Failure of stainless steel water pump couplings

A number of lift pump couplings, that had been manufactured in India to a long established design, were submitted to determine the reasons for their “in-service” failure. Past history for this type of water pump would suggest that failures of this artefact were a very rare occurrence. However, failures were being encountered with a particular type of stainless steel coupling that had seen service in a range of different well locations. The manner by which the material had been worked to shape had resulted in couplings that were put into operation in a heavily cold worked condition. High residual stress along with raised chloride levels found in brackish water had combined to cause increased sensitivity to stress corrosion cracking, ultimately leading to premature failure.