Chemglass AF-0350 Welch Vacuum Pump - Manual (Page 6)

Section 2: OPERATION
2.1 Starting Procedures
2.1a Starting a DUOSEAL Pump
Before attaching the pump to a system it is well to familiarize yourself with the function and action of the
pump which you have now required.Remove the intake and exhaust port plugs and temporarily provide a
stopper for the intake and a dust cap for the exhaustReview the power requirements as described in Section
1.6.
CAUTION
Do not run this pump with the intake open directly to the atmosphere.
The pump will overheat, excessive oil mist will be emitted from the
exhaust and the pump will eventually seize.
2.1b Starting of the Model 1392 with Diffusion Pump.
1. Turn on Mechanical pump ONLY until a pressure of 100 millitorr or less has been reached.
WARNING
Do NOT operate diffusion pump until a pressure of 100 millitorr
has been reached.Turning on the diffusion pump before a pressure
of 100 millitorr has been reached will damage your diffusion pump
and may cause serious damage to surroundingequipment and personnel.
2. After a pressure of 100 millitorr had been reached by the mechanical pump, plug in the diffusion pump.
Make sure diffusion pump has oil in it at an appropriate level before turning it on. Check the oil indicator sight
glass to confirm oil level. Also, make sure that fan is on when operating diffusion pump. Note that it will take
the diffusion pump a few minutes to warm up.
Refer to the Varian diffusion pump manual for more information.
2.1c Cleanliness
Take every precaution to prevent foreign from entering the pump. A fine mesh screen is provided for this
purpose in the intake passage of all DUOSEAL pumps.
2.1d Oil Level Determination
The amount of oil suitable for efficient and satisfactory performance should be determined after the pump has
reached its operating temperature. Initially, however, the pump should be filled with fresh oil while the pump is
idle. Fill the pump until the oil level falls half way of the oil level window. If after a short period of operation
the level should fall, it is likely the result of oil entering some of the interior pockets of the pump. If the oil level
rises, this signifies oil has drained into the pump cavity while pump was idle. Shut off pump, then drain oil
down to proper level.
If a gurgling sound occurs, additional oil must be added. Mechanical pumps will gurgle in varying degrees
under four conditions of performance: [a] when operating at high pressure as in the beginning cycles of
evacuation of a chamber; [b] when the oil level in the pump reservoir is lower than required; [c] when a large
leak is present in the system; and [d] when the gas ballast is open. Awareness of the possibilities will save
time in setting up a system. Best performance of a mechanical pump is generally obtained after sufficient time
has been allowed for the pump to come to operating temperature.
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