Many commercial leak detection fluids contain trace amounts of ammonia, ammonium salt, or amines for pH control. The leak detection fluids are routinely applied to threaded outlet connections of compressed gas cylinder valves. Cracking was recently discovered in a number of compressed gas cylinder valve outlet connections fabricated from forging brass. Failure analysis indicated the cracking initiated from the external surface of the outlet connection and propagated intergranularly. The crack morphology was indicative of stress corrosion cracking. Exposure to commercial leak detection fluids was the only common link among the cracked brass valves. Thus, a laboratory test program was initiated exposing brass alloy U-bends to commercial leak detection fluids. The test results showed that crack initiation occurred when the leak detection fluids were allowed to concentrate on the stressed u-bend specimens. This testing has become the catalyst to develop an ASTM standard for screening commercial leak detection fluids.

Subject
Test methods, Intergranular stress corrosion cracking, Cylinders, Valves, Leaks, Wetting, Leak detection, Ammonium, U bends, Amines, Fluids, Brass, Stress corrosion cracking
Keywords:
leak detector fluids, leak detector solutions, leak detector soap solutions, bubble solutions, forging brass, UNS C37700, cartridge brass, UNS C26000, cylinder valves, stress corrosion cracking
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2003
Association for Materials Protection and Performance (AMPP)
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