Fixed Speed Control System, Functional Description - Sullair TSR32 User Manual

TSR32 USER MANUAL R00
2.6 FIXED SPEED CONTROL
SYSTEM, FUNCTIONAL
DESCRIPTION
Refer to Figure 2-7. The purpose of the compressor
control system is to regulate the amount of air being
compressed to match the amount of compressed air
being used.
The capacity control system consists of a spiral valve
and an inlet butterfly valve. The functional description
of the control system is described below in 4 distinct
phases of compressor operation. For explanatory
purposes, this description applies to any compressor
with an operating range of 100 to 110 psig (6.9 to 7.6
bar). A compressor with any other pressure range
would operate in the same manner except for the
stated pressures.
START MODE - 0 TO 50 PSIG (0 TO 3.4 BAR)
When the compressor (ON) pad is depressed, the
sump pressure will quickly rise from 0 to 50 psig (0 to
3.4 bar). During this period, both of the pressure
regulators and the solenoid valve are closed and the
Sullicon Control and spiral valve are inop- erative.
The spring on the control holds the butterfly valve
fully open while the spiral valve is fully closed
(maximum) position and the compressor pumps at
full rated capacity. The rising compressor air pres-
sure is isolated from the service line in this phase by
the minimum pressure valve set at approximately 50
psig (3.4 bar).
A standard closed inlet system is provided which
uses air pressure to close the butterfly and opens the
spiral valve to reduce motor torque for starting.
FULL LOAD MODE - 50 TO 100 PSIG (3.4 TO 6.9
BAR)
When the compressed air pressure in the sump rises
above 50 psig (3.4 bar), the minimum pres- sure
valve opens, allowing compressed air to flow into the
service line. From this point on, the line air pressure
is continually monitored
solenoid valve remain closed during this phase,
keeping the Sullicon Control and spiral valve
inactive. Both the spiral valve as well as the inlet
butterfly valve remain in the full load position as long
as the compressor is running at 100 psig (6.9 bar) or
below.
MODULATION - 100 TO 110 PSIG (6.9 TO 7.6 BAR)
As air demand drops below the rated capacity of the
compressor, the line pressure will rise above 100
18
by the Supervisor
psig (6.9 bar). As a result, the differential pressure
regulator for the spiral valve gradually opens, apply-
ing air pressure to the spiral valve actuator. Air
pressure at the actuator expands the diaphragm. The
rack, in turn, engages with the pinion mounted on the
spiral valve shaft assembly. This results in a rotary
motion. As the spiral valve rotates, it starts opening
the bypass ports gradually. Excess air is then being
returned back internally to suction end of compressor
unit. Now the compressor is fully compressing only
that amount of air which is being used. As air
demand keeps dropping further, the spiral valve
keeps opening more and more until all the bypass
ports are fully open. At this point, the spiral valve has
moved into the minimum position.
The spiral valve provides a modulation range from
100 to approximately 50%. During this period, the
pressure rises approximately from 100 to 108 psig
(6.9 to 7.4 bar). As the air pressure exceeds 108 psig
(7.4 bar), the differential pressure regulator
controlling the Sullicon Control opens. This allows
the air pressure to expand the diaphragm chamber of
the Sullicon Control, which starts partially closing the
inlet butterfly valve. The inlet butterfly valve pro-
vides modulation range from 50 to 40%. During this
period, the pressure rises approximately from 108 to
110 psig (7.4 to 7.6 bar). During this range, the spiral
valve remains in the full open position.
UNLOAD MODE - IN EXCESS OF 110 PSIG (7.6
BAR)
When a relatively small amount or no air is being
used, the service line pressure continues to rise.
When it exceeds 110 psig (7.6 bar), Supervisor
allowing line pressure to be supplied directly to the
Sullicon diaphragm keeping the inlet butterfly closed;
the spiral valve is in the fully open (minimum)
position. Simultaneously, the solenoid valve sends a
pneumatic signal to the blowdown valve. The
blowdown valve opens the sump to the atmosphere.
This reduces the sump pressure to approximately 30
psig (2.1 bar) which results in low horsepower
consumption. The check valve in the air service line
prevents line pressure from returning to sump while
the compressor is running in the unloaded mode.
Both the spiral valve and the butterfly valve remain in
the unload position.
When the line pressure drops back to 100 psig (6.9
bar) due to an increase in the air demand, Supervisor
the air pressure behind the Sullicon Control to be
vented through the solenoid valve exhaust port. The
SECTION 2
es the solenoid valve
solenoid valve allowing