Failure Analysis Expert Witness Analyzes a Pipe Fatigue Failure

Failure analysis expert analyzes a pipe failure. In this case the failed brass pipe supported a gauge. The gauge was cantilevered on the 6" long pipe and valve assembly. This assembly was attached to a pump, and the pump vibrations acted on the assembly and caused a metal fatigue failure to initiate ar the root of the male pipe thread where the thread exited the 'T' fitting. This is the most vulnerable point. The moment is maximum at this point and the root of the thread was a stress concentrator that magnified the stresses caused by the vibrations. The photographs above summarize the failure. Upper left shows an overview of the failure. The pipe failure occured where the pipe entered into the 'T' fitting. Upper right is an 8X photomicrograph ofthe fracture surface. The fatigue failure initiated at the root of the pipe thread. It then proceeded to the left as shown by the arrows. Fundimentally, the vibrating weight of the cantilevered, unsupported gauge caused the failure.