Control System, Functional Description - Vanair ADHD Powertech Installation, Operation, Maintenance And Parts List Manual

DESCRIPTION
2.5

Control System, Functional Description

Refer to Figure 2-1. The purpose of the control system is to regulate the amount of air
intake in accordance with the amount of compressed air demand. The Control System
consists of an air inlet valve, a control regulator, blowdown valve, and tubing
connecting the various components together.
The functional descriptions of the Control System are given below in two distinct phases
of operation. These descriptions will apply to all control systems.
Start - 0 to 40 PSIG
The sump pressure will quickly rise from 0 to 40 psig. During this period the compressor
inlet valve control chamber has received no air signal from the pressure regulator. The
spring attached to the control plunger holds it in a wide open position allowing the
compressor to work at full-rated capacity. As the compressor operates at full-rated
capacity, the engine speed control remains fully open enabling the trucks engine to run at
full speed. The rising sump pressure begins to pass air through the minimum pressure
orifice.
Modulation - 100 to 115 PSIG
Should less than the rated capacity of air be used, the service line pressure will rise above
100 psi. The control pressure regulator gradually opens, applying pressure to the spring
side of the inlet valve piston. This causes the inlet valve to partially close. With the
service line closed and no air demand, the control pressure regulator opens fully, closing
the inlet valve.
When air demand then increases, the sump pressure will fall below 115 psig (7.9 bar).
The control pressure regulator valve will close, and the inlet valve to open. The
compressor will then be operating at full load condition.
Shutdown
The blowdown valve is normally closed. When the compressor is shut down, system
pressure backs up to the inlet valve causing the check spring in the inlet valve to close the
air inlet valve. This sends a pressure signal to the blowdown valve causing it to open and
vent the pressure in the system. After the pressure is vented, the blowdown valve spring
returns the blowdown valve to the closed position.
Section 2 - Pg 05