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Technical Information
Startup Procedure
To start the pump:
1
Evacuate the diffusion pump using a mechanical roughing pump to below 0.5
Torr (0.67 mbar). The diffusion pump will not function unless the discharge
pressure is less than the tolerable forepressure.
2
Turn on the cooling water supply to the pump body and check that adequate
flow is provided by examining the amount of water discharged at the visual
drain points
To prevent harmful collection of condensate on the boiler plate, heater, and
CAUTION
heater terminals, do not operate the Quick Cool coil when the pump is cold
or out of service.
3
Switch on the power to the diffusion pump heater.
4
Check inlet and forepressure performance by means of the system
instrumentation.
Humid Environments
Due to their inherent design, diffusion pump heaters absorb moisture. This results
in a decrease in heater insulation resistance (higher leakage current). Under normal
conditions, the decrease in insulation resistance is a momentary condition that
occurs on startup. The amount of moisture adsorbed is depends on the
temperature, humidity, and the length of time the heaters have been exposed to this
environment without power being applied. If diffusion pumps are started in high
humidity environments, the heaters may be damaged on startup at full power. To
overcome the effect of moisture absorbed in the heaters, start pumps at a low line
voltage, e.g., 50% of line voltage, for a period or time to slowly expel any moisture.
High Throughput Diffusion Pumps User Manual
57
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