Sullair LS-20S Operator's Manual And Parts List page 19

NORMAL OPERATING MODE - - 50 TO 100 PSIG
(3.5 TO 6.9 BAR)
When the compressed air pressure rises above 50
psig (3.5 bar), the minimum pressure valve opens
and delivers compressed air to the service line.
From this point on, the line air pressure is continually
monitored by the Supervisor II. The pressure regu-
lators and the solenoid valve remain closed during
this phase, keeping the Sullicon Control and spiral
valve inactive. Both the spiral valve as well as the in-
let butterfly valve remain in the full load position as
long as the compressor is running at 100 psig (6.9
bar) or below.
MODULATING MODE (STANDARD CONTROL) - -
100 TO 110 PSIG (6.9 TO 7.6 BAR)
If less than the rated capacity of compressed air is
being used, the line pressure will rise above 100 psig
(6.9 bar), and a pressure regulator starts feeding an
air signal to the pneumatic Sullicon actuator. The
linear action of this device begins to close the butter-
fly valve via a rod--and--lever linkage, throttling the
mass of air entering the compressor and thereby re-
ducing the latter's air delivery. The air throttling of
the Sullicon control system increases proportion-
ately with a rise of line pressure from 101 to 110 psig
(7 to 7.6 bar).
MODULATING MODE WITH OPTIONAL SPIRAL
VALVE - - 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 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
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 spi-
ral 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) posi-
tion.
The spiral valve provides a modulation range from
100 to 50%. During this period, the pressure rises
approximately from 100 to 105 psig (6.9 to 7.2 bar).
As the air pressure exceeds 105 psig (7.2 bar), the
differential pressure regulator controlling the Sulli-
con Control opens. This allows the air pressure to
expand the diaphragm chamber of the Sullicon Con-
trol, which starts partially closing the inlet butterfly
valve. The inlet butterfly valve provides modulation
range from 50 to 40%. During this period, the pres-
sure rises approximately from 106 to 110 psig (7.3 to
7.6 bar). During this range, the spiral valve remains
in the unload position.
DESCRIPTION
Figure 2-6 Air Inlet System
AIR FILTER
AIR FILTER
UNLOAD MODE - - IN EXCESS OF 110 PSIG (7.6
BAR) LINE PRESSURE
When little or no air demand is present, the line pres-
sure increases beyond 110 psig (7.6 bar). At this
point, the Supervisor II Module energizes a solenoid
valve which feeds an air signal to a) directly close
the butterfly valve via the Sullicon actuator, and
open the spiral valve, and b) open the blowdown
valve and de--pressurize the package to its unload
level of 40 to 50 psig (2.8 to 3.5 bar). The minimum
pressure valve now isolates the sump vessel from
the service line.
If the Supervisor II Module is operating on an "I"
mode, the unit runs unloaded until the line pressure
falls below 100 psig (6.9 bar), at which point it pro-
ceeds to the Normal Modulating Mode. If on the oth-
er hand, the Supervisor II Module is operating in the
" " mode, the unit runs unloaded for a pre--set
length of time, and unless the line pressure falls be-
low the 100 psig (6.9 bar) level, it stops at the end of
this period. Once the line pressure falls below the
100 psig (6.9 bar) level,the compressor automati-
cally restarts, followed by package operation in the
Load mode.
When the line pressure drops back to 100 psig (6.9
bar) due to an increase in the air demand, Supervi-
Section 2
WATER-COOLED
MACHINES
AIR-COOLED
MACHINES
13