Specifications

16. Insert new upper piston O-ring (22) into
piston follower (23). Screw piston follower
on piston rod (14). Insert new lower piston
o-ring (24) into bottom side of piston
follower. Place new piston (25) on piston
rod with machined side of piston toward
piston follower. Secure piston assembly to
piston rod with stop nut (26). Pack concave
area of piston seal with McLube M&,-793.
17. Using a putty knife, prepare gasket surfaces
of cylinder (27) and cylinder heads (13 and
30) for new gaskets by removing any old
gasket material or dirt. Wipe with a clean
shop towel.
18. Place new upper cylinder head gasket (19)
on upper cylinder head (13). Place new
lower cylinder head gasket (29) on lower
cylinder head (30).
19. Install upper cylinder head (13) and piston
assembly onto cylinder (27). Install lower
cylinder head (30) on cylinder.
20. Secure upper cylinder head (13) to lower
cylinder head (30) with cylinder studs (28)
and nuts (12).
21. Place cylinder bearing blocks (17) onto
upper cylinder head (13). Place cylinder
assembly in frame assembly and secure
cylinder bearing blocks to frame assembly
with scwxs (18), washers (16) and nuts
(13.
22. Insert end of cylinder lever (2) into slot of
clevis (3).
23. Align holes in clevis (3) with hole in
cylinder lever (2). Drive clevis pin (4) in
securing clevis to cylinder lever. Tighten
cylinder lever set screw (1).
24. Open supply air valve. and test for air
leakage around cylinder head. Use aleak
detector, such as “Snoop”, and send an air
signal to power positioner. If leak is
detected, repair as necessary.
25. Calibrate power positioner stroke; refer to
Section N. Return power positioner to
service.
f. Cylinder Replacement. To replace the
assembled cylinder with a new cylinder follow
the procedures outlined in paragraph 7-2.e,
Cylinder Head Gaskets, Piston and Rod Packing.
Steps 1 through 9 cover cylinder removal, and
steps 17 through 2.5 provide installation
procedures.
g. m. Use the following procedure to replace cam.
1. Remove power positioner from service.
2. Remove screws (16, Figure 7.6), washers
(15) and cam (14) from cam mounting
bracket (12).
3. Place new cam (14) against cam mounting
bracket (12). Secure in place with screws
(16) and washers (15).
4. Refer to Section IV and calibrate power
positioner.
5. Return power positioner to service.