Boiler Flame Failure Procedures

Power Failure and Equipment Response

• An electrical power failure requires immediate and effective operator response.
• Operators must be well versed in plant blackout procedures and follow them closely.
• Considerations for responding to a power failure include:
  • Control valve failure positions (open, shut, or last)
  • Equipment fed by standby power and what is not
  • Equipment on uninterrupted power
  • Manual starting of standby generators and automatic transfer switches
  • Plant load shedding strategies
  • Restarting equipment after power is restored
  • Sequence of starting equipment after power is restored

Equipment Restart after Power Restoration

• Some equipment will restart automatically when normal power is restored, including:
  • Lighting and power receptacles
  • Pumps and fans that cycle on or off regularly
  • Smaller air compressors, refrigeration compressors, and air dryers
• Equipment that requires manual restart includes:
  • Fuel oil pumps
  • Boiler feedwater pumps
  • Chilled water pumps
  • Condenser water pumps
  • Boiler draft fans
  • Condensate transfer pumps
  • Large air compressors
  • Refrigeration compressors and chillers
  • Air handling unit fans

Valve Failure

• Valves go to a fail-safe position during a power failure.
• Some valves fail open, while others fail shut or closed.
• Control valves fail as follows:
  • Heating system control valves fail open
  • Fuel line safety shut-off valves fail closed
  • Fuel line bleed valves fail open
  • Boiler feedwater regulating valves fail closed (unless self-powered)

Plant Response to Power Outage

• Plants without backup power remain "dead" until normal utility power is restored.
• In this case, the operator's job is to put the plant in a safe state until power returns.
• Tasks required in this situation include:
  • Monitoring the boiler as it cools down
  • Isolating the boiler feed pumps
  • Closing the feedwater control valves
  • Closing the fuel line test firing valves
  • Closing the boiler steam outlet valves
  • Opening the boiler non-return valve drain
  • Opening the vents and drains on the steam headers

Plants with Emergency Power Supply Systems (EPSS)

• EPSS have backup diesel engines, natural gas engines, or gas turbines operating standby generators.
• The generators are connected to automatic load transfer switches.
• Essential loads are typically:
  • Control room panels and instrumentation
  • Emergency lighting
  • Feedwater control valves
  • Fuel control valves
  • Boiler feedwater pumps
  • Condensate pumps
  • Turbine seal oil pumps
  • Turbine lubricating oil pumps
  • Fire water pumps

Plants with Uninterruptible Power Supply (UPS)

• UPS maintains power to critical equipment through a system of batteries, rectifiers, power inverters, and automatic transfer switches.
• UPS powered equipment is typically short-term, with a battery capacity of up to 6 hours.
• UPS systems are designed for low capacity loads, such as instrumentation and controls, computers, and lighting.

Loss of Water Level

• Causes of a loss of water level include:
  • Problem with the feedwater system
  • Problem with the boiler
• Feedwater system problems include:
  • Pump failure
  • Control valve failure
  • Failure to return condensate to the plant
• Boiler problems include:
  • Boiler blowdown or blowoff valves accidentally left open
  • Damaged boiler tubes
  • Boiler feedwater pump failure

Boiler Trips on Low Water

• If the cause of low water cannot be determined quickly, and the water level restored, the boiler must trip on low water.
• After it trips, close the pilot and main test firing valves.
• When the boiler stops steaming, close the non-return valve and header valve, and open the non-return valve drain.
• The boiler should not be restarted until the cause of feedwater loss has been rectified.### Flame Failure Signals
• Do not result from boiler permissive actions such as low water cut-off, fuel pressure switch, or pressuretrol.
• Require shutting pilot and main test firing valves, investigating the cause, and testing flame safeguard controls before restoring boiler to service.

Inadequate Pilot Flame

• Can occur if pilot flame is too small to light main burner due to defective or improperly adjusted pilot fuel regulator.
• ASME CSD-1 recommends annual pilot turndown test to establish minimum pilot flame size for safe ignition of main burner.
• Requires certified burner mechanic (Class A gas fitter) to perform test and adjust pilot flame.

Unstable Main Flame Causes

• Excessive fuel pressure
• Inadequate fuel pressure
• Excessive combustion air
• Inadequate atomizing air or steam
• Dirty atomizer spray plate
• Defective fuel pumps
• Blocked fuel strainers
• Utility gas supply failure

Excessive Fuel Pressure Effects

• Causes over-firing, lifting flames, smoky furnace conditions, and flame instability
• Requires adjustment of fuel pressure and high fuel pressure cut-off to manufacturer specifications by certified burner technician, oil fitter, or Class A gas fitter

Inadequate Fuel Pressure Causes

• Improperly adjusted fuel pressure regulator
• Failure in utility fuel supply system
• Blockage in fuel strainer (for oil burners)
• Defective fuel oil pump
• Requires adjustments by certified burner technician, oil fitter, or Class A gas fitter