Section 2
DESCRIPTION
9
amount of cool water to enter the cooler and re-
move the heat of compression from the fluid. From
the cooler, the fluid then flows through the filter, and
on to the compressor unit.
The water---flow regulating valve is also used to
conserve water during periods of varying load on
the compressor. The same valve also shuts off the
water supply when the compressor is shut---down.
On both air---cooled and water---cooled compres-
sors, a portion of the fluid is routed to the anti---fric-
tion bearings which support the rotors inside the
compressor unit.
2.5 COMPRESSOR DISCHARGE SYSTEM, FUNC-
TIONAL DESCRIPTION
. The compressor
unit discharges the compressed air/fluid mixture
into the combination receiver/sump. The receiver
has three functions:
1. It acts as a primary fluid separator.
2. It serves as the compressor fluid sump.
3. It houses the final fluid separator.
The compressed air/fluid mixture enters the sump
and is directed against the side of the tank. Its di-
rection of movement is changed and its velocity
significantly reduced, thus causing the large drop-
lets of fluid to fall to the bottom of the sump. The
fractional percentage of fluid remaining in the com-
pressed air collects on the surface of the separator
element as the compressed air flows through the
separator. A return line (or scavenge tube) leads
from the bottom of the separator element to the in-
let region of the compressor unit. Fluid collecting
on the bottom of the separator is returned to the
compressor by a pressure differential between the
receiver and the compressor inlet. A sight glass is
located in the return line to observe this fluid flow.
There is also an orifice in this return line (protected
by a strainer) to assure proper flow. A gauge, lo-
cated in the instrument panel indicates if abnormal
pressure drop through the separator develops. At
this time, separator element replacement is neces-
sary.
The receiver is ASME code. A minimum pressure/
check valve, located downstream from the separa-
tor, assures a minimum receiver pressure of 50
PSIG (345kPa) during all conditions. This pressure
is necessary for proper air/fluid separation and to
assure adequate fluid circulation.
A terminal check valve is also built into the mini-
mum pressure/check valve to prevent compressed
air in the service line from bleeding back into the re-
ceiver on shutdown and during operation of the
compressor in an unloaded condition.
A pressure relief valve (located on the wet side of
the separator) is set to open if the sump pressure
exceeds 200 PSIG (1379kPa). A temperature
switch will shut down the compressor if the dis-
charge temperature reaches 240
_
F (116
_
C).
All compressor models are equipped with a high
pressure shutdown switch to shut down the com-
pressor at 135 PSIG (931kPa). This prevents the
pressure relief valve from opening under routine
conditions, thereby preventing fluid loss through
the pressure relief valve.
WARNING
!
DO NOT remove caps, plugs, and/or other com-
ponents when compressor is running or pressur-
ized.
Stop compressor and relieve all internal pres-
sure before doing so.
Fluid is added to the sump via a capped fluid fill
opening, placed low on the tank to prevent overfill-
ing of the sump. A sight glass enables the operator
to visually monitor the sump fluid level.
2.6 CONTROL SYSTEM, FUNCTIONAL DESCRIP-
TION
Refer t o Figure
. The purpose of the compres -
sor control system is to regulate the compressor air
intake to match the amount of compressed air be-
ing used. At a 0 to 10 percent air output, the control
system will automatically blow down the compres-
sor and greatly reduce the unload power con-
sumption. The control system consists of an inlet
valve, (located on the compressor air inlet), blow-
down valve, solenoid valve, pressure switch, and a
pressure regulator. The functional descriptions of
the control system are given below in four distinct
phases of compressor operation. The following
guidelines apply to all Series 10B compressors.
For explanation purposes this description will apply
to a compressor with an operating pressure range
of 115 to 125 PSIG (792 to 862kPa). A compressor
with any other pressure range would operate in the
same manner excepting stated pressures.
START -- 0 TO 50 PSIG (0 TO 345kPa)
When the compressor START button is depressed,
the sump pressure will quickly rise from 0 to 50
PSIG (0 to 345kPa). During this period both the
pressure regulator and the solenoid valve are
closed, the inlet valve is fully open due to inlet air
flow, and the compressor pumps at full rated ca-
pacity. The rising compressor air pressure is iso-
lated from the service line in this phase by the mini-
mum pressure valve, set at approximately 50 PSIG
(345kPa).
NORMAL OPERATING MODE -- 50 TO 115 PSIG
(345 TO 792kPa )
When the pressure air rises above 50 PSIG
(345kPa), the minimum pressure/check valve
opens and delivers compressed air to the service
line. From this point on, the line air pressure is con-
tinually monitored by a line pressure gauge and a
Summary of Contents for 10B 25HP
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