The complication of helium desorption in the helium leak method

The phenomenon of helium adsorption on the glass and metal surfaces of the standard HC-37/U cold weld base is investigated. Testing laboratories implement the interpretation of MIL-STD-202 method 112 in various ways. These methods are compared. A comparison of the leak rate of bombed units (units subjected to high pressure of known tracer gas) is made against units which are back filled with the same tracer gas, helium. The difference in the leak rate due to helium adsorption in the base is shown and the decay curve for the helium desorption of the HC-37/u base is given. Techniques for purging helium from the glass surface are also investigated and the results given.