History
Nitrile rubber sleeves of valves used in the conveyance of mains gas at a pressure of 5
MPa had been operated successfully in many installations. However, in one particular
application premature failures occurred frequently. This involved only one size of valve
and the pressures were not abnormal, although the temperature was 38 °C as opposed to
the more usual 10-20 °C.
It was expected that valves in these applications would suffer ‘explosive decompression’
due to the expansion of absorbed gas on depressurisation. However, the failures in this
case occurred at operating pressure, and took the form of splits on the outer side of the
sleeve and what appeared to be foaming at discrete spots around the inside of the sleeve.