Main Valve Maintenance - Emerson ANDERSON GREENWOOD 727 Installation And Maintenance Instructions Manual

ANDERSON GREENWOOD TYPE 727 DUAL PILOT MANIFOLD
INSTALLATION AND MAINTENANCE INSTRUCTIONS

2 MAIN VALVE MAINTENANCE

Depending on the vintage of the main valve,
the cap may be equipped with drain plunger
assembly (refer to Figure 2A, items 16, 17,
and 18). This arrangement is found typically
in earlier production models. In more recent
production, this feature has been eliminated
as shown in Figure 2B. Please refer to
the appropriate section below for detailed
disassembly and assembly instructions.
Disassembly – Main valve with drain plunger
in cap
(Refer to Figures 2 and 3)
1. Note: for ease of repair, the tools and repair
kits specified in Section 12 and Section 13
should be used.
2. Disconnect tubing from unloader to outlet
flange.
3. Reposition main valve with the cap (2) up.
Remove the cap nuts (7). If the cap is
stuck to the valve body, free it by tapping
around the cap edge with a brass hammer.
Carefully raise the cap about 1 inch from the
body and determine whether the damper (8)
has moved upward while remaining in
contact with the underside of the cap.
If the damper did not rise freely, proceed
with extreme caution in removing the cap.
The dome spring (10) is under compression
and the spring loaded damper may be stuck
in the piston. The damper could suddenly
release after the cap is removed possibly
causing personal injury. Remove the cap
and manifold assembly. Eyebolt holes are
located on the cap diameter for handling
purposes.
Remove damper (8), dome spring (10) and
filter assembly (19). Filter may be removed
by grabbing sleeve with pliers. Set filter
assembly aside for cleaning and inspection.
Re-use if not damaged. Remove and discard
seal (20) at filter port on both cap and body.
Remove plug (18) in cap (2) and remove
drain plunger (17) and spring (16). For valves
in vapor service with a pressure snubber
(93C) (see detail C in Figure 2), remove
and inspect pressure snubber visually
for blockage. Clean snubber if blocked.
For valves in vapor service with remote
sense options, (see detail D in Figure 2)
inspect remote sense fitting (93D) visually
for blockage. Remove and clean fitting if
blocked.
4. Remove piston assembly. For sizes 6 x 8 and
8 x 10, a ½-13 UNC eye bolt can be threaded
into back of piston to aid in removal. The
weight of 6" and 8" pistons may require use
of a lift assist device. Protect disk seat face
from damage.
5. Before removing liner (5), remove and
discard compacted liner seal (13) being
careful not to damage metal surfaces.
Remove liner (5).
6. Use only a 12 point socket to remove
nozzle retaining screws (9) and spring
washers (23). To remove nozzle (3), reinstall
two screws 180 degrees apart without the
spring washers. Tap lightly on screws and
drive nozzle (3) free of seal (15). Remove
screws, nozzle (3), nozzle seal (15) and
extrusion ring (14). Discard screws (9),
washers (23) and nozzle seal (15). Under
no condition re-use items 9, 23 and 15.
Repair – Main valve with drain plunger in cap
Refer to Section 12 'Repair kits' and
Section 13 'Repair tools'.
1. Inspect the nozzle (3) and disk (29) seat
surfaces for nicks or scratches. Restoration
of disk and nozzle seat surfaces should only
require lapping and polishing. If the seat
surfaces are damaged more extensively,
machining may be required. Refer to
Section 14.
2. Inspect piston rings (11 and 12) for
scratches or galling. If replacement
is required refer to ring kits listed in
Section 12. To replace rings, remove rings
and centralizer springs (21 and 22). Discard
rings and springs. Assemble new rings
and centralizers on piston following the
instructions supplied in each kit. If piston
ring expanders described in Section 13
are not available, both rings can be hand
installed on the piston. Carefully expand
correct ring over piston OD. Place brass
shim stock under ring gap end to prevent
scratching piston. Slide ring into groove.
3. Inspect liner (5) interior for damage or
foreign deposits. Replace liner if damaged.
Chemical and/or oxide deposits may be
removed by polishing with 600 grit paper.
3