SECTION 2 600H, 750, 750H, 750HH, 825, 900 & 900H USER MANUAL
25
LOW PRESSURE - 80 TO 100 PSIG (5.5 TO 6.9
BAR)
With the HIGH/LOW valve in the “LOW” position, and
the START/RUN valve in the “RUN” position, the
service valve can now be opened. Pressure from the
60 psig (4.1 bar) reducing regulator opens up the
inlet valve and the Controller increases the engine
speed to full load (1800 rpm). As the demand for air
decreases, the Controller commands the engine to
reduce speed to idle (1400 rpm) and the inlet valve
closes, where it stabilizes until the air demand is
required again. If the machine is not marked with an
“H” or “HH”, it is a single pressure machine and will
not have a HIGH/LOW valve. The machine will run
as if it is in the “LOW” position.
HIGH PRESSURE - 80 TO 150 PSIG (5.5 TO 10.3
BAR) FOR “H” MODELS OR 80 TO 175 PSIG (5.5
TO 12.1 BAR) FOR “HH” MODELS
When the HIGH/LOW valve is switched to the “HIGH”
position, the low pressure regulator is blocked off
allowing the high pressure regulator to take over
control of the machine. The 60 psig (4.1 bar)
reducing regulator fully opens the inlet valve and the
Controller commands maximum speed (1800 rpm)
from the engine. As the pressure reaches the set
point of the system the high pressure regulator
cracks open and closes the inlet valve and the
Controller returns the engine back to idle, until a
demand for air is seen.
SHUTDOWN
To shutdown the unit, slowly close the service valve.
The blowdown valve is normally closed. When the
compressor is shutdown, system pressure backs up
to the inlet valve causing the check spring in the inlet
valve to close the air inlet valve. This sends a
pressure signal to the blowdown valve causing it to
open and vent the pressure in the system. After the
pressure is vented, the blowdown valve spring
returns the blowdown valve to the closed position.
Push the START/STOP switch to the STOP position.
This will shut the engine off. Once the engine off,
Push OFF/ON switch to the OFF position to shutoff
the controller. Note: The controller can not be shutoff
unless the engine is stopped.
2.6 COMPRESSOR DISCHARGE
SYSTEM, FUNCTIONAL
DESCRIPTION
The Sullair compressor unit discharges compressed
air/fluid mixture into the receiver tank.
The receiver tank has three functions:
1. It acts as a primary fluid separator.
2. Serves as the compressor fluid storage sump.
3. Houses the final fluid separator.
The compressed air/fluid mixture enters the receiver
tank and is directed against the tank side wall. By
change of direction and reduction of velocity, large
droplets of fluid separate and fall to the bottom of the
receiver tank. The fractional percentage of fluid
remaining in the compressed air collects on the
surface of the final separator element as the
compressed air flows through the separator. As more
and more fluid collects on the element’s surface, the
fluid descends to the bottom of the separator. A
return line (or scavenge tube) leads from the bottom
of the separator element to the inlet region of the
compressor unit. Fluid collecting on the bottom of the
separator element is returned to the compressor by
the pressure difference between the area
surrounding the separator element and the
compressor inlet. An orifice (protected by a strainer)
is included in this return line to help assure proper
flow.
The receiver tank is code rated. A minimum
pressure/ check valve, located downstream from the
separator, helps assure a minimum receiver
pressure during all conditions. This pressure is
necessary for proper air/fluid separation and proper
fluid circulation.
A minimum pressure/check valve at the outlet of the
receiver is installed to prevent compressed air in the
service line from bleeding back into the receiver on
shutdown when the compressor is being run in
parallel with other compressors tied to a large air
system.
Fluid is added to the receiver tank via a capped fluid
filler. A fluid level gauge glass enables the operator
to visually monitor the receiver tank fluid level.
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