Sullivan-Palatek D185PKR, Operation & Service Manual

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20 COMPONENT DESCRIPTION
4.6 CAPACITY CONTROL SYSTEM
The control system is designed to match air supply to air demand and to prevent excessive discharge
pressure when the compressor is operating but air is not being used.Control of air delivery is accomplished
both by inlet valve regulation and engine speed control as directed by the adjustable discharge pressure
regulator valve.
The following overview explains the operation of the control from a condition of “no load” to a condition of
“full capacity” at working pressure. For the working pressure range of your machine, refer to applicable data
in the Specifications section.
The inlet valve cylinder pressure chamber is pneumatically connected to the dry side of the receiver via the
pressure regulator valve. When the receiver tank pressure is below the set point of the regulator valve no
pressure will exist in the inlet valve chamber. Under these conditions, the inlet valve will remain wide open,
causing the compressor to deliver full capacity.
As the demand for air decreases, the receiver pressure will rise, and when this pressure level exceeds the set
point of the pressure regulator valve, control signal pressure will be allowed to enter the inlet valve chamber,
which in turn will move the modulating piston and the valve plate to a closed condition, thereby throttling
the incoming air.
When less than full capacity is required, receiver pressure increases, thereby opening the pressure regulator,
which allows a signal from the pressure transducer to reduce the engine speed until it matches the air
requirements from 100% down to 60%. From 60% down to 0% both engine speed reduction and inlet valve
modulation act together to reduce air output.
NOTE! The compressor can only produce its maximum rating of air flow at rated pressure (rated CFM at rated psig).
If the tank pressure continues to decrease when the machine is at full speed and the inlet valve fully open, a
larger capacity compressor or multiple compressors may be required for the customer’s job needs.
4.6.1 INLET VALVE
The inlet valve assembly is the heart of the control system, which regulates the amount of air entering the
compressor. The engine speed is regulated by the Sullivan-Palatek Electronic Controller (SPEC). From full
to approximately 60% capacity, the delivery is controlled by engine speed and a gradual closing of the inlet
valve. When unloaded the inlet valve is closed to prevent atmospheric air from entering the compressor.
4.6.2 START-RUN VALVE
The start-run valve is used to bypass the compressor pressure regulator valve. This results in reduced
engine load at start-up. Once the engine is warmed up, the valve can be moved to the RUN position. In the
START position, the start-run valve is open. In the RUN position, it is closed.
4.6.3 AUTOMATIC BLOWDOWN VALVE
The automatic blowdown valve relieves pressure in the system upon shutdown. It is closed when the
compressor is in operation; however, at shutdown, the inlet valve closes, the unit becomes pressurized and
sends a pressure signal to open the normally closed blowdown valve.
4.6.4 RECIRCULATION VALVE
The recirculation valve allows air under the inlet to keep the compressor from cavitating, thereby increasing
air end life. The recirculation valve functions automatically in response to the regulated control pressure.
When it receives the unload signal to the inlet valve, the recirculation valve opens, allowing a small amount
of pressurized sump air to be recirculated through the compressor. This air holds a positive pressure signal
on the inlet side of the air end to prolong the shaft seal life.
4.7 NOISE CONTROL SYSTEMS
Noise control systems incorporated in this compressor have been designed to meet the requirements
of federal noise control regulations. The principal components of the noise control systems include the
enclosure, engine exhaust system, and compressor intake system. The enclosure has been designed to
provide the required noise reduction while maintaining a good distribution of cooling airflow to the radiator
and oil cooler.