Sullair LS-120 series Operators Manual And Parts Lists page 40

Section 7
MAINTENANCE
Figure 7-5 Pressure Switch
(P/N 040694) 50-75 HP/ 30-55 KW
Relieve all pressure from the sump tank and all
compressor lines.
1. Disconnect all piping connected to the sump
cover to allow removal (return lines, service
lines, etc.).
2. Loosen and remove the eight (8) hex head cap-
screws (5/8 x 2") from the cover plate.
3. Lift the cover plate from the sump.
4. Remove the separator elements.
5. Inspect the receiver/sump tank for rust, dirt, etc.
6. Scrape the old gasket material from the cover
and flange on the sump. Be careful not to let the
scraps fall in the sump.
7. Reinsert the separator elements into the sump
taking care not to dent them against the tank
opening.
8. Clean the underside of the receiver/sump tank
cover and remove any rust.
9. Replace the cover plate, washers and cap-
screws. Torque to 55 ft-lbs. (75 Nm).
10. Reconnect all piping making sure return line
tubes extend to the bottom or 1/4" (6mm) above
the bottom of the separator element. This will
insure proper fluid return flow to the compressor.
34
12. Clean the return line strainers before restarting
the compressor.
CONTROL SYSTEM ADJUSTMENT
Refer to Figure 7-5. Prior to adjusting the Control
System, it is necessary to determine the desired
operating pressure range and also the maximum
pressure at which your compressor is to operate.
The pressure must not exceed the maximum oper-
ating pressure which is stamped on the compressor
serial number nameplate. The following explanation
applies to a typical installation with a desired
operating range of 125 to 135 psig (8.6 to 9.3 bar).
This information will apply to a compressor with any
other operating range excepting the stated pres-
sures.
Remove the cover of the pressure switch. With the
shut-off valve closed (or slightly cracked open)
start the compressor. Observe the line pressure
gauge and pressure switch contacts. When the line
pressure reaches 135 psig (9.3 bar), the pressure
switch contacts should open. If the pressure switch
contacts do not open or they open prior to the
desired pressure, the pressure switch setting will
require adjustment (refer to Figure 7-5).
FOR PRESSURE RANGE ADJUSTMENT:
1. Remove cover to pressure switch.
2. Turn the range-adjusting screw to the high pres-
sure setting. Turning the screw counterclock-
wise lowers both the high and low pressure
equally.
FOR DIFFERENTIAL ADJUSTMENT:
Differential is the difference between the high and
low pressure settings. 10 psig (0.7 bar) is typical.
1. Turn the differential adjusting screw to the lower
(reset) setting. Turning the screw counterclock-
wise widens the differential by lowering the reset
(lower) setting only.
2. When the pressure switch adjustment is com-
plete, the pressure regulator should be adjusted
for the pressure at which modulation of air deliv-
ery should begin. In this case that pressure will
be 126 psig (8.7 bar). The regulator is adjusted
by loosening the jam nut on the end of the cone
shaped cover of the pressure regulator. When
the jam nut is loose, turn the adjusting screw
clockwise to increase or counterclockwise to
decrease the setting.
3. To set the regulator, continue closing the service
valve until the line pressure is 126 psig (8.7 bar).
At this point regulator should pass a signal to the
inlet valve to start closing it. If the line pressure