Both, IEC EN 61386 and PMA DO 9.21-4320 describe a test designed to evaluate conduit resistance to compression forces. Excessive deformation of a conduit under compression could potentially cause damage to cables being protected within it.
The force required to compress the conduit between two square plates to a specific % of its original diameter is measured. Relaxation over time and recovery after removal of the force are evaluated.
The tests are performed at 23°C and 50% r.h.
IEC EN 61386 uses two 50mm x 50mm plates and allows 25% deformation.
PMA DO 9.21-4320 records results with 50mm x 50mm and 100mm x 100mm test plates and allows 20% deformation.