Safety Valve Leaking After Set-Pressure Adjustment
A 125 psig steam boiler has a safety valve that began weeping at about 118 psig. A contractor's technician, without documentation, adjusts the valve's adjusting ring and compression to stop the weep, then tells the operator the valve is 'good to go.' Two weeks later the valve lifts at what the operator estimates is well above 125 psig, and the boiler's operating pressure gauge reads 130 psig before the valve opens. The plant has no record of the valve's original set pressure or of the adjustment. The boiler is due for its annual certificate inspection in three weeks.
1. What is wrong with what the technician did, and what must happen before the boiler continues in service?
Read the worked answer
A safety valve is a code-required safety device set to protect the boiler at or below its maximum allowable working pressure. Field adjustment of the ring and compression without documentation, testing, or authorization is not an acceptable repair. The result - a valve that now appears to lift above the boiler's operating pressure - means the boiler may be operating with inadequate overpressure protection.
Before continued service:
- Take the boiler out of service or reduce pressure so it is not relying on a suspect safety valve.
- Have the valve removed and either replaced or repaired and re-set by a qualified valve facility, with the set pressure established and documented.
- Verify the set pressure is at or below the boiler's maximum allowable working pressure, consistent with the valve's capacity and the boiler's rating.
- Record the set pressure, the date, and who performed the work, and retain it with the boiler records.
- Report the situation honestly during the upcoming certificate inspection rather than presenting the valve as compliant.
Operating on an undocumented, field-modified safety valve is a serious violation and a direct hazard.
2. The operator wants to simply lower the boiler's operating pressure to 115 psig and keep running until the inspection. Is that a valid interim measure?
Read the worked answer
Reducing operating pressure can lower the immediate risk of lifting the suspect valve, but it does not make the installation compliant and is not a substitute for correcting the valve.
Why it is not sufficient:
- The valve's actual set pressure is now unknown; lowering operating pressure does not establish that the valve will protect the boiler at its maximum allowable working pressure.
- A valve that has been field-modified may fail to reseat or may stick, so 'it hasn't lifted yet' is not evidence of function.
- The certificate inspection will require the safety valve to be in proper condition and properly set; the underlying deficiency remains.
A defensible interim step is to reduce pressure and load as a precaution while arranging prompt removal and re-setting or replacement of the valve, with the correction completed before the boiler is returned to normal service. The reduction is a bridge to repair, not a fix.