Pump Troubleshooting - Agilent Technologies VacIon Plus 150 Instruction Manual

Pump Troubleshooting

Tab. 1
Symptom
1) – Slow starting
2) – Slow starting
(more than 30 minutes).
3) – Slow pump-down
due to long exposure of
viton parts to air.
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.
8) – System fails to
achieve desired UHV
vacuum pressure.
VacIon Plus 150 pumps Instruction Manual
Possible cause
Starting vacuum pressure too high.
Air leaks which limit pressure to above 10
mbar and cause longer starting time.
Viton releases considerable gas after long
exposure to air. (A bell-jar system which
reached 2 x 10 mbar in 24 hours after 30
-8
minutes air exposure, will only reach 1 x 10
mbar in 24 hours after 20 hours air exposure)
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
base pressure.
System not appropriately cleaned for UHV.
Excessive outgassing from walls limits base
pressure.
/ 87-900-102-01 (E)
Technical Information

Pump Troubleshooting

Correction procedure
Reduce pressure to 10
recommended 10
-4
minimum.
Leak check the vacuum system
-6
with a helium leak detector.
With the system under vacuum,
pump for several days, or heat
to 100-150 °C for up to 15
hours.
-7
Bake the system walls, thereby
accelerating the desorption
process. Baking mobilizes the
vapours so they can be cracked
and pumped by discharge (see
section "BAKEOUT
OPERATION").
Replace the feedthrough.
Highpot 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
section "BAKEOUT
OPERATION").
Clean all components for UHV
and bake the system again.
5
mbar
-5
mbar
79/88