylindrical form
is adopted and fitted into the bow as a single unit. Floors are fitted at every frame space in
the bulb, and a centre line wash bulkhead is introduced when the bulb is large. Transverses
are fitted at about every fifth frame in long bulbs. Shell plating covering the bulb has an
increased thickness similar to that of a radiused plate stem below the waterline.
6.8 RUDDERS
Many of the rudders which are found on present-day ships are semi balanced, i.e. they have
a small proportion of their lateral area forward of the turning axis (less than 20 per cent).
Pintles on which the rudder turns in the gudgeons have a taper on the radius, and a
bearing length which exceeds the diameter. Rudder stock may be of cast or forged steel, and
its meter is determined in accordance with the torque and any bending moment it is to
withstand. The weight of the rudder may be carried partly by the lower pintle and partly by
a rudder bearer within the hull.
Figure 6.6 Rudder
6.9 PROPELLERS
It is important that the propeller is adequately immersed at the service drafts and that there
are good clearances between its working diameter and the surrounding hull structure. The
bore of the propeller boss is tapered to fit the tail shaft and the propeller may be keyed onto
this shaft; a large locking nut is then fitted to secure the propeller on the shaft. For securing
the propeller a patent nut with a built in hydraulic jack providing a frictional grip between
the propeller and tail shaft is available. A fairing cone is provided to cover the securing nut.
CHAPTER 7- TANKER SYSTEM
7.1 CARGO TANK VENTILATORS
The cargo tank ventilators are to be entirely separate from air pipes from other
compartments of the tanker and positioned so that flammable vapour emissions cannot be
admitted to other spaces or areas containing any source of ignition.
7.1.1 High Velocity Vents
Tank vapours can be released and sent clear of the decks during loading through large high
velocity vents. This type has a moving orifice, held down by a counterweight to seal around
the bottom of a fixed cone. Pressure build up in the tank as filling proceeds causes the
moving orifice to lift. The small gap between orifice lip and the fixed cone gives high
velocity to the emitted vapour. It is directed upwards with an estimated velocity of 30m/s.
Air drawn in by the ejector effect dilutes the plume.
Figure 7.1 High Velocity Vent
Source: Marine Auxiliary Machinery
7.1.2 Simple High Velocity Vent
A simpler design has two weighted flaps which are pushed open by pressure build up to
achieve a similar nozzle effect. The gauze flame traps and vents tend to collect a sticky
residue which should be cleaned off regularly to ensure unimpeded venting.
Figure 7.2 Simple High Velocity Vents
Source: Marine Auxiliary Machinery
7.1.3 Pressure Vaccum Valve
Moderate pressures of 0.24 bar acting on the large surface in liquid cargo tanks are
sufficient to cause damage and rupture. The pressure on each unit of area multiplied by the
total area gives a very large loading on the underside of the top of a tank or other surfaces.
Distortion can result or the metal plate may be ruptured.
7.2 INERT GAS SYSTEM
The inert gas system is to be so designed and operated as to render and maintain the
atmosphere of the cargo tanks non-flammable, other than when the tanks are gas free.
Hydrocarbon gas normally encountered in oil tanks cannot burn in an atmosphere
containing less than 11 per cent of oxygen by volume, thus if the oxygen content in a cargo
tank is kept below, say, 8 per cent by volume fire or explosion in the vapour space should
not occur. Inert gas introduced into the tank will reduce the air (oxygen) content.
On an oil tanker, inert gas may be produced by one of two processes:
(1) Ships with main or auxiliary boilers normally use the flue gas which contains typically
only 2 to 4 per cent by volume of oxygen. This is scrubbed with sea water to cool it and to
remove sulphur dioxide and particulates, and it is then blown into the tanks through a fixed
pipe distribution system.
(2) On diesel engine ships the engine exhaust gas will contain too high an oxygen level for
use as an inert gas. An inert gas generating plant may then be used to produce gas by
burning diesel or light fuel oil. The gas is scrubbed and used in the same way as boiler flue
gas.
Non-return barriers in the form of a deck water seal, and non-return valve are
maintained between the machinery space and deck distribution system to ensure no
petroleum gas or liquid petroleum passes back through the system to the machinery space.
The double hull and double bottom spaces of tankers required to have an inert gas
system are to have connections for the supply of inert gas.
Figure 7.3 Inert Gas System
Source: Internet
7.2.1 Deck Seal
The fan discharge to the deck main via a seal which prevents back flow of gases. The seals
can be classified as wet or dry seals. Both types involves feeding inert gas through a flooded
trough. In dry seal type a venture gas outlet is used which effectively pulls the water away
from the end of the gas inlet at high flows allowing the inert gas to bypass the water trough.
The reason for developing this type of seal was because early wet-type seals frequently
caused water carry-over into the system. As with other components in the inert gas system
the internal surfaces of the deck seal must be corrosion protected usually by a rubber lining.
CHAPTER 8 – CONCLUSION
A suitable design was selected. The material used for the hull is wood and the material used
in the construction of the superstructure is hard board. All the equipments on the deck are
made of plastic mouldings. The minute details on the deck are in accordance with the design
of the vessel we had selected as the base.
As our project was supposed to be a still model we have not performed any test and trials on
the model. Thus we believe we have been able to construct the model in a satisfactory
manner and have provided the model with all the necessary details to the best of our
knowledge.
REFERENCES
1. Dr. Cowley James, (2004) Fire Safety at Sea, IMarEST, London.
2. Eyres, D. J., (2007) Ship Construction, MPG Books Ltd, Great Britain.
3. McGeorge, H.D., (1995) Marine Auxiliary Machinery, MPG Books Ltd, Great
Britain.
4. Dr. Taylor, D. A., (1998) Merchant Ship Construction, IMarEST, United Kingdom
5. Consolidated Edition, (2005) Load Lines, IMO Publications, United Kingdom

model of an oil tanker

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