Compressor Discharge System - Sullair LS-32 Operator's Manual And Parts List

rises above 40 psig (2.8 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 by the Supervisor
Controller. The pressure regulators and the sole-
noid 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 com-
pressor is running at 60 psig (4.2 bar) or below.
MODULATION - 60 TO 70 PSIG (4.2 TO 4.8 BAR)
As air demand drops below the rated capacity of the
compressor, the line pressure will rise above 60
psig (4.2 bar). As a result, the differential pressure
regulator for the spiral valve gradually opens, apply-
ing air pressure to the spiral valve actuator. Air pres-
sure at the actuator expands the diaphragm. The
Figure 2-4 Compressor Discharge System
DESCRIPTION
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 com-
pressing 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 61 to 66 psig
(4.1 to 4.6 bar). As the air pressure exceeds 68 psig
(4.7 bar), the differential pressure regulator con-
trolling the Sullicon Control opens. This allows the
air pressure to expand the diaphragm chamber of
Section 2
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