ISTA 3E Update: What Changed in Compression Testing for Unitized Loads
ISTA 3E was recently updated, and the biggest change affects how compression testing is calculated and performed for unitized loads.
The recent revision essentially reverts the compression calculation back to the older method used in the 2009 version of the standard. It also makes the use of a pallet as a load applicator optional during compression testing.
While the update is not a complete rewrite of ISTA 3E, it changes how compression force is calculated, how the test is set up, and how labs document the test.
What Is ISTA 3E?
ISTA 3E is a general simulation performance test for similar packaged-products shipped as unitized loads.
The test is designed to evaluate how a unitized load performs when exposed to common distribution hazards, including shock, compression, vibration, and handling stresses. It can also help assess load stability during transportation.
What Changed in the Newest ISTA 3E Revision?
The most important technical change is in the compression section.
The updated version returns to the older-style compression calculation method. In simple terms, the compression test force is now based on the gross weight of the unitized load, the number of loads that may be stacked, and the safety factor.
The standard defines the key compression calculation terms as:
- Wt = gross weight of the unitized load
- S = total number of potential unitized loads in a stack, including the bottom load
- F = safety factor
- C = compensation factor
For apply-and-release compression testing, the compensation factor is included in the calculation. For apply-and-hold testing, the calculation does not include that compensation factor.
Why the Compression Calculation Matters
Compression testing is used to evaluate whether a unitized load can withstand stacking pressure during warehousing or transportation. If the compression force is calculated incorrectly, the test may not accurately represent the intended distribution environment.
A test plan based on an older calculation method may produce different results than a test plan based on the current version. If you have any questions, it’s best to consult with your packaging testing lab. Contact us and we would love to help!
What This Means for Shippers and Packaging Engineers
For shippers, the main takeaway is simple: you should not assume your previous ISTA 3E compression setup is still correct.
This is especially important for heavy palletized products, tall unitized loads, or loads that may be stacked during warehousing or transportation.
A small change in the compression calculation can lead to a meaningful difference in the force applied during the test.
Rotational Edge Drop and Pallet Load Applicator
Rotational Edge Drop Clarification
The updated standard also includes a clarification related to rotational edge drop testing.
The note states that Test Block 6 drops should be performed on the edge or edges opposite those used during Test Block 3. This helps ensure the unitized load is challenged from more than one direction during the shock portion of the test.
While this is a smaller change than the compression update, it is still important for labs to follow the correct sequence when conducting ISTA 3E testing.
Pallet Load Applicator Is Now Optional
Another important update is that using a pallet as a load applicator is now optional.
A pallet load applicator is used to simulate the way another palletized load may sit on top of the test item. In some cases, this can create a more realistic compression scenario. However, it can also concentrate the applied load differently than a flat platen or load spreader.
Because of that, the updated language notes that extra consideration should be given to the safety factor when this option is used.
This gives packaging engineers and test labs more flexibility, but it also means the test setup needs to be chosen carefully. The decision to use a pallet load applicator should be based on the actual shipment configuration and the purpose of the test.
Common Questions About the ISTA 3E Update
Did ISTA 3E completely change?
No. The recent update does not completely change ISTA 3E. The most important changes are related to compression testing and a clarification for rotational edge drop testing.
Is the pallet load applicator required?
No. The updated language makes the pallet load applicator optional. If it is used, the safety factor and test setup should be carefully reviewed.
Does this affect previous ISTA 3E tests?
Not necessarily. Previous tests were performed to the version of the standard in effect at the time. However, new testing should follow the current version of ISTA 3E.
Should companies retest their products?
Not automatically. Retesting may be needed if packaging changes, distribution conditions change, customer requirements change, or the company needs certification to the latest version of the standard.
How Applus+ Keystone Can Help
Keystone provides ISTA 3E testing for unitized loads and palletized shipments. Our team can help review the current standard, confirm the correct compression calculation, and determine whether a pallet load applicator is appropriate for your test.
Need ISTA 3E Testing?
If your company ships unitized loads by full truckload, ISTA 3E testing can help evaluate package performance before products enter distribution.
Contact us today to request a quote or speak with our packaging testing team about the latest ISTA 3E requirements. For additional ISTA testing information, visit the links below: