We already have an image that presence of water is not good during Helium leak testing specially using Sniffer method.
We want to test our vertical type high pressure exchanger ( installed in area) for any leaks in tube-to-tube sheet seal welds using helium leak test( sniffer method based on mass spectrometry). Now the problem during testing bottom tube sheet of this vertical exchanger, we are unable to remove water from annular space of tube sheet (because the drain nozzle is an inch above bottom tube sheet).
Now the question is, "by pressuring the shell with helium, will this helium be able to diffuse through this layer of water and come out of leaks of seal welds and in turn be detected"
We performed an experiment and concluded that Helium does not pass thru water, however Helium molecules do penetrate in water at pressure. These molecules are given off when pressure is removed. Bottom line that successful Helium leak test using sniffer method cannot be performed when there is water present/ trapped in the leaking path.