AIR SYSTEM COMPONENTS
SUB-SECTION SC
C. Remove the snap ring securing the closure plate
OVERHAUL. Overhaul of this valve should be limited to
the replacement of the parts furnished in the repair kit for
D. Disassemble and wipe all parts free of grease and dirt.
this valve. To overhaul the valve, proceed as follows (see
Coat the cam follower with a film of light grease,
then install the closure plate and secure the plate with
a new snap ring.
1. Disconnect the air lines attached to the outlet body of
the valve. Remove the capscrews. lockwashers, and nuts
securing the va!ve to the mounting bracket. and remove the
E. lnstall new friction plates and secure the plates with
the special screw.
valve.
2. Remove the six body screws and remove the outlet
F. Assemble the handle mechanism on the mounting
plate and inlet body, and secure the assembly with
body. Remove the barrier plate assembly and lift out the
the four assembly screws.
balance piston. The barrier plate assembly may be dis-
carded, as a new assembled replacement is included in the
G. Adjust the three Allen head set screws until the de-
repair kit.
sired amount of handle drag is obtained.
3. Remove the balance spring and wear shim from the out-
let body. Wash the parts in cleaning solvent. Then inspect
8. Install the handle and secure it with the handle screw.
the outlet body for excessive wear in the area where the
piston contacts the body bore.
9. Install the O-ring in the inlet body counterbore. Install
the outlet body on the inlet body with a slight turning
4. Remove the balance piston U-cup and thrust ring. These
motion to seat the O-ring. Install six new body screws.
items can be easily replaced without disturbing the seal
retainer. as the nylon thrust ring is split and the U-cup will
10. Install the valve on the mounting bracket with the four
stretch the small amount necessary for removal and installa-
capscrews. lockwashers, and nuts. Reconnect the air lines to
tion. Install a new thrust ring and U-cup on the balance
the outlet body.
piston. Be sure the sealing surface of the U-cup is pointing
toward the retainer.
11. Test the operation of the overhauled hand throttle
valve by performing the Operating and Leakage Test.
5. Install the wear shim and balance piston in the outlet
body cavity.
ADJUSTMENT. An adjustment is provided to vary the
6. Wipe a coating of light grease on the body bore and on
amount of handle drag. Some operators prefer a heavy drag,
the face and small diameter of the assembled balance pis-
while others like a lighter drag. Adjust the handle drag as
ton. Install the balance piston in the outlet body; then
follows:
place the new barrier plate assembly in position on the
outlet body. Make sure the plate is set into the mating
1. Remove the handle screw, and remove the handle by
counterbore of the body, and the small diameter of the
pulling it outward.
balance piston engages the bore in the bottom of the outlet
body.
2. Turn the three Allen head set screws clockwise to in-
crease the drag. Turn the screws counterclockwise to de-
7. Remove the handle screw, and remove the handle by
crease the drag. Be sure each screw is turned an equal
pulling it outward. Determine at this point whether or not
amount to ensure uniform drag.
the friction plates are excessively worn. If the plates do not
require replacement, proceed to the next step. If the fric-
NOTE
tion plates require replacement, proceed as follows:
If the adjustment screws do not produce the desired
A. Remove the four assembly screws. Separate the
handle drag, introduce several drops of heavy oil
handle mechanism from the mounting plate and inlet
down the handle screw bore. Take care not to over
body.
lubricate or spill lubricant on the friction plates.
B. Remove the special screw, and remove the friction
plates from the handle shaft.
3. Install the handle and secure it with the handle screw.
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