TM 5-4310-352-14
b.
Installation.
(2) Loosen screw and remove heater element
(5) from the open starter (4).
(1) Install pressure switch box on the air re-
(3) Remove mounting screw (3), then lift the
ceiver.
open starter (4) from the enclosure (2).
(2) Install electrical conduit to pressure switch
(4) Remove locknut from stem of selector
box (fig. 6-2).
switch knob, then remove knob from kit enclosure cover
(3) Connect tagged electrical leads to pressure
(2).
switch.
c. Cleaning, Inspection, and Replacement.
c. Adjustment. The pressure switch has a cut-out
(1) Use low pressure (25 psi) compressed air
ad- justment and a differential adjustment. The cut-out is
and remove all dust or dirt from motor starter components.
the pressure at which the switch contacts open, and the
(2) Check continuity of heater element and the
differential is the span between the cut-in and cut-out set-
open starter. Replace a defective open starter or heater
tings.
element.
NOTE
(3) Check selector switch continuity and stem
There is interaction between these two adjust-
action. Replace a defective selector switch.
ments. If the cut-out is increased, so will the differ-
d. Reassembly.
ential increase. Or, if the differential is reduced, the
(1) Install locknut on stem of selector switch
cut-out will be reduced. This factor must be consid-
knob. Position knob on kit enclosure cover (2) and secure
ered, and compensated for when adjusting.
by tightening locknut.
(1) Increase the cut-out point by turning the
(2) Position open starter (4) on enclosure (2)
range nut (fig. 6-4) clockwise.
and secure with mounting screws (3).
(3) Install heater element (5) on open starter
and secure with heater mounting screw.
(4) Install switch A on kit enclosure (2) and open
starter (4).
(5) Install electrical leads on selector switch (6)
and tighten connections securely.
e. Installation.
(1) Position motor starter on the mounting
bracket and secure with mounting bolts.
Figure 6-4. Pressure switch adjustment.
(2) Install electrical conduits to motor starter
and connect all electrical leads.
(2) Decrease the cut-out point by turning the
(3) Replace motor starter cover.
range nut counterclockwise.
(3) Note the pressure gage readings at which
6-4. Pressure Switch
the motor starts or stops. Reestablish the differential set-
a. Removal.
ting if necessary.
(4) Increase the differential by turning the dif-
(1) Release pressure from the air receiver.
(2) Remove electrical conduit from pressure ferential (fig. 6-4) nut clockwise. Turning the nut counter-
switch box (fig. 6-2), then disconnect and tag the electrical clockwise decreases the span.
leads from pressure switch.
NOTE
(3) Unscrew pressure switch box from the air
It is advisable to have as wide a differential as pos-
receiver.
sible to avoid frequent starting and stopping of the
compressor.
Section II. AIR COMPRESSOR
starting, and to minimize wear on bearings and shaft of
6-5. General
the drive motor.
The air compressor is a 2-cylinder, 2-stage air cooled
compressor. It has a capacity of 5 cfm at 610 rpm, and
6-6. Air Compressor
the electric motor drive cuts-in at 175 psi. The compres-
sor stops when the air pressure gage indicates 200 psi,
plus or minus 5 psi. The compressed air is cooled by a
the air compressor.
finned inter-cooler tube between the first stage cylinder
b. Disassembly.
and the second stage cylinder. The second stage com-
(1) Disconnect tube and remove tube fitting
pression is cooled by an aftercooler tube on its way to the
from pilot valve (fig. 4-2). Loosen locknut and remove
air receiver. These tubes remove most of the heat of
pilot
compression before the air reaches the receiver. The
compressor is equipped with a centrifugal unloader and
pilot valve system, to unload internal pressure for ease in
6-5
