Hazard points of boilers and their control measures

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Hazard points of boilers and their control measures ▓ One steam pump trips during operation. Hazard factors and hazard analysis: 1. The steam pump trips, and improper adjustment after the electric pump is started leads to damage of the check valve； 2. If adjustments are not made in a timely manner during the process of activating a backup pump in response to a trip, it can lead to a water shortage in the boiler, resulting in equipment damage ； 3. The tripped electric feedwater pump does not operate properly in conjunction with the other systems, and it cannot be started manually; the failure to reduce the load in a timely manner leads to a shutdown due to water shortage, or improper adjustments result in a shutdown caused by flameout ； 4. One steam pump tripped; after the electric feedwater pump started operating, no action was taken promptly to have the turbine shut down the electric pump’s recirculation function. As a result, the feedwater supply failed automatically, and the boiler could not be supplied with water in time, leading to a water shortage. Specific control measures: 1. After one steam pump trips, it is necessary to check whether the electric pump activates automatically; prompt contact should be made with the steam turbine to restart the electric pump. If it cannot be restarted, the load must be reduced urgently, and the output of the operating steam pump should be adjusted until the feedwater flow and steam flow are in balance. 2. During the process of adjusting the water level after a backup electric pump activates following the trip of one steam pump, the personnel responsible for adjusting the water level must do so based on the steam flow and feedwater flow. If the water level in the steam drum is low, the feedwater flow should be slightly higher than the steam flow to allow the water level to rise steadily ； 3. When adjusting the scoop tube of the electric pump, operate it in short bursts; after each operation, check the change in the feed water flow rate. If it is not sufficient, operate it again and check the flow rate once more. Under no circumstances should the adjustment valve of the feed water pump’s scoop tube be kept open or closed for an extended period, as large-scale adjustments should be avoided ； 4. If the electric pump is successfully linked, contact the steam turbine promptly to close the recirculation valve ； 5. During the handling process after the feed water pump trips, if the water level protection reaches the MFT activation value but the MFT does not activate, the MFT should be activated manually immediately ； ▓High-altitude work at heights of 12.6 m in the boiler and at the top of the furnace: Hazard factors and hazard analysis: 1. Falls of workers from high altitudes ； 2. Injury to others caused by falling objects from heights ； 3. Burns are likely to occur when working with high-temperature and high-pressure pipelines ； 4. Burns are likely to occur when working near the fire viewing hole and charring hole ； 5. It is easy to slip and fall when going up and down stairs. Specific control measures: 1. Operators must wear their safety belts properly when working ； 2. In the event of falling objects from heights, temporary fences should be installed at appropriate locations, such as at 9 meters height ； 3. When working near high-pressure and high-temperature pipes, heat-resistant work clothes should be worn ； 4. When working near the fire viewing hole and charring holes, a flame-resistant suit should be worn ； 5. Hold the handrail when going up and down stairs ； 6. Operators should apply even force when opening and closing valves to prevent the hook from slipping, which could lead to falls from a height ； 7. When working for extended periods, contact the chief operator and place a warning sign on the panel. ▓The boiler water seal baffles are not properly designed, which can lead to accidental activation. Hazard factors and hazard analysis: 1. Sudden power supply results in all the water seal baffles opening ； 2. After power is supplied, the operator will not perform any operations ； 3. The actuator for the water seal baffle is inadequate ； 4. Cause the boiler to shut down or overheat, affecting its safe operation ； 5. There are people around, which can lead to physical injury. Specific control measures: 1. Strictly enforce the work order system; no one is allowed to carry out work on the water seal baffles without permission ； 2. After the water seal baffle is closed, contact the electrical department to cut off the power supply to the hydraulic pump; when restoring power, permission from the boiler operator must be obtained and supervision on site is required ； 3. After the electrician supplies power, the operator should first check whether the current status of the water seal baffle matches the status of the control buttons; if not, the actuator button for the water seal baffle must be reset before proceeding with the operation ； 4. Regularly conduct tests on the water seal baffle switch ； 5. Strengthen inspections; if damage to the actuator of the water seal baffle or a lack of oil is detected, maintenance should be carried out promptly. If the hydraulic pump fails to generate pressure, maintenance personnel should be notified immediately. If the water seal baffle becomes stuck due to burning, it should be removed right away, and the water seal baffle should be closed ； 6. Before operating the water seal baffle, coking removal should be stopped and all manholes should be closed ； 7. The operator shall stabilize the combustion, stop adjusting the load, make significant changes to the combustion process, start and stop the coal grinding system, etc., and post warning signs at the control panel such as “Slag extractor under maintenance – pay attention to combustion” ； 8. All work is prohibited around the slag skimmer to prevent burns from red ash being sprayed out. ▓Name of hazard: High bearing temperature during turbine operation. Hazard factors and hazard analysis: 1. Oil emulsification, resulting in poor lubrication effects ； 2. Burned bearings or bushings ； 3. When the temperature of the critical transition bearing reaches its upper limit, a protection mechanism is activated, which affects the unit’s load; in severe cases, this can lead to the shutdown of the unit. Specific control measures: 1. Improve the quality of inspections; during inspections, carefully check whether the lubricating oil and cooling water are functioning properly, as well as whether the temperatures and vibrations are stable ； 2. The monitoring of the rotor shaft temperature is carried out simultaneously with the routine inspections of the rotor; inspections are conducted at regular intervals, while readings are taken at halfway points, to ensure that the rotor shaft temperature remains within the monitored range at all times ； 3. Always pay attention to the lubrication system for the motor bearings involved in drawing, feeding, ball movement, and sealing processes, to ensure that all bearings and bearing shells are properly lubricated ； 4. For bearings with forced circulation, it is necessary to control the amount of oil supplied properly, ensuring that the oil level remains below 1/2 of the maximum level. Too little oil can lead to an excessively low oil level or a lack of oil in the bearing, which may result in damage to the bearing or the spindle. On the other hand, too much oil can cause the oil level to rise too high, leading to oil leakage or an inability to dissipate heat, thereby increasing the temperature of the bearing ； 5. For bearings equipped with oil rings, it is necessary to pay attention to whether the oil ring is discharging oil properly ； 6. The shaft temperature gauges in the control room should be regularly checked both in the control room itself and on-site to ensure their reliability; in case of any abnormalities or a significant discrepancy between the readings and those obtained on-site, thermal engineering personnel should be notified promptly ； 7. The readings taken must be accurate; it’s not allowed to use fictional readings ； 8. The oil inlet valve for the transfer gear bearings may close due to prolonged vibration, resulting in a lack of oil supply to the bearings or the main bearing housings; it is necessary to check this during inspections ； 9. Careful inspection is required before starting a backup transfer unit, especially one that has been overhauled: check whether the foot screws are loose, whether there is sufficient cooling water, whether the oil level is normal, whether the oil quality is satisfactory, whether the shaft temperature sensors are properly connected, and whether the electrical wiring is in good condition ； 10. When the oil level is found to be too low, lubricant of the same type should be added promptly; if the oil becomes emulsified or turns black, it is necessary to notify someone to replace it immediately ； 11. For bearings with severe oil leakage, the oil level should be checked regularly to ensure it remains at the proper level ； 12. In summer, as the ambient temperature rises, the temperature of the bearings also increases. Water must be used to cool the bearings, but care must be taken to prevent water from entering the bearings and deteriorating the oil, as this would prevent proper lubrication of the bearings and could lead to an increase in temperature or even damage to them ； 13. Protection tests for bearings equipped with protection systems should be carried out properly to ensure reliable operation of such protection mechanisms ； 14. Countermeasures should be taken to prevent vibration-induced automatic shutdown when the throttle is increased during operation. ▓Unclear view on the steam and water side of the on-site water level gauge in the drum, as well as dirty glass plates. Hazard factors and hazard analysis: 1. The unclear view on the steam and water side makes it difficult to monitor the drum’s water level in case of an accident ； 2. Unclear conditions on the soda side lead to incorrect assessments of water level by operators, resulting in improper operations ； 3. If the steam and water sides of the in-situ level gauge are not clear, it eliminates the basis for comparing with other level gauges, which can easily lead to an inability to determine the water level and result in water level-related accidents. Thus severely damaging the boiler’s heating surfaces ； 4. The local water level gauge is dirty, preventing proper observation of the water level; it also makes it difficult to detect cracks in the glass plate in a timely manner. It can easily cause leaks in the level gauge and ruptures of the glass plate, and handling it can lead to burns. Specific control measures: 1. If the operators notice that the color of the water level gauge is unclear, they should promptly notify the maintenance team to make adjustments or replace it ； 2. In case of abnormal water level during operation, compare it with relevant meters such as feedwater flow and steam flow. Propose potential accident scenarios and countermeasures in a timely manner; avoid operating blindly ； 3. Regular attention should be paid to the calibration of local level gauges and other water level gauges; any inaccuracies in the readings of these gauges in low-lying areas should be reported promptly so that repairs can be carried out ； 4. The glass plate of the water level gauge should be cleaned promptly if it becomes dirty; regular cleaning of the water level gauge cannot be taken lightly ； 5. Safety measures should be implemented slowly before maintaining the water level gauge, and anti-scalding precautions should also be taken to prevent accidents ； 6. During inspections, operators should pay attention to the condition of the light tubes, checking whether they are functioning properly and whether the light output is sufficient. ▓Damage to the large bearing of the ball mill: Hazard factors and hazard analysis: 1. Interruption of lubrication oil supply to the ball mill, tripping of the low-pressure oil pump, failure of the oil pump interlock ； 2. The quality of the lubricating oil is substandard, resulting in poor lubrication or the presence of impurities in the oil ； 3. Interruption of lubrication oil due to vibration causing the feed valve for the large bearing of the ball mill to close ； 4. Damage caused by poor cooling due to a disruption in the cooling water supply for the large bearings of the ball mill, or due to insufficient cooling water flow ； 5. Friction occurs after the ball mill is started due to the displacement of the large bearing pads caused by thermal expansion ； 6. High ambient temperatures can cause high oil temperatures, while low ambient temperatures can result in excessive oil viscosity; these conditions lead to poor lubrication of the large bearings and thus cause damage ； 7. The thermal protection did not function properly when a fault occurred in the oil system. Specific control measures: 1. Strengthen routine inspections; in the event of a disruption in lubricant supply, the ball mill should be shut down immediately. Then identify the cause and eliminate it. If any abnormality is detected in the quality of the lubricating oil, the oil maintenance team should be notified promptly to take samples for testing ； 2. Tie a wire around the oil inlet for the large bearing of the ball mill; if it becomes loose during operation, tighten it promptly ； 3. During operation, it is necessary to regularly check the alignment of the ball mill’s shaft journals as well as the condition of the cooling water. Any issues such as misalignment of the shaft journals or inadequate cooling of the bearings should be promptly identified and resolved ； 4. When the ambient temperature is high, a cold oil cooler should be activated promptly; it should be turned off after autumn ； 5. Strengthen the management of regular tasks to ensure that they are indeed carried out. Upon discovery, thermal treatment should be contacted promptly to ensure that the thermal protection systems function properly ； 6. During inspections, it is necessary to go to the large tiles to check the oiling condition of those tiles ； 7. Improve the quality of the large bearings in the maintenance ball mill. ▓ Rinsing of the drum level gauge: Hazard factors and hazard analysis: 1. Operating at too fast a speed may cause damage to the level gauge ； 2. If both doors on the sides of the soda machine are closed at the same time, it may cause the glass to cool down rapidly and get damaged ； 3. During operation, personnel may be scalded or injured by soda due to improper handling or incorrect standing position ； 4. The monitoring personnel, unaware of the flushing water level timer, make incorrect judgments leading to improper operations and resulting in overfilling or underfilling of water ； 5. Improper timing of water level recovery leads to inaccurate water level readings, causing misjudgment by the operators monitoring the system. 6. The water level gauge protected by a flushing mechanism fails to have its protection removed, resulting in erroneous activation of that protection mechanism ； 7. The valve is damaged due to improper or excessive force applied by the operator during operation ； Specific control measures: 1. Gloves must be worn, appropriate clothing shall be used, and the valves should be turned from the side; operations must be carried out slowly ； 2. Strengthen communication with the operator during flushing and keep a close eye on the water level ； 3. During flushing water level timing, the opening degrees of the steam and water side doors cannot be closed simultaneously ； 4. Flushing is not allowed when the water level gauge is defective ； 5. The opening degree of the steam and water side doors must not be too large when flushing the water level ； 6. If the water level gauge explodes, do not shut it down blindly to prevent steam and water from spraying and causing injury ； 7. The gauge protected by a flushing strip should signal the shift supervisor to remove the protection, in order to prevent accidental activation of the protection ； 8. Apply even force when operating the valve; do not use excessive force to avoid damaging it ； 9. When timing the flushing of the water level gauge, follow the steps outlined in the operation card for it strictly. 10. During the flushing process, if cracks or leaks are detected in the glass plate, stop flushing the water level gauge immediately and isolate it. Contact Company Two right away to handle the situation. ▓ Frequent coking and collapse of the boiler: Hazard factors and hazard analysis: 1. This leads to improved heat transfer resistance in the heated surfaces, resulting in overheating of some tube walls and eventual tube failure ； 2. Large collapses can easily damage the water wall tubes ； 3. Excessive focus leads to fire extinguishment ； 4. Excessive deflection of the lens causes positive pressure injuries ； 5. Frequent coking and collapse of the coke increases the difficulty of removing it, prolongs the time required for this process, and poses a risk of burns to workers ； 6. It is likely to cause failures in the slag skimmer and slag crusher. Specific control measures: 1. Strengthen combustion adjustment during operation, ensure proper air supply, conduct frequent inspections, and remove coke in a timely manner ； 2. Hang a warning sign on the disk that reads “Firing in progress; be aware of combustion.” ； 3. Personnel responsible for removing slag must wear fire-resistant clothing and gloves to prevent burns ； 4. Before starting to cause charring, it is necessary to plan in advance where to take cover in case of positive pressure or tube rupture ； 5. When removing slag, pay attention to the slag skimmer, water seal, and ash drain ； 6. The slag removal platform should be kept tidy; there should not be too many people on it, with a maximum of four persons allowed to stand on the same side of the platform ； 7. The focusing shield should be placed on the side of the body, not directly over the chest. Focusing should be done from top to bottom, and it is not allowed to place the head above the focusing shield in order to observe the interior of the furnace until the focusing shield has been removed. ▓There are many cross-tasking activities when the boiler is shut down; hazard factors and hazard analysis: 1. The safety measures specified in different work orders conflict with each other ； 2. For tasks where safety measures conflict with each other, the work is carried out in overlapping time periods; however, the work order guarantee system is not implemented during handovers ； Safety measures were not checked and restored before work began ； 3. Testing some equipment after maintenance affects the safety measures for other related work orders ； 4. When the safety measures were removed after ticket cancellation, the safety measures of other work orders were compromised ； 5. Failing to conduct on-site inspections and make corrections when handling work orders. Specific control measures: 1. When issuing work orders, it is necessary to carefully and promptly keep proper records; no details should be omitted. Shift supervisors and team leaders must be aware of all operations related to the equipment under their responsibility, as well as the safety measures specified in each work order. When processing work orders, they must be carefully reviewed; if any conflict is found with the safety measures specified in existing work orders, such orders cannot be processed. In such cases, the conflicting work orders must be revoked, and work can only proceed after those conflicts are resolved ； 2. When issuing work permits, changes in the working environment must be taken into account. When various tasks carried out simultaneously affect safety, additional safety measures must be implemented, and reliable isolation measures must be put in place (such as those to prevent objects from falling from heights). If reliable safety measures cannot be established, work permits shall not be issued ； 3. If the trial operation of the equipment after maintenance affects the safety measures specified in other work orders, those work orders should also be withdrawn; the trial operation can only be carried out after the relevant work has been stopped. Otherwise, no trial operation should take place for now ； 4. When processing work orders, it is necessary to examine them carefully and follow the <<Safety Regulations>> strictly; if the safety measures are unreliable or incomplete, the work order should be resubmitted or additional safety measures should be implemented ； 5. Before removing the safety measures after canceling a ticket, it is necessary to clarify the safety measures for the remaining work orders; those safety measures that affect the other work orders must not be removed ； 6. When issuing work orders, it is essential to inform the person in charge of the work that the equipment must not be touched without permission, and safety measures must not be removed arbitrarily. The personnel on duty should regularly check the site to oversee the repair work, and any violations must be stopped immediately ； 7. During shutdown for maintenance, sufficient safety warning signs must be prepared first. If the warning signs run out, work orders cannot be issued; it is necessary to borrow signs from other boilers or obtain them from the site supervisor before the work orders can be issued ； 8. When processing each work order, the work permit issuer and the person in charge of the work must go to the site to verify that the safety measures have been properly implemented before marking it in the column indicating that the safety measures have been carried out“√” ； 9. No matter how busy they are, the captain and the work permit issuer must carefully examine the work order, focusing on the work content and safety measures ； 10. In cases where there is cross-operation and the safety measures affect each other, only one work order can be approved at a time, and the safety measures should be rechecked before starting the work. ▓ Poor accident response capability of new operators during independent shifts; Hazard factors and hazard analysis: 1. The boiler is affected during the oil injection process** ； 2. Accidents that occur during disk monitoring, and the handling of such accidents leads to an expansion of the incident ； 3. During normal operation, an accident occurs suddenly, and blind actions are taken ； 4. When an abnormality is detected in the equipment, it cannot be accurately identified nor properly handled ； 5. When the equipment operates under special conditions, its ability to predict accidents is poor ； 6. Get scalded or burned during the focusing process. Specific control measures: 1. When restarting fuel supply after the boiler has stopped burning, an experienced veteran must be assigned to oversee the process; new workers should not carry out this task alone as it can lead to unstable combustion. New workers should be given clear instructions on the precautions to take, and the combustion condition should be checked before starting the fuel supply. It is also necessary to provide additional technical training for new workers ； 2. When new employees are monitoring the system, they should be under the supervision of experienced staff; during accident handling as well, experienced staff must provide oversight. Important operations and accident resolutions should not be carried out by new employees ； 3. When assigning a new worker to operate independently, it is necessary to explain to them the precautions and what to do in case of any changes in circumstances ； 4. Regularly explain to new crew members the impact that the shutdown of various equipment has on other systems, as well as under what circumstances those equipment play a crucial role in the boiler system and thus require emergency shutdown ； 5. When the equipment is operated under special conditions, the supervisor should remind the new workers of what to pay attention to, how to handle any changes that occur, and arrange for other personnel to check the operations if necessary ； 6. Before new workers start operating, they should be informed of the precautions. The performance of their operations needs to be monitored; if any doubts arise, they should stop working immediately and report to the chief operator or supervisor ； 7. Before new workers start working on coking, they must be clearly informed of the precautions related to coking, the symptoms that occur before the boiler shuts down or the coke collapses, and how to deal with positive pressure in the furnace. ▓Abnormal oil quality in the rotating machine: Risk factors and risk analysis: 1. Increased temperature of the rotating machine bearings, leading to their damage ； 2. Increased vibration in the transfer gear bearings ； 3. Abnormal wear of the converter leads to increased noise and overload, causing the motor to burn out. Specific control measures: 1. Conduct thorough inspections to identify problems promptly, and carry out testing and oil replacement as early as possible ； 2. Strengthen monitoring of the temperature and vibration of the rotating machinery, and shut it down in case of dangerous conditions ； 3. Seal areas such as the swing bearing, fuel tank, and fuel pipes where leakage may occur or where debris might enter ； 4. Strictly adhere to regular refueling during layovers; the fuel used must be fuel that has passed inspection by the fuel management team ； 5. Strictly implement the new oil intake system; oil that fails inspection shall not be used ； 6. Fueling equipment should be kept clean, and oils of different grades must not be mixed together ； 7. Report to the chief operator in a timely manner. ▓Hazard factors and hazard analysis for the maintenance of drum level gauges: 1. The level gauge that has just been taken out of service is hot, posing a risk of scalding to workers ； 2. If the valve on the soda side is not properly sealed, high-temperature and high-pressure steam from the water level gauge can cause burns; moreover, mistakes in judgment may occur during boiler accident handling, leading to water level-related issues ； 3. The area where the level gauge is located is narrow, and it is prone to being scalded by steam and water ejected from other level gauges and high-pressure pipes in that area ； 4. During the maintenance of the protected water level gauge, the protection was not disabled, resulting in accidental activation of the protection mechanism ； 5. The water level gauge does not operate properly after maintenance, and the water level indication is inaccurate. Specific control measures: 1. When working, it is necessary to wear heat-resistant work clothes and gloves; if the side door for accessing the soda compartment does not close properly, work must be prohibited ； 2. During operation, it is necessary to ensure that the primary and secondary valves on the steam and water sides of the local water level gauge in the drum are properly closed ； 3. Before starting work, check the accuracy of the water level gauge on the other side of the steam drum ； 4. While working, check the temperature of the water level gauge by touching it; if the temperature is high, stop working ； 5. Open the drain valve to relieve pressure ； 6. During operation, select the optimal working position and prepare in advance for potential accidents involving steam or water leakage from other level gauges and high-pressure steam pipes ； 7. When removing the screws, do so slowly and carefully, standing on the side away from the water level ； 8. When maintaining a water level gauge with protection, it is necessary to contact the shift supervisor in advance to deactivate the protection before starting the maintenance work ； 9. After the maintenance work is completed, the operating procedures for the level gauge must be followed, and the doors on the steam and water sides should be fully opened. ▓ Inspection and maintenance of thermal protection systems – Hazard factors and hazard analysis: 1. Activation of thermal protection systems ； 2. When an accident occurs and all protection setpoints are reached, the thermal protection fails to operate ； 3. Other thermal protection actions unrelated to the operation ； 4. Automatic failure of the unit, with dampers and control valves operating randomly ； 5. Thermal power supply interruption. Specific control measures: 1. Strengthen the training of boiler operators on thermal protection knowledge ； 2. Before starting work, it is necessary to inform the relevant supervisors and clearly explain the safety precautions to the personnel on duty ； 3. Personnel on the post should anticipate accidents that may require protective actions or other measures unrelated to their tasks ； 4. Improve the quality of monitoring; pay attention to changes in the operating parameters of the unit. If the parameters reach the conditions for protective action but no protection is triggered, prompt measures should be taken, such as shutting down the unit ； 5. If any of the unit’s automatic controls fail, operation should be stopped and manual control should be used instead; contact the thermal control team ； 6. In the event of a disruption in the thermal power supply, and provided that it does not currently affect the safe operation of the unit, contact the thermal engineering staff immediately to restore power supply ； 7. Thermal engineers should maintain close communication with operators ； ▓Hazard factors and hazard analysis for thermal systems with compression bolts: 1. Poor working environment, with many high-temperature and high-pressure pipes in the vicinity ； 2. Insufficient lighting ； 3. The flanges and bolts may leak or break at any time due to prolonged operation ； 4. High temperature of flange bolts ； 5. Improper operation can cause soda to spray and injure people, as well as damage other equipment. Specific control measures: 1. The on-site lighting should be sufficient ； 2. Before starting work, cover the electrical meters and control panels located around the work site with something ； 3. Before starting work, check the screws and valve packing; if the screws are severely rusted, use a loosening agent. Stop working if the valve packing is already properly tightened or has become ineffective ； 4. The staff must be experienced individuals, and there must be on-site supervisors; they must work under the supervision of these supervisors, using correct methods, tightening screws to an appropriate degree, and paying attention to the operating position ； 5. Staff should wear heat-resistant work clothes, as well as heat-resistant gloves and helmets ； 6. If the leakage is not severe, approval from the site manager is required, as well as consent from the shift supervisor; in special emergency situations, approval from the chief engineer is necessary ； 7. Before starting work, check the flange screws for signs of rust, mechanical damage, etc.; if any such issues are present, work should be suspended ； 8. When significant operations are carried out that could affect the work in progress, staff should be notified to evacuate the work site. ▓Hazard factors and risk analysis for boiler flame suppression and blasting: 1. Distorted monitoring of the flame by the television screen, leading to incorrect judgments by the operators; 2. After the flame goes out, the MFT fails to activate, and the monitor fails to detect this in time, resulting in failure to cut off the power supply promptly ； 1. The operator performs illegal operations, or failure to act promptly after detecting a fire ； 2. Shutdown of the machine and boiler during fire suppression and blasting operations, affecting the load ； 3. Severe equipment damage during boiler fire extinguishing and blasting ； 4. Injury to personnel caused by boiler fire suppression and blasting. Specific control measures: 1. Improve the quality of monitoring to prevent the boiler from going out ； 2. Improve combustion adjustment and pay attention to an appropriate excess air coefficient to prevent incomplete combustion and secondary combustion in the flue ； 3. Upon detecting a fire, all fuel supply to the furnace should be cut off as soon as possible, and ignition can be resumed only after adequate ventilation has been ensured ； 4. Adjust the baffles of the operation, feed, and delivery units as necessary to prevent positive pressure from occurring due to the downward movement of the stator blades ； 5. Accidents must be dealt with decisively; when coking collapse leads to severe and unstable burning, fire extinguishing measures should be taken, and one should not attempt to put out the fire blindly ； 6. Strengthen the publicity on the hazards of boiler fire suppression and blasting, and enhance the study of safety regulations* ； 7. Reduce the assessment related to boiler shutdown, or omit such assessments depending on actual circumstances, thereby lowering the pressure on the main operator and preventing mistakes due to excessive pressure and a tendency to take risks ； 8. In the final stages of shutting down the boiler, oil should be used to maintain stable combustion; thereafter, each grinding system should be shut down one by one. After the boiler is shut down, the oil circulation system for that boiler must be stopped promptly, and the tightness of the manual valves for each oil injector should be checked ； 9. When starting up the boiler, it is necessary to pay close attention to the stable operation of the oil injectors; if an injector stops working, the fuel solenoid valve should be turned off promptly ； 10. When the primary air duct of the furnace is blocked, it should be blown out in a step-by-step manner to prevent the duct from being cleared suddenly, which could allow a large amount of coal powder to enter the furnace and cause an explosion ； 11. When starting the furnace, there must be sufficient flue gas temperature and air temperature, and the oil gun must be burning fully before powder can be fed in ； 12. If it is found during operation that the negative pressure indication is inaccurate, maintenance should be contacted immediately to ensure the accuracy and sensitivity of the negative pressure indication ； 13. During maintenance, thoroughly inspect the rigid beams of the furnace body ； 14. Strengthen the maintenance of the boiler’s fire suppression system; contact the maintenance team promptly in case of any abnormalities ； The negative pressure in the furnace for fire protection should be regularly purged, and the pressure switch used for controlling this negative pressure should be regularly calibrated. ▓ Farmers setting off fireworks near oil depots: Risk factors and risk analysis: Fireworks entering the depot area can ignite oil tanks or accumulated oil, leading to accidents. Specific control measures: 1. Consciously remind farmers living near the oil depot that it is a sensitive area where open flames and smoking are strictly prohibited” ； 2. There should be no accumulation or leakage of oil around the pipes in the tank farm system; any accumulated oil must be removed promptly, and any oil leaks must be reported to the maintenance team immediately ； 3. As New Year’s Eve approaches, the duty officers should increase their patrols; if they notice anyone setting off fireworks or firecrackers in the vicinity, they must immediately stop such activities and inform the factory’s security department. ▓Replacing the viewing ports, soot blowing doors, and flame detection probes while the boiler is in operation – Hazard factors and hazard analysis: 1. Injury from flames ejected under positive pressure from the boiler ； 2. Staff failed to pay attention to the working environment, resulting in burns ； 3. Workers falling from heights. Specific control measures: 1. A work order or work request form must be obtained, and maintenance personnel are required to wear fire-resistant clothing; if it is found that they are not wearing such clothing during the work, the work must be stopped immediately ； 2. Before starting work, it is necessary to remind the maintenance personnel to keep an eye on the escape routes on both sides, so as to be able to take cover in time in case of sudden collapse of the coke bed ； 3. During this period, it is strictly prohibited to make any adjustments related to combustion or to start or stop the coal grinding system; if such operations are necessary, maintenance personnel must be notified to leave first ； 4. Cleaning of coke is strictly prohibited during maintenance work. ▓ Inspection of the temperature at the cable ends of high-voltage motor cables – Hazard factors and hazard analysis: 1. Explosion caused by a cable short circuit at the motor junction box, which can injure people ； 2. Electric shock occurs due to the operator’s inspection without using tools. Specific control measures: 1. During inspections, a thermometer should be used for temperature measurement; it is strictly prohibited to touch the surface with bare hands to check the temperature ； 2. When it is detected that the temperature at the cable connector of the auxiliary equipment is high, an immediate shutdown report should be submitted to arrange maintenance ； 3. In cases where the temperature at the cable connections of auxiliary equipment is high and the equipment cannot be shut down promptly, enhanced monitoring should be implemented, and safety barriers should be installed around those cable connections to prevent injuries caused by a sudden explosion of the cables ； 4. The inspection of the cable connector temperature should be carried out by persons with electrical expertise; it is strictly prohibited for those without such knowledge to touch or handle it, in order to prevent electric shock accidents and injuries ； 5. During inspections, attention should be paid to the temperature of the cables; if an abnormally high temperature is detected, electrical personnel should be notified to take action. ▓Oil cut-off in the ball mushroom machine’s large rotor: Risk factors and risk analysis: 1. The large rotor shuts down due to vibration while operating with oil supply ； 2. Improper operation when switching filters or clogged filters; 3. Severe leakage in the oil pipeline between the oil pump outlet and the large bearing; 4. The oil pump trips while the backup pump does not activate ； 5. The circulating short-circuit door is opened accidentally during operation or due to human error ； Specific control measures: 1. After adjusting the oil supply volume for the large bearings of each grinder, tie them down with wire for fixation ； 2. Check for blockages in the filters regularly during operation; try to replace the filters after the mill has stopped running. 3. Conduct a low oil pressure test, a interlock trip test, and protection tests on the mill before starting it – it can only be started if these tests are successful. 4. Strengthen routine inspections, and contact Company 2 promptly in case any leaks are detected. 5. Adjust the oil pressure gradually to prevent the circulation short-circuit valve from opening too much, which could lead to an excessively low oil pressure. ▓ Risk factors and risk analysis related to emergency load increase of the unit: 1. An emergency load increase by the unit can cause the boiler to experience overpressure ； 2. The unit reduced load urgently, causing the boiler to overheat ； 1. The unit reduced load urgently, resulting in the boiler running either at full water level or with insufficient water ； 2. The unit reduced load urgently, resulting in overpressure and overheating in the boiler; during the manual reduction of combustion in the boiler, the combustion condition deteriorated, which led to the boiler going out of operation and experiencing explosions ； 3. The unit reduced load urgently to address the drum water level, which caused a failure in the feed water pump ； 4. The unit reduced load urgently, causing the reverse power protection and electrical overspeed protection to activate ； 5. During the unit’s emergency load reduction process, excessive operational adjustments were made, resulting in the downward movement of the exhaust air static vanes and the supply air dynamic vanes; this led to severe positive pressure as well as severe negative pressure in the boiler. Specific control measures: 1. In the event of an emergency load reduction in the unit, if the safety valves do not function, the PCV valve should be opened promptly. The steam turbine should be instructed to activate the primary and secondary bypass systems. At the same time, the boiler’s coal grinding system should be stopped immediately to reduce the thermal load on the boiler. If necessary, the drain valves can be opened to lower the pressure, thereby preventing the boiler from overpressuring ； 2. The unit should reduce its load urgently by activating the primary and secondary feedwater cooling systems promptly. The exhaust valves should also be opened in a timely manner to reduce the boiler’s heat load. If necessary, the drain valves on the steam collector can be opened to increase the steam flow, thereby preventing the boiler from overheating ； 3. In the event of an emergency load reduction by the unit, automatic control should be disabled immediately, and water level monitoring should be intensified. During the process of adjusting the water level, attention should be paid to the readings of various water level gauges: when the water level is high, the reading from the highest gauge should be used as a reference; when it is low, the reading from the lowest gauge should be used. At high water levels, it is important to check whether the water level protection system is activated. If it does not function properly, the emergency drain valve should be opened promptly. If, during the adjustment process, the water level reaches a level that requires an emergency shutdown of the unit, such a shutdown should be carried out without delay. If the feed pump fails to operate during these procedures, immediate contact should be made with the turbine team to have a backup pump ready. If starting the backup pump is not successful, an emergency shutdown of the unit is necessary ； 4. When the unit reduces load urgently and the boiler slows down its combustion, special attention must be paid. If the combustion deteriorates, manual fire suppression should be carried out immediately in accordance with the fire extinguishing procedures. When the boiler’s combustion is unstable, care must be taken when introducing oil to prevent the boiler from going out of operation or experiencing explosions ； 5. When the unit reduces load urgently and switches to electric pumps, it is necessary to properly control the water level in the steam drum; adding or removing water should be done carefully to avoid large fluctuations that could lead to high oil temperatures in the feed pump, thereby causing damage to its seals and rendering it ineffective. While adjusting the steam drum water level, attention must also be paid to the speed of the feed pump and the opening degree of the feed water control valve, ensuring that the pressure in the feed water main does not exceed the specified value ； 6. When the turbine reduces load urgently, the boiler cannot allow the turbine to do so blindly based on parameters such as steam temperature, steam pressure, and drum water level; otherwise, a reverse power protection mechanism will be activated. Meanwhile, the boiler must be prepared to activate this reverse power protection mechanism during the load-reduction process ； 7. When the unit reduces load urgently and the boiler slows down its combustion process, adjustments to the intake and exhaust air flow should not be made in drastic ways. During operation, attention must be paid to the negative pressure in the furnace as well as the operation of the exhaust air static vanes and the intake air dynamic vanes. If a decline occurs, it is necessary to monitor changes in the furnace’s negative pressure while taking additional corrective actions to prevent severe positive or negative pressure conditions in the boiler due to delayed adjustments. ▓ Inspection of rigid beams at the corners of the boiler body: Hazard factors and hazard analysis: 1. During the inspection process, maintenance workers may fall from a height ； 2. During the maintenance process, the maintenance staff were scalded ； 3. During maintenance work, falling objects from a height injured a pedestrian at 12.6 meters height ； 4. During maintenance, when electric or gas welding is required, sparks falling can injure pedestrians at a distance of 12.6 meters, and such sparks can also cause fires. Specific control measures: 1. Maintenance personnel must wear safety belts and safety nets to prevent falls from heights ； 2. Maintenance personnel and operators must have reliable communication facilities; in the event that the burning condition worsens, maintenance personnel should be notified to evacuate the work site. A “Beware of Burning” warning sign should be placed on the boiler panel, and operation under positive pressure is strictly prohibited ； 3. A prominent warning sign reading “Beware of falling objects from above” should be installed at 12.6 meters, and a safety net to prevent falling objects should also be in place ； 4. Install safety fences and post safety warning signs; this work may only be carried out after all flammable materials have been removed, such as oil and powder accumulations on the ground. ▓Maintenance of safety valves during boiler operation: Hazard factors and hazard analysis: 1. Burns to maintenance personnel during the maintenance process ； 2. During their work, maintenance personnel may be startled by the activation of the safety door ； 3. The operation of the safety door injures maintenance personnel ； 4. Maintenance workers falling from heights. Specific control measures: 1. Based on the leakage and temperature conditions of the safety door, if the leakage is severe and the temperature is high, maintenance should be suspended. If maintenance is to be carried out, the boiler must first have its pressure and load reduced. Moreover, reliable communication facilities are necessary between the maintenance crew and the operators. If, during the maintenance process, the unit loses load or the powder feed mechanism fails to supply sufficient powder, causing the pressure to rise rapidly, the maintenance personnel must be immediately informed to evacuate the site; at the same time, steam should be discharged to the atmosphere and the turbine operator should be contacted to activate the bypass system ； 2. There must be reliable communication facilities between maintenance personnel and operators; if pressure rises rapidly and this could lead to a safety shutdown, maintenance personnel should be notified immediately. Additionally, operators should maintain stable combustion and assign someone to monitor the pressure ； 3. Pay attention to monitoring the pressure; if it rises rapidly, immediately notify the maintenance staff to evacuate the site and suspend the work ； 4. During maintenance, a dedicated person should monitor the local pressure; in case of any abnormalities, immediate action should be taken to evacuate the personnel ； 5. Before starting work, maintenance personnel should plan in advance where they will take cover if the safety door operates ； 6. Maintenance personnel should be careful when adjusting the safety door springs to prevent the safety door from bouncing due to improper handling. ▓ Test of accident drain valve operation – Hazard factors and hazard analysis: 1. The secondary valve was not set to the manual position, resulting in both the primary and secondary accident drain valves opening simultaneously when the water level reached a high value ； 2. When the water level control is set to automatic, the adjustment of the water level setpoint occurs too rapidly, resulting in an excessive rotation speed of the feed pump and the burning out of the soluble plug ； 3. Without checking the effect during operation, even when the water level reached +150 and the red light indicated that emergency drainage should be initiated, the setting value continued to be increased, resulting in the water level reaching +200 MFT and triggering the corresponding action ； 4. During testing, the accidental opening of the emergency water release valve led to injuries caused by high-temperature and high-pressure water ； 5. After the test was completed, the switch for the accident drain secondary valve was not returned to its normal position (to the remote control mode), resulting in the water level protection system activating when the water level was high and the secondary valve failing to open, thereby causing an accident ； 6. Pipeline vibration is caused by the operation of the accident drain valve. Specific control measures: 1. Before conducting the test, send someone to the site to switch the secondary door to the manual position; after the test is completed, restore it to the remote control position ； 2. When adjusting the water level set values, it is necessary to do so slowly, increasing or decreasing them one by one ； 3. When increasing the water level, it is necessary to observe the effects; once the water level reaches +150 and the red light on the emergency discharge valve lights up, the water level should be reduced to return to normal ； 4. Conduct tests on the operation of the accident drain valve; all work orders related to this boiler as well as maintenance work on the level gauges must be suspended, and the drainage systems connected to the drain tanks should also be stopped (deaerator drainage, drainage to the drain tanks) ； 5. After vibration occurs in the accident drain pipe, the integrity of the supports and hangers should be checked. ▓ Pressure reduction and fault resolution in the soda water system: Hazard factors and hazard analysis: 1. The relevant systems are not isolated ； 2. There is still residual pressure in the soda system ； 3. No isolation measures were taken for bottom heating of the furnace. Steam from the adjacent furnace flows back into the water wall tubes or into the main steam pipeline ； 4. When draining water from the hot furnace, the water in the feedwater system was not completely drained. Specific control measures: 1. a. Contact the turbine to shut down the primary and secondary bypasses as well as the main steam valve, and inform the electrical department to cut off the power supply. b. Close the feedwater control valve, the feedwater isolation valves before and after, the main feedwater bypass valve, and the minor feedwater bypass valve, and request an electrical power shutdown. c. Close the regular discharge door, continuous discharge door, chemical dosing door, sampling door, bottom water supply door and drain door, as well as the switch door between regular discharge and continuous discharge. d. Close the backwash valves of the superheater and reheater, the regular drainage backwash valves and the main backwash water inlet valve, close the emergency drain valve, and close all desuperheating water valves. e. Hang a “Personnel at work, do not operate” warning sign on each of the aforementioned doors ； 2、a. Open the exhaust valves of the superheater and reheater to the atmosphere. b. Drain the steam before opening the main steam valve, as well as from the superheater header, the encircling header, and the suspension tubes; there are also drains for the high-pressure reheat section and the low-pressure reheat section. c. Open the drain valves of the economizer and the feedwater pipeline, as well as all the air vents in the steam-water system; open the regular drainage valves No. 1, 2, and 3 ； 3、a. Close tightly the connection door from the bottom heating main pipe of this furnace to the furnace itself, and open the drain valve of the bottom heating main pipe of this furnace. b. Close tightly the door of the primary bypass from this furnace to the furnace bottom heating main pipe, and coordinate with the turbine to close the shaft seal heating door on the primary bypass to the furnace bottom heating main pipe. c. Close the main bottom heating valve of this furnace as well as the various secondary valves for bottom heating. e. Connect the power supply to the main valve for electric bottom heating of the furnace. f. Hang a “Personnel at work, do not operate” sign on each door of the elevator ； 4. a. When draining water from the hot furnace, follow the procedures strictly. b. During the water discharge process, the temperature difference between the upper and lower walls of the steam drum must not exceed 40 degrees. c. When draining water, the water in the drum should be drained first, followed by the water in the drain cooling wall and the economizer. e. When the drum pressure drops to 0, open all air valves in the steam-water system and slightly open the vent valves of the headers; fully open all primary and secondary drain valves of the economizer. Coordinate with the turbine to open the drain valve before the main steam valve is opened. Drain water for 6 hours to ensure that any remaining water and steam have been removed, after which close all air valves and drain valves ； 5. The work order was not properly reviewed, and safety measures were not adequately implemented. a. Before signing the work order, it is necessary to recheck that the safety measures have indeed been properly implemented. b. Verify that the equipment under inspection and maintenance has been isolated from the operating equipment. c. Confirm that the equipment under maintenance is free of excess steam and water; work may be permitted only after the excess pressure has been removed ； 6. When working inside the steam drum, explosion relief measures must be in place. a. Explosion-proof lighting fixtures should be used for lighting inside the steam drum. b. If electric welding is required, a hot work permit must be obtained. c. Confirm that the pressure in the drum has been relieved ； 7. When handling work orders for the steam and water system, operators should check whether the pressure gauge of this system shows zero, and whether all the drain water from the system has been removed ； 8. Before starting the maintenance work, the maintenance personnel should be informed about the remaining water in the U-tube and the precautions to take to avoid burns. ▓ Failure of the boiler fire suppression protection system to activate: Hazard factors and hazard analysis: 1. Delayed detection and delayed handling ； 2. Misjudgment, misoperation ； 3. Protection not activated. Specific control measures: 1. Ensure high quality of monitoring; strengthen the supervision of important instruments such as water level gauges, negative pressure meters, oxygen levels, and flame monitors ； Upon detecting the conditions for engine shutdown, immediately handle it as a fire extinguishing incident ； 2. Strengthen theoretical knowledge learning, enhance accident-prevention drill training, and improve professional competence ； 3. The furnace negative pressure gauge tube should be cleaned regularly ； 4. Before starting up the furnace, a test must be conducted to ensure that the fire protection system is functioning properly and that the MFT operates as intended ； 5. Strengthen the maintenance of flame detectors; immediately notify the thermal engineering team in case of burnout, contamination, or malfunction ； 6. After the boiler is in operation, it is essential to ensure that the protection systems are properly activated. ▓Start/stop of soot blowers: Hazard factors and hazard analysis: 1. Inadequate water drainage, resulting in pipe vibration ； 2. Injury caused by steam pipe leakage during on-site soot blowing ； 3. Jamming during the insertion and removal of the long soot blower ； 4. When attempting to manually remove the soot blower in case it gets stuck, the steam supply and power supply were not disconnected, resulting in steam leaking from gaps and causing injuries ； 5. During dust blowing, poor sealing can cause steam to spray out from the rear, posing a risk of injury ； 6. When there is no steam supply for the soot blower, the blower gets damaged when it is turned on ； 7. The soot-blowing and flushing water valves of the air preheater do not close properly, resulting in water entering the air preheater. Specific control measures: 1. When putting the soot blower into operation, all water accumulated in its steam pipeline must be completely drained before it can be used ； 2. The temperature in the soot blowing steam pipeline is high, and steam leakage occurs; therefore, long-sleeved work clothes and gloves must be worn when performing soot blowing tasks, on-site