49 CFR § 178.980 - Stacking test.
(b) Special preparation for the stacking test.
(c) Test method.
(1) All Large Packagings must be placed on their base on level, hard ground and subjected to a uniformly distributed superimposed test load for a period of at least five minutes (see paragraph (c)(5) of this section).
(2) Fiberboard and wooden Large Packagings must be subjected to the test for 24 hours.
(3) Rigid plastic Large Packagings which bear the stacking load must be subjected to the test for 28 days at 40 °C (104 °F).
(4) For all Large Packagings, the load must be applied by one of the following methods:
(5) Calculation of superimposed test load. For all Large Packagings, the load to be placed on the Large Packaging must be 1.8 times the combined maximum permissible gross mass of the number of similar Large Packaging that may be stacked on top of the Large Packaging during transportation.
(d) Periodic Retest.
(2) The packaging may be tested using a dynamic compression testing machine. The test must be conducted at room temperature on an empty, unsealed packaging. The test sample must be centered on the bottom platen of the testing machine. The top platen must be lowered until it comes in contact with the test sample. Compression must be applied end to end. The speed of the compression tester must be one-half inch plus or minus one-fourth inch per minute. An initial preload of 50 pounds must be applied to ensure a definite contact between the test sample and the platens. The distance between the platens at this time must be recorded as zero deformation. The force “A” to then be applied must be calculated using the applicable formula:
(e) Criterion for passing the test.
(2) For fiberboard or wooden Large Packagings, there may be no loss of contents and no permanent deformation that renders the whole Large Packaging, including the base pallet, unsafe for transportation.
(4) For the dynamic compression test, a container passes the test if, after application of the required load, there is no permanent deformation to the Large Packaging which renders the whole Large Packaging; including the base pallet, unsafe for transportation; in no case may the maximum deflection exceed one inch.