6
ANDERSON GREENWOOD
SERIES 93T PILOT OPERATED SAFETY RELIEF VALVES
INSTALLATION AND MAINTENANCE INSTRUCTIONS
5 ACCESSORY REPAIR
5.1 Check valve
The check valves used on the dual pilot,
backflow preventer, and field test consist of an
upper body, a lower body, and a diaphragm.
Refer to Figure 5.
The check valve diaphragm is the only part
that should require servicing. If the diaphragm
is to be replaced, care should be taken not to
scratch or distort it in the center nozzle sealing
area. When reassembling the check valve,
uniformly tighten the body bolts, first one side,
then the opposite side until all are tight. DO
NOT OVERTIGHTEN bolts as this will distort the
diaphragm and cause leakage.
PARTS LIST
Item
Description
1
Hex head cap screw
2
Upper body
3
Diaphragm
4
Nut
5
Lower body
6
Spring pin
7
Lockwasher
8
Diaphragm support washer
FIGURE 5
Flow
Inlet
Outlet
6 LEAK TESTING ASSEMBLY
6.1 General
The complete valve assembly should be leak
tested for internal and external leaks using a
pressure equal to 10% and 90% of set.
6.2 Internal leak test
Cover valve outlet with wet piece of paper and
observe paper for movement. Any outward
movement indicates a leak. If leakage is
detected, remove paper and spray leak test
solution around nozzle/seat to locate leak.
Cause of leakage may be damaged nozzle
seating surface or wrinkled PTFE film seat.
6.3 External leak test
Following the internal leak test, check for
external leakage by applying leak test solution
to all joints and seals. Tighten bolts or fittings
as required.
7 PILOT SET PRESSURE FIELD TEST
PROCEDURE
7.1 General
The pilot set pressure can be checked in the
field by applying an external test pressure to
the pilot through the field test hand valve as
shown in Figure 6.
Note:
if the process pressure at the time of test
is less than approximately 30% of the pilot set
pressure, the main valve will not open. If the
process pressure is greater than 30% and the
main valve must remain closed, temporarily
replace the pilot exhaust vent with an orifice
plug having an orifice diameter of .040”/.060”.
This orifice must be removed on completion of
field testing as it prevents the main valve from
opening.
7.2 Procedure
A. Connect test gas bottle as shown in
Figure 6.
B. Close vent valve “C”.
C. Open field test valve “B”. Test gauge will
read process pressure.
D. Open block valve “A” SLOWLY to increase
pressure until pilot “pops”. The set pressure
will be the pressure indicated on the test
gauge at the time of pop.
E. To remove test set up, close valves “A” and
“B”, open valve “C”.
