52 Troubleshooting and Maintenance Manual
3 CI Troubleshooting
Air Leaks
How do I know if I have an air leak?
Large air leaks can be detected by vacuum symptoms: loud gurgling noise
from the foreline pump, inability of the turbo pumps to reach 95% speed, or, in
the case of smaller leaks, high pressure readings on the high vacuum gauge
controller.
The mass flow controller is calibrated for methane and the high vacuum gauge
controller is calibrated for nitrogen, so measurements are not accurate in
absolute terms:
Familiarize yourself with the measurements on your system under operating
conditions. Watch for changes that may indicate a vacuum or gas flow
problem.
There should not be any peak visible at m/z 32 (O
2
). This almost always
indicates an air leak.
Figure 5 Looking for air leaks
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