
15
COMPONENT DESCRIPTION
3.4
PROTECTIVE DEVICES
The compressor package is equipped with several safety devices to protect the equipment and the end
user. A pressure relief valve is mounted on the sump tank to prevent the compressor package from exceed-
ing the rated pressure of its components. A temperature sensor and pressure transducers will send a
signal to the microprocessor to shut the compressor down if temperature or pressure limits are exceeded
3.4.1 RECEIVER PRESSURE SENSOR (P1)
This sensor is supplied to protect your compressor in case the pressure in the sump tank or compres-
sor unit discharge exceeds their rated pressure. This sensor is the first line of protection in the system,
followed by the tank relief valve. The second feature utilized by this sensor is start-up protection due to
reverse rotation. If the sensor does not see a positive pressure at time of start-up, the compressor will
be shut-down in the attempt to protect the compressor unit due to reverse rotation (anti-start protection
– ASP). This sensor is located to the right of the electrical control panel by the pressure regulating control
valve. It compressor is equipped with optional enclosure, removal of the access panel located to the right
of the electrical control panel will expose the sensor and regulating control valve.
3.4.2 PRESSURE RELIEF VALVE
The pressure relief valve will open to relieve excess pressure in the sump tank if the pressure exceeds the
set point. The valve will automatically reset to its reset pressure point after the excess pressure is relieved.
The pressure relief valve is ASME compliant and rated at 200 psig to match the rating of the tank. It is
located on the upper side (wet side) of the sump tank.
3.4.3 COMPRESSOR DISCHARGE TEMPERATURE (CDT) SENSOR
This sensor is supplied to control shut-down of the compressor in the presence of high unit discharge
temperature. The sensor is non-adjustable and preset at 240°F(116°C). The sensor probe is located in
the compressor unit discharge outlet side port.
3.5
AIR/OIL DISCHARGE SYSTEM
After compression, the high pressure air and oil mixture travels to the sump tank where the air and oil is
separated by change of direction and reduction in velocity. The oil is stored in the bottom portion (sump) of
the tank until it is recirculated through the system.
The remaining oil in the air is reduced to 2 ppm by the air/oil separator in the top portion of the sump
tank. Oil removed by the separator collects the bottom pan of the element and is returned to the low pres-
sure side of the compressor unit by the scavenger line. After passing through the air/oil separator, the
compressed air then continues through to the minimum pressure valve.
Initially, the pressure is held by the valve until the set point of the valve is reached. Once the minimum
pressure is met, the minimum pressure valve will allow air to pass through to the aftercooler to reduce
the temperature of the air from a nominal 180°F to 100°F (82°C to 38°C). This change in temperature
condenses the water so that it can be removed by a water separator equipped with an electric drain valve.
After leaving the water separator, the compressed air can then begin building pressure in the air system for
use.
3.5.1 SUMP TANK (RECEIVER)
The sump tank (also referred to as a receiver, reservoir or separator tank) collects and holds oil to be
circulated through the compressor cooling system. Air and oil discharged from the compressor unit are
separated in the sump tank by change of direction and reduction in velocity. The sump tank is an ASME
pressure vessel rated for 200 psig maximum operating pressure.
3.5.2 AIR/OIL SEPARATOR
The air/oil separator (also referred to as a separator element) separates the majority of the remaining oil
in the air before the air passes through the minimum pressure valve to the aftercooler. The air/oil separa-
tor is supplied with staples in the gaskets to ground the separator to the sump tank to prevent flash fires
created by build-up of static electricity. The air/oil separator is located in the upper part of the sump tank
under the lid.