Owner's manual

This procedure and Figure 7-4 are set up
for direct acting power positioners. In a
reverse acting power positioner, increasing
signal supply air hose (10, Figure 7-4) would
be at bottom of cylinder and decreasing
signal supply air hose (11) would be at top
of cylinder.
4. Remove increasing signal supply air hose
(10, Figure 7-4) from 90” elbow (9) at upper
cylinder head (8). Mark supply air hose
“upper”.
5. Remove decreasing signal supply air hose
(11) from 90” elbow (9) at lower cylinder
bead (16). Mark supply air hose “lower”.
6. Remove retaining rings (1) and drive out
clevis pin (2) from clevis bead (3).
7. While supporting cylinder (18), remove
trunnion screws (7).
8. Remove assembled cylinder from trunnion.
Move it to a workbench to continue
disassembly.
CAUTION
Do not scratch piston rod. Use caution when
removing and handling upper cylinder bead,
piston, and piston rod. If piston rod is
scratched, power positioner will produce
lower torque and decreased packing life will
result.
9. Remove hex nuts (13), washers (14), and tie
bolts (15).
CAUTION
Do not pull piston and shaft assembly out of
cylinder bead. Damage to packing gland
bushings and V-packing may occur.
10. Remove upper cylinder bead (8) by sliding
piston (21) out of cylinder (18).
11. Remove and discard upper and lower
cylinder head gaskets (17).
12. If piston is to be replaced, remove stop nut
(19). o-ring (ZO), and piston (21). Replace
with new piston and o-ring, securing with
same stop nut.
13. If piston was not replaced, clean old grease
off piston (21) and piston rod (22). Wipe
with commercial grade dry cleaning solvent
and let air dry.
14. Remove hex head cap screws (4) and
washers (5) securing packing cover (6) to
upper cylinder head (8). Remove packing
cover from upper cylinder bead.
15. Remove and inspect female adaptor (23).
Replace female adaptor, V-packing (24), and
male adaptor (25) as a set if any one appears
damaged or if air was leaking through
packing.
16. Install male adaptor (25), V-packing (24)
and female adaptor (23). Pack area around
female adaptor with McLube grease or
equivalent. Secure packing cover (6) to
upper cylinder head (8) with hex bead cap
screws (4) and washers (5).
17. With a clean shop towel and commercial
grade dry cleaning solvent, wipe interior
surface of cylinder (18). Allow to air dry
before assembly.
18. Pack concave area of piston with McLube
MoS,793 type grease or equivalent. Lightly
coat piston rod (22) with McLube
M&-793 grease. Wipe excess grease off
with clean shop towel.
19. Install tie bolts (15) through lower cylinder
head (16).
20. Install cylinder (18) with a new cylinder
bead gasket (17) onto lower cylinder head
(16).
21. Place new upper cylinder bead gasket (17)
on top of cylinder. Making sure both gaskets
are in place, slide piston (21) into upper
cylinder head (8) and onto cylinder (18).
22. Align tie bolts (15) through upper cylinder
head (8) boles and secure with hex nuts (13)
and washers (14). Tighten hex nuts evenly,
using a diagonal tightening sequence.