Section 6: Maintenance And Troubleshooting - Welch 8890 Owner's Manual

Section 6: MAINTENANCE AND TROUBLESHOOTING

6.1 Vacuum Problems
Inability to attain sufficient vacuum in a system is usually due to leakage, contamination, or unusual outgassing. A
system must be thoroughly clean and free from leaks to operate efficiently. If the system is found to be clean and
leak-free, but vacuum problems still exist, the pump should be checked. A simple way to test the pump is to
measure its ultimate pressure capability. This can be done by disconnecting the pump from the rest of the system
and connecting a pressure gauge directly to the pump intake. (Be sure to seal the pump intake from the
atmosphere.) The gauge can be any type that is suitable for the pressure levels expected. Run the pump until the
gauge indicates no further reduction in pressure, and compare the pressure reading to the pump's ultimate pressure
rating.
If the pump meets its ultimate pressure specifications only when disconnected from the rest of the system, the
fault must be elsewhere in the system. If the pump's ultimate pressure is unusually high, the pump may be badly
contaminated, low on oil, or mechanically defective. However, if the pressure is only slightly higher than the
pump's guaranteed pressure, an oil change may be all that is needed to bring performance up to specifications.
Be sure to use only DIRECTORR® Premium Oil in the Model 8905 Vacuum Pump; the ultimate pressure
guarantee does not apply if other types of oil are used.
The most common cause of efficiency loss in a vacuum pump is contamination of the oil, which is usually caused
by foreign particles and/or condensed vapors. The condensate emulsifies with the oil, and when the oil is
recirculated, the condensate evaporates. The resulting vapor then reduces the ultimate vacuum attainable in the
system.
Some foreign particles and vapors from sludges with the oil. The presence of sludge in the oil impair its sealing
and lubricating properties, and eventually could cause pump seizure. Therefore, periodic oil changes are
necessary to maintain efficient operation of the system. The interval at which oil changes are required is different
for each system; experience will help you determine the proper interval for your system and process.
6.2 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.
WARNING
The drain oil is hot and can cause burns. Operating temperature of the oil
is typically 140 degrees Fahrenheit or higher. Avoid skin contact with the oil.
Oil Removal: Drain the oil into a container by removing the black plastic drain plug located below and to the left
of the oil sight glass. The container should hold at least one quart of oil. The pump may be tilted to remove
residual oil out of the oil reservoir.
Oil fill: Replace the oil drain plug, remove the black 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 as seen from 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.
NOTE
When filling the pump with oil, be sure to use only DIRECTORR® Premium
Oil.The ultimate pressure quarantee applies only if this oil is used.
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