VS Series Helium Mass Spectrometer Leak Detectors
DRAFT 4/23/15
B-7
Figure B-8 Vacuum System
B.3.3.2 Pressurized Systems
Many different types of pressurized systems also need to be leak-free. These systems can be
charged with helium or some mixture of helium and another gas such as nitrogen. If a
diluted helium mixture is used, the helium signal is diminished proportionally. For example,
if a mixture of 10% helium and 90% nitrogen is used, the signal reads 10% of the actual
value of the leak, or a decade lower. This may be acceptable in many cases as system leak
checking is usually to locate rather than quantify leaks. Once the system has been charged
with an appropriate amount of helium, leak checking can be performed by means of a
sniffer probe, or by bagging suspected leak sites so that leaking helium accumulates to a
detectable level.
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