SECTION 6 OPERATION
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6
6.4 Shutting Down
CAUTION
After having operated the turbo molecular pump for evacuation of corrosive gas, keep the
pump internal as vacuumed even after shutdown. Inflow of water content in the air to the pump
internal would cause rapid corrosion trouble of the pump internals. The pump corrosion may
result in damaging the vacuum vessel interior and other units, causing pressure fluctuation by
stopping the pump and dispersal of parts.
CAUTION
When reducing internal pressure of the turbo molecular pump up to around the atmospheric
pressure by use of inert gas, etc., adjust the pressure reducing valve so that the internal pressure
of the same pump does not exceed 20 kPa [GAUGE].
For shut-down of the turbo molecular pump, follow the sequence below.
Preparations Prior to Shutting Down Operation:
(1) Check that process gas inflow is in complete stop. When main valve is provided between
the turbo molecular pump and vacuum chamber, close the valve, too.
(2) When purge gas is being fed into the turbo molecular pump, stop the gas feed, too.
(3) When forevacuum valve is provided between the turbo molecular pump and backing
vacuum pump, close the valve, too.
Shutting Down Sequence in LOCAL Mode:
(1) For more information regarding an operation, please refer to the Power Supply Unit
Instruction Manual.
(2) Stop the cooling water flow. (for cooling water method)
When the turbo molecular pump is turned off after pumping a corrosive gas, maintain a vacuum
inside the turbo molecular pump or purge the interior of the pump with an inert gas.
Further, in such a case when a hydraulic rotary vacuum pump is used as backing vacuum
pump and there is possible reverse flow and diffusion of oil from the backing vacuum pump,
return the pump internal pressure to atmospheric pressure using dry nitrogen gas, after complete
shut-down of the pump [ROTATION lamp goes out], to prevent the turbo molecular pump from
being contaminated with oil vapor.
For shutting down the turbo molecular pump in running at high speed with infeed of dry nitrogen
gas to the pump, keep the nitrogen gas flow rate at 1500 mL/min maximum.
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