Unusual Operating Conditions; Pump Troubleshooting; L/S Pump Replacement Parts And Accessories - Varian 919-0520 Manuel D'instructions

UNUSUAL OPERATING CONDITIONS

If the pump current reads lower than normal for the
pressure, the discharge
extinguished.
To check for the pump being "out of strike"
(discharge extinguished), remove the magnet and
observe the residual current. If the current is the
same with and without the magnet in place, no
discharge exists in the pump.

PUMP TROUBLESHOOTING

SYMPTOM
1) - Slow starting (more than 30
minutes).
2) - Slow pump-down due to
absorption of vapours on pump and
system walls.
3) - Slow starting or slow pump-
down.
4) - Current higher than expected at
any given pressure.

2 l/s PUMP REPLACEMENT PARTS AND ACCESSORIES

Basic pump
Magnet Samarium-Cobalt
HV Bakeable cable,
radiation resistant,
13' (4 m) long with safety
interlock
MicroVac 120 Vac input
MicroVac 220 Vac input
For a complete overview of Varian's extensive vacuum product line, please refer to the Varian Vacuum
Catalogue.
may have been
POSSIBLE CAUSE
Air leaks which limit pressure to
-6
above 10 Torr (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 are
very difficult to remove, even by
baking.
High voltage feedthrough is leaking.
Ion pump leakage current causing
higher pressure reading.
919-0520 919-0521
Cables
Control Unit
14
TECHNICAL INFORMATION
1. To restart the discharge, tap the pump body
with a penny held between the thumb and
forefinger, or heat the pump body locally with
a small soldering iron. This should liberate
surface gas within the pump and restart the
discharge. NEVER strike the pump with hand
tools.
2. If the magnet strength is below its rated level,
the pump discharge and speed will be
reduced and the discharge may extinguish at
a pressure below 1 x 10
CORRECTION PROCEDURE
Leak check the vacuum system
with a helium leak detector.
Heat the system walls, thereby
accelerating the desorption
process. Baking mobilizes the
vapours so they can be cracked
and pumped by discharge.
Replace the feedthrough.
Highpot the pump.
PART NUMBER
919-0522 919-0523
919-0038
929-0706
929-0200
929-0201
-7
mbar.
919-0524
87-900-091-01(B)