Agilent Technologies 5975C TAD VL MSD, Troubleshooting And Maintenance Manual

Page: 53 / 276

General Troubleshooting
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5975 Series MSD Troubleshooting and Maintenance Manual 53
Air Leaks
Air leaks are a problem for any instrument that requires a vacuum to operate.
Leaks are generally caused by vacuum seals that are damaged or not fastened
correctly. Symptoms of leaks include:
•
Higher than normal analyzer chamber pressure or foreline pressure
•
Higher than normal background
•
Peaks characteristic of air ( m/z 18, 28, 32, and 44 or m/z 14 and 16)
•
Poor sensitivity
•
Low relative abundance of m/z 502 (this varies with the tune program used)
Leaks can occur in either the GC or the MSD. The most likely point for an air
leak is a seal you recently opened.
In the GC, most leaks occur in:
•
GC inlet septum
•
GC inlet column nut
•
Broken or cracked capillary column
Leaks can occur in many more places in the MSD:
•
GC/MSD interface column nut
•
Side plate O-ring (all the way around)
•
Vent valve O-ring
•
Calibration valve(s)
•
GC/MSD interface O-ring (where the interface attaches to the analyzer
chamber)
•
Front and rear end plate O-rings
•
Diffusion pump KF seal
•
Diffusion pump baffle adapter O-ring
•
Turbo pump O-ring