Advertisement
Operation
SIZING THE OIL LINES FOR OIL PRESSURE
SWITCHES
Sizing the oil lines to the bellows of
the control, as outlined, will minimize
the pressure drop in these lines and
permit the switches to detect the pres-
sure changes more quickly, avoiding
the possibility of damage to the com-
pressor bearings due to slow acting
switches.
When the oil pressure switches are shipped separately,
for remote mounting, all the lines to the control bellows
should be sized as follows, depending upon the length
of the tubing required to connect the control bellows to
its point of sensing:
TABLE 7 – OIL PRESSURE SWITCH TUBING SIZING
LENGTH OF LINE
0 FT. TO 15 FT.
15 FT. TO 45 FT.
PRE-ROTATION VANE OPERATION
If the system is automatically controlled, the pre-rota-
tion vanes should automatically modulate in accordance
with load requirements.
If the pneumatic system fails, and the compressor is
equipped with a hand wheel, adjust the pre-rotation
vanes manually as follows:
Operation of the compressor in the
manner will require constant moni-
toring of compressor operation to al-
low changing of PRV position if local
conditions change.
1. Disconnect the linkage to the vane motor.
2. Connect the linkage to the hand wheel, located on
a bracket at the coupling end of the compressor.
3. Turn the pre-rotation vane hand wheel. A pointer
is mounted on the operating linkage and the open,
closed and reverse positions ("O", "C" and "R"
respectively), are stamped on the arc of pointer
travel. Turning the hand wheel so that the pointer
moves past the open position to "R" reverses the
angularity of the vanes and changes the pre-rota-
30
Air Pressure
If the compressor is equipped with an air motor for au-
tomatic pre-rotation vane operation, the supply air pres-
sure to the motor should be CLEAN, DRY AIR, at 100
PSIG maximum and 50 PSIG minimum for 26 inch com-
pressors, 60 PSIG minimum for 38 inch compressors
and 70 PSIG minimum for 55 inch compressors.
Air consumption will vary from 0.40 to 0.80 cfm de-
pending upon the air supply pressure.
STOPPING THE COMPRESSOR
To properly shut down the compressor, proceed as
follows:
TUBING SIZE
3/8"
1/2"
tion of the suction gas entering the first stage im-
peller. Under certain conditions, this will increase
compressor capacity (refer to the application data
sheet). There may be an adverse impact on power.
1. Stop the compressor driver.
If the compressor stops due to a power
failure, the auxiliary pump can not
start. This should not damage the com-
pressor because the main oil pump will
supply oil while the compressor slows
down, and residual oil will prevent
bearing damage.
2. As the compressor slows down, the main oil pump
pressure falls until the auxiliary oil pump starts au-
tomatically. The control system may also automati-
cally start the pump on a command to shut down.
3. After the compressor driver stops, a check valve in
the compressor discharge line, when required, may
minimize reverse rotation of the compressor
(caused by gas equalizing from the discharge to
the suction through the compressor). If interstage
inlets are applied, an automatic valve should close
to halt the flow of gas, which may cause reverse
rotation.
4. If either automatic pre-rotation vanes or automatic
hot gas bypass are employed, a solenoid valve in
the air signal line closes the vanes. In some refrig-
eration applications the system valve sequence
should be tailored and controlled to prevent the freez-
ing of water cooled components, due to the poten-
tial for low settleout pressures. Certain applications
may require additional consideration for draining liq-
uids to protect them from freeze damage.
FORM 220.11-NM2 (602)
YORK INTERNATIONAL
Advertisement
