Page 137 - Webster Service Manual

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In open loop system, install standpipe, back pressure
valve, vacuum breaker or over-sized drop pipe
Check to assure that pressures at OSV inlet does not
exceed maximum of 60 PSI
Check for leaking or damaged OSV
Check for line failure between OSV and burner pump
Check burner for fuel pump failure or ignition problems
Burner pump seal damaged
Install OSV to assure pressure at burner pump does
not exceed 3 PSI
Install pressure relief valve if entrapment condition is
suspected
Pressure increases in supply line after shutdown
Check to assure that pressures at OSV inlet does not
exceed maximum of 60 PSI
Install pressure relief valve if entrapment condition is
suspected
OIL SAFETY VALVE PROBLEMS
Oil Safety Valve does not open
Too much pressure at inlet of valve
Flow exceeds recommended flow rate for valve.
Entrapment condition (expansion of oil in supply line)
Check for air leaks between the OSV valve and burner
pump