NDT tests are most often performed at the production stage. Less common but equally important are in-service tests. They make it possible to determine whether in a given component, as a result of working conditions and the environment, any operating defects have appeared, which could cause potentially dangerous and costly failures.
Some time ago we received an order to examine shafts to determine the possibility of their continued operation. In this case, we were able to find a crack around the entire circumference of the shaft already after an initial visual inspection, and this was confirmed by MT testing. It was recommended that the shaft be taken out of service and replaced with a new one.