Unit Load NL 9-04 - Center for Unit Load Design

Center for Unit Load Design
Virginia Tech
Volume 5, Number 3
In this issue ...
• Creature Feature Anobiid Powderpost
Beetle, Page 3
• Vacuum Technology
Project Update, Page 3
• New Packaging Science
Program, Page 4
New Members
Bison Pallet (Miller Dowel)
Michael Miller
Cooper Tire (renewal)
Brett Pogan
Fastec
Bob Dickinson
Great Salt Lake Minerals
Mark Kaschmitter
Hewlett Packard
Matt Daum
National Nail Corporation
Hollis Henderson
Protective Pallets
Tony Kohlhaas
Smurfit-Stone Container
Corporation
Richard Owen
TriEnda/Creative Packaging
Robert Shimmel
John Shoop
W.W. Henry
Ron Juncal
Summer 2004
Topographical Mapping of the Mechanical
Stresses of Wood Pallets During Use
Peter Hamner
While the level of forces to which pallets are exposed has been documented to some extent by
measuring the reaction forces of handling equipment, the localized stress levels have not been
documented. The locations of applied forces on the pallet or container are only known when
the force level exceeds the resistance of the pallet and causes failures. Understanding the
location, frequency of occurrence, and stress levels associated with the shocks and impacts
during pallet and unit load movement can lead to improvements in pallet design efficiency. A
technique to map the applied stresses could lead to an understanding of the best locations for
applying labels or RFID tags to pallets. Further, understanding the distribution of static stresses
imposed by loads on the pallet during warehouse rack storage or stack storage could lead to
better unit load designs. For every action there is an equal an opposite reaction; therefore, under
these static conditions the pallet will impose a stress on the packaged product. Package
designers must know what stresses are being imposed by the pallet to design a package that
protects the product. Perhaps the most significant result of understanding the distribution of
stresses applied to pallets would be the opportunity to improve the designs of unit load material
handling equipment in such a way as to reduce the stress levels and frequency of stresses
applied to pallets during use.
One possible technology for mapping the distribution of dynamic and static stresses on pallets
during use is pressure sensitive films, also called tactile pressure indicating films, such as
Pressurex® (manufactured by Sensor Products, Inc.). These pressure sensitive films are
available for sensing stress levels that increment from less than 1 psi to an excess of 20,000
psi. For technical reasons, no single film can measure the entire range; therefore, a variety of
films are manufactured and used to detect smaller pressure variations. The total range
represented by these commercially available films appears to be appropriate for testing pallets,
continued on page 2
Topographical Mapping continued from page 1
however, which will be most effective has yet to be discovered. In addition, methods of securing and protecting the film on pallet
surfaces will need to be developed.
The Center for Unit Load Design has begun preliminary testing of pressure sensitive films to map stress levels on pallets in use
by experimenting with both localized impact (fork lift and stringers) and static load stress distribution testing (deckboard
loading). The previous two images show a small section of SPI Pressure® film attached to the exterior side of a pallet stringer.
The film shows before and after contact by forklift tines with the shaded areas documenting the exact locations of direct contact. The
degree of color-coded shading can be matched with a key to estimate the pounds per square inch of mechanical stress incurred.
Packaging designers typically assume the stress imposed on the packaged product is reinforced by and across the pallet. Our
preliminary research using pressure tape has shown that stress distributions across deckboards between stringer locations are
not uniform. In fact, depending on deckboard thickness, stress is localized around the area where it contacts a stringer and
abruptly disappears moving into the middle of the span between deckboards. This is demonstrated in the following images. In
this case, both deckboards are the same length with the deckboard on the left being thinner and narrower than that on the right.
The thicker, wider, and stiffer deckboard on the right allows the load to be distributed more extensively across the span, thus
reducing stress potential on the packaged product.
The effects of this phenomenon have relevant and practical implications to unit load design. Take for example the following
image depicting pallets loaded with plastic bottle containers of oil packed in corrugated boxes. When these unit loads are stacked
on top of each other, the high concentration of stress around the outside stringer location is more than the outside oil bottle can
resist and has begun to collapse at the neck. The bottles located away from the stringer location, more to the center of the bottom
deckboard span, are not damaged because there is little or no stress being applied. Thus, a packaging designer can either specify
a stronger oil container design, or require a stiffer pallet design. The latter option will
be significantly cheaper.
Research efforts to better understand the location, frequency of occurrence, and
degrees of stress levels associated with impact shocks on pallets during use, as well
as the load distributions on pallet deck surfaces during use, are just beginning. Our
preliminary results using pressure sensitive films indicate that these techniques will
be useful in helping pallet, packaging, and materials handling equipment designers
improve the function and efficiency of unit load designs. This preliminary research
is being funded by the Pallet Foundation of Alexandria, Virginia.
Visit us at...
November 7-11, 2004
McCormick Place - Chicago, Illinois
Booth C8
Join the Center
The Center for Unit Load Design is an Industry/University Partnership. Industry
members help fund the center’s activities in exchange for priority access to our
technical assistance team, research laboratories, member’s only section of the
Website, this quarterly newsletter, and copies of all non-proprietary research and
publications. Our team includes experts in packaging, palletization, material
handling, and unit load design optimization. Members also receive reduced rates on
center-sponsored seminars. Member fees are based on predicted annual use,
starting at $1000 per year. Call (540) 231-5370 today to learn more about
opportunities to partner with the Center for Unit Load Design.
What's Bugging You?
Creature Feature –
Anobiid Powderpost Beetles
Euvrilletta peltata
Insect: Small, brown beetles;
body oval and with short
antennae. Adult beetles are
about 1/8 inch long, brown
and with the head projecting
downward. The larval stage is
cream colored and slightly Cshaped.
Damage: Round holes (about 1/8 inch) in the
surface of the wood, gritty frass falling from
some holes.
Wood Species: Primarily softwoods, but also
hardwoods
The larvae tunnel below the wood surface creating
galleries that are filled with the powdery frass.
The exit holes are about 1/8 inch in diameter and
are scattered over the surface or grouped in
specific locations. The frass falling from the exit
holes is cream colored and gritty when rubbed
between fingers. Galleries below the surface
may weaken the wood.
Life Cycle: Two to three year life cycle, adults
emerge in spring.
The adult beetles usually emerge in April and
May, and live for about two weeks. They mate
immediately and the females lay eggs on the
surface of untreated wood or in the exit holes.
Larva development time depends on
environmental conditions. One year may be
sufficient in wood with a high moisture content.
They may re-infest the wood for several years.
Prevention: Reducing the exposure of pallets to
outdoor conditions in the spring and remove all
pallets with an active infestation.
Control: Liquid application to the surface of the
infested wood.
The surface of infested wood can be treated with
a liquid insecticide; this will penetrate to a limited
depth but provide a lethal concentration below
the surface where the larvae and emerging adults
will contact it.
Thank you to Bill Robinson, our local
entomologist, for providing this information.
Vacuum Technology Project to Control
Insects in Wood (Phase II) Investigates
Technology Commercialization
Phase I of the Vacuum Technology Project is now complete with Phase II
well underway. In review, current phytosanitary measures require that
wood pallets and containers that pack goods imported or exported should
be heat treated or fumigated. The objective of the project at the center is
to develop the basis for vacuum control of insects in solid wood packaging
materials, which would serve as an alternative to eliminate insects in wood.
PHASE I (complete)
The materials tested were Southern pine, yellow-poplar and green red oak.
Larvae of the longhorn beetle, Hylotrupes bajulus, was used for all
evaluations and served as a substitute for the Asian Longhorn Beetle,
Anoplophora glabripennis (life stages are approximately the same), which
is thought to have been introduced in infested shipping materials. The
results indicated that removal of body water under the vacuum caused
whole-body dehydration of the larva. Larvae were found dead at body
weight loss ranging from 25 to 60%. Larvae were killed in less than 96
hours in the yellow-poplar and pinewood. The lethal vacuum time was
related to wood moisture content and larval weight. The lower the moisture
content, the fewer hours required for mortality; and the lower the larval
weight, the longer the time required for mortality.
PHASE II (ongoing)
The objective of this phase is to demonstrate that the low-pressure control
method for insects in solid wood packaging material can be commercialized
and become one of the accepted treatments in the International Standards
for Phytosanitary Measures. The tests in this study are commercial scale
tests conducted in a laboratory environment and will represent an
intermediate step of development of the process. The final step is a
commercial demonstration with an industry partner. The effectiveness of
low-pressure vacuum to control pinewood nematodes will also be evaluated
in this study. An economic analysis will be done on a hypothetical system
that a pallet treating facility can annually treat 4400 mbf of cut stock used
in the pallet manufacturing plant that can produce 1000 pallets daily, 250
day a year.
It is hoped that the project will benefit wood pallet and container
manufacturers and hardwood sawmill businesses. The proposed vacuum
controlling system does not release ozone-depleting chemicals, eliminates
the need for a heating system, and will save energy.
Principal investigators are Dr. Zhangjing Chen, Dr. Marshall (Mark)
White, and Dr. William H. Robinson. Dr. Chen has been working in the
wood and moisture relation under the vacuum, especially in the field of
vacuum drying. Dr. Robinson is an entomologist who has extensive
knowledge on wood insects.
1650 Ramble Road
Blacksburg, VA 24061
(540) 231-5370
Fax (540) 231-8868
E-mail: unitload@vt.edu
website: www.unitload.vt.edu
Unique Packaging Science Option
to Focus on Unit Load Logistics
graduates trained in the use of unit load
systems-based design technologies
Starting fall 2004, undergraduate students in the department
of wood science and forest products at Virginia Tech will
have a new educational study option in packaging science.
Significant opportunities exist to improve the efficiency and
safety of the global unit load logistics system for product
storage and distribution by understanding how critical
components in the system interact during use.
Graduates of this program will be unique in the industry with
an understanding of transport packaging and unit load
systems-based design technologies, which include the
interactions of packaging, pallets, and unit load material
handling equipment. Interdisciplinary education and research
will include all components of the unit load logistics system,
including packaging design, pallet design, unit load
stabilization, dunnage, blocking, and bracing, unit load
handling equipment design, and associated interactions, and
includes courses in wood science and forest products,
industrial and systems engineering, material science
engineering, and graphic arts.
The first program graduates, anticipated in spring of 2006,
can expect employment in a variety of industry groups
including box plants, wood pallet and container
manufacturers, folding carton suppliers, and corporate
packaging, warehouse, shipping, and logistics departments.
Future plans also include a proposed graduate program in
packaging and logistics science.
How to Contact the Center
Question/Topic
Who To Call
PDS User Support
General Technical Assistance
John McLeod III
Ph: 540-231-7082
jamiii@vt.edu
General Technical Assistance
ASTM, ASME, & ISO Pallet Standards
PDS User Support
Marshall (Mark) White
Ph: 540-231-7134
mswhite@vt.edu
PDS Telefax Design Service
PDS User Support
General Technical Assistance
Peter Hamner
Ph: 540-231-3043
phamner@vt.edu
General Assistance
Member Services
Bonnie Maccubbin
Ph: 540-231-5370
bjmac@vt.edu
Publications
PDS Lease Info
Sharon Daley
Ph: 540-231-7105
FAX: 540-231-8868
daley@vt.edu
Pallet, Container, and Fastener Testing
Unit Load Performance
Material Handling/Equipment & Pkg.
Ralph Rupert
Ph: 540-231-7106
rrupert@vt.edu
Website: www.unitload.vt.edu
The Center for Unit Load Design is a center in the Department
of Wood Science and Forest Products in the College of Natural
Resources at Virginia Tech.