Welch Vacuum 8925 Direct Drive Rotary Vane Pump - Manual (Page 19)

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6.02 Oil Change
The best time to change the oil is when the pump is warm and the oil is less viscous.
Before attempting an oil change, the pump must be disconnected from the power outlet.
6.02.1 Changing the Oil on Models 8907, 8912 and 8917
To drain old oil, rotate the drain valve counter-clockwise until the handle will no longer turn. A 6-12 in.
length of 3/8” I.D. tubing can be fitted on the oil drain nipple to direct the flow of oil neatly into a bottle
or other container. When the old oil has been removed, close the drain valve by rotating it clockwise
until the handle will no longer turn.
6.02.2 Changing the Oil on Models 8905, 8920 and 8925
Oil Removal: Drain the oil into a container by removing the plastic plug located below and to the left
of the oil sight glass. The pump may be tilted to remove residual oil out of the oil reservoir.
6.02.3 Oil Fill
Replace the oil drain plug, remove the plastic oil fill plug located on the top of the oil reservoir. Fill
the pump with vacuum oil until the level reaches the FULL mark of the label next to the oil sight glass.
Do not overfill the pump. The excess oil tends to splash out of the exhaust. Replace the oil fill plug.
Check the oil level again after the pump warms up to its normal operating temperature. Add or remove
oil as needed. It is normal for the oil level to change upon initial start up.
6.02.4 Frequency of Oil Changes
The oil change interval is completely dependent upon the running conditions of temperature, operating
pressure, hours of daily operation, and upon the materials pumped. Clean, dry air at pressures below 50
mtorr are the most forgiving conditions. To determine your own oil change interval, visually monitor
the pump oil conditions at regular intervals. If you suspect harsh operating conditions, daily visual
checks are recommended. When the oil becomes cloudy, dark or includes particles of solids, it is time
to change the oil. Oil may be visually checked through the oil level window. However, a much better
check is to use the drain to draw out 20-50 ml into a small glass beaker and view the oil with a light
behind it. Clean oil can be returned to the pump through the oil fill port.
Be sure to use only DIRECTORR® Premium or Gold Oil.
The ultimate pressure guarantee applies only if those oils are used.
6.03 Developing a Maintenance Schedule
After studying many examples of pump failure, Welch has found the most common reason is poor
condition of the oil. This is why a regular maintenance schedule for the oil is critical to obtain the
longest service life out of your Vacuum Pump. Welch recommends that you examine the condition of
the oil on a daily basis in the early days of a new process or experiment. Look for discoloration of the
oil and whether the oil level is rising. The discoloration can indicate deterioration of the oil, and a rising
oil level can indicate condensation of vapors is occurring in the pump.
Once you have determined how long it takes for the oil to break down in your application, or become
contaminated, choose your oil change interval, so that the pump always operates with good quality,
uncontaminated oil.
WARNING
Hot oil can cause burns. Operating temperarue of the oil
is typically 140 degrees Fahrenheit or higher.
Avoid skin contact with oil.