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COMPONENT DESCRIPTION
3.5.3 MINIMUM PRESSURE VALVE
The minimum pressure valve maintains the minimum pressure in the sump tank necessary to circulate
oil throughout the compressor and also prevents reverse airflow into the compressor upon unloading or
shutdown. At start-up, the valve remains closed and no output air is supplied until the minimum pressure
is reached. Once the minimum pressure is reached, the valve will open and allow air to enter the system
for use. At shutdown or unloading, a built-in check valve closes to prevent reverse airflow. The minimum
pressure valve is located on top of the sump tank lid.
3.5.4 SCAVENGER LINE
The scavenger line (also referred to as an oil return line) is a small diameter steel tube that picks up any
oil removed from the air by the air/oil separator. Oil picked up by the scavenger line passes through a
sightglass assembly containing an orifice sized for the compressor and a screen to filter the oil before it is
injected back into the compressor unit. The scavenger line is mounted to a tab located on the side of the
tank. The tab fully supports the weight of the assembly for reduced vibration.
3.5.5 FLUID LEVEL SIGHTGLASS AND FILL
The fluid level sightglass and fill allows visual monitoring of the oil level in the sump tank and is the port
through which oil is added. The fluid level sightglass and fill is supplied with a SAE O-ring plug and is
located on the side of the sump tank behind the front right access panel door.
3.5.6 SUMP TANK DRAIN VALVE
The sump tank drain valve allows oil to be drained from the sump tank. It is a ball-type valve that is
plumbed to the frame for external draining. The sump tank drain valve is mounted to the frame end for
easy access.
3.5.7 WATER SEPARATOR (WITH ELECTRIC DRAIN)
The water separator removes condensed moisture from the compressed air after it is cooled in the after-
cooler. The separator is equipped with a condensate drain controlled by an electric solenoid which has an
adjustable timer range that can be changed based on seasonal requirements.
3.6
COOLING AND LUbRICATING SYSTEM
Oil is circulated through the compressor cooling and lubricating system by the minimum pressure main-
tained in the sump tank by the minimum pressure valve. Oil flows from the sump tank to the temperature
control valve where cool oil is allowed to initially bypass the fluid cooler. As the temperature of the oil rises,
the temperature control valve begins to redirect the oil to the oil cooler and eventually all of the oil will
pass through the oil cooler.
In the oil cooler, heat from the oil is transferred to the cooler fins. Airflow produced by the electric-driven
cooling fan removes the heat from the oil cooler. Cool oil then flows through the oil filter where particulate
is removed before entering the compressor unit. Oil in the compressor unit lubricates the internal compo-
nents, cools the compressor unit by absorbing the heat of compression and seals the compressor unit’s
internal clearances.
3.6.1 LUBRICANT
The compressor lubricant is also referred to as compressor fluid or simply as oil. During the compression
cycle, lubricant is injected directly into the compressor unit. The lubricant in a rotary screw compressor
serves three primary functions.
1.
It is a lubricant, supplying constant flow between the moving parts along with the bearings and seals.
2.
It is a coolant, removing the generated heat of compression during operation. The controlled
temperature rise across the unit will be around 40°F.
3.
It is a sealant, sealing the rotors to reduce leakage paths between the rotors and between the stator
housing.
Rotary screw compressor units require specialized lubricant to maintain proper performance. Use of
Sullivan-Palatek lubricants is recommended. Refer to
8.4 Compressor Lubricants
.
3.6.2 TEMPERATURE CONTROL VALVE (THERMOSTATIC VALVE)
The temperature control valve (also referred to as a thermostatic valve) regulates the flow of oil to the oil
cooler based on temperature. When the compressor is first started, the valve allows cool oil to bypass the
oil cooler. As the oil temperature rises, the valve gradually redirects the hot oil through the oil cooler. The
temperature control valve is mounted directly to the pick-up tube from the sump tank.