600H, 700HH, 750, 750H, 750HH, 825, 900H, 1050 USER MANUAL SECTION 2
26
2.5 CAPACITY CONTROL
SYSTEM, FUNCTIONAL
DESCRIPTION
Refer to Figure 2-3, Figure 2-4 and Figure 2-5. The
purpose of the control system is to regulate the
amount of air intake in accordance with the amount
of compressed air demanded. The control system
consists of an inlet valve, the high and low pressure
regulators, the pressure reducing regulator, the
blowdown/ running blowdown valve, the controller, a
<ON> switch, and the <PRESSURE> selector
switch.
START—0 TO 65 PSIG (0 TO 4.5 BAR)
Keep the <ON> switch to the “ON” position to
initialize the controller. Once the controller says
“READY” on LCD, press <ON> switch to the
“START” position. In the “START” position, the inlet
valve is held closed by the springs in the inlet valve.
The valve is cracked open by a vacuum in the
compressor and is allowed to build up to 65 psig (4.5
bar). The reason for keeping the valve closed during
start is to allow the engine to warm up without being
loaded by the compressor. Air pressure is contained
in the receiver tank by the minimum pressure valve
which has a set point of 65 psig (4.5 bar). At this
point the valve opens allowing the air to pass to the
service valve. After the engine has warmed up the
machine automatically transitions to “RUN” mode.
LOW PRESSURE/SINGLE PRESSURE—
80 TO 100 PSIG (5.5 TO 6.9 BAR)
With the <PRESSURE> switch in the "LOW"
position, and the controller in "RUN" mode, 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 left in the idle state (>1400 rpm) for
periods exceeding 10 minutes the engine rpm will
drop down further to a low idle state (1000rpm) until
a demand for air is seen, in order to reduce fuel
consumption when not needed. If the machine is not
marked with an "H" or "HH", it is a single pressure
machine and will not have a <PRESSURE> switch.
The machine will run as if it is in the "low" mode.
HIGH PRESSURE—80 TO 150 PSIG (5.5 TO
10.3
BAR) FOR “H” MODELS OR 80 TO 200
PSIG (5.5 TO 13.8 BAR) FOR “HH” MODELS
With the <PRESSURE> switch in the “HIGH”
position, the low pressure regulator is blocked off by
the high/low solenoid valve 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
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.Compressor Discharge System, Functional
Description
Refer to Figure 2-3. The Sullair compressor unit
discharges a 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
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