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Boilers often experience failures during operation, and if not addressed promptly, they can lead to serious safety accidents. If abnormalities can be detected early and fault issues resolved, losses can be minimized. Today, we bring you 9 abnormal phenomena in boiler operation, 8 mechanical faults, along with solutions. Let’s take a look! Abnormal boiler water level; boiler is overfilled. Phenomena: ① The water level alarm sounds, and the high-water-level indicator light turns on ； ②All indicator lights of the electric contact water level gauge are on ； ③The drum water level is above the highest visible level ； ④The water supply flow is abnormally higher than the steam flow ； ⑤The salt content in the steam increases ； ⑥Decrease in superheated steam temperature ； ⑦In severe flooding conditions, water hammer occurs in the steam pipes, and steam emerges from the flanges. Reason: ① Automatic water supply failed, and the water supply control device malfunctioned. ②Incorrect readings from the water level gauge, steam flow meter, and feedwater flow meter lead to misjudgments by operators, resulting in incorrect operations. ③The feed water pressure suddenly increased. ④The operators were careless, failed to monitor the water level properly, made untimely adjustments, or performed incorrect operations. Handling: ① When the boiler steam pressure is normal and the feedwater pressure is normal, and if the drum water level exceeds +75mm and it is confirmed that the drum is full of water, the cause must be identified immediately. ②If the water level is affected due to a failure of the automatic water supply system, immediately switch from automatic to manual mode and close the control valve to reduce the water supply. If the water level continues to rise, open the emergency drain valves to release water. ③If the drum water level continues to rise by more than +100 mm, reduce or close the feedwater valve (open the economizer recirculation valve when feeding water is stopped) and increase drainage. ④Depending on the decline in steam temperature, reduce or close the feedwater cooling valve, and open the superheater drain valve if necessary. ⑤If the drum water level exceeds the visible range of the gauge, stop the boiler immediately, close the main steam valve, and notify the electrical and turbine departments to increase the water drainage until the drum reaches a normal water level. When the water level rises due to abnormal feedwater pressure, contact the turbine immediately to restore normal conditions as soon as possible. ⑥Once the fault is resolved, resume the operation of the boiler unit as soon as possible. Boiler water shortage condition: ① The water level alarm goes off, and the low water level indicator light turns on. ②All the negative value indicator lights of the electric contact level gauge are on. ③The drum water level is below the lowest visible level. ④The water supply flow is abnormally lower than the steam flow. ⑤The temperature of the superheated steam increases. Reason: ① Automatic water supply failure. ②Incorrect readings from the water level gauge, steam flow meter, and feedwater flow meter lead to misjudgments by operators, resulting in incorrect operations. ③The boiler load dropped suddenly. ④A failure in the feed water pump causes a drop in feed water pressure. ⑤Leakage in the boiler blowdown pipe and valves, resulting in excessive blowdown volume. ⑥Rupture of the water wall or economizer tubes. ⑦The operators were careless, failed to monitor the water level properly, made untimely adjustments, or performed incorrect operations. Handling: ① When the boiler steam pressure and feedwater pressure are normal but the drum water level is below –75 mm, verify the accuracy of the water level gauge; if automatic control fails, switch to manual operation and increase the feedwater supply appropriately. ②If the water level continues to drop below –100 mm, in addition to increasing the water supply volume, check whether the sewage valves and drain valves are properly closed, and reduce the load if necessary. ③If the drum water level continues to drop and disappears from the drum level gauge, the boiler must be shut down immediately, the main steam valve must be closed, and water must continue to be supplied to the boiler. ④If, due to the negligence of the operators, the water level disappears from the drum level gauge and the electric contact level gauge is unable to determine it, the boiler must be stopped immediately, and the main steam valve as well as the feedwater valve should be closed. After shutting down the boiler, perform a water call; if no water is drawn, it is strictly prohibited to feed water into the boiler. Once water level appears on the gauge after the water call, water can be added to the boiler, while making sure to restore the proper water level. ⑤If the water level drops due to low feedwater pressure, immediately notify the turbine to increase the feedwater pressure. Soda surge phenomenon: ① The drum level gauge experiences severe fluctuations; in serious cases, it becomes impossible to see the water level in the gauge. ②The temperature of the superheated steam drops sharply; in severe cases, water hammer occurs in the steam pipes and steam escapes from the flanges. ③The salt content in steam and boiler water increases, leading to a rise in conductivity. Reason: ① The quality of the boiler water does not meet the standards; the salt content in the suspended solids is too high. ②Waste discharge was not carried out in accordance with regulations. ③The row spacing is too small or not set. ④The load increases significantly. ⑤The drum water level remains too high. Treatment: ① Appropriately reduce the boiler’s evaporation rate and maintain stability. ②Operate the continuous discharge at full capacity; if necessary, open the emergency release valves and regular discharge valves to increase water inflow and outflow, keeping the water level slightly below normal. ③Stop adding the chemical. ④Open the superheater drain valve and inform the turbine to increase drainage. ⑤Notify the laboratory staff to test the boiler water and take measures to improve its quality. ⑥The boiler load is not allowed to be increased until the quality of the boiler water improves. ⑦After the fault is resolved, the water level gauge must be flushed. Abnormal boiler combustion and boiler coking. Symptoms: ① The bed temperature rises sharply and exceeds 1000°C. ②The oxygen level indicates a decrease, even down to zero. ③When observing the flame, the fluidization is poor, and the flame appears white in localized areas or over a large extent. ④When ash is discharged, the amount of ash is low or it cannot be discharged. ⑤In severe cases, the negative pressure continues to increase, and the current of the primary fan decreases. Reason: ① During the ignition and voltage-raising process, coal was added too quickly or in excessive amounts, or coal was added without air supply. ②Improper operation during fire suppression. ③The primary air flow is too low, falling below the critical fluidization air volume. ④The combustion load is too high, resulting in excessively high combustion temperatures. ⑤The coal particles are too large, or the deformation temperature of the ash is low. ⑥Excessive slag discharge causes a low bed material level or complete depletion. ⑦The return material from the returner is abnormal or there is a blockage. ⑧Coal feed interruption; improper handling procedures. ⑨The load was increased too quickly, and the operation was improper. ⑩The air cap is damaged, allowing ash to fall into the air chamber and resulting in uneven air distribution. ⑾The bed temperature gauge is inaccurate or malfunctioning, leading to misjudgments by the operators. ⑿The bed material was too thick; slag was not discharged in time. ⒀The magnet separator does not separate well, and iron particles end up in the furnace, causing poor boiling. Treatment: ① Shut down the furnace immediately. ②Release the circulating ash, and try to remove as much slag as possible from inside the furnace. ③Check for coking. ④Open the manhole door, and pry loose the coke as much as possible to remove it from the furnace in a timely manner. ⑤If coking is not severe, the coke mass is removed from the furnace and then ignition is carried out to start operation. ⑥Coking is severe and cannot be removed while hot; it will be dealt with after cooling. Coking prevention: ① Keep the particle size of coal fed into the furnace below 8 mm. ②The coal feed rate is strictly controlled during the ignition process. ③When increasing or decreasing the load, it is essential to first supply air and then add coal when increasing the load, and first reduce coal and then reduce air when decreasing the load. ④When adjusting combustion, it is necessary to use a method of making small adjustments frequently in order to avoid large fluctuations in bed temperature. ⑤Regularly check the coal feeding condition of the coal feeder, observe the color of the flame in the furnace bed, and ensure that the return conveyor is functioning properly. ⑥During slag discharge, feed it in small amounts frequently based on the pressure difference in the material layer; after the discharge is complete, conduct a thorough inspection. Only after confirming that the slag discharge door is tightly closed can one leave the site. Boiler shutdown phenomenon: ① The temperature of the fluidized bed drops sharply, and the flue gas temperature also decreases. ②The steam temperature and pressure drop. ③The combustion chamber darkened, and the flame could no longer be seen. ④The oxygen level indication increased significantly. Reason: ① A failure in the coal feeder or an accumulation of coal that was not detected in time resulted in an excessively long period with no coal supply. ②The secondary return material is abnormal; there is excessive ash accumulation, which suddenly flows into the furnace. ③Poor coal quality or changes in coal quality, combined with untimely adjustments, lead to poor combustion and engine shutdown. ④The ratio of wind coal is improper. Handling: ① If the coal feeder fails, shut down the furnace immediately and address the issue as soon as possible to restart ignition. ②If the return material is abnormal, discharge ash urgently while increasing the ash discharge rate; under such circumstances, it is strictly prohibited to feed coal into the boiler. ③Strictly control the steam temperature, shut off the desuperheating water and open the superheater drain valve. Clogging of the return feeder: Symptoms: ① It is difficult to control the bed temperature; a slight increase in coal supply causes the bed temperature to rise rapidly and become uncontrollable. ②The steam pressure drops. ③The pressure difference between the upper and lower parts of the furnace decreases. Treatment: ① First, enhance ash discharge to restore smooth flow of the return material as much as possible. ②When the blockage is severe and cannot be resolved, report to the shift supervisor and higher-level management to shut down the furnace and extinguish the fire. Inspect the return feeder; remove any foreign objects, and empty all the ash from the feeder. ③After processing, ignite and increase voltage. Clogging of the slag discharge pipe: Reasons: ① Large foreign objects remained in the furnace before it was started up and were not removed. ②During the fire suppression process, some local charred residues were not completely removed. ③A portion of the furnace wall inside the furnace has fallen off. ④Poor combustion and a high carbon content in the slag lead to re-ignition and coking inside the tubes. Treatment: ① Reduce the load or operate at no load. ②Take safety measures; use rebar to poke at the bottom of the slag discharge area, trying to break up and remove any foreign objects inside the pipe. ③If it cannot be handled properly in a short time, shut down the furnace for treatment. Coal feeder failure. Cause: ① Larger debris has gotten mixed into the coal feeder and caused a jam. ②The coupling pin is broken. ③Fault in the variable-frequency motor. ④The motor is damaged. Handling: ① When two coal feeders are damaged, stop the operation of those feeders and increase the coal feeding rate of the other feeder (under normal coal quality conditions, one feeder can supply sufficient coal for full load operation). ②If all three coal feeders fail simultaneously, shut down the furnace immediately and extinguish the fire. ③Notify for maintenance and emergency repair; restart once normal operation is restored. Secondary combustion of combustibles in the flue: ① A sharp increase in exhaust gas temperature. ②The negative pressure in the flue and furnace changes drastically. ③1. The temperature of the primary and secondary air increases and exceeds the specified value. ④The chimney is emitting black smoke. ⑤Sparks are emerging from the areas where the air ducts are not airtight. ⑥In severe cases, the flue explosion-proof door activates. Reason: ① Excessive air intake volume, resulting in excessive negative pressure. ②The return feeder is malfunctioning, causing a large amount of unburned fuel to enter the flue. ③The separator is damaged and cannot separate properly. Handling: ① When an abnormal increase in flue gas temperature is detected, first identify the cause and verify the accuracy of the instrument readings. ②Strengthen combustion regulation to maintain stable combustion. ③Maintain stable operating parameters. ④If the flue gas temperature continues to rise and exceeds 220°C, shut down the furnace immediately. ⑤Close all access doors and baffles; ventilation is strictly prohibited. ⑥After the temperature drops and it is confirmed that there are no sources of fire, the exhaust fan can be started to ventilate for 5–10 minutes to remove the accumulated dust, after which ignition can be attempted again. Damage to the pressure-bearing components of the boiler; damage to the water wall. Symptoms: ① The water level indicated by the drum level gauge drops rapidly. ②The water flow rate is abnormally higher than the steam flow rate. ③In the case of a minor leak, there is a sound of steam escaping; in severe cases, there are explosions inside the furnace along with steam release, and the furnace shuts down. ④Steam pressure and feedwater pressure decrease. ⑤The smoke exhaust temperature decreases. Reason: ① Poor quality of boiler feed water, inadequate chemical monitoring, and failure to carry out blowdown as required, leading to scaling and corrosion inside the pipes. ②During maintenance and installation, the pipes became clogged with debris, resulting in poor water circulation and causing the pipes to overheat and crack. ③Defective manufacturing, substandard materials, improper installation, and poor welding quality. ④Improper operation due to severe water shortage in the boiler. ⑤Improper start-up and shutdown procedures led to excessively high temperatures in certain sections of the pipe wall. ⑥The wear-resistant layer of the water wall is defective, resulting in severe wear. ⑦Poor expansion of the pipe led to cracks at the weld seam. Handling: ① If the water wall tubes burst and it becomes impossible to maintain the drum water level, shut down the boiler immediately, inform the shift supervisor and relevant supervisors, and keep the induced draft fan running. ②Increase the feedwater pressure and volume to maintain the drum water level. ③If the damage is severe and the boiler’s steam pressure drops rapidly, and increasing the water supply still fails to maintain the drum water level, stop feeding water. ④After the steam in the furnace has been exhausted, stop the exhaust fan. ⑤If the damage to the boiler’s water wall is not severe, and it is possible to maintain the normal water level without the fault worsening rapidly, the boiler’s evaporation rate can be reduced appropriately. At the same time, the shift supervisor and relevant managers should be informed, awaiting instructions to shut down the boiler. However, if the fault continues to worsen (with increased noises, more leakage, and risk to adjacent pipes), the boiler must be shut down immediately. Damage to the economizer tubes: Phenomenon: ① The feedwater flow rate is abnormally higher than the steam flow rate; in severe cases, the water level in the drum drops. ②The return flow from the secondary return feeder is abnormal; in severe cases, the ash discharge pipe fails to discharge ash, or water is discharged (Plant No. 1). ③The smoke resistance increases, causing the current drawn by the exhaust fan to rise. ④The flue gas temperature in the economizer and air preheater decreases, resulting in an increased temperature difference between the two sides. ⑤There is a leaking sound in the economizer flue. Reasons: ① Large fluctuations in the water temperature and flow rate of the economizer, severe water hammer, and improper operation of the recirculation circuit. ②Poor water quality causes corrosion of the pipe walls. ③Fly ash wear. ④The material of the economizer tubes is of poor quality, or the manufacturing or welding is inadequate. ⑤The pipe is blocked by debris, causing localized overheating in the pipe. Actions to take: ① Reduce the boiler’s evaporation rate, and bring the standby boiler online as soon as possible or increase the evaporation rate of other boilers. Report this to the shift supervisor and senior management; only after obtaining their approval can the boiler be shut down. ②If the normal water level cannot be maintained during operation, or if the degree of damage increases, shut down the boiler immediately; keep the exhaust fan running, and stop it once all the steam has been discharged. ③To maintain the drum water level, water can be continued to be fed into the boiler; all drain valves should be closed, and it is strictly prohibited to open the economizer recirculation valve. Superheater tube damage: Phenomenon: ① The steam flow rate is abnormally lower than the feedwater flow rate. ②When the damage is severe, the steam pressure of the boiler drops sharply. ③The negative pressure at the boiler outlet is abnormal; in severe cases, steam sprays out from the leaky areas. ④The flue gas temperature after the superheater is low, or the temperature difference between the two sides is large. ⑤The temperature of the superheated steam changes, there is leakage on the inlet side, and the steam temperature is high ； Leak on the outlet side, low steam temperature. ⑥There is a noise at the overheater leak. Reason: ① Lax chemical supervision and poor separation in the steam-water separator led to poor steam quality, as well as scaling inside the superheater tubes, causing overheating of the tube walls. ②Improper operation during ignition and voltage boosting, along with insufficient steam flow to the superheater, led to overheating. ③The normal operating temperature is too high, and overheating is caused by improper operation. ④The flow rate of the water used for temperature reduction is too high, and there are leaks in the temperature reduction pipes; this results in the formation of water plugs in the superheater, causing localized overheating. ⑤The superheater material does not meet the standards, and its manufacturing and installation were poor. ⑥The superheater tubes are blocked by debris. ⑦Fly ash causes severe wear; lack of maintenance over time leads to tube creep. Handling: ① Appropriately reduce the load and decouple the desuperheater. ②Activate the drains on the superheater and main steam pipes as necessary. ③Report to the supervising manager and shift supervisor. Cooler damage. Symptoms: ① The temperature of the superheated steam decreases, and the temperature difference between the various steam conduits increases. ②In severe cases, shock occurs in the steam pipes, causing a sharp drop in temperature. Reasons: ① Excessive variation in the amount of desuperheating water. ②The desuperheater is fouled, has defects, and the water pipes are bent too much. ③Poor installation or maintenance. Handling: ① Appropriately reduce the load and decouple the desuperheater. ②Open the drain valves on the superheater and main steam pipes as necessary. ③Report to the supervising manager and shift supervisor. Damage to steam and feedwater pipes: Phenomenon: ① When there is a slight leak in the pipes, the insulation layer becomes damp, steam leaks out, or water drips. ②When the pipe is blown up, it makes a loud noise and sprays water and steam. ③The readings on the steam or water flow meter show abnormal changes; upstream of the rupture point, the flow rate decreases, while downstream of it, the flow rate increases. Reason: ① Poor pipeline installation; the material, manufacturing, or welding do not meet the requirements. ②The pipe supports and hangers are not installed correctly, which affects the free expansion of the pipes. ③The water supply quality is substandard, causing corrosion of the pipe walls. ④The water supply system is not operating properly; there are large pressure fluctuations, causing water hammer or vibration. ⑤Insufficient warming of the steam pipes led to severe water hammer. Handling: Damage to the feed water pipe: ① When normal water supply can still be maintained, operation may be continued for a short period. In such cases, report the situation to the shift supervisor and relevant supervisors; subsequent handling or boiler shutdown will be determined accordingly. If the fault worsens to the point that the normal water level cannot be maintained, posing a threat to equipment and human safety, the boiler must be shut down immediately. ②Shut down the furnace immediately in case of a water pipeline explosion. Steam pipe damage: ① In the event of a minor leak that allows operation for a short period, report to the shift supervisor and senior management, and wait for further action. ②Shut down the furnace immediately in case of severe leakage or explosion. ③Disconnect from the system immediately when the steam main bursts. Water hammer in boiler pipes: Phenomenon: ① The pressure gauge on the pipe where water hammer occurs shows unstable readings, and in some cases the gauge gets damaged. ②There is a sound of water impact; in severe cases, the pipes vibrate and steam emerges from the flanges. Reason: ① Sudden changes in feedwater pressure and temperature. ②The check valve or water supply control valve in the water supply pipeline is not functioning properly. ③Air was not exhausted during water pressurization, resulting in an excessive water flow rate. ④The amount of water used for temperature reduction is too small, causing the cooling water to vaporize; the feedwater temperature is too high, leading to vaporization as well. ⑤The water inlet temperature to the cold furnace is too high or too rapid. ⑥The pipes were not warmed sufficiently, and the drain water was not completely removed. ⑦The steam temperature is too low or the steam contains water. Handling: ① When there is a shock in the water supply pipeline, reduce or close the water supply valve, and slowly open it once the shock has passed. ②When there is pipeline shock behind the feed water valve, it can be closed partially, the economizer recirculation valve can be opened, and then closed once the issue disappears. ③When a shock occurs in the desuperheater, reduce the load and disconnect it; restart it once the shock has passed. ④During water hammer in the steam pipeline, shut off the desuperheating water, open the drain valve on the main steam pipeline, and inform the turbine to pay attention to the steam temperature and increase drainage. Electrical system failure, sudden load reduction. Phenomenon: ① The steam pressure in the boiler rises sharply. ②The steam flow dropped sharply. ③The drum water level drops momentarily before rising again. ④In severe cases, the safety doors activate (superheater, drum). ⑤The electrical load suddenly decreased. Treatment: ① Immediately open the exhaust valve to release steam. ②Reduce the coal and air supply accordingly, and stop coal feeding if necessary. ③Change all to manual. ④Adjust the air volume, coal quantity, and water supply amount based on steam pressure and water level. ⑤Depending on the steam temperature, reduce the amount of cooling water used or shut off the cooling water supply; if necessary, open the superheater drain valve. ⑥If the safety door does not operate or return to its position at the specified value, manually operate it to lift and return it to place. Power outage in the boiler plant: ① Motors trip, indicator lights flash, and the accident alarm goes off. ②The thermal instruments lose power, resulting in abnormal readings. ③The voltmeter and ammeter readings return to zero. ④The boiler’s steam temperature, steam pressure, and water level all dropped sharply. Handling: ① Immediately switch the motor switch to the stop position and proceed with shutting down the furnace. ②In the event that the power supply for the entire plant is lost, stop coal feeding immediately, shut down the boiler and extinguish the fire, close the main steam valve and the feedwater valve, open the economizer recirculation valve, close the drain valve, and try to maintain the water level. ③If the feed water pump has power, it maintains normal water supply to the boiler. ④If the power supply to the boiler control panel is lost, a dedicated person must monitor the water level on-site to ensure proper water supply to the boiler. ⑤Once power is restored, the shift supervisor gives unified instructions to start the motors one by one to prevent simultaneous startup. ⑥If the power supply is out for an extended period and the water level in the drum cannot be seen via the gauge, water must first be admitted into the system; only after water can be introduced can more water be added. It is strictly prohibited to add water if no water can be drawn out. All the bed material must be removed first, and the boiler must be completely cooled before water can be supplied to it.