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ANDERSON GREENWOOD TYPE 91 AND 94 PILOT OPERATED SAFETY RELIEF VALVES
INSTALLATION AND MAINTENANCE INSTRUCTIONS
3 PILOT MAINTENANCE
Refer to Figure 3, 4 and 5
3.1 Disassembly
To facilitate assembly, place all parts removed
in an orderly arrangement so the correct
parts are assembled in the proper sequence.
Refer to the appropriate figure for parts
description and location.
3.1.1 Begin by removing spring bonnet
(remove the spring compression
before attempting to remove bonnet).
Remove case bolts and upper case.
Loosen tube fittings on boost tube at lower
case and body. Remove spindle nut while
holding hex spacer. Remove diaphragms,
sense and boost plates and spacers.
Remove lower case and spindle/seat
assembly. Remove blowdown adjustment
screw and supply port tube fitting.
3.1.2 Clean all parts and replace all soft goods.
The spindle/seat assembly in the Type 94
pilot is factory assembled and must be
replaced as a unit. If the nozzle in this
pilot is nicked or scratched, it should be
replaced. To remove it, use a deep socket.
The nozzles used on plastic seated pilots
can be reworked, if scratched, by lapping
flat a 2 microinch (0.05 micrometer) finish.
3.2 Assembly
Assembly is done in the reverse order of
disassembly. Lubricate all screw threads and
end of spring adjusting screw that bears against
spring washer. Use Dow Corning No. 33 Silicone
grease or equivalent. When assembling pilot,
the following should be observed:
3.2.1 The holes in spindle diaphragm must
be aligned with all holes in the body.
The small hole in lower case must be
aligned with hole in the body. Two of the
six case bolts for the medium pressure
pilot (Figures 4 or 5) must be assembled
through holes in the lower case before it
is attached to the body. After attachment
there is insufficient clearance to do so.
3.2.2 For the medium pressure Type 94 pilot
(Figure 5), the hole in the boost (lower)
diaphragm and spacer ring must be
aligned with boost tube port in lower case.
The hole in the upper diaphragm must be
positioned away from boost tube part.
3.2.3 Before tightening spindle nut, align holes
in lower case, spacer ring and diaphragms
with case bolts.
Tighten spindle nut snugly but not
excessively. Three diaphragms are
sandwiched in the spindle/stack assembly
and excessive tightening will damage them.
Hold the hex spacer when torquing spindle
nut to prevent the stack from rotating.
3.2.4 Type 91 pilots used on valves for marine
service have a PTFE sense diaphragm.
Standard Type 91 pilots use a stainless
steel sense diaphragm.
Both Type 91 and Type 94 pilots
use gaskets on the sense and boost
diaphragms.
The Type 91 pilot also has gaskets on
the spindle diaphragm.
4
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