Agilent Technologies 9191610, User Manual

Page: 90 / 98

5 Technical Information
Pump Troubleshooting
90/98 VacIon Plus 300 pumps User Manual / 87-900-103-01 (H)
Pump Troubleshooting
Tab. 2
Symptom Possible cause Correction procedure
1) – Slow starting Starting vacuum pressure too high. Reduce pressure to
10
-5
mbar recommended
10
-4
mbar minimum.
2) – Slow starting (more than 30
minutes).
Air leaks which limit pressure to
above 10
-6
mbar and cause longer
starting time.
Leak check the vacuum
system with a helium leak
detector.
3) – Slow pump-down due to long
exposure of viton parts to air.
Viton releases considerable gas
after long exposure to air.
(A bell-jar system which reached
2 x 10
-8
mbar in 24 hours after 30
minutes air exposure, will only
reach 1 x 10
-7
mbar in 24 hours
after 20 hours air exposure).
With the system under
vacuum, pump for several
days, or heat to 100-150 °C
for up to 15 hours.
4) – Slow pump-down due to
absorption of vapours on pump and
system walls.
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.
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”).
5) – Slow starting or slow pump-
down.
High voltage feedthrough is
leaking.
Replace the feedthrough.
6) – Current higher than expected
at any given pressure.
Ion pump leakage current causing
higher pressure reading.
Highpot the pump.