The PMA DO 9.21-4420 test procedures describes a demanding test for conduit fatigue when exposed to continuous repetitive bending.
The conduit is fixed at the top of the apparatus, it passes over and under two pulley wheels.
A weight is suspended at the bottom end simulating the weight of cables within the conduit.
The pulley wheels move up and down continuously bending the conduit twice through 180° over its entire length.
The test is performed at 23°C and 50% r.h. and continues until the first signs of damage occur.