TL;DR

A lifting safety valve means the pressure controls failed to cut the burner at the operating setpoint. Inspect the operating pressure control and high-limit control for proper setpoint and contact operation. Do not attempt to adjust or prevent the safety valve from lifting.

What you might see

safety valve lifting and discharging steam
boiler pressure rising above the operating pressure setpoint
operating pressure limit control not cutting the burner at setpoint
burner running continuously past the normal cutout point

Likely causes

Tap to mark as ruled out

Operating pressure control set too high or its contacts not opening at the setpoint
High-limit pressure control failed or set above the safety valve setpoint
Safety valve lifting at set pressure due to normal operation, then not re-seating cleanly
Pressure gauge reading incorrect, leading to a wrong setpoint adjustment

Required tools

LOTO kit
Calibrated test pressure gauge
Multimeter for pressure control contact test

Safety first

A boiler with a lifting safety valve is over-pressure. Keep all personnel away from the steam discharge area.
Never block, bypass, or tamper with a safety valve. This creates an explosion hazard and is a regulatory violation.
After any safety valve lift, have the valve inspected and tested before returning the boiler to service.

Procedure

8 steps · ~60 min

1
Do not interfere with the safety valve while it is lifting. The safety valve is the last line of protection.
Warning: Never wire, block, or weight a safety valve open or closed. This is illegal and creates an imminent explosion hazard.
2
Observe the boiler pressure on the calibrated pressure gauge. Confirm whether the operating pressure limit control has opened its contacts and cut the burner.
3
If the burner is still firing above the operating cutout setpoint, manually trip the burner from the emergency stop.
Warning: Do not attempt to reduce boiler pressure by opening blowdown valves or increasing steam load to process. Allow the safety valve to control pressure.
4
Lock out the burner after the manual trip. Allow the boiler to cool before any electrical inspection.
5
Inspect the operating pressure control: verify its setpoint, clean the contacts, and check that the contacts open cleanly at the set pressure using a calibrated test gauge.[1]
6
Inspect the high-limit pressure control for the same. Both controls should be tested and calibrated annually by a qualified boiler technician.[1]
7
After the pressure controls are verified or replaced, have the safety valve inspected by a valve service shop. A safety valve that has lifted may not re-seat correctly and should be replaced.
8
Document the event in the boiler log and notify the facility manager and the boiler insurance inspector.

Sources

Cleaver-Brooks CB Firetube Boiler Operation, Service, and Parts Manual, Cleaver-Brooks
Cleaver-Brooks CB Boiler Operation, Maintenance and Parts Manual, pressure control system and safety valve maintenance (general)
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