ASTM D5331 Standard Test Method for Evaluation of Mechanical Handling of Unitized Loads Secured with Stretch Wrap Films
The scope of ASTM D5331 is to evaluate and compare unitizing films by assessing their ability withstand various types of mechanical handling. The test method applies to common means of handling which includes forklift, push/pull, clamp truck, crane, and spade lift-type handling systems. The test levels can change to better reflect known levels of intensity in the field. ASTM D5331 focuses on the sample preparation and evaluation when assessing the performance of stretch film for load unitizing.
For the purposes of this standard the following terms are defined:
- Large shipping case or crate- a shipping container (any material) of size and weight that requires mechanical handling. This unit can weight from 100lbs to many tons. It can be secured or carried by a base or pallet. A frame may be provided to stabilize rigidity throughout the container.
- Spade lift attachment- a lift truck attachment that is used for top handling products. The products can include interlocking flange cartons (IFC), folded cap, or folded flap style cartons.
- Unitized load- two or more packages that are wrapped or banded together as one shipping unit. When unitized they normally weigh more than 100 lbs. the packages can be unitized using shrink wrap, banding, strapping, taping, or gluing. The unitized load can but does not necessarily have to include a pallet or slip sheet.
ASTM D5331 is often used to compare the performance of unitizing films. However, it can also be used to compare one kind of wrapping material used in different wrap cycles. It is important to note that there has not been a direct correlation established between test result and field performance. Rather, the test simulates mechanical handling during all distribution phases. A user can customize the test to simulate a particular distribution environment. To do this the user may use discretion to establish test levels and the number of test cycles.
The two apparatuses used in this test are the load wrapping apparatus and the mechanical handling apparatus. The load wrapping apparatus is a machine that wraps the test load. This method should by as close as possible to the actual method of wrapping that is used in production prior to shipping. The mechanical handling will be determined by the test method. To prepare the test loads, begin by arranging the packages in a manner that is similar to actual production. They may be loaded in layers or stacked on a pallet or slip sheet. The load should then be wrapped with the unitizing film using a predetermined percent stretch and wrap cycle. Again, this is predetermined by the user using their discretion. Then, the unitized load should be left untouched for a minimum of 16 hours before conducting the test. This time allows the stretched wrapping material to reach equilibrium of its stress retention forces. The test will then be conducted according to the test procedure chosen. The test procedures include palletized load, spade lift, clamp handling, and push/pull handling. At the conclusion of the test, the laboratory will record data and compile a test report that includes all the information outlined in the ASTM D5331 standard.
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