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MOISTURE IN THE OIL SYSTEM – During periods of low ambient temperatures, light duty cycles, high
humidity, or in the event of thermal mixing valve malfunction, the oil charge residing in the sump may not
reach a high enough temperature to keep water vapor from condensing as liquid water, a condition that
contaminates the oil charge, may cause excessive oil carryover, or result in compressor failure.
To help the end user determine if the compressor package is operating under potential water condensing
conditions, the charts in Fig 5-3 and 5-4 have been provided. To use, find the prevailing ambient
temperature along the horizontal scale of the chart, move vertically from this point until intercepting the
slanted line corresponding to the operating discharge pressure; and finally, move horizontally from this
point to read the corresponding water vapor dew point on the vertical scale. The compressor discharge
temperature must be maintained at a minimum of 10°F (5.5°C) above this dew-point temperature to
prevent condensation accumulation in the lubricant reservoir. Note that the charts conservatively assume
100% relative humidity for the ambient air.
The presence of water in the oil may be identified by one of the following means:
Oil drawn from the oil sampling valve attached to the sump (see Fig 1-3).
Oil volume drained during an oil exchange.
Periodic (e.g., every 2000 hours) oil sample analyzed by a reputable laboratory.
If water is found in the oil, drain sufficient volume of oil until no visible water is found, the heavier water
will collect at the low elevations of the oil system, thus it will likely be expelled first. If this condition
persists, consider the following solutions to avoid water condensation in the compressor oil:
Make sure that the correct setting for the thermostatic mixing valve element is used, value is
stamped on valve body.
If the standard thermostatic element (85º/185°F) does not prevent water condensation, consult
your application with Gardner Denver. The standard thermostatic element may be replaced with
a high temperature one (98ºC/208°F) and the oil charge changed (see "Lubricant Change
Procedure in this section) with a high temperature one (AEON 9000TH). Depending on the
prevailing ambient temperature, the controller setting for the high discharge temperature
shutdown may have to be reset to 240ºF also.
THERMOSTATIC MIXING VALVE. This device, housed within the compressor body, mixes hot and
cooled oil and delivers a tempered mixture to the oil filter and finally the compressor injection port, see Fig
1-3 for its location.
Its thermostatic element expands with heat, it will stroke from just opening to fully open state within a
27°F (15°C) temperature change. Within these two temperature limits the valve gradually mixes hot
separator oil with cooled heat exchanger oil to maintain a nearly constant compressor discharge
temperature. Above this range of oil temperature, the valve blocks all hot oil and only cooled oil is
delivered.
The valve's nominal setting is stamped on the valve body. It may be verified by immersing the valve
assembly into an open container with lubricating oil, raising its temperature to its nominal setting and
checking that the element strokes fully from closed to open.
Standard valve opening temp = 158°F (70°C), fully open temp = 185°F (85°C)
Optional valve opening temp = 181°F (83°C), fully open temp = 208°F (98°C)
Optional Element. If the compressor is used in a predominantly cold (<32ºF, 0ºC) and/or humid
environment, proper oil viscosity and avoidance of water vapor condensation in the oil system may be
achieved by using a higher setting (208ºF, 98ºC) thermostatic element. Consult Gardner Denver for
details.
OIL SUMP (RESERVOIR) - This device provides the inertial separation of air and oil streams discharged
by the compressor - the bulk (98%) of the air/oil separation is done at this step. It also serves as a
holding and degassing volume for the major portion of the oil charge. It provides limited air storage for
control and gauge actuation.
13-25-629 v03
Page 45
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