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TM 10-4310-391 -13&P
the sound of the exhaust Is similar to that of a pump operating against a large leak Because of the increased
pressure Introduced Into the compression stroke, the pump must work a little harder to function, thus resulting
In an Increased operating temperature of approximately 8°C over a prolonged period of time Tests have shown
that continuous and prolonged operation for several weeks under these condition Is not injurious to the pump.
II-4f. Other Forms of Contamination Control
The application of the vented-exhaust valve Is a moderate and very successful method for the removal of
condensable vapors For very heavily laden systems, other means of removal such as ail separators may be
required For gild cases of contamination the simple expedient of a cold trap or a change of ail may serve the
purpose.
III. MAINTENANCE
III-1.
VACUUM PROBLEMS
III-1a.
Pressure Determinations
Leakage, contamination and unusual outgassing are the general causes of problems associated with poor
vacuum To operate at maximum efficiency a system must be thoroughly clean If the system Is completely
clean and free from leaks, and unwarranted vacuum problems still exist, the pump should be checked A simple
criterion for the condition of a mechanical pump is a determination of bits ultimate pressure capability This can
be accomplished by attaching a gauge directly to the pump The gauge may be any suitable type provided
consideration Is given to the limitations of the gauge being used Refer to Paragraph 1-9 for further suggestions
If the pressure s unusually high the pump may be badly contaminated, low on ail or malfunctioning On the
others hand. If the pressure Is only slightly higher than the guaranteed pressure of the pump. an ail change may
be all that Is required.
III-1b. Oil Contamination
The most common cause of a loss In efficiency m a mechanical pump Is contamination of ail It Is caused by
condensation of vapors and by foreign particles The undesirable condensate emulsifies with the ail which Is re-
circulated and subjected to re-evaporation during the normal cycle of pump activity thus reducing the ultimate
vacuum attainable Some foreign particles and vapors may form sludge’s with the oil impair sealing and
lubrication and cause eventual seizure A vented-exhaust valve Is helpful In removing vapors, especially water,
but it Is not equally effective on all foreign substances, therefore, periodic ail changes are necessary to
maintain efficient operation of the system The required frequency of changes will vary with the particular
system Experience with the process will help you determine the normal period of operation before an ail
change Is required.
III-2. OIL CHANGES AND OIL LEVEL
III-2a. Draining the Pump
An ail change Is most easily accomplished when the pump Is warm and the ail Is less viscous Use a container
large enough for the ail In the particular pump Stop the pump, and open the drain valve A thorough Job may be
accomplished by tipping the pump slightly If this Is possible The small residue remaining In the pump may be
forced out by hand-rotating the pump pulley with the exhaust port partially closed and the intake port open
Closing the exhaust port completely under these condition will create excessive pressure at the drain valve
which may cause the ail being brained to splatter.
III-2b. Flushing the Pump
After removing all the ail close the drain and pour about four ounces of clean DuoSeal ail into the intake port.
Open the exhaust port and operate the pump for about a minute with the Intake port alternately opened and
closed to agitate and circulate the fresh ail Again stop the pump, drain the flushing ail and force out the residue
as before The amount of flushing ail and the number of flushes will be determined by the extent of
contamination and the color of the ail Under no circumstances should anything other than DuoSeal ail be used
for flushing a mechanical pump The higher vapor pressures of other types of ail will cause difficulty later In the
attainment of a high vacuum.
III-2c. Refilling the Pump
After you are satisfied that the pump has been thoroughly flushed, refill the pump by pouring new DuoSeal ail
into the exhaust port fill to the Indicated level and start the pump with the Intake closed .
(Continued on page 11)
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