• Pressure inside the Furnace will Increase
  • Drum Level will start fluctuating(Sub-Critical Units)
  • Flame will become Unstable
  • Running I.D. Fan Motor current will increase


Possible Causes

  • Electrical System Failure (Fault in the HT Motor/Supply Failure in the Bus/High Winding Temperature)
  • Lube Oil System Failure (Lube Oil Pump Failure/ Lube Oil Pressure Low)
  • Bearing Temperature High
  • Failure of Cooling Water (**For Motor & Lube Oil)
  • High Bearing Vibration
  • Furnace Pressure Very High
  • Furnace Pressure Very Low
  • APH(Air Pre Heater) Tripped


  • Put Furnace Pressure on Manual
  • Decrease load on the running I.D.
  • Cut the Mill & Take Oil Guns in Service for Flame Stability
  • Adjust Load (MW) to boiler condition
  • Stabilize Furnace draft by controlling the remaining fans(ID & FD) & Adjust the SADC(Secondary Air Damper Control) Dampers
  • Stabilize Drum water level(Due to sudden load reduction, there is an increase in the drum level) by opening EBD(Emergency Blow Down)
  • In case Steam Temperature plummets, watch Turbine differentials.

Local Operator Actions

  • Check furnace flame condition.
  • Check tripped fans for causes,
  • Ready them for restart, inform control room.

**I.D. Fan – Induced Draft Fan



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