Sullair LS-25S-257KW, Operator'S Manual And Parts List

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Section 2
DESCRIPTION
8
The compressor is also equipped with high pres-
sure shutdown protection to shut down the com-
pressor at 135 psig (9.3 bar). This prevents the re-
lief valve from opening and dumping fluid under
normal conditions. Also, a high discharge tempera-
ture control with three (3) sensing probes is pro-
vided to shut down the compressor if the discharge
temperature reaches 235
_
F (113
_
C).
WARNING
!
DO NOT remove caps, plugs, and/or other com-
ponents when compressor is running or pressur-
ized.
Stop compressor and relieve all internal pres-
sure before doing so.
Fluid is added to the sump via a capped fluid filler
opening, located on the tank to prevent overfilling
of the sump. A sight glass enables the operator to
visually monitor the sump fluid level.
2.6 CONTROL SYSTEM, FUNCTIONAL DESCRIP-
TION
R e f e r t o F i g u r e s
2 --- 3 A a n d 2 --- 3 B . T h e p u r p o s e o f
the c ompr essor c ontr ol system is to r egul a te the
amount of air being compressed to match the
amount of compressed air being used. The capac-
ity control system consists of a spiral valve and an
inlet butterfly valve. The functional description of
the control system is described below in four dis-
tinct phases of operation. The following description
text applies to all LS---25S Series compressors
ranging from 200 --- 350 HP/150 --- 261 KW models.
For explanatory purposes, this description will ap-
ply to a 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 at stated pressures.
START MODE --- 0 TO 50 PSIG (0 TO 3.4 BAR)
When the compressor ON/OFF pad is depressed,
the sump pressure will quickly rise from 0 to 50 psig
(0 to 3.4 bar). During this period, both the pressure
regulator and the solenoid valve are closed and the
Sullicon Control is inoperative. 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 pressure is isolated from the
service line in this phase by the minimum pressure
valve set at approximately 50 psig (3.4 bar).
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 by the Supervi-
sor. The pressure regulator and the solenoid valve
remain closed during this phase, keeping the Sulli-
con Control inactive. Both the spiral valve, as well
as the inlet butterfly valve, remain in the full load po-
sition 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 psig (6.9 bar). As a result, the differential pres-
sure regulator for the spiral valve gradually opens,
applying 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 the 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 unload (minimum)
position.
The spiral valve provides a modulation range from
100 to 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 Sul-
licon Control opens. This allows the air pressure to
expand the diaphragm chamber of the Sullicon
Control, which starts partially closing the inlet but-
terfly valve. The inlet butterfly valve provides modu-
lation 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 unload 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
de---energizes the solenoid valve allowing line
pressure to be supplied directly to the Sullicon dia-
phragm keeping the inlet butterfly closed; the spiral
valve is fully open (minimum) position. Simulta-
neously, the solenoid valve sends a pneumatic sig-
nal to the blowdown valve. The blowdown valve
opens the sump to the atmosphere. This reduces
the sump pressure to approximately 30 to 50 psig
(2.1 to 3.4 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, the Su-
pervisor energizes the solenoid valve allowing the
air pressure behind the Sullicon Control to be