Control System, Functional Description - Sullair E900H User Manual

E900H USER MANUAL
is routed back to the thermal valve.
Before the temperature of the fluid reaches the valve
set point, cooled fluid is mixed with warmer fluid.
When the temperature of the fluid reaches 190°F
(88°C), the thermal element shifts completely
causing all fluid to flow to the cooler. After the fluid
passes through the thermal valve it is then directed
through the main fluid filter. There, the fluid is filtered
in preparation for injection into the compression
chamber and bearings of the compressor unit. The
filter has replaceable elements. After the fluid is
properly filtered, it then flows on to the compressor
unit where it lubricates, seals and cools the
compression chamber as well as lubricates the
bearings and gears.
2.7 CONTROL SYSTEM,
FUNCTIONAL DESCRIPTION
The purpose of the compressor control system is to
regulate the amount of air being compressed to
match the amount of compressed air being used.
The capacity control system consists of a pneumatic
inlet valve. The functional description of the control
system is described below in four distinct phases of
compressor operation. For explanatory purposes,
this description applies to any compressor with an
operating range of 150 to 165 psig (10.3 to 11.4 bar).
A compressor with any other pressure range would
operate in the same manner except for the stated
pressures.
START MODE—0 TO 50 PSIG (0 TO 3.4 BAR)
When the compressor
depressed, the sump pressure will quickly rise from 0
to 50 psig (0 to 3.4 bar). During this period, both of
the pressure regulators and the solenoid valve are
closed and the pneumatic inlet valve is inoperative.
The internal spring holds the inlet valve fully closed
to reduce motor torque for starting. After six (6)
seconds the solenoid valve will open, opening the
inlet valve, and the compressor will run 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 150 PSIG (3.4 TO 10.3
BAR)
When the compressed air pressure in the sump rises
above 50 psig (3.4 bar), the minimum pressure valve
opens, allowing compressed air to flow into the
service line. A load signal is provided through a
20
<START> button is
02250203-986 R01
pressure reducing regulator set at 70 psig (4.8 bar) to
maintain the inlet valve in an open position. The inlet
valve will remain in the full load position as long as
the compressor is running at 150 psig (10.3 bar) or
below.
MODULATION—150 TO 165 PSIG (10.3 TO 11.4
BAR)
As air demand drops below the rated capacity of the
compressor, the line pressure will rise above 150
psig (10.3 bar). As the air pressure exceeds 150 psig
(10.3 bar), the differential
controlling the inlet valve opens. This allows the air
pressure into the unload chamber of the inlet valve,
which starts partially closing the inlet valve, providing
modulation. During this period, the pressure rises
approximately from 150 to 165 psig (10.3 to 11.4
bar).
UNLOAD MODE—IN EXCESS OF 165 PSIG (11.4
BAR)
When a relatively small amount or no air is being
used, the service line pressure continues to rise.
When it exceeds 165 psig (11.4 bar), the pressure
switch energizes the solenoid, applying pressure to
the unload chamber of the inlet valve, which fully
closes the valve. Simultaneously, the solenoid valve
sends a pneumatic signal to the blowdown valve.
The blowdown valve opens the sump to the
atmosphere. This reduces the sump pressure to
approximately 25 psig (1.7 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. The inlet valve remains in the
unload position. When the line pressure drops back
to 150 psig (10.3 bar) due to an increase in the air
demand, the pressure switch de-energizes the
solenoid valve removing air pressure from the unload
chamber, opening the inlet valve. The blowdown
valve closes, and the inlet valve opens.
2.8 AFTERCOOLED AIR
SYSTEM, FUNCTIONAL
DESCRIPTION
Refer to Figure 2-3 and Figure 2-4 The purpose of
the aftercooled air system is to operate the air
compressor in conditions when compressed air
temperatures are required to be 10 to 25 ̊ F (5 to 13
̊ C ) over ambient temperature. A 3-valve bypass is
provided to switch between standard and aftercooled
air. The ambient air, which is blown through the
aftercooler by the motor-driven fan, cools the
compressed air as it passes through the aftercooler
core. Cooled air enters the moisture separator where
condensation is removed from the cooler air and
SECTION 2
pressure regulator