VS Series Helium Mass Spectrometer Leak Detectors
DRAFT 4/23/15
B-3
Figure B-2 Selective Ion Pump Detector
B.3 Methods of Leak Testing
There are many different ways to leak test parts using helium as a tracer gas. In general, the
leak detection method is selected based on the actual working conditions of the part being
tested. It is recommended that during leak testing, the same pressure differential be
maintained and in the same direction as exists during the actual use of the part. For
example, a vacuum system is tested with a vacuum inside the chamber, while a compressed
air cylinder should be tested with a high pressure inside the cylinder.
There are two general concerns when leak testing. One is the location of leaks and the other
is the measurement of the total leakage rate of the part, as some leakage may be acceptable.
In many cases, parts may be first tested to determine if they pass an acceptable level, and if
not, the part may be taken off line and subjected to a second test with the intent of locating
the leak. Additionally, many parts may be tested in batches. If a batch fails, the individual
parts in that batch may then be tested separately to identify the leaking part(s).
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