Boilers are the heart of any thermal power plant, process industry, or utility system. Whether it is a water tube boiler, fire tube boiler, AFBC boiler, or HRSG, smooth boiler operation is critical for plant reliability, safety, and efficiency.
In real plant conditions, boiler operators and engineers frequently face operational disturbances such as pressure fluctuation, flame failure, high stack temperature, tube leakage, drum level instability, and feedwater issues. Effective troubleshooting requires systematic analysis, technical knowledge, and practical experience.
This detailed guide covers common boiler problems, root causes, diagnostic steps, and corrective actions, making it useful for plant engineers, shift in-charges, and BOE aspirants.
Following is the detailed guide for Boiler troubleshooting.
| SL No. | Problem | Cause | Remedy |
| A | Start up | ||
| 1 | Boiler Pressure not building up | Low furnace temperature | Raise the furnace temperature up to ignition temperature of fuel being burnt. |
| More/less fuel | Adjust the fuel feeders | ||
| Low/High furnace draft | Adjust the fan speeds and dampers | ||
| High moisture fuel | Use low moisture fuel | ||
| 2 | High main steam temperature | High firing rate | Reduce and adjust the firing rate |
| Excess combustion air | Optimise the FD and SA air | ||
| Negative draft | Maintain balanced draft in furnace (+2 or -2 mmwc) | ||
| High moisture fuel | Use low moisture fuel | ||
| More steam flow | Control start up vent control valve | ||
| Attemperator control valve not in operation | Take attemperator valve in line | ||
| 3 | Low main steam temperature | Low firing rate | Adjust the firing rate |
| Less combustion air | Increase the FD and SA air | ||
| More furnace draft | Maintain balanced draft in furnace (+2 or -2 mmwc) | ||
| Low moisture fuel | Use right moisture fuel | ||
| Less steam flow | Increase start up vent valve | ||
| More Attemperator water flow | Reduce the attemperator valve, operate the valve manually as per requirement | ||
| 4 | Frequent high drum level | More firing rate | Reduce firing rate |
| Fast start up | Follow start up | ||
| Feed water valve passing | Check and isolate the required valve | ||
| IBD valve not operated | Check and open the valve | ||
| Sudden opening of start-up vent valve | Open the valve gradually. Or close start up vent suddenly when drum level is on higher side | ||
| More feed water flow | Reduce the feed water flow | ||
| 5 | Low drum level | Sudden pressure rises | Follow start up curve |
| Low feed water flow | Increase feed water flow | ||
| IBD valve is more open | Control the IBD valve | ||
| Sudden closing of start-up vent control valve | Close valve gradually. | ||
| 6 | Clinker formation | Low bed height | Increase the bed height-250-280 mm for start up |
| Sudden bed temperature rise | Follow the start-up curve | ||
| Lack of FD air | Increase FD air flow and maintain wind box pressure | ||
| Foreign materials in coal | Use good quality coal | ||
| High moisture coal | Use good quality coal | ||
| Poor light up skills | Deploy skilled operators for operation | ||
| Over feeding of coal | Adjust the coal feeding | ||
| Bed material contamination | Drain and top up the bed | ||
| 7 | APH jamming | More cold air from APH during start up | Partially by pass the APH |
| 8 | Uneven thermal expansion in headers | Poor start up curve | Follow controlled start up curve |
| Obstacles for expansion | Check and remove the obstacles | ||
| 9 | Feed pump Cavitation | Low deaerator level | Maintain Deaerator level around 65-75%. Maintain NPSH |
| Air ingress in suction line | Ensure all the joints are properly sealed | ||
| High feedwater temperature | Maintain feed water temperature within design limit to avoid the formation of vapour at pump’s suction | ||
| Suction strainer choking | Clean the strainer | ||
| 10 | Tube leakage | Rapid firing rate | Control firing rate |
| Improper venting | Ensure proper venting, close the vent valves at pressure more than 3 Kg/cm2 | ||
| Low water level | Maintain water level | ||
| Low steam flow from super heater coils | Open start up vent. Do not start the Boiler with start up vent valve close | ||
| Cold water thermal shock | Warm up the Boiler gradually | ||
| Header blow down at higher pressure and temperature | Do not operate the water wall bottom headers at higher firing rate. Can be opened at 10-15% of the working pressure | ||
| B | Normal operation | ||
| 1 | Boiler pressure fluctuation | Poor fuel quality | Correct the fuel quality |
| Unbalanced draft | Maintain balanced draft | ||
| No fuel | Check bunker/silo level | ||
| More steam demand | Reduce the steam demand | ||
| 2 | High main steam temperature | High firing rate | Reduce and adjust the firing rate |
| Excess combustion air | Optimise the FD and SA air | ||
| Negative draft | Maintain balanced draft in furnace (+2 or -2 mmwc) | ||
| High moisture fuel | Use low moisture fuel | ||
| More steam flow | Control start up vent control valve | ||
| Attemperator control valve not in operation | Take attemperator valve in line | ||
| 3 | Low main steam temperature | Low firing rate | Adjust the firing rate |
| Less combustion air | Increase the FD and SA air | ||
| More furnace draft | Maintain balanced draft in furnace (+2 or -2 mmwc) | ||
| Low moisture fuel | Use right moisture fuel | ||
| Less steam flow | Increase start up vent valve | ||
| More Attemperator water flow | Reduce the attemperator valve, operate the valve manually as per requirement | ||
| 4 | Super heater coil leakage | Rapid firing rate | Control firing rate |
| Low load operation | Maintain load more than 50% | ||
| Pop up of both drum safety valves | Ensure super heater safety valve is set at lower pressure than drum safety valve. Note: Pop up of drum safety valve before line safety valve leads to starvation of super heater coils | ||
| Overheating of coils | Check the flue gas path and maintain the temperature profile | ||
| 5 | Low Boiler pressure | No/Low fuel | Check the bunker level and adjust the feeding rate |
| Poor quality fuel | Ensure right quality fuel | ||
| High moisture fuel | Replace the high moisture fuel Increase excess air | ||
| Higher steam demand | Reduce the steam demand | ||
| Improper air and fuel mixture | Adjust the air fuel mixture | ||
| 6 | Low drum level | Low feed water flow | Check pump speed, control valve opening and increase the feed flow |
| Sudden trip of Boiler feed pumps | Check the cause and restore the pumps operation | ||
| Sudden closing of feed station control valves and motorized valves | Check the cause and restore the valves operation | ||
| 7 | High furnace draft | Sudden trip of ID fan | Check the cause and restart |
| Interlocks not working | Set the interlocks of fans properly | ||
| More fuel in furnace | Adjust the fuel feeding | ||
| High moisture fuel | Get the low moisture fuel | ||
| Failure of auto combustion logic | Check and correct the auto combustion logic | ||
| 8 | Low furnace draft | Sudden trip of FD fans | Check and start the fans |
| FD fans speed reduction | Check and maintain the desired speed | ||
| Low or no fuel in furnace | Adjust the air fuel mixture | ||
| Human error | Select skilled operators | ||
| 9 | High stack temperature | Poor performance of APH | Clean the APH tubes in every shutdown |
| Poor performance of Economiser | Clean the Economiser tubes in every shutdown | ||
| APH bypass damper is open | Check and close the APH bypass damper | ||
| Soot accumulation on pressure parts | Operate soot blowers regularly Clean the tubes in every shutdown | ||
| 10 | High silica in drum water | Feed water silica is more | Maintain feed water silica within limit less than 0.02 ppm Increase CBD valve |
| Sudden increase in steam demand | Control steam demand Increase CBD valve | ||
| 11 | Sudden drop of Boiler water pH | Feed water pH is less | Improve feed water pH |
| HP dosing is stopped | Check and restore the pump operation | ||
| Contamination in feed water or process return condensate | Check conductivity and pH and isolate the contaminated water | ||
| 12 | Pop up of all safety valves (Drum and super heater line safety valves) | Sudden cut off of more than 80% of the Boiler load | Inform process steam and try to normalise the load Reduce firing rate |
| Turbine trip | Reduce firing rate Normalise the Turbine operation | ||
| C | Shut down | ||
| 1 | Furnace explosion | Residual unburnt coal in bed | Follow shutdown procedure |
| Sudden air reduction | Check and maintain the desired air flow | ||
| Furnace pressure fluctuation | Maintain balanced draft | ||
| Do not open inspection doors immediately | |||
| 2 | Drum Level Collapse (Shrink Effect) | Rapid firing stop | Gradually reduce the firing rate Control feedwater manually |
| Sudden load rejection | Reduce boiler load gradually | ||
| 3 | Thermal Shock & Tube Leakage | Quick water filling in hot boiler | Controlled cooling rate |
| Rapid temperature drop | Avoid cold water injection | ||
| Excessive cold air entry | Maintain gradual depressurization | ||
| 4 | Clinker Solidification in AFBC/CFBC | Bed temperature drops | Maintain fluidization air during cooling |
| Molten ash solidifies | Gradual bed temperature reduction | ||
| Avoid sudden air cut-off | |||
| 5 | Vacuum Formation in Boiler Drum | All vents closed | Open drum vent after pressure drops |
| 6 | Feed Pump Running Dry | Steam demand drops, so Feedwater flow reduces | Maintain minimum recirculation line open & Stop pump after stabilization |
| 7 | Refractory Cracking | Sudden FD fan shutdown | Gradual cooling |
| Rapid depressurization & Cold air exposure | Maintain small airflow for uniform cooling | ||
| 8 | Steam Line Water Hammer | Steam condenses in pipeline | Open drain valves |
| 9 | Economizer Steaming | Residual furnace heat | Monitor economizer outlet temperature |
| No water circulation | Maintain feedwater circulation |
Why start up of the Boiler is more risky than normal operation?
Because;
- Combustion is unstable
- Metal parts are expanding
- Water chemistry is stabilizing
- Control loops may be in manual mode
What are the consequences of improper shutdown of the Boiler?
Improper shutdown can lead to:
- Furnace explosion
- Tube leakage
- Drum level accidents
- Thermal stress damage
- Vacuum formation
- Refractory cracks
- Equipment seizure
What are some common mistakes done during Boiler shut downs?
- Stopping fans before purging
- Rapid depressurization
- Closing vents early
- Ignoring drum level shrink
- Stopping feed pump immediately
- Not maintaining bed fluid
