2-1
switch. This should be done only after the root cause of a problem has been determined and
the appropriate corrective action taken.
SECTION II
CAUTION
________
Damage to Pump
Do not turn on the heater without fluid in the pump. This may ruin the
heaters and damage the pump.
Damage to Pump Fluid
• Do not air-release the pump while the boiler is hot. Most diffusion pump
fluids are heat-sensitive and will break down under these conditions.
• Do not operate the pump without the internal splash baffle or foreline
baffle in place. If the splash baffle is omitted, the pump may be unsta-
ble and operate at low speed. If the foreline baffle is omitted, there
may be more than usual fluid loss.
• Do not operate the pump for extended periods at inlet pressures above 1
micron (.133 Pa). High-pressure operation may cause excessive back-
streaming.
• Do not operate the pump heater unless the cooling water is circulat-
ing. It wlll cause the pump and fluid to overheat.
OPERATION
2-1
STARTUP PROCEDURE
a
During initial operation of the diffusion pump, a fresh charge of diffusion pump oil may go
through a degassing process. This may result in inlet and foreline pressure fluctuations. These
pressure fluctuations are normal.
b
Visually inspect the sight glass assembly to ensure that the diffusion pump has been charged
with the proper amount of diffusion pump fluid. When properly filled, the oil level (when the
pump is cold) will be even with the FULL/COLD mark on the oil level indicator.
c
Evacuate (rough pump) the diffusion pump with a mechanical backing pump (customer-
supplied). The pressure must be reduced to less than 0.5 Torr. The backing pump should
remain connected to the foreline of the diffusion pump.
d
Turn on the cooling water supply to the pump body. Check that the cooling water is not being
supplied to the quick cool coil at this time.
e
Turn on the power to the diffusion pump heater.
f
Monitor inlet and foreline pressures.
g
During operation of the diffusion pump, the gas load at the inlet should not exceed the
maximum throughput capability of the pump. The forepressure should not exceed the
specified tolerable forepressure.
Summary of Contents for VHS-6
Page 27: ...Replacement Parts 5 2 ...
Page 28: ...Replacement Parts 5 3 ...
