Daily Walk-down Checks in Pulverized Coal fired Boiler - Furnace area

Daily walk-down checks in a power plant and process boilers gives a good feel about the boiler performance and health of the boiler to the shift in-charge and the operators. The main components of walk-down check are visual, sound, feel control room data and local gauges. This information will help to understand the performance of the equipment and take any action required to improve or sustain its performance.

• Walk-down starts from the boiler control room. Note the load on the boiler, all other major parameters which you would like to have with you while going around, the vibration levels of rotating equipment, when the wall blowing was done to know time lapse after wall blowing and soot blowing, the excess air, the percentage combustibles and coal analysis available as the latest. Make sure that the walk-down is taken up only when the load is steady and not when transient. During transient and fluctuations of load you may have need to look at certain specific parameter and behavior to look at. This will be a list from your daily walk-down and control room data.
• After noting down the details from control room it will be a good idea to go to the top floor of the boiler and start the walk-down from there. Normally drum floor is the top most floors and the pent house above this.
• It will be a good practice to open the pent house man hole door and using a light just look for any division from the regular appearance, like any hanger rod bent, any ash puff at any location, the rocker arm position, etc. Also carefully watch and listen for any steam leak noise.
• Coming down to drum area look for
  • Leakage of steam from any valves
  • Leakage of steam from the drum man hole gasket – if yes this need immediate shutdown of boiler and attending. This is a very rare occurrence but has taken place.
  • Look at the local water level gauge level indicated simultaneously verifying with the control room reading used for drum level control. Note any large variations for corrective action.
  • Check the safety valves for any leak or abnormality
  • Look at the expansion guides at the drum floor for any abnormality
  • Look at the corner connections of the buckstays / furnace rap
• Watch and listen for any abnormal noise or steam leak noise at each location – If steam leak detection system is provided in the boiler then take extra care to listen in areas where the frequency indicated is higher but lower than alarm level.
• Open the first peep hole from top available and watch for flame licking or high deposit on the tubes. Also look for any black particles on the ash deposited on the peep hole frame inside portion.
  • Note: Opening peep hole while boiler is under operation must be done carefully. Be on the door side of the peep hole and slowly open to see any positive pressure inside the furnace. Wait for a second or two to be sure of absence of furnace puffing. Never put you head and eyes too close to the peep hole. Always hold the door handle as you can close the door if you suspect any furnace pressurization.
• Each floor as you are coming down go round the furnace and note each corner connections, the valves for any leaks, any abnormal sound, any vibration, the flame condition and fluctuations, the deposition on walls and panels, the carbon particles on the peephole inside, note also if any bridging of the opening with slag note also if it is flowing or solid, look for any expansion restraint in each area.
• It will be a good practice to carry few small bags and a scope to collect the carbon particles seen and any deposit noticed. Care must be taken not to hurt you as these will be at a much higher temperature.
• When you are in the burner floor look at the various damper positions and correlate with the control room data and flame condition. Look for any oil leak in the start-up oil burners.
• Look for any ash leak from any area as you are coming down and note this location.
• After reaching the bottommost peephole (Normally at the bottom hoper level), open this and watch the deposit fall to the bottom hopper. Note the size, frequency, have an idea about the quantum, the brightness as it falls, is there any brightening and dimming in this location inside the furnace. All this will aid you to evaluate the flame and combustion behavior of the boiler.
• Further below look at the seal turf water level, any ash accumulation and overflow.
• Coming to the ground level look at the bottom ash for large clinkers, unburnt carbon, and watch the quantity too.
  • Note: This is possible only if it is a continuous evacuation system, however in water impounded hopper watch for these during evacuation

About the Author

Dr V T Sathyanathan is a boiler consultant with 35 years of experience in various areas of high pressure boiler trouble shooting. He holds a PhD in coal combustion in boilers.

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