Operation
d.Check inlet and forepressure performance by means of the system instrumentation.
e.During operation, the gas load at the inlet of the diffusion pump should not exceed the maxi- mum throughput capability of the pump. This means that the pressure at the inlet flange should not (except in transient conditions) exceed approximately 1 x 10-3Torr (.133 Pa). Dur- ing operation, the discharge or fore pressure must be below the specified tolerable forepres- sure.
2-2 SHUTDOWN PROCEDURE
WARNING
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Boiler temperatures reach 530°F (275°C) which can cause serious burns when touched. Always ensure surfaces have cooled near room temperature before touching them.
Air release or admitting air to a pump with a hot boiler, especially when it is under vacuum, permits a strong oxidizer to contact the hot pump oil and thereby increases the risk of an explosion.
CAUTION
Do not operate the quick-cool coil when the pump is cold or out of ser- vice to prevent harmful collection of condensation on the boiler plate, heater, and heater terminals.
a.Switch off the power to the diffusion pump heaters.
b.Admit cooling water to the quick-cool coil if necessary and continue to circulate it until the pump body just above the boiler heat shield can be touched (approximately 130°F or 54°C). In valved systems which have tight inlet and foreline connections, it is possible to close valves to isolate the diffusion pump at inlet and discharge, to air-release the remainder of the sys- tem, shut off the heat to the diffusion pump, and stop the mechanical pump. With this method, the quick-cool coil does not have to be used. However, the water flow through the pump must be maintained until the boiler cools down below approximately 300°F (150°C).