Failure of a Copper Condenser Dashpot

A copper condenser dashpot in a refrigeration plant failed prematurely. The dashpot was a long tubular component with a cup brazed at each end. Stereomicroscopic examination of the fracture surface at low magnification revealed a typical ductile mode of failure. The failure was attributed to insufficient component thickness, which made the dashpot unable to withstand internal operating pressure, and to extensive annealing in the heat-affected zones of the brazed joints. It was recommended that the condenser dashpot design take into account the annealing effects of brazing. Hydrostatic testing at a pressure times greater than the maximum operating pressure prior to placing the component in service was also suggested.