Gardner Denver AirSmart EAU99T Operating And Service Manual page 60

THERMAL CONTROL (THERMOSTATIC MIXING) VALVE is installed in system as shown in
page 48. This valve is used to control temperature of the oil in both air-cooled radiator and water-cooled
heat exchanger type oil cooler systems. On start-up with unit cold, element is open to bypass, allowing
oil to pass directly from the reservoir to compressor during warm-up. As oil warms, element gradually
closes to the bypass allowing more of the oil from the cooler to mix with oil from the bypass.
After the unit is warmed up, the mixing valve maintains oil injection temperature into the compressor at a
minimum of 150° F (66° C). This system provides proper compressor warm-up and helps prevent
moisture contamination of oil.
To check the element, heat in oil -- it should be fully extended at 150° F (66° C). If the unit shuts down
due to high air discharge temperature, it may be that one or both thermostatic mixing valve elements
( , page 48) are stuck open. Remove the mixing valve and clean all parts thoroughly when
Figure 5-3
flushing the oil system.
Air/oil under pressure will cause severe personal injury or death. Shut down
compressor, relieve system of all pressure, disconnect, lockout and tagout
power supply to the starter before removing valves, caps, plugs, fittings, bolts
and filters.
Compressor, air/oil reservoir, separation chamber and all piping and tubing
may be at high temperature during and after operation.
It is mandatory that any water cooled unit be installed in a shelter heated to
temperatures above freezing (32° F, 0° C).
COMPRESSOR OIL COOLER - WATER-COOLED HEAT EXCHANGER (
exchanger oil cooler is a multiple pass type, with water in the tubes and oil in the shell. The oil
temperature is controlled by the thermal (thermostatic mixing) valve. The optional water control valve
may be used to conserve water.
Oil cooler malfunction may be traced by checking pressure at oil inlet and outlet. At normal operating air
service pressure 65 psig to 150 psig, (4.5 bar to 10.3 bar) with the unit warm, a pressure drop of 3 psi to
15 psi (.2 to 1 bar) can be expected between the oil inlet and the oil outlet.
Water pressure drop from water inlet to outlet will vary with the inlet pressure and amount of water
flowing. A normal pressure drop may range from 5 psi to 10 psi (.3 bar to .7 bar). Any change in the
pressure drop from that normally held may indicate tube leakage or fouling and should be investigated.
13-10-618 Page 59
Figure 5-3
, page 48) - The heat
Figure 5-3
,