Pressure Testing
In pressure testing, the object to be
tested contains helium gas, the pressure of which is greater
than one atmosphere. A “sniffer” probe is connected
to the leak detector through a flexible hose. When the sniffer
probe approaches a leak, the escaping helium enters the vacuum
system by way of the sniffer probe and is detected by the mass
spectrometer tube. This method of leak detection is useful for
testing large tanks and other objects which are not easily
evacuated or which cannot withstand the stress of internal
vacuum. However, this method is less sensitive than vacuum
testing because the sniffer will take in some surrounding air,
which dilutes the helium concentration taken into the
leak detector.
