Pump Troubleshooting - Agilent Technologies VacIon Plus 800 Manual Del Usuario

Technical Information

Pump Troubleshooting

Table 1
Symptom
1) – Slow starting
2) – Slow starting
(more than 30 minutes).
4) – Slow pump-down
due to absorption of
vapours on pump and
system walls.
5) – Slow starting or
slow pump-down.
6) – Current higher than
expected at any given
pressure.
7) – System fails to
achieve desired UHV
vacuum pressure.
226
Possible cause
Starting vacuum pressure too
high.
Air leaks which limit pressure to
above 10-6 mbar and cause
longer starting time.
Vapours and gases admitted to
a system are absorbed on the
walls of the system and pump.
Subsequent reduction in pressure depends on the rate of
depletion of this vapour. Heavy
hydrocarbons are most
troublesome because of their
relative low vapour pressure and
they are very difficult to remove,
even by baking.
High voltage feedthrough is
leaking.
Ion pump leakage current
causing higher pressure reading.
System not fully baked. Water
vapor limits the base pressure.
Correction procedure
Reduce the starting pressure to the value
recommended in Table 1.
Leak check the vacuum system with a
helium leak detector.
Bake the system walls, thereby
accelerating the desorption process.
Baking mobilizes the vapours so they can
be cracked and pumped by discharge (see the section "BAKEOUT OPERATION").
Replace the feedthrough.
Verify that leakage current (see the
dedicated paragraph) occurs and then
high-pot the pump.
Bake the system walls, thereby
accelerating the desorption process.
Baking mobilizes the vapours so they can
be cracked and pumped by discharge
(see the section "BAKEOUT OPERATION").
Agilent VacIon Plus 800 User Manual