Ames Fire & Waterworks 6000HMB Portable Hydrant Meter Backflow Preventers with Meter Housing - Manual (Page 7)

7
Problem Identification Procedures
Troubleshooting Guide
PROBLEM CAUSE SOLUTION
A. Assembly discharges from differential
relief valve during no flow condition.
Fouled first check
Fluctuating inlet pressure
Outlet pressure higher than inlet pressure
& leak in No. 2 check valve
Leak through diaphragm or around flange
bolt holes of relief valve
Pressure relief valve does not close
Disassemble and clean No. 1check valve
Control supply line water pressure
Disassemble, clean #2 check valve &
identify cause of back pressure.
Service relief valve (page 3)
See problem D
B. Assembly discharges from differential
relief valve during a flow condition.
No. 1 check valve wedged open
O-ring displaced from groove in 1st check
Pressure relief valve does not close
Fluctuating line pressure
Disassemble and clean No. 1 check valve
Disassemble and replace
See problem D
C. Differential pressure relief valve does
not open during test due to leaking
outlet gate valve.
Differential pressure across No. 1 check
valve stays above 2psi due to leaking
outlet gate valve
Weak or broken relief valve spring
Shut off seat tube bound in body
Plugged hydraulic hose
Repair shut-off valves
Disassemble and replace relief valve spring
Disassemble and repair
Disassemble and repair
D. Pressure relief valve does not close Debris on sealing surface
Plugged hydraulic hose
Damaged seat or rubber shut off disc
Ruptured diaphragm
Wrinkled or improperly installed diaphragm Remove relief valve and clean
Disassemble and clean
Remove relief valve assembly and replace
Disassemble and replace diaphragm
Disassemble and properly position
diaphragm
When using differential pressure gauge:
A. Check differential across No. 1 check valve
READING
PROBLEM
2 to 3 psid Leak in No. 1 or No. 2 check valve
4 to 7 psid and steady Malfunctioning pressure relief valve
2 to 7 psid Inlet pressure fluctuation
Without using differential pressure gauge:
A. Close gate valve No. 2
RESULT
PROBLEM
If discharge stops Leak in No. 2 check valve
If discharge does not stop Go to B
B. Open No. 4 testcock to produce a flow greater than
differential relief valve discharge
RESULT PROBLEM
If discharge stops Leak in No. 1 check valve
If discharge does not stop Malfunctioning pressure relief valve