PDS Version 3.3 Offers Easier, More Flexible Program
Latest version of Pallet Design System computer software includes improvements to pallet component quality grades and has ability to set custom unit load specifications.
By Chaille Brindley
Date Posted: 7/1/2003
If you’re a customer of the Pallet Design System (PDS), you should have received version 3.3, the latest edition of the software. You may be wondering if it contains any new, noteworthy features. While version 3.3 may not be as revolutionary as the previous upgrade, which included data on repaired components, the latest edition does tackle some areas needing improvement.
The biggest changes are improvements to the pallet component quality grades and the ability to set customized unit load specifications, according to John McLeod, senior research associate at the Sardo Pallet Lab at Virginia Tech. The Pallet Lab developed PDS in 1984 in conjunction with the National Wooden Pallet & Container Association (NWPCA) and the U.S. Forest Service.
PDS is a reliability based design procedure for wood pallets. It is based on engineering fundamentals, matrix structural analysis techniques, and the results of laboratory and field testing. PDS estimates strength, deformation, and durability for user specified descriptions of the pallet and its handling environment. According to the Pallet Lab, "Using PDS to design and select pallets will improve safety for workers, reduce solid waste, improve utilization of standing timber and material handling costs."
The pallet component grades used in PDS have been simplified and improved, which will make specification simpler and more accurate. The number of grade levels has been reduced from 18 different grades from the six different sets of specifications to five major grade categories.
"The new grade names were chosen to promote common understanding and reflect industry practice," said John. The grades are consistent with old NWPCA pallet standards, the uniform standard for wood pallets and the national grading rules for dimension lumber (as far as possible). For a more complete review of the changes, see tables 1 & 2. Version 3.3 will automatically convert old grade names based on their equivalence and will alert users of the change.
The previous versions did not provide users the flexibility to test a pallet design for a customized load. And despite all the talk about standardization, odds sizes and unusual stacking arrangement continue to be common. With version 3.3, users can calculate pallet performance based on load type, stacking pattern and load stabilizers used to secure the load. The load carrying capacity and deflection estimates will be specific to the unit load specified.
Unit loads exhibit different behavior when racked or stacked depending on container type, stacking pattern and load stabilizers. The uniformly distributed load specification used in the past can still be utilized. The new system will simply make performance estimations more accurate. For example, PDS will indicate a greater safe load capacity and less deflection for boxes, pails and bulk boxes than the uniform load. Load stabilizers (stretch wrap, shrink wrap or strapping) will improve racked performance compared to the standard load. Interlocked stacking pattern for boxes improves performance. These conditions affect the load as it moves down the road in the back of a truck or sits in a warehouse rack.
The latest PDS version includes new deflection estimates for wood pallets. Deflection is the vertical distance the pallet will bend or sag under a load. A stiffer pallet leads to less deflection under the load. Some unit loads are less flexible than others, and the custom load specification in PDS will allow more accurate deflection estimates.
In general, deflection negatively impacts pallet performance. Large deflections can result in stress concentrations and product damage. Large deflections make entry and handling of the pallet more difficult, which can cause pallets to hang up in automated storage and retrieval systems.
The deflection in a loaded pallet will change over time. Most of the deflection in a loaded pallet takes place over the first few days. Thereafter, the rate of increase subsides. Keep in mind, as the pallet dries, it changes shape impacting the deflection rate. PDS version 3.3 will allow users to more accurately estimate the long term changes in deflection.
Over the past year, the NWPCA has sought to crack down on illegal use of PDS research. The new version includes the option of adding a watermark and copyright legend to all reports developed with the software. The new safety features are intended to discourage illegitimate use by others of PDS reports/research created by a PDS license holder. Any PDS report lawfully belongs to the license holder who created it. Customers of license holders do not have the legal right to take the data and use it for their own purposes. Piracy dilutes the value of PDS for everyone. The NWPCA encourages anyone to report PDS piracy.
After tossing around many ideas, the NWPCA and the Pallet Lab have decided to change the installation and distribution procedures for PDS. Starting with version 3.3, each basic license will allow installation of the software on two computers. Companies wanting additional installations, either at the same or different physical locations, can purchase more licenses from the NWPCA. PDS can only be licensed directly from the NWCPA. For more information, call 703 519 6104 or e mail firstname.lastname@example.org.
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