Agilent Technologies 7000 Triple Quadrupole GC/MS, Maintenance Manual

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132 Troubleshooting and Maintenance Manual
6
Vacuum System
Common Vacuum System Problems
Air leak symptoms
The most common problems associated with any vacuum system are air leaks.
Symptoms of air leaks include:
• Loud gurgling noise from the foreline pump (very large leak)
• Inability of the turbo pump to reach 95% speed
• Higher than normal high-vacuum gauge controller readings
The 7000 Triple Quad will not pump down successfully unless you press on the
side boards (analyzer doors) when you turn on the MS power. Continue to
press until the sound from the foreline pump becomes quieter.
Pumpdown failure shutdown
The system will shut down both the high-vacuum and the foreline pump if the
system fails to pump down correctly. It takes approximately 10 minutes for the
foreline pump to achieve 300 mTorr, which then starts the turbo pump. If the
turbo pump speed is below 80% after an additional 10 minutes, the system
shuts down.
This is usually because of a large air leak: either the side plates have not
sealed correctly or the vent valve is still open. We suggest this pumpdown
sequence:
1 Leave the vent valve partially open.
2
Start the pumpdown while holding the side plates closed.
3
When you hear a hissing sound, release the side plates and close the vent
valve.
To restart the MS, find and correct the air leak, then switch the power off and
on. Be sure to press on the side plates when turning on the MS power to
ensure good seals.