Both IEC 61386 and PMA DO 9.21-4425 describe tests designed to evaluate conduit resistance to fatigue when exposed to continuous cycles of repetitive bending.
The test procedure involves bending back and forth around a central pivotal point.
Although the test procedure is the same for both standards there are differences in the test parameters and the classification of results.
For a “pliable” classification according to IEC EN 61386-22 a conduit must withstand
3 cycles at the minimum declared operating temperature.
For a “flexible” classification according to IEC EN 61386-23 a conduit must withstand
5000 cycles at the minimum declared operating temperature.
PMA DO 9.21-4425 tests the conduit at 23°C and 50% r.h. but the test is not limited to a fixed number of cycles. It continues until the first signs of damage occur in order to find the actual performance limit.