5
Servicing Relief Valve
Prior to servicing the relief valve, it is mandatory to shut down
water system by closing both the inlet and outlet shutoff
valves and relieving pressure within the assembly by opening
the #2, #3 and #4 test cocks.
DO NOT REMOVE SPIDER BUSHING FOR SERVICING.
1.
Disconnect the hose from the bottom cover plate to the relief
valve.
2.
An O-ring seals the relief valve body to the main housing. It is
not necessary to tighten the connection beyond firm hand
tightening. The relief valve should be able to be removed by
hand untightening. Unscrew the relief valve from the housing.
3.
Remove the cover plate of the relief valve by removing the
four connecting screws.
4.
Remove the rubber diaphragm from the relief valve.
Be aware of how the diaphragm is configured so that it can
be reinstalled in the same manner. The hard rubber tab in the
diaphragm fits into a similar socket in the head of the piston.
(Figure 1)
Test No.1
Purpose:
To test check valve No. 2 for tightness against
reverse flow.
Requirements:
Valve must be tight against reverse flow under
all pressure differentials. Slowly open the ‘high’ valve A and
the ‘vent’ valve C, and keep the ‘low’ valve B closed. Open
test cock #4. Indicated pressure differential will decrease
slightly. If pressure differential continues to decrease (until
the vent opens) check valve #2 is reported as ‘leaking’.
Test No. 2
Purpose:
To test shutoff #2 for tightness.
Requirements:
After passing Test No. 1, continue to Test No. 2
by closing test cock #2. The indicated pressure differential will
decrease slightly. If pressure differential continues to decrease
(approaching ‘zero’), shutoff #2 is reported to be ‘leaking’.
Test No. 3
Purpose:
To test check Valve No. 1 for tightness.
Requirements:
Valve must be tight against reverse flow under
all pressure differentials. Close ‘high’ valve A and open test
cock #2. Close test cock #4. Disconnect vent hose at test
cock #4. Open valves B and C, bleeding to atmosphere. Then
closing valve B restores the system to a normal static condition.
Observe the pressure differential gauge. If there is a decrease in
the indicated value, check valve No. 1 is reported as ‘leaking’.
Test No. 4
Purpose:
To test operation of pressure differential relief valve.
Requirements:
The pressure differential relief valve must
operate to maintain the ‘zone’ between the two check valves at
least 2psi less than the supply pressure. Close ‘vent’ valve C.
Open ‘high’ valve A. Open the ‘low’ valve B very slowly until the
differential gauge needle starts to drop. Hold the valve at this
position and observe the gauge reading at the moment the first
Figure 1
Figure 2
discharge is noted from the relief valve. Record this as the
opening differential pressure of the relief valve.
Note: It is important that the differential gauge needle drops slowly.
Close test cocks #2 and #3. Use ‘vent’ hose to relieve pressure from
test kit by opening valves A, B and C Remove all test equipment and
open shutoff #2.
5.
Hold the relief valve in both hands with the threaded end up
and both thumbs on the head of the piston. Push up on the
piston until the piston shaft with the attached E-clip is
exposed. Remove the E-clip (Figure 2)
6.
Remove the piston and spring from the relief valve housing
and thoroughly clean all parts including the diaphragm.
Inspect all rubber parts for damage and if damaged, replace
them with new parts.
7.
Reassemble the relief valve in the reverse order that it
was disassembled.
Testing — Reduced Pressure Zone Assemblies
Ball Type Test Valves
A
C
B
Needle
Valve
High Hose
(Yellow)
Low Hose
(White or Red)
Vent Hose
(Blue)
Test Cock
Test Cock
Test Cock
Test Cock
No. 1
No. 2
No.3
No.4
