Plumbing, Ammunition, and Horses: Embrittlement Failures of Copper Alloys

A series of brittle fractures occurred in copper alloy components of a building’s domestic water supply. The longest section of pipe failed first. Then the second longest section failed. Coupons cut from the pipe were tested and found to be ductile. In the subsequent investigation, we found that the mode and sequence of failures related to an interaction of residual stress, constraints imposed by fittings, and stress corrosion cracking. We were also able to observe the residual stress/constraint interaction with a simple experiment that required no special instruments. In the discussion, we will also relate this plumbing failure to historical failure analysis cases, including how in the First World War, the British army learned why they should not store their ammunition too close to the cavalry stables.