Chemglass AF-0349 Welch Vacuum Pump - Manual (Page 17)

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Section 5: OPERATION
5.01 Starting Procedure
Before using the pump for the first time, it is a good idea to spend a few minutes inspecting the pump and its electrical
and vacuum connections. Review Section 1: Installation as required.
Check the AC power outlet to be sure that it is the same voltage and phase as the pump motor. Connect the power
cord to the power outlet and recheck the oil level.
Close off the pump intake and the gas ballast valve, and run the pump at blankoff for a few minutes. The gurgling
noise should go away after a few minutes of running; it is caused by the high volume of air that flows through the
pump when the pump is first turned on. If the gurgling noise does not stop, check the oil level to see if it is low, and
check the pump intake fitting to be sure that it is tight. Once proper pump operation has been verified, the pump intake
can be opened to the vacuum system.
After running the pump for a few minutes, check the oil level again. If the level is too high or too low, stop the pump
and add or remove oil as needed. Stop the pump and vent it to the atmosphere before adjusting the pump fluid level.
Before starting the pump when connection to the vacuum system, check all vacuum connections.
5.02 High Pressure Operation
The Vacuum Pumps are designed to be most efficient when operated at or near their ultimate blankoff pressure.
When operated at elevated pressures for long periods of time, the pump will run hotter. Additional cooling may be
required for both the pump and the motor. At elevated ambient temperatures under these conditions, the thermal
protection switch may cut out. The oil may tend to thin out at these temperatures, losing its ability to lubricate
effectively.
During operation at these pressures, oil mist may be generated at the exhaust port. The mist has the appearance of
a small cloud of smoke. Use of an Exhaust Filter with coalescing element is required. An exhaust filter with an oil
drain back feature is highly recommended. See Section 9: Accessories.
NOTE: If operating this pump for prolonged periods of time at or above 10 Torr,
contact the Welch Vacuum Technical Service Department for further information and precautions.
5.03 Shutdown Procedures
A few simple precautions are necessary before performing a pump shutdown. If a gauge is connected to the system,
first isolate the gauge, then turn off the power to the pump and open the system to the atmosphere.
NOTE: The intake isolation valve will automatically close when power to the pump
is turned off. This will maintain vacuum in the system (if the pump remains
connected to the rest of the system). For Model 8925, if the gas ballast is open, the
system will not maintain vacuum (same as section 2.06).
If the pump is disconnected from the system for any length of time, cover the pump intake with a rubber stopper or
other suitable cover to protect the pump against contamination. An intake screen is furnished to prevent loose
particles from entering.
If the exhaust port is open, that should also be covered. If the pump oil is contaminated and the pump is going to be
stored for a prolonged period, the oil should be changed before the pump is stored. Even if a pump is stored for a long
period with oil initially in good condition, check the oil when the pump is restarted, and change the oil if necessary.