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All Sullair compressor models are equipped with a
high pressure shutdown protection to shut down the
compressor at 190 psig (13.1 bar). This prevents the
pressure relief valve from opening under routine
conditions, thereby preventing fluid loss through the
pressure relief valve. A temperature switch will shut
down the compressor if the discharge temperature
reaches 240_F (115_C).
!
DO NOT remove caps, plugs, and/or other com-
ponents when compressor is running or pressur-
ized.
Stop compressor and relieve all internal pressure
before doing so.
Fluid is added to the sump via a capped fluid filler
opening, placed low on the tank to prevent overfilling
of the sump. A sight glass enables the operator to
visually monitor the sump fluid level.
5.6 CONTROL
SYSTEM,
SCRIPTION
Ref er t o
F igur es 5 -- 4A t hr ough 5 --
of the compressor control system is to regulate the
amount of air being compressed to match the
amount of compressed air being used. The capac-
ity control system consists of a pressure switch,
solenoid valve pressure regulator(s) and a con-
trol line filter. The functional description of the con-
trol system is described below in four distinct
phases of operation. For explanatory purposes, this
description will apply to a compressor with an oper-
ating 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 stated pres-
sures.
START MODE - - 0 TO 50 PSIG (0 TO 3.5 BAR)
When the Supervisor II module "I" or "A" pad is de-
pressed, the unit starts and the pressure quickly
rises from 0 to 50 psig (0 to 3.5 bar). The pressure
regulator(s) and the solenoid valve(s) remain
closed, and the inlet poppet valve and spiral valve
are inoperative. The spring loaded poppet is forced
open by the intake air flow. The minimum pressure
valve (MPV) isolates the compressed air from
reaching the service line while building enough
backpressure (40--50 psig [2.8--3.5 bar]) to maintain
adequate lubricant fluid flow. If the optional Closed
Inlet Start assembly is provided, an accumulated air
signal is used to maintain the inlet poppet valve fully
closed, minimizing the compression load for special
drivers (i.e., Wye--Delta electric motors) during the
start--up phase. After a pre--determined amount of
time, the accumulated air signal is removed and the
poppet is allowed to open by the air flow.
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
WARNING
FUNCTIONAL
4D. T he pur pos e
COMPRESSOR SYSTEMS
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 inlet poppet valve and spiral
valve inactive. Both the spiral valve as well as the in-
let poppet 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 close the inlet poppet valve, throttling
the mass of air entering the compressor and thereby
reducing the latter's air delivery. The air throttling of
the inlet poppet valve 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)
DE-
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 the 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 105 psig (6.9 to 7.2 bar).
As the air pressure exceeds 105 psig (7.2 bar), the
differential pressure regulator controlling the inlet
poppet valve starts opening and forcing the poppet
closed, thus throttling inlet air flow to the compres-
sor. The inlet poppet valve provides a 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.
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 inlet poppet valve, and b) open the blowdown
valve and depressurize the package to its unload
level of 40 to 50 psig (2.8 to 3.5 bar). The minimum
Section 5
17
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