Thirty detailed emergency response plans for turbine accidents in power plants

Please provide the materials on [Thirty Detailed Plans for Handling Accidents Involving Turbines in Power Plants] to complete the topic.

01 Contingency plan for tripping due to high water level in high- and low-pressure heaters, as well as for water side leaks. I. System overview: The turbine feedwater reheating system at XX Power Plant has a total of seven extraction stages. The first three stages are connected to the high-pressure heaters; the fourth stage supplies the deaerator; and the remaining three stages are connected to the low-pressure heaters. The condensate passes through three low-pressure heaters before entering the deaerator, where it is heated and degassed. The feedwater is then heated by three high-pressure heaters before being sent to the boiler. The heaters’ drain water in this unit flows by gravity stage by stage; the drain water from the high-pressure heaters flows by gravity to the deaerator, while that from the low-pressure heaters flows to the condenser. Each heater has an emergency drain line leading to the condenser; a large bypass is used on the high-pressure feedwater side, while small bypasses are employed for LP heaters #5, #6, and #7. II. Conditions prior to the accident: Both high-pressure and low-pressure heaters were in operation, with all corresponding parameters within normal ranges (suction steam pressure and temperature, feedwater temperature rise, heater terminal difference, etc.). The water levels in each heater were normal, and the accident drain valve was not open. III. Accident phenomena: 1. The analog water level gauge of a certain heater indicates an increasing water level or maintains it at a high level; there is a corresponding water level alarm on the display, and the accident drain valve may open. The temperature rise of the faulty heater decreases, while the terminal difference increases. If the water level is high, there may be a mismatch between the feedwater flow rate and the flow rate at the outlet of the feedwater pump, resulting in an excessively high speed of the electric pump ； If the low-temperature heater water level is high, there may be a discrepancy between the amount of condensate entering the deaerator and the flow rate at the outlet of the condensate pump. 2. When a heater fails, the level gauge on the display indicates that the tank is full of water; as a result, the steam extraction check valve and the electric valve associated with it shut down. The emergency drain valve may open, and the electric valve on the water side switches automatically, causing the unit’s load to increase momentarily before decreasing again. If the high-pressure heater is shut down, the load increases suddenly, the feedwater temperature drops, while the metal temperature of the thrust bearings in the working area and the oil return temperature rise. The extraction pressures at various stages after the high-pressure heater are increased, and the feedwater is automatically switched to the large bypass circuit ； If the low-temperature heater is shut down, the temperature of the condensate water entering the deaerator drops, resulting in a reduced deoxygenation effect; meanwhile, there are slight fluctuations in the water level and load of the deaerator. 3. When the faulty heater becomes severely flooded, it is flooded both locally and remotely. The temperature difference between the upper and lower walls of the extraction steam pipe increases; the extraction steam temperature drops. There are impact sounds and vibrations in the extraction steam pipe, steam escapes from flange connections, water may enter the cylinder, axial displacement increases, and there is an alarm for excessive thrust bearing temperature. IV. Causes of the accident 1. Leakage or rupture of the heater tube bundle. 2. The drain control valve of the heater is stuck; the regulator malfunctions; or the upstream and downstream shut-off valves are accidentally closed. 3 Significant changes in load or excessively high load cause the automatic water level regulation to fall short. 4 Severe fluctuations in condensate flow rate and pressure cause the low-temperature economizer to shut down. 5 Severe fluctuations in water supply flow and pressure cause the high-pressure heater to fail. V. Accident Handling 1. When the unit is operating under high load conditions and the high-pressure heater fails, the boiler should promptly reduce combustion intensity, immediately lower the load to below 260 MW, and closely monitor the temperature of the turbine thrust bearings. Strictly prevent overloading of the medium and low-pressure cylinders to avoid damage to the unit. 2. The crew should pay attention to controlling the amount of water used for temperature reduction; after the high-pressure heater is removed, the amount of water required for temperature reduction in the boiler increases significantly under the same load conditions. 3. After the high-pressure heater fails, due to the increase in the pressure of the fourth extraction steam, the feedwater flow rate may rise instantaneously. Due to the loss of drain water from the high-pressure heaters and the increase in the pressure at the fourth extraction point, the water level in the deaerator dropped suddenly. Operating personnel must monitor the water levels in the steam drum, deaerator, and condenser to prevent the deaerator’s water level from dropping too low, which could cause the feed pumps to shut down. The condensate flow rate should be higher than under normal operating conditions. 4. The failure of a low-temperature reheater has little impact on the unit’s operation, but it can sometimes cause other low-temperature reheaters to shut down as well. Timely contact should be made for maintenance and repair so that it can return to normal operation. 5. If it is confirmed that water has entered the turbine, the vacuum must be broken to initiate an emergency shutdown. 02 Emergency response plan for increased back pressure in the exhaust system or tripping of the air-cooling fans. For condensing steam turbines, improving the thermal cycle efficiency is achieved by increasing the initial parameters and reducing the final parameters. The establishment of the condenser vacuum is intended to reduce the final parameters of the turbine exhaust steam; therefore, monitoring and adjusting the condenser vacuum during actual operation is particularly important. If the vacuum level drops abnormally, it not only affects the thermal efficiency of the cycle; in severe cases, it can lead to an increase in the exhaust temperature of the low-pressure cylinder, causing deformation of that cylinder and an imbalance in the center of the turbine rotor, which in turn triggers vibration in the turbine. Therefore, once a decrease in the condenser vacuum is detected during operation, it should be reported promptly, the cause should be identified, and measures should be taken to resolve the issue. Phenomena of rising back pressure: The exhaust steam temperature in the low-pressure cylinder increases; all back pressure gauges indicate a rise in exhaust pressure. The unit load decreases, the condensate temperature rises, and the end differential of the condenser increases. The “Low condenser vacuum – Levels I and II” alarm indicators may be activated. When maintaining a constant load under coordinated control conditions, the steam flow rate increases, the coal feed rate rises, and the current drawn by the vacuum pump also increases. I. Causes of vacuum decrease: 1. Reduction or interruption of cooling air flow ； The air-cooling fan is not working properly ； 2. The level of the hot well water is too high ； 3. Abnormal operation of the water ring vacuum pump ； 4. The fins of the air-cooled heat exchanger are dirty, resulting in a reduced heat exchange efficiency. 5. Air is leaking from the negative pressure section of the unit ； 6. Malfunction of the shaft sealing system or failure of the water seal on the shaft ； 7. Air leakage from the vacuum break door or the low-pressure cylinder safety valve ； 8. Low-pressure bypass leakage or other hydrophobic substances leaking into the condenser. II. Handling of vacuum drop: It can be divided into handling of rapid drop and handling of gradual drop. Search order during handling: Check the gauge to determine whether the vacuum level has indeed decreased —> Operations that were recently performed and may affect the vacuum —> Air cooling system —> Shaft seal system —> Vacuum system —> Other systems. ✔ 1. When the vacuum level drops sharply: (1) First, report to the shift supervisor, unit manager, and captain, and check for any operations related to the negative pressure system; (2) Check the operation of the air-cooling fans – for example, if there is a fault with the air-cooling units, or if strong winds prevent the fans from functioning properly and thus prevent air from reaching the air-cooling radiators, which can lead to a sudden sharp increase in back pressure ； (3) Malfunction of the shaft seal system, especially improper adjustment of the steam seals before and after the low-pressure cylinder ； (4) A lack of water in the water ring vacuum pump, or its absence, causes a large amount of air to leak into the condenser ； (5) Incorrect activation of the low-pressure bypass. In the event of the above situations, the operations that were just carried out should be resumed promptly. If the vacuum level continues to drop, load reduction must be carried out immediately in accordance with the procedures: disengage coordination, enable automatic air supply on the furnace side, reduce the load rapidly, maintain a low excess air coefficient, and pay attention to the negative pressure in the furnace. The standby water ring vacuum pump and the standby circulation pump should be activated, while the vibration of the unit must be closely monitored. When the back pressure rises suddenly and approaches the emergency stop condition, the plant power should be switched over in advance to prepare for shutdown. When this occurs due to strong winds or other reasons, the load should be reduced immediately to keep the backpressure within the specified range defined by the protection curve; if necessary, measures such as shutting down the boiler can be taken to rapidly reduce the backpressure. When the exhaust pressure of the condenser rises to the level specified by the protection conditions, the low vacuum protection triggers an emergency shutdown. If the low vacuum protection fails to function, an emergency shutdown must be carried out manually, with all other operations following the procedures for shutting down without damaging the vacuum. ✔ 2. Handling in the event of a slow decline: (1) First, report to the shift supervisor, unit leader, and machine operator, and check whether the operations that were just performed can be reversed. (2) Adjust the opening degree of the steam supply valve for the main engine’s steam seal ； The steam supply valve can be adjusted to be opened wider appropriately ； (3) If the level in the hot well is too high, it is necessary to activate the standby condensate pump promptly to increase the water supply to the deaerator, and stop the make-up water pump. If the pump that was in operation fails and shuts down, the standby pump should be started immediately to restore normal operation of the condensate system. If the automatic control valve for the condensate fails, switch to manual control, increase the water supply, and it is also possible to open the electric valve at the outlet of the No. 5 low-temperature heater to release water until the level in the condenser returns to normal ； (4) When the water level in the water ring pump is too low and its output is insufficient, water should be added promptly, or the backup vacuum pump should be started. If air is leaking from the body of the operating water ring pump, the backup pump should be started while the faulty pump is shut down, and the faulty pump must be properly isolated ； (5) The air-cooling spray system can be activated promptly to enhance flushing due to dirty radiator tubes ； (6) If air leaks into the negative pressure section, the current of the water ring pump increases significantly; check the systems one by one in the order mentioned above ； (7) After the maintenance of the high and low pressure heaters, when the manual valves before and after the accident drain valves are operated, this can also affect the vacuum. If the vacuum continues to decrease, it is necessary to quickly restore it to its original state; check whether the positions of the steam-side air release and water release valves are correct ； (8) A poor-sealing vacuum break electric door, as well as the safety valve of the low-pressure cylinder, can also cause a drop in vacuum; these should be checked and sealed properly promptly ； Or contact maintenance to seal the leak ； (9) When the water level in the shaft seal cooler is too low, open the multi-stage water-seal steam-water valves to replenish water, and adjust the inlet valve of the shaft seal cooler fan ； (10) During operation of the water-ring vacuum pump, the inlet butterfly valve was accidentally closed. Contacted the thermal engineering personnel to open it, and promptly started the standby pump. In summary, a drop in vacuum is a common occurrence during normal operation. The principle for dealing with this situation is first to consider the operations that have just been carried out and those related to the vacuum system; when the vacuum drops rapidly, it is necessary to reduce the load according to the procedures, decrease the steam supply to the condenser, and promptly start the backup water ring pump and backup circulation pump (when only one circulation pump is in operation). If emergency shutdown conditions are met, an emergency shutdown should be initiated. If the vacuum drops slowly or reaches a certain level and then stops dropping, an increase in the current through the water ring pump can help identify that the cause is usually air leakage in the negative pressure section, and the systems should be checked one by one in order to find the problem. 03 Emergency Response Plan for High Water Level in the Steam Drainage System
I. Symptoms of high water level in the steam drainage system:
1. Alarm for high water level in the condenser, including: alarm on the transmitter water level gauge displayed on the OM screen, high-level alarm on the local water level gauge; it is also possible that the water level in the deaerator may drop. 2. A drop in vacuum may occur. 3. The subcooling of the condensate water is high. 4. Without coordinated operation, the load may decrease. 5. The operating condensate pump tripped, but the standby condensate pump did not start up. 6. The shaft seal temperature of the low-pressure cylinder may change due to variations in the condensate water pressure. 7. The indication of the opening degree of the main condensate control valve drops suddenly. II. Reasons for high water level in the exhaust steam device: 1. Abnormal operation of the condensate pump, or accidental opening of the recirculation valve in the condensate system and accidental closing of the main control valve for condensate. 2. A fault occurred in the operation of the condensate pump, and the standby pump was not started. 3. Automatic failure of the water supply system; 4. Leakage in low-pressure heaters No. 4 and No. 7; 5. The auxiliary steam systems operate in parallel, resulting in large load variations among the units and cross-steam flow between them; 6. The units suddenly reduce their load, the low-pressure bypass valves open, and the amount of steam discharged into the condenser increases; 7. When the units are shut down, the water supply valves are not closed, or the seal water valves of the condensate pumps are not closed. III. Handling of high water level in the exhaust system: 1. If a high water level is detected in the condenser when the unit is shut down, it is necessary to check the system for leaks and repair them. 2. If the operating pump fails or stops working, and the backup pump has not been started, the backup pump should be activated immediately while the faulty pump is stopped. Attention should also be paid to reducing the water level in the deaerator, adjusting the unit’s load as appropriate, and contacting the maintenance team promptly to address the issue with the faulty pump. The crew leader should report this situation to the shift supervisor and relevant management personnel. 3. When the automatic make-up water system for condensate fails, automatic operation should be stopped immediately, and manual adjustment should be used along with the drainage method: a. Open the drain valve; ensure that there are no leaks in the drainage system. b. Open the drain valve located before the outlet of the 5# low-temperature heater; check that the system is unobstructed before doing so. c. Maintain a high level of water in the deaerator. 4. If the leakage is caused by the 7# low-temperature heater, isolate it and carry out repairs on it. 5. If the issue is due to steam leaking between different units, contact the shift supervisor to adjust the operation mode of the auxiliary steam systems, and activate the drain valve of that unit. 6. If the problem is caused by the bypass system activating as a result of the unit losing load, identify the cause; accident handling should be carried out under the unified command of the machine operator. 7. If the operating pump fails and the standby pump cannot be brought online, resulting in an excessively high water level in the condenser, do not shut down the plant by breaking the vacuum. IV. Division of responsibilities in accident handling: 1. Upon detecting a high water level in the condenser, the Chief Engineer, Deputy Chief Engineer for Turbines, and turbine patrol personnel shall jointly determine the cause of the fault. 2. The Chief Engineer is responsible for reporting the incident and diagnosing the fault, as well as directing the crew to perform system switching and shutdown operations. 3. The Shift Supervisor is responsible for reporting to relevant supervisors and the Central Dispatching Center. The Chief Engineer shall notify maintenance personnel to proceed to the site and stand by. The Deputy Chief Engineer for Boilers shall, based on the unit’s operating conditions, assist in reducing the load. The boiler patrol personnel and electrical patrol personnel shall cooperate with the turbine patrol personnel during the system switching process, after which they return to their posts to await further instructions. In summary, a high condenser water level not only reduces the vacuum of the unit and increases the subcooling of the condensate, but also severely affects the economic efficiency and safety of the unit. Therefore, it is very important and necessary to handle the issue of high condenser water level in a correct, safe, and reasonable manner. 04 Emergency Response Plan for the Failure of a Single Water Ring Pump. The function of a water ring pump is to remove non-condensable gases such as air from the steam in the condenser, as well as those present in various heaters. When a fault occurs in the water ring pump, the amount of non-condensable gases like air in the condenser increases, which leads to a significant rise in the exhaust pressure and temperature. This results in thermal deformation of the low-pressure cylinder, damaging the center of the turbine rotor and causing vibration. I. Phenomena of a single water-ring pump tripping
1. “0” and “F” alarms appear on the screen.
2. The current indicator for Pump A shows 0 on the OS screen.
3. The vacuum level drops slightly.
4. The inlet valve of Pump A closes automatically.

II. Handling procedures for a single water-ring pump tripping:
(1) If the standby pump starts up normally:
1. Verify that the inlet butterfly valve of the standby pump opens automatically, and that the inlet butterfly valve of the faulty pump closes automatically.
2. Immediately send personnel to the site to restore the water level in Pump B to normal levels. Ensure that Pump B operates normally; also inspect Pump A on-site for any obvious faults.
3. Monitor the trend of the vacuum level on the screen to confirm that the vacuum system is functioning properly.
4. Report to the shift supervisor; contact maintenance personnel and have an electrical inspector check whether the insulation of Pump A remains intact.

(2) If the standby pump fails to start automatically and manual startup is also ineffective:
1. When manual startup of Pump B proves ineffective, promptly reduce the load while closely monitoring changes in the vacuum level. Since Pump B fails to start, inform the shift supervisor immediately and coordinate with personnel from mechanical, electrical, and thermal control departments.
2. Promptly switch to auxiliary shaft-sealing steam supply and increase the opening of the steam seals both before and after the low-pressure turbine.
3. During rapid load reduction, there is a risk of furnace flameout due to unstable combustion or delayed load reduction. Should the vacuum level reach preset limits, automatic shutdown may occur; manually deactivate the bypass system and proceed with other shutdown procedures.
4. Prior to and after addressing issues with the water-ring pumps, start them up again and verify whether the safety valves of the low-pressure turbine are functioning normally.

III. Preventive measures:
1. Regularly inspect operating pumps; pay special attention to motor operation. Ensure that motor switches operate correctly, cable insulation at junction boxes remains intact, and operating currents shown on the OS screen are within normal ranges. Report any abnormalities immediately.
2. Conduct periodic insulation tests; verify that indicator lights on the standby pump control panel function properly to ensure the standby pump remains ready for use.
3. During normal operation, anticipate potential accidents in advance and define clear responsibilities so that all personnel can act swiftly under emergency conditions, thereby preventing further escalation of incidents.

IV. Personnel responsibilities:
1. Shift supervisor: Overall responsibility; coordinates with maintenance personnel.
2. Chief engineer: Provides specific instructions; coordinates with maintenance personnel.
3. Assistant chief engineer: Carries out on-site operations during emergencies related to machinery.
4. Assistant boiler operator / Boiler inspector: Assists in rapidly reducing load on the machinery side.
5. Machinery inspector: Supports the assistant chief engineer in on-site operations.

05 Tripping of one oil-fume exhaust fan during operation

I. Brief description of operating conditions:
The oil-fume exhaust fan is one of the key components in the main engine’s lubricating oil system. It is installed atop a sealed oil tank; its purpose is to extract fumes from within the tank, thereby creating negative pressure inside the tank and along return oil pipelines. This facilitates smooth oil return and prevents oil or oil fumes from leaking out, ensuring safe operation of the entire oil system. Negative pressure within the oil tank should not be excessively high; it must be maintained between 0.2–0.5 kPa (20–25 mm Hg) to prevent ingress of water, air, and dust into the lubricating oil via the shaft seal area.

During startup of the oil system, one exhaust fan is activated prior to starting the AC lubricating oil pump (a coordinated test is conducted). Generally, after the unit is shut down, following completion of hydrogen extraction from the generator and deactivation of the sealing oil system, the exhaust fan may be turned off. While the unit remains operational, one exhaust fan must always remain active to maintain negative pressure within the main oil tank; the other fan serves as a standby unit linked via interlocks.

II. If one oil-fume exhaust fan trips during unit operation, immediate action must be taken to prevent further escalation of the incident and minimize associated risks. Symptoms following such a trip include:
1. The standby fan starts up automatically; alarms appear on the OS screen.
2. Oil level rises (as indicated by both the screen and local oil-level gauges).
3. Should operators fail to notice these changes promptly due to lack of concentration, oil fumes may escape from the bearing areas at 12.6 meters height or from any leaks in the oil system; oil leakage may also occur.
4. Due to impaired oil return, oil temperature may rise.

III. Common causes of oil-fume exhaust fan tripping:
1. Motor malfunctions or problems related to oil return.
2. Mechanical failures or jams within the fan itself (e.g., damaged bearings).
3. Blocked or clogged oil drain holes at the base of the fan; this results in excessive oil accumulation inside the fan, increasing rotational resistance.
4. Poor performance of oil-fume separators or blockages at the fan inlet can also reduce fan output, producing effects similar to an actual trip.

IV. Handling procedures for oil-fume exhaust fan tripping:
1. Immediately report the incident to the shift supervisor and chief engineer ； Get the walkie-talkie and flashlight ready ； 2. When the backup fan is started in conjunction with the main fan, the fan interlock should be disabled on the OS screen; immediately send a duty operator to the site to check things out, close the inlet door of the fan that is being shut down, open the inlet door of the fan that is starting up as well as the exhaust door at the bottom of the fan, and adjust the opening degree of the inlet door so that the negative pressure in the oil tank remains at 2025 mm. 3. During this process, while adjusting the opening degree of the inlet door and monitoring the negative pressure in the oil tank, the duty operator and the personnel monitoring the control panel must maintain regular communication via walkie-talkies, and pay close attention to any changes in the oil level ； 4. Immediately send someone to check whether smoke or oil is coming from the main shaft bearings and the oil system, and clean it up right away ； 5. If no issues are detected or no actions are taken for an extended period, it is necessary to closely monitor any changes in the lubricating oil. Additionally, personnel should be dispatched to check on-site the opening degree of the cold oil cooler control valve and to inspect the oil flow through the transparent flanges on the oil pipes ； 6. Send an electrical inspector to determine the cause of the shutdown. First, cut off the power supply, manually rotate the fan to check if it moves smoothly, examine whether the motor itself is hot to the touch, and test the motor’s insulation; if the insulation is satisfactory, the motor can be tried again. In the event of a motor failure or an oil system malfunction, contact the electrical maintenance personnel immediately for handling; in case of a mechanical failure, contact the mechanical and boiler maintenance personnel right away. Report the progress of the repairs to the shift supervisor ； V. Precautions: 1. Maintain full concentration while monitoring the system to detect problems in a timely manner; this includes changes in oil level and oil temperature, as well as alarm signals indicating malfunctions in auxiliary equipment. 2. If such problems go unnoticed and unaddressed for an extended period, it can lead to oil leakage or smoke emission from the bearing areas. This not only causes environmental pollution but also results in high temperatures in the oil system and bearing areas, increasing the risk of fire. Therefore, cleanup must be carried out promptly. 3. If oil return is hindered, oil temperature can rise rapidly, potentially reaching levels that trigger an emergency shutdown. It is necessary to closely monitor oil temperature changes and the operation of the oil coolers; load reduction may be required if necessary. 4. Sometimes, due to poor performance of the oil smoke separator, lack of regular cleaning, or blockages at the fan inlet, the fan’s output may decrease, leading to a drop in negative pressure in the main oil tank. This can have effects similar to those caused by a fan malfunction. If such issues are detected, the fan should be switched immediately, and the mechanical and thermal engineering teams should be notified to handle the situation. 06. Plan for dealing with a drop in water level during the heating process of the deaerator. I. When the unit starts up and the deaerator is heated using auxiliary steam from the plant, with water supplied by the desalination water pump, sudden drops in the deaerator’s water level can occur for the following reasons: 1. Faults in the desalination water pump or a decrease in its output. 2. The emergency drain valve of the deaerator was accidentally opened. 3. A false high water level signal from the deaerator was generated, causing the deaerator drain valve to open. 4. The auxiliary steam pressure rises, and the deaerator water level drops. 5. The drain valve at the outlet of the 5# low-temperature heater was opened, causing water to leak from the deaerator. 6. The water filling rate of the boiler increases suddenly, and the water level in the deaerator drops. 7. The drain valve of the deaerator water tank was accidentally opened, causing water to leak from the deaerator. II. Handling of water level drop during the heating process of water fed into the deaerator: 1. Check the operation status of the desalination water pump, as well as the outlet flow rate of the water feeding pump and the current associated with water feeding. 2. Check and adjust the pressure of the auxiliary steam. 3. Adjust the water feeding rate to the boiler drum via control. 4. Inspect the deaeration system and close the following valves: a. Manual valve from the deaerator to the fixed drain. b. Electric valve at the deaerator condensate inlet. c. Deaerator tank drain valve. d. Electric valve for drain at the outlet of the 5# low-temperature reheater. e. Deaerator accident drain valve. III. Division of responsibilities: 1. The captain is responsible for promptly analyzing the reasons behind the drop in water level, anticipating potential accidents, and coordinating and directing the crew during accident handling. 2. The first officer shall promptly report the captain’s condition, check the feedwater heating system of the deaerator, and analyze the reasons for the drop in water level. 3. Assistant furnace engineer, controls the water feed rate to the steam drum. 4. Conduct routine aircraft inspections, follow the instructions of the captain and first officer, inspect the systems on site, and report promptly. 07 Emergency Plan for Sudden Drop in Deaerator Water Level I. Conditions prior to the accident: One condensate pump was in operation; the automatic regulation of the deaerator water level was functioning properly. Two electric pumps were operating, and the automatic regulation of the drum water level was also working correctly. The unit was running normally. II. Symptoms of a sudden drop in the deaerator water level: 1. The water level indicated on the deaerator OS display, the water level indicated by the electrical contact gauge, and the water level shown by the local gauge all decrease, either partially or entirely. 2. The condenser water level may rise, and the drum water level may rise as well. 3. When the water level drops to the level indicated on the OS screen, a low water level alarm is triggered. 4. When the water level drops to the Low II level, it will cause the feed pump to trip. 5. The current of the condensate pump, outlet pressure, flow rate, speed of the feedwater pump, and feedwater flow rate may experience significant changes. III. Causes of the sudden drop in deaerator water level: (I) Faults in the condensate system, including: 1. Failure of the main condensate control valve mechanism, resulting in the valve closing. 2. The automatic deaerator water level control system has failed. 3. Pump A for condensate circulation tripped (or tripped due to inverter failure), and the backup Pump B was not started in time. 4. Abnormal operation of the water-side valve after the heater trips causes a disruption in the condensate flow. 5. When the condensate start recirculation valve or the condensate recirculation valve opens accidentally, when automatic adjustment and tracking are not timely, or when the deaerator water level setting value is incorrectly set. (II) Perturbations in the water supply system, including: 1. Failures of the feed water pumps, resulting in an increase in rotational speed, and inadequate tracking of the deaerator water level. 2. Other faults cause a sharp increase in the water demand of the boiler, resulting in delayed tracking of the deaerator water level. (III) Faults in the deaerator system, including: 1. The deaerator overflow valve and emergency drain valve opening unintentionally or failing to close after being activated. 2. A fault in the water level measurement section is causing false water level signals. 3. During the unit startup process, improper operation caused the deaerator to be connected to the condenser. 4. During high load, the emergency drain of the high-pressure heater is activated, resulting in delayed makeup of condensate water. IV. Handling of sudden drop in deaerator water level: 1. Upon detecting a sudden drop in the deaerator water level, it is necessary first to determine the cause by examining the changes in the water level indicated by the two OS displays as well as that shown by the electric contact gauge. If it is a fault with the control transmitter, automatic adjustment of the deaerator water level should be switched to manual adjustment; if it is a fault with the indicating transmitter, closer monitoring is required and the thermal engineering team should be informed. In the event of a fault with the electric contact, the thermal engineering team should be contacted to short-circuit the contacts that control the start of the electric pump, and the issue should be resolved promptly. 2. If all the water level gauge readings drop sharply, it is necessary to assess the situation based on the opening degree of the main condensate control valve (the opening degree controlled by the inverter), the current drawn by the condensate pumps, the outlet pressure, and the condensate flow rate. The cause should be identified promptly, and appropriate actions taken. If it closes due to a fault in the main control valve, this is indicated by a decrease in the condensate pump current, an increase in outlet pressure, and a decline in flow rate. In such cases, the bypass electric valve associated with the main control valve should be opened immediately to supply water, the condensate flow rate should be monitored, and condensate recirculation should be used to assist in adjusting the flow rate; if necessary, the bypass electric valve can be adjusted manually ； If the trip is caused by a heater failure and water supply is interrupted due to abnormal operation of the water-side valves, the faulty valve will turn yellow; the current of the condensate pump will decrease, the outlet pressure will rise, and the flow rate will drop. In such cases, the faulty electric valve should be manually opened on-site to maintain the water supply ； If the automatic adjustment of the deaerator level fails, it should be immediately switched to manual adjustment ； If the frequency converter trips or the motor of pump A fails, and the backup pump is not started in a timely manner, the backup pump should be started manually ； If it is due to an accidentally opened system valve, it should be closed; if it is a result of an incorrect setting, the captain should be informed so that the situation can be corrected immediately ； In the case of disturbances on the furnace side, priority should be given to addressing those issues; if necessary, start the backup pump to supply water in order to prevent the accident from escalating ； In the event of a drop in water level caused by reasons such as improper operation of valves in the deaerator system, these valves should be closed promptly; if it is a fault with the overflow valve, the manual valve should be closed ； During startup, it is necessary to carefully check the valves of the deaeration circulation pump system as well as the position of the condensate startup circulation valve, in order to prevent water from the deaeration tank from entering the condenser. If a drop in water level occurs, the system should be isolated immediately ； During high load conditions, if the emergency drain of the high-pressure heater is activated, the load should be reduced appropriately as necessary to shut down the emergency drain; otherwise, notify the thermal control team to do so. 3. During the handling of an emergency drop in the deaerator water level, the boiler side should carry out load reduction operations to slow down the rate of water level decline; simultaneously, the water supply to the boiler can be reduced temporarily. If the water level drops to the protection value due to untimely handling, the furnace should be shut down to prevent equipment damage. 08 Treatment plan for generally increased temperatures of all bearings or an increased temperature of a single bearing. Operating mode before failure: load of 180MW–300MW, with only the cold oil cooler on Side A of each unit in operation. I. Temperatures of all bearings have generally increased: (I) Symptoms: 1. Temperatures of all bearings have generally risen; 2. Alarms are triggered due to the increase in bearing temperatures and oil return temperatures. 3. The lubricating oil temperature rises. 4. Unit vibration may increase. 5. Axial displacement may increase. (II) Handling: 1. Check whether the valves of the lubricating oil cooler are operating properly; if a valve is fully closed, it should be opened manually or a bypass valve should be used to adjust the oil temperature to normal levels, and the thermal control maintenance team should be contacted. 2. Check whether the cooling water supply is interrupted or whether the industrial water pressure is normal. Handle it according to the situation. 3. If the A cold oil cooler fails, it should be switched to the B cold oil cooler for operation, and the turbine and boiler units should be informed. 4. In the event of water entering the cold oil cooler, reduce the cooling water outlet valve, open the inlet valve, remove any air from the system, and then adjust the oil temperature to the normal range. 5. Check whether the vibration of each bearing in the unit is increasing gradually, and take appropriate action accordingly; if the vibration level reaches the value that triggers shutdown, the unit should be shut down immediately. 6. If the adjustment is ineffective and the bearing temperature reaches the emergency stop value, an emergency stop will be triggered. 7. Strengthen monitoring of lubricating oil pressure, bearing temperature, vibration, and axial displacement. If the bearing bush loses oil supply or the oil flow is low, causing the temperature to rise to the point where an emergency stop is required, an emergency stop should be initiated. II. Increase in the temperature of a single bearing: (I) Symptoms: 1. Increase in the temperature of the bearing metal. 2. The bearing may smoke. 3. Damage to the thrust bearing or an increase in the metal temperature of the thrust pads. 4. Black gold fragments were found in the return oil. 5. Single-axis vibration or cover vibration may increase. (II) Handling: 1. Check whether there is any metallic friction sound from the individual bearing to determine if there is a lack of oil or if the bearing is damaged. 2. Is the lubricating oil pressure normal? ； Is the oil return temperature rising sharply? ； If the return oil temperature reaches 82°C and the bearing shells start smoking, the machine shall be shut down immediately due to an accident. 3. The unit should immediately reduce its load, alter the stress distribution in the shafting system, and monitor any changes in temperature. III. Precautions: 1. When adjusting the lubricating oil temperature, the cooling water valve should be adjusted as slowly as possible to avoid large fluctuations in the oil temperature, which could cause changes in the oil film and lead to excessive vibration of the unit and its shutdown. 2. When the temperature of a single bearing rises, it is necessary to promptly and accurately determine whether the cause lies at the measurement point or in a bearing failure; when an emergency stop is required, the relevant regulations for such stops must be strictly followed. 09 Emergency Response Plan for Cooling Water System Abnormalities I. Water quality abnormalities: Upon receiving a notification from the chemistry team or a report indicating that the water quality exceeds acceptable levels, it is necessary to confirm this promptly, check the operation of the ion exchangers on site, appropriately open the manual valves at the inlet and outlet of the ion exchangers, and ensure that the valves for supplying condensate water are closed. Change the water in the tank according to the level of water pollution. If the ion exchanger has failed, it should be disconnected promptly and the chemistry department notified. If the above measures are ineffective and it is suspected that circulating water leaking from the cooler has mixed with the chilled water, a cooler switch operation should be performed. During the above operations, attention should be paid to the changes in the flow rate and pressure of the cooling water. II. Abnormal flow (pressure): 1. If pump A stops operating and pump B, which is in standby, has not been connected, the standby pump should be started immediately. If the flow is interrupted due to a human error in operating the system, such as accidentally closing the system valves, it should be restored immediately. If a flow interruption is not addressed in a timely manner, it can cause the unit to trip; in such cases, an emergency stop should be initiated, and the shift supervisor should be informed. Once the fault is resolved, the unit can be connected again to the grid. 2. In the event of a decrease in abnormal flow, it should be confirmed based on pressure. If it is an error in the flow indication, the thermal simulation signal should be notified for inspection, and water pressure should be monitored closely during the inspection. In cases where flow rate is indeed reduced, the chilled water recirculation valve should be closed to increase system pressure, and the operation of pump A, the water level in the tank, the positions of the system valves, and the degree of dirtiness of the filters should all be checked. If Pump A has insufficient output, the water pump should be replaced ； If it is due to a decrease in the water tank level, add water to restore normal levels ； If the filter screen becomes dirty, it should be replaced promptly ； The system valves should return to normal if they are not operating properly. III. Abnormal water level: In the event of a water level alarm or if an abnormal drop in water level is detected locally, manual replenishment of water should be carried out to restore normal levels. It is necessary to check whether the drain and vent valves have been opened incorrectly, as well as to determine whether there are leaks in the system or coolers. By considering the humidity of hydrogen gas and the liquid level in the oil-water relay, it can be determined whether the generator is leaking water, and appropriate measures should be taken. If the water replenishment solenoid valve fails and automatic water replenishment is not possible, manual water replenishment should be used along with enhanced monitoring. If the water level rises abnormally, it is necessary to check whether there is internal leakage in the water supply valve; if such leakage exists, it should be repaired promptly and the water level should be brought back to normal. IV. Temperature anomalies: In the event of temperature changes, it is necessary to determine whether they are normal by referring to both local and remote meters, as well as the ambient temperature and load conditions. Notify the thermal engineering department promptly in case of meter errors. If the water temperature is too low in winter, reduce the flow of cooling water promptly ； If the water temperature is too high in summer, make adjustments promptly; if necessary, deploy a backup cooler. Faults in certain valves of the cooler make it difficult to regulate the water temperature, so a backup cooler should be brought into operation. 10 Emergency Plan for Low Pressure of Instrumentation Compressed Air I. Phenomenon of low pressure of instrumentation compressed air: 1. An alarm stating “Low pressure of air for control” appears on the OM screen. 2. The cooling water control valves for the main engine shaft seal, as well as those for the furnace side and reheater cooling water, may turn yellow or become inoperable. 3. The pressure gauge at the 6.3M control air supply station shows a decrease in pressure. II. Reasons for low pressure of compressed air for instrumentation: 1. Mechanical failure of the air compressor, resulting in shutdown. 2. Dryer tower switching fault. 3. Built-in protection actions of the air compressor (low cooling water pressure, low lubricating oil pressure, etc.). 4. Tripping due to a fault in the air compressor motor. 5. Severe leaks in the compressed air system, or heavy usage of air in the precision processing areas and peripheral workshops, without timely notification. 6. Incorrect switching of the compressed air system. III. Handling of low pressure in the compressed air used for instruments: 1. Immediately send someone equipped with a walkie-talkie to the site for inspection, confirm that the alarm is accurate, report to the shift supervisor, and at the same time contact maintenance personnel to go to the site. 2. If it is for use in peripheral workshops, notify them to restore service immediately. 3. Notify the auxiliary control team to check the operating air compressor, start the backup air compressor, or switch the system. 4. Stop the operation that was just performed, and restore the contents of that operation as appropriate. 5. Try to maintain boiler combustion and minimize the operation of pneumatic control dampers and control valves. 6. When the supply air temperature for the low-pressure shaft seal or the temperature of the cooling water changes, personnel can be sent to make manual adjustments on-site; special attention should be paid to the operation of the minimum flow valve of the electric pump, and the water level in the steam drum should be monitored. In cases of high load, the boiler should be instructed to reduce its load promptly ； The drain valve of the turbine itself will open; be aware of changes in back pressure ； Close the extraction check valves in each section; pay attention to the deaerator water level ； Open the desuperheating water control valve on the furnace side, and promptly contact the inspector to adjust the electric valve on-site. 7. During the processing process, if the emergency stop conditions are met, the emergency stop must be implemented without hesitation. When shutting down the machine, it is necessary to ensure that the steam extraction electric valves close properly and that the turbine speed decreases; if the compressed air pressure cannot be restored, a shutdown request should be submitted. 8. Prepare on the electrical side to switch the plant power to the standby transformer. IV. Division of responsibilities: 1. The captain is responsible for notifying the shift supervisor and the maintenance crew to enter the site; once the shift supervisor arrives, the captain works together with the assistant captain in charge of the turbine and boiler, under the overall supervision of the shift supervisor. 2. The inspection of the steam turbine and the electrical system are carried out simultaneously to switch over the compressed air system and start up the standby air compressor, with measures taken to avoid any communication gaps throughout this process. 3. Operations are performed via the control panels by the assistant captains in charge of the boiler and the steam turbine; when it is necessary to switch to auxiliary power, the assistant captain in charge of the steam turbine carries out the operations while being supervised by the shift supervisor. 11. Emergency response plan for high and low pressure bypass activation: I. Activation of the high pressure bypass (1) Symptoms: 1. A sudden increase in load of around 20,000 units. 2. The drum water level rises suddenly. 3. Sudden drop in main steam pressure. 4. The main steam flow decreases. 5. The reheat steam pressure increases. 6. The temperature and pressure increase behind the high-pressure bypass relief valve. 7. The axial displacement increases, and the temperature of the working pads on the thrust disc rises. (II) Reasons: 1. Malfunction caused by deviations in the thermal control system settings, or human error. 2. Inconsistent attention during monitoring; the control valve is not opened in a timely manner when the load increases or the coal quality improves; the main steam pressure is not monitored when closing the control valve. This causes the main steam pressure to rise. (III) Handling: 1. Notify the thermal engineering team to investigate the cause of the malfunction and report to the management. 2. The shift supervisor shall provide unified command and coordination; when the trip value is reached, tripping shall be initiated. 3. When no tripping occurs, the low-pressure bypass activates to shut down the high-pressure bypass and reduce the reheat steam pressure. Reduce the boiler load, maintain the drum water level, adjust the main and reheat steam temperatures, and stabilize combustion. For the steam turbine, pay attention to the deaerator level, condenser level, shaft seal temperature, and main engine vibration. 4. Keep a certain opening degree for the valve next to Gao. Prevent it from being turned off completely and then turned on again. 5. Identify the cause, eliminate the fault, and restore normal operation. 6. If either main steam valve or main control valve shuts down suddenly during operation, notify the turbine, boiler, and thermal control teams to conduct an inspection. Monitor the turbine vibration; initiate an emergency stop when it reaches the tripping value. If a main steam valve movement test is conducted after load reduction, when closing the main steam valve and then opening it again, pay close attention to monitor until full stability is achieved. If it cannot be opened, report and request a shutdown. II. Low bypass operation (I) Phenomenon: 1. The load suddenly decreases by about 20,000. The reheat steam pressure decreases. 2. The condenser water level rose sharply. 3. The exhaust pressure of the host increases, and the exhaust temperature rises. 4. The axial displacement of the host tends to become negative, and the temperature of the non-operating tiles on the thrust disc rises. 5. The low-side pressure control pointer on the display indicates an increase. 6. The third-level water spray valve on the OS screen is activated. (II) Reasons: 1. Malfunction caused by deviations in the thermal control system settings, or human error. 2. High exhaust pressure, high load, and low low-pressure bypass activation value. (III) Handling: 1. Notify the thermal engineering department to investigate the cause of the malfunction. Report to the leader. 2. The shift supervisor provides unified command and coordination. When the trip value is reached, it is treated as a trip. 3. When no tripping occurs, reduce the boiler load, maintain the drum water level, adjust the main and reheat steam temperatures, and stabilize combustion. For the steam turbine, pay attention to the deaerator level, condenser level, shaft seal temperature, and main engine vibration. 4. Reduce the low-pressure bypass flow to prevent repeated activation of the fast shutdown low-pressure bypass protection. 5. Identify the cause, resolve the fault, and return to normal operation. 6. It is caused by the closure of the medium-pressure main steam valve and the main control valve. Notify the boiler operator for inspection. Monitor the turbine vibration; initiate an emergency stop when it reaches the tripping value. After reducing the load, perform a movement test on the medium-pressure main steam valve; when closing and opening the valve, pay close attention to monitor until it reaches complete stability. If it cannot be opened, report and request shutdown through the dispatching system. 3. Full operation of the high and low bypass systems. (1) Symptoms: 1. The load decreases after increasing, or it decreases directly. 2. The drum water level rises suddenly. 3. Sudden drop in main steam pressure. 4. The main steam flow decreases. 5. The reheat steam pressure rises and then falls. 6. The temperature and pressure increase behind the high-pressure bypass relief valve. 7. The condenser water level rose sharply. Values for the first year of high school and the second year of high school may appear. 8. The exhaust pressure of the main engine rises, and the exhaust temperature increases. (II) Reasons: 1. False operation. 2. Inconsistent attention during monitoring; the control valve is not opened in a timely manner when the load increases or the coal quality improves; the main steam pressure is not monitored when closing the control valve. (III) Handling: 1. Notify the thermal engineering department to investigate the cause of the malfunction. Report to the leader. 2. The shift supervisor provides unified command and coordination. When the trip value is reached, it is treated as a trip. 3. When not tripped. Reduce the boiler load, maintain the drum water level, adjust the main and reheat steam temperatures, and stabilize combustion. For the steam turbine, pay attention to the deaerator level, condenser level, shaft seal temperature, and main engine vibration. 4. Reduce the low-pressure bypass flow to prevent repeated activation of the fast shutdown low-pressure bypass protection. 5. Keep a slight opening in the low bypass valve to prevent it from opening again after being closed. 6. Leave a certain opening at the high-pressure valve to prevent it from being closed completely and then reopened. 7. When any main steam valve or main control valve is suddenly closed during operation. Notify the boiler operator for inspection. Monitor the turbine vibration; initiate an emergency stop when it reaches the tripping value. If a main steam valve movement test is performed after load reduction, when closing and opening the valve, pay close attention to monitor until it reaches complete stability. If it cannot be opened, report and request a shutdown. 8. If it is caused by load shedding, handle it as load shedding. 12 Emergency Plan for Abnormal Expansion Discrepancy in High and Low Pressure Cylinders of Turbines I. Operating conditions prior to the incident: During the startup or shutdown of the turbine unit, the unit was running at a constant speed or connected to the grid; all major auxiliary equipment was functioning properly, the temperatures of the main steam and reheater were normal, the temperatures and pressures of the shaft seals were normal, and the vacuum level in the condenser was normal. II. Abnormal expansion difference phenomena in the high and low pressure cylinders of the steam turbine: 1. On the OS display, the expansion difference between the high and low pressure cylinders increases or decreases abnormally, approaching the shutdown threshold of 1.5 mm or +16.5 mm. The temperature of the turbine rotor and cylinders may increase or decrease. Sudden rise or fall in main and reheat steam temperature. The shaft seal temperature and pressure increase or decrease abnormally, with significant variations in vacuum. 2. On-site inspection for severe steam absorption in the steam seal system or white steam emission. Mainly, white steam appears at the steam pipe flanges and valves; a sound of static and dynamic friction from the turbine may be heard. III. Plan 1: 1. The expansion difference of the turbine increases or decreases significantly, and high/low value alarms may be triggered. 2. The first officer monitoring the instruments noticed a significant change in the turbine expansion difference, with a trend of further increase. Report to the captain and shift supervisor immediately, and send an inspector to the site promptly to check for any metal friction or other abnormal conditions in the main engine. 3. The shift supervisor shall arrange the adjustment of the unit’s load in the control room, and make arrangements for the emergency shutdown of the unit. The captain instructed the other inspectors to prepare their walkie-talkies to maintain timely communication on-site. If necessary, arrange for the first officer to conduct an on-site inspection directly. The mechanical inspector promptly went to the site to inspect the turbine seal system and vacuum system, and reported back in a timely manner. 4. The captain instructs the deputy furnace officer to adjust the main and secondary steam temperatures as well as the load accordingly. The first officer adjusts the openings of the high and low bypass valves, while closely monitoring changes in the expansion difference. When the expansion difference reaches the shutdown value of 1.5 mm, or +16.5 mm, and adjustments prove ineffective, it should be treated as a emergency stop, and the cause of the change in expansion difference should be identified. Reason and handling: 1. Jamming in the turbine slip system – Contact the mechanical and thermal maintenance personnel to arrive and handle the issue by injecting oil between the sliding surfaces to ensure proper lubrication and free movement. Phenomenon: The expansion value experiences sudden increases or decreases during the expansion or contraction process. 2. Rate of change in steam temperature rise (fall) and flow rate: Adjust the temperature rise/fall rates and flow rate appropriately based on actual conditions; that is, reduce the rate of temperature rise when there is a positive expansion difference, and do the opposite in the case of a negative expansion difference. Adjust the high-pressure bypass opening to control the steam volume, thereby ensuring uniform heating of the cylinder. 3. Variation in shaft seal temperature: Adjust the steam supply temperature for the shaft seal appropriately, and switch the steam source in a timely manner to prevent rapid cooling and contraction of the main shaft in the shaft seal section. 4. Effect of condenser vacuum: During startup, while maintaining a certain speed and load, changing the vacuum allows the expansion difference to be adjusted within a certain range. 5. Effects of cylinder insulation and water drainage: Poor insulation can lead to an uneven temperature distribution within the cylinder, with temperatures being on the low side. It affects the full expansion of the cylinder, resulting in an increased expansion difference. Contact the maintenance staff to repair the insulation. Poor hydrophobicity may lead to a lower temperature in the cylinder, affecting expansion and increasing the risk of deformation. At startup, make sure to open the steam trap to enhance water drainage from the cylinder. IV. Plan 2: The OS display in the control room shows that there is no alarm regarding the expansion difference of the high and low pressure cylinders in the vertical shaft; the expansion difference value is within the normal range. The vibration of a certain bearing and the vibration of the bearing cover increase abnormally. Inspect on-site for sparking due to friction in the host’s local shaft seal and oil baffle ring. After ruling out thermal measurement issues, it was determined that uneven expansion in the main unit led to an increased expansion difference, thereby causing static and dynamic friction. At this time, the emergency stop was executed decisively in accordance with the procedures. Prevent the escalation of host failures. The main shaft suffered local friction damage, resulting in permanent bending. 13 Emergency Plan for Large Axial Displacement of Turbines I. Operating conditions prior to the accident: The unit was operating normally, the auxiliary equipment was also functioning properly, and all parameters were within normal ranges. II. Accident symptoms of large axial displacement in the turbine: 1. The OS display shows a high value for axial displacement (or a very high value). 2. The following phenomena may occur: ① Alarm for high temperature of the turbine thrust bearing, alarm for high temperature of the return oil temperature of the thrust bearing. ② The turbine is making abnormal noises, with clear sounds of metal friction inside, and the vibration of the unit has increased. ③ The turbine expansion difference, as well as the pressures before and after each stage, change. ④ Unit load drops (water hammer) or rises (deactivation of the high-pressure heater). III. Causes of large axial displacement accidents in steam turbines: 1. Operation of the high-pressure bypass or low-pressure bypass. 2. Water hammer occurs in the turbine. 3. The thrust bearing is faulty. 4. The heater is disabled. 5. The flow-through section is damaged. 6. Severe scaling on the blades. 7. Drop in condenser vacuum. 8. Generator rotor play. 9. The load changes rapidly. IV. Handling of large axial displacement in steam turbines: 1. When a large axial displacement occurs, it is first necessary to determine whether the issue lies with the measurement points, by checking for alerts related to high temperatures of the turbine thrust bearings, high temperatures of the oil returning to these bearings, as well as any abnormal changes or internal factors that could lead to accidents. If it is determined that the problem lies with the thermal control measurement points, the shift supervisor should be informed so that the protection systems can be disabled promptly, and thermal control personnel should be contacted to address the issue. When it is determined that the issue does not lie with the thermal control measurement points, it should be handled in accordance with the following principles. 2. When an alarm is triggered due to an axial displacement exceeding the first threshold value but not reaching the second threshold value, and at the same time the vibration of the unit increases without any abnormal noises, the vacuum should be broken immediately to shut down the unit. 3. When a large axial displacement binary value is detected, the protection should activate; if it fails to do so, the vacuum should be manually broken to shut down the machine immediately. 4. The steps for emergency shutdown due to vacuum breakdown are as follows: ① The main controller presses the shutdown button or performs an on-site circuit breaker operation ； Inspect the high and medium pressure main steam valves, throttle valves, as well as the extraction check valves and high-pressure exhaust check valves; the extraction electric valves should be closed promptly, and check that the unit load is reduced to zero. ②The generator is disconnected from the system, and it is confirmed that the turbine speed has decreased ； ③Start the circulation lubricating oil pump and check that the oil pressure is normal ； ④Open the condenser vacuum break valve and stop the water ring vacuum pump ； ⑤Check that the following operations are carried out automatically; otherwise, do them manually: a. Activate the hydrophobic interlock of the machine body ； b. The condensate recirculation valve shall open automatically; otherwise, adjust it manually, paying attention to the water levels in the condenser and deaerator ； c. Low-pressure cylinder spray valve opened ； d. Check that the steam source switch for the deaerator is functioning properly ； e. The shaft seal steam supply switch operates normally; pay attention to adjusting the shaft seal temperature ； f. Manual resection of high and low paraganglia ； g. Check that the automatic operation of the steam traps for each heater is functioning properly. ⑥Reduce the rotational speed to 600 r/min, and start the high-pressure thrust oil pump ； ⑦Pay attention to the unit’s coasting condition and record the coasting time ； ⑧The remaining operations are carried out as for a normal shutdown. 14 Emergency Handling Plan for Trip of Condensate Pump I. Operating conditions prior to the accident: The unit’s load was 300 MW; the auxiliary equipment was operating normally, and the plant power supply system was also functioning properly. II. Symptoms of the condensate pump tripping accident: An alarm for a serious fault in the frequency conversion system appears on the DCS screen, and an alarm message for a serious fault is displayed on the local frequency converter display; the current of motor A of the condensate pump is 0. III. The handling process is carried out according to the following two scenarios: 1. When pump A operates in frequency conversion mode, pump B starts up normally after pump A trips. 2. When pump A operates in frequency conversion mode, pump B does not start up after pump A trips, or it starts up but then trips again. Note: A serious fault in the frequency conversion system of pump A can cause the pump to trip; after such a fault occurs, error alarms are displayed on both the OS screen and the local frequency converter display. IV. Accident Handling: 1. When the A condensate pump operates in variable-frequency mode and trips, and the B condensate pump starts operating normally: ⑴ The assistant pump operator shall immediately report to the pump operator, who in turn shall notify the shift supervisor. ⑵ The assistant pump operator shall check that the outlet valve of the A condensate pump closes properly after it trips; after starting the B condensate pump, he/she shall verify that the current returns to normal levels and that the outlet pressure of the B condensate pump is within the normal range. ⑶ The assistant boiler operator shall appropriately reduce the boiler load and monitor the water level in the steam drum as well as in the deaerator. ⑷ The assistant pump operator shall keep an eye on the main condensate flow rate and the water level in the deaerator, ensure that the outlet valve of the 1A condensate pump closes properly, and confirm that the 1B condensate pump is operating normally. Depending on the situation, the automatic control valves for the main condensate flow and the recirculation valves can be activated. ⑸. Note that after the 1B condensate pump starts up, the main condensate control valve should be adjusted and immediately closed to a certain opening degree corresponding to the load condition (for a 300MW load condition, it should be closed to 50%). At this time, it is necessary to manually adjust the opening degree of the main condensate control valve in order to maintain a normal water level in the deaerator. Additionally, if the recirculation control valve is used to maintain the main condensate pressure in automatic mode, this automatic function can be disabled, and manual adjustment should be carried out instead to keep the deaerator water level normal. ⑹. The chief engineer and assistant engineers should pay attention to monitoring and adjusting the temperature of the low-pressure steam seal, in order to maintain a normal water level in the deaerator as well as a normal temperature for the low-pressure steam seal. ⑺The captain immediately sent an inspector to the site to check that the B condensate pump was operating properly, including verifying the sound level, vibration, proper operation of the motor cooling water system, proper operation of the bearing seal water system, normal oil level in the motor bearings, and correct readings on the pressure gauge at the outlet. Once everything was normal, the inspector reported the results of the inspection. ⑻The captain instructed the electrical maintenance personnel to investigate the reason for the shutdown of Pump A for condensate removal, and asked the on-site inspection team to check whether it was a fault alarm from the frequency converter. The cause was to be identified and addressed as soon as possible; if restoration was not possible in the short term, then Pump A should be switched to its normal frequency operation mode as a backup. 2. Handling of the situation where Pump A operates in variable-frequency mode and, after it stops working, Pump B does not start up or stops working again once it does start: ⑴ The assistant engineer immediately reports to the chief engineer, who then notifies the shift supervisor and prepares for an emergency shutdown. ⑵ The chief engineer assigns specific tasks to each person: <1> The assistant engineer in charge of the furnace reduces the load urgently; <2> The person responsible for furnace monitoring adjusts the water level in the drum; <3> The assistant engineer in charge of the turbine performs relevant operations and monitors the screens. ⑶ If Pump B does not start up, it should be started manually as quickly as possible. If it still cannot start, the emergency shutdown procedures must be followed strictly. ⑷ The assistant engineer should disable the automatic control of the turbine, reduce the load at a faster rate, and closely monitor changes in the water level of the drum and the deaerator. ⑸ The shift supervisor informs the maintenance staff to determine the reason why Pump B does not start up or stops working again after starting. It is not allowed to start the pump until the cause is identified. The chief engineer also sends engineers from the turbine and electrical teams to conduct on-site inspections. ⑹ When both condensate pumps stop working, it directly affects the water level in the deaerator, which in turn prevents the feedwater pump from starting ； For the low two-value feedwater pump, due to the aforementioned alarms and protections, if it cannot be rescued in a short period of time, it should be shut down ； ⑺Due to the failure of the two condensate pumps and the excessively high level of water in the condenser, which met the conditions for shutting down the system, an emergency shutdown was carried out without disrupting the vacuum. ⑻Inspect pumps A and B for condensate. If pump A fails due to an inverter issue, it can be switched to operate at the mains frequency; once the startup conditions are met, the unit should be started as soon as possible. 15 Emergency Plan for Failure of a Single Feed Water Pump I. Operating conditions before the accident: The unit operates in a coordinated manner, with a load of 300MW. Pumps A and B operate in parallel, while pump C is in standby mode. All auxiliary equipment is functioning normally, and there are no abnormalities in the system. II. Symptoms of failure of a single feed water pump: The corresponding pump stops operating, and the water level in the steam drum drops. III. Principles for handling the accident: The turbine and boiler should work together to reduce the load rapidly. It is important to monitor and coordinate the operations to prevent the boiler from stopping or to avoid further escalation of the accident. After pump A stops operating, two possible scenarios must be considered: (1) Pump C starts automatically or manually; (2) Pump C does not start automatically or stops operating after being started. IV. Procedures for dealing with the failure of a single feed water pump: (I) Scenario 1: Pump C starts automatically or manually: (1) The shift leader assigns specific tasks to each person: the auxiliary equipment supervisor is responsible for monitoring and adjusting the air and flue gas systems ； The furnace inspector is responsible for adjusting the drum water level ； The first officer is responsible for the operations and monitoring related to the aircraft side ； The mechanical inspector is responsible for adjusting the steam temperature. (2) The assistant furnace operator should immediately take action to disable automatic air supply, reduce combustion, and lower the air flow. (3) The mechanical inspector should check that the electric pump starts properly (including the ability to start it manually in a timely manner), as well as that the cooling water for the oil cooler is functioning correctly. (4) The furnace inspector should check on the control panel to ensure that the electric valve at the outlet of pump A operates properly and that the minimum flow valve is open. Once the speed of pump C reaches 1480 rpm, the automatic mode of the electric pump should be disabled, and the pump should be switched to manual operation so that the flow rate corresponds to the required load. (5) The furnace inspector should increase the output of pump B to 5400 rpm to check if the flow rate increases; meanwhile, the output of the electric pump should be adjusted to maintain the water level in the steam drum, taking into account the load, the evaporation rate of the steam drum, and the amount of water supplied. (6) The mechanical inspector should hand over the monitoring screen showing the steam temperature to the furnace operator or another person, and then carry out on-site inspections of the electric pump’s operation under the supervision of the furnace operator, performing the necessary operations (bringing a walkie-talkie, flashlight, gloves, and door hook) to ensure that the cooling water for the electric pump is indeed in use. (7) If improper handling results in a low water level, the procedures outlined in the \"Boiler Fire Extinguishing Plan\" can be followed for fire suppression. (8) The shift supervisor should be informed once the treatment is completed. (II) Plan 2: The C electric pump fails to start up or trips after starting up: (1) The shift leader assigns specific tasks to each person; the assistant boiler operator is responsible for making adjustments to the air and flue gas systems ； The furnace inspector is responsible for adjusting the drum water level ； The first officer is responsible for the operations related to the aircraft side as well as screen monitoring ； The turbine inspector is responsible for adjusting the steam temperature. (2) The chief engineer should immediately arrange for the assistant chief engineer to coordinate the operation, enable automatic air supply, and significantly reduce combustion; the current supplied to the fans should be reduced to 40A, and the burner output should be adjusted to correspond to a load of 180MW–200MW. (3) The turbine inspector must closely monitor changes in steam temperature and make appropriate adjustments to prevent sharp drops or rises in steam pressure. (4) The assistant chief engineer should disengage the automatic control of the turbine and gradually reduce the load to around 180MW–200MW, while closely monitoring changes in main steam pressure and drum water level to avoid significant fluctuations in the drum water level. (5) The boiler inspector is responsible for checking the shut-off valves at the outlet of pump A and at the intermediate taps, etc.; they should also quickly increase the speed of pump B to 5400 rpm, and closely monitor the drum water level. If the water level drops rapidly, they must immediately report this to the chief engineer. (6) The shift supervisor should inform the maintenance staff to determine the reason why the pump did not start or tripped after starting. The pump must not be started until the cause is identified, and the chief engineer should send someone to conduct an on-site inspection. The goal is to reduce the load so that the plant can operate using the capacity of a single pump; all relevant teams must work closely together to achieve this. 16 Emergency Response Plan for Hydrogen Side Seal Oil Pump Failures: The handling of such failures is analyzed in two scenarios. I. The operating hydrogen side seal oil pump stops working while the backup pump starts up successfully: (I) Symptoms: 1. The hydrogen side seal oil pump stops functioning, and a low differential pressure alarm is triggered ； 2. The DC pumps start up together normally. (II) Reasons 1. Mechanical failure of the oil pump ； 2. Oil pump loses power ； 3. The thermocouple triggers the contactor to disconnect. (III) Handling: After the standby pump is started in conjunction, check that it operates normally on-site and that the oil pressure is normal. If the reason for the oil pump trip is the disconnection of the contactor triggered by the thermocouple, restore power supply after verifying that the insulation is in good condition. If maintenance is required for other reasons, the faulty pump shall be inspected and repaired. Case 2: The operating pump fails while the DC pump does not start: (I) Symptoms: 1. The hydrogen-side seal oil pump stops operating, and an alarm is triggered due to a low pressure difference at the inlet and outlet. 2. The standby pump as well as the interlock system issue alarms ； 3. It is possible that a high-level alarm for the seal oil tank on the hydrogen side will be triggered, as well as a high-level alarm for the oil level in the defoaming tank. (II) Reasons: 1. Both oil pumps have mechanical failures ； 2. Interlock is abnormal; the backup pump does not start ； 3. Both oil pumps have lost power ； (III) Handling: 1. The dual-ring seal ring allows the hydrogen side to operate without fuel for a short period of time; when fuel supply to the hydrogen side is suddenly interrupted, the seal ring can operate in single-ring mode, thereby sealing off the hydrogen inside the machine. 2. After the fuel supply to the hydrogen side is cut off, if this situation persists for an extended period, the purity of the hydrogen inside the generator will decrease, which in turn increases the amount of hydrogen required for drainage and replenishment. Additionally, over time, as the seal oil from the air side leaks into the hydrogen side, the oil level in the seal oil tank rises rapidly. In cases where the automatic oil drainage system fails, operators must monitor the situation closely and carry out manual oil drainage. 3. If the standby pump is in good condition and has not been started before, the duty officer should start it immediately; if it starts properly, it should be adjusted to normal operating mode ； If it cannot be started or operates abnormally, it should be stopped; close monitoring should be carried out on the operation of the air-side seal oil as well as the oil level in the seal oil tank’s defoamer, and maintenance personnel should be contacted for handling. 4. If the oil pressure drops due to a low level of oil in the seal oil tank, top up the oil immediately to the normal level ； If a low-binary error occurs, notify the thermal control team for immediate handling ； In the event of a mechanical failure in the oil pump, notify maintenance personnel immediately for repair. 5. After the fuel supply to the hydrogen side is cut off, the balance valve opens fully; once the oil pump resumes operation, the delayed response of the balance valve can cause oil to be injected into the generator, leading to oil ingress into it. Therefore, the balance valve should be released after the fuel supply is cut off. After the oil pump resumes operation, manually adjust the bypass valve to maintain normal oil pressure. Once normal, switch to operation with a balance valve. 17 Emergency shutdowns of the antifouling fuel pump during operation and procedures for dealing with oil leaks in the fuel pipelines. I. Procedures for handling emergency shutdowns of the antifouling fuel pump during operation: (I) Symptoms: 1. An “antifouling fuel pressure low” alarm appears on the OS screen. 2. An alarm is issued for the tripping of the anti-fire fuel pump on the OS screen. (II) Handling: 1. Check that the operating pump tripped due to an accident, and the standby pump started up properly. ⑴Check that the backup pump operates normally after being started in conjunction with the main pump. ⑵Check that there are no abnormal changes in the main steam valve and control valves, and the engine speed remains at 3000 RPM. ⑶Check that the oil pressure of the anti-fire fuel pump, the oil temperature, the differential pressure across the filter, the oil level in the tank, and the flow rate are all within normal ranges. ⑷Switch the fuel pump for accident tripping to the stop position and cut off its power supply. ⑸Contact the maintenance team to inspect and address the issue with the accident-induced tripping of the fire-resistant fuel pump. 2. Check that the pump in operation tripped due to an accident, and the standby pump failed to start. ⑴In the event of a pump failure, the pump shuts down; the standby pump does not start up. The OS screen is used to monitor the turbine speed as well as the operation of the high and low pressure main steam valves. ⑵Immediately start the standby pump on-site; during this time, the resistance fuel pressure drops below 9.31 Mpa. Check that the turbine protection systems are functioning properly; if not, the procedures for an emergency shutdown without damaging the vacuum must be followed. ⑶ After the unit is shut down, verify that its speed decreases normally, that the high-pressure exhaust check valves and the extraction check valves are closed, and that the unit’s drainage valves are open. Follow all other standard procedures for a proper shutdown. ⑷The standby pump did not start on-site, and the operating pump also failed to resume operation; maintenance was contacted for inspection and repair. Once both anti-fire fuel pumps were functioning properly, the interlock test was conducted successfully. The main unit is shut down, spun up, and the normal operation of the unit is restored. II. Handling of oil leakage in the antifouling fuel pipelines: (I) Symptoms: The antifouling fuel pump on the OS screen triggers an \"antifouling fuel pressure low\" alarm, and on-site inspection shows an increase in the flow rate of antifouling fuel. (II) Handling: 1. Check that when the EH oil pressure reaches 11.03 Mpa, the standby EH oil pump starts automatically; otherwise, start it manually. 2. Check that there are no external leaks in the system, and report the situation along with contacting the maintenance team for handling. If the leak cannot be fixed, immediately inform the shift supervisor to shut down the machine; stop the operation of the EH oil pump right after the shutdown is initiated. 3. Check for external leaks in the system; if the leakage is minor, contact maintenance for repair. While repairing the leak, closely monitor the EH oil pressure and the oil level in the EH oil tank. In case the emergency shutdown conditions are met, the relevant shutdown procedures must be followed. 4. If the leakage is severe and it may pose a threat to personal safety or the safety of other equipment, the shift supervisor should be informed immediately to shut down the machine; the EH oil pump should be stopped right after the circuit breaker is disconnected. 5. When the EH oil pressure drops to 9.31 MPa, the turbine protection system shall activate as intended; otherwise, the machine shall be stopped manually. 18 Plan for handling failures in the air-side seal oil pump: The air-side AC seal oil pump is in operation, with high-pressure standby oil pumps and DC pumps available as backups. The AC oil pump on the hydrogen side is in operation, while the DC pump on the hydrogen side is in standby mode. The hydrogen pressure is 0.31 Mpa, and the balance valve and pressure difference valve are set to automatic mode. There are two scenarios for such accidents: in one case, the standby pump starts up properly after the operating pump stops; in the other case, the standby pump fails to start up properly. I. After the operating pump trips, the standby pump starts up normally: (I) Phenomena: 1. The AC oil pump on the air side trips, and an alarm for an accident trip of the AC oil pump on the air side is issued. 2. The air-side DC oil pump starts up simultaneously; the air-side oil pressure drops momentarily before returning to normal. (II) Handling: 1. Check the OS screen to confirm that the oil pressure and temperature were normal before the hydrogen-oil accident occurred, and that the hydrogen pressure was also normal. 2. Conduct on-site checks to ensure that the DC pump operates properly after it is started, that the outlet pressure is normal, and that the balance valve and pressure difference valve function as intended. 3. Otherwise, make appropriate adjustments to identify the cause of the tripping of the air-side AC oil pump, and inform the maintenance personnel to handle it. 4. Strengthen the monitoring of the DC bus and DC oil pumps. II. After the operating pump trips, the standby pump fails to start properly: (I) Symptoms: 1. The AC oil pump on the air side trips, and an alarm is generated for this trip. 2. After the air-side DC oil pump is started in conjunction, it is turned off again or fails to start; the standby differential pressure valve operates properly, maintaining a hydrogen pressure of 0.31 MPa. (II) Handling: 1. Check that the oil-hydrogen differential pressure remains at 0.056 MPa, with no tendency to decrease. 2. Immediately notify the maintenance team to inspect the AC seal oil pump and the DC seal oil pump. 3. If operation can be restored promptly, start the air-side AC seal oil pump. 4. If it is not possible to restore operation of the AC seal oil pump in a timely manner, and the DC oil pump on the air side is functioning properly, then start the DC seal oil pump manually. 5. Closely monitor the hydrogen differential pressure until the AC seal oil pump resumes operation. III. When the operating pump stops working, the standby pump does not start properly: (I) Symptoms: 1. The AC oil pump on the air side stops working, and an alarm is triggered for this condition. 2. After the air-side DC oil pump is started in conjunction, it stops operating again or fails to start; the backup differential pressure valve does not function properly, resulting in a drop in hydrogen pressure. (II) Handling: 1. Disengage and restore the interlock block, and manually start the air-side DC oil pump. 2. If it still cannot be started, immediately send someone to manually open the bypass valve door on site and monitor the hydrogen pressure. 3. Immediately start reducing the load based on the hydrogen pressure drop, and notify the maintenance team to handle it. 4. Ensure that the temperatures of the rotor coils and core do not exceed the specified values. 5. As the hydrogen pressure decreases, reduce the pressure of the stator cooling water to ensure that it is 0.04 MPa lower than the hydrogen pressure. 6. If recovery can be achieved promptly, then start the recovery process. 7. If recovery is not possible, reduce the load urgently to 0. Operate the generator in isolated mode. The minimum operating hydrogen pressure for the generator is 0.14 Mpa. (The lubricating oil supply for the main engine should be able to maintain a certain hydrogen pressure.) 8. After maintenance work is completed, start the air-side AC oil pump; once the purity of the hydrogen used for charging the generator is satisfactory, the unit can begin to resume operation. 19 Emergency Plan for the Lubricating Oil System of the Host Machine I. System Overview: The reliability of the oil supply system for steam turbine generators is of great importance for the proper operation of the equipment. Any interruption in the oil supply, even if it is brief, can have serious consequences for the unit. Moreover, to ensure the proper functioning of the control system, the oil supply pressure must remain quite stable. This unit employs a supply system that uses a main oil pump and injectors. During normal operation, the oil system is supplied with oil by the main oil pump; the oil coming out of the main oil pump is sent through high-pressure oil pipes to the injectors, as well as to the turbine’s mechanical overspeed shutdown device. It also serves as a high-pressure backup source of oil for the generator’s hydrogen sealing system. The injectors draw oil from the tank, raise its pressure, and then supply this oil to the inlet of the main pump and to the lubricating oil coolers. Pressurized oil is supplied to the inlet of the main oil pump in order to prevent negative pressure at the oil suction port of the main oil pump, which could lead to poor oil suction and cavitation. The lubricating oil at the outlet of the cold oil cooler supplies oil to each bearing of the steam turbine generator set, the barring device, the oil pipes of the lifting device, and the air-side seal oil pump. During shutdown or startup, when the speed of the main engine has not reached its rated value, the auxiliary oil pump supplies oil, while the hydrogen seal oil standby pump provides low-pressure safety oil for the main engine; the AC lubricating oil pump takes over the function of the lubricating oil injector. The DC oil pump starts when the oil pressure drops below 0.075 Mpa, providing lubricating oil to prevent a loss of oil supply due to the interruption of station power during the free-run phase following a turbine shutdown accident. II. Analysis of common faults in the lubricating oil system: The common faults in the lubricating oil system generally include the following: 1. Drop in oil pressure with unchanged oil level; 2. Unchanged oil pressure with dropping oil level; 3. Drop in both oil pressure and oil level. (I) Drop in oil pressure with unchanged oil level: 1. Causes: (1) Abnormal operation of the main oil pump’s injector; (2) Leakage of pressure oil into the centralized oil tank or bearing box; (3) Inadequate sealing of the outlet check valve of the lubricating oil pump or the backup hydrogen seal oil pump; (4) Abnormal operation of the overflow valve; (5) Improper switching of the cold oil cooler or defects in the equipment resulting in incomplete switching. 2. Remedies: (1) If the main oil pump or its injector is malfunctioning, report to the shift supervisor and shut down the equipment due to the fault ； (2) If it is caused by a faulty check valve in the oil pump, report to the shift supervisor and contact the maintenance team for handling ； (3) The oil overflow valve is not functioning properly; contact maintenance for adjustment ； (4) When the lubricating oil pressure drops below the normal value, the cause should be identified; if necessary, the AC lubricating oil pump should be started manually. An alarm is triggered when the oil pressure falls to 0.082 Mpa, at which point both the AC lubricating oil pump and the hydrogen-sealed standby pump are started. When the pressure drops to 0.075 Mpa, the DC pump is started as well. If the lubricating oil pressure drops to 0.048 MPa, the steam turbine shuts down automatically, resulting in a loss of vacuum. (II) Oil pressure remains unchanged while the oil level drops. 1. Causes: (1) Abnormality in the oil level gauge ； (2) Accidental activation of the fuel tank emergency drain valve ； (3) Oil leakage from the oil cooler and oil pipelines (the air valve on the water discharge side of the oil cooler releases oil along with water; when there is significant oil leakage, oil droplets appear on the surface of the water tank) ； (4) Generator oil inlet ； (5) High liquid level in the oil purification unit causing oil overflow ； 2. Handling: (1) Contact the thermal engineering team to check the oil level gauge in the tank ； (2) If the oil release valve or water release valve opens accidentally, it should be closed promptly ； (3) In the event of a leak in the cold oil cooler, disconnect it promptly or switch to the backup cold oil cooler for operation ； (4) Top up the oil in a timely manner according to the fuel tank level ； (5) Check and adjust; the oil level in the seal oil tank is normal ； (6) If the oil purification unit malfunctions, shut it down immediately and isolate the system ； (7) If the oil level drops to 563 mm, the vacuum should be broken to trigger an emergency shutdown. (III) Both oil pressure and oil level drop simultaneously. 1. Causes: (1) Leakage in the pressure oil pipeline ； (2) Oil leakage from the oil cooler ； 2. Handling: (1) Quickly start the AC oil pump and the hydrogen-sealed standby oil pump to maintain oil pressure ； (2) Quickly identify the leaking pipeline and take measures to prevent oil from reaching the surface of the hot components and causing a fire, thereby avoiding the escalation of the incident ； (3) If the inspection reveals oil leakage from the cold oil cooler, the faulty cold oil cooler should be removed immediately ； (4) If the oil pressure drops to 0.048 Mpa, the turbine shuts down automatically; otherwise, it is shut down manually in case of vacuum breakdown ； (5) Refill the fuel tank as necessary; when the fuel level drops to 563 mm, the vacuum should be broken to trigger an emergency shutdown ； III. Precautions for handling: 1. Upon detecting potential accident hazards, report them promptly to the shift supervisor and the captain; 2. When shutting down parallel cold oil coolers, take into account the ambient temperature, and reduce the load if necessary ； 3. Pay special attention to oil leaks at the bearing shells, as oil dripping onto the insulation layer can lead to fires and the escalation of accidents. 4. Oil pressure is of critical importance for the operation of the turbine; any issues detected should be addressed promptly to prevent accidents such as bearing damage ； 5. When dealing with accidents, it is essential to have sufficient flashlights and walkie-talkies available. 6. In the event of a disruption in the supply of lubricating oil, attention should be paid to ensuring that the oil source on the air side of the generator’s seal system is a pressurized oil supply, in order to prevent excessive hydrogen leakage. Additionally, attention must be paid to the oil level in the seal oil on the air side, as this oil is replenished from the lubricating oil, thereby preventing serious accidents due to low oil levels. IV. Accident handling plan: If the oil level in the main oil tank of the turbine drops abnormally, an alarm indicating a low oil level is displayed on the OS screen. The deputy operator monitoring the system detects an alarm signal indicating that the oil level in the main tank is low; the oil level indicator on the OS screen shows a significant drop. The operator immediately reports this to the captain and the shift supervisor, and assigns a inspector to go to the site promptly to check the oil level in the main tank. The shift supervisor arranges for the adjustment of the unit’s load in the control room and makes preparations for an emergency shutdown. The captain instructed the other inspectors to prepare their walkie-talkies so as to maintain timely communication with the personnel on site, and if necessary, arranged for the co-pilot to go there directly for an inspection. The turbine inspector rushed to the site to check the oil level in the main oil tank and reported that the level had indeed dropped. The captain arranged for adjustments to the load on the furnace side, while the first officer kept a close eye on the decline in the oil tank’s oil level, preparing for an emergency shutdown in case of further issues. When the fuel level in the tank drops rapidly and reaches the emergency shutdown value of 563 MM, and refueling does not work, an emergency shutdown must be initiated; at the same time, efforts should continue to determine the cause of this rapid drop in fuel level. Cause and Handling 1: Oil overflow due to high liquid level in the oil purification unit. ——If the oil purification unit malfunctions, shut it down immediately; isolate the accident drain valve of tank 2, and prevent the water drain valve from opening accidentally ； —— If the throttle or drain valve was accidentally opened, it should be closed promptly. Oil leakage in the oil pipelines or the cooler – If an inspector finds oil droplets in the circulating water of the water tower, it can be determined that the leak is caused by the cooler. Open the air release valve on the water side of the oil cooler to determine which side is leaking; if oil bubbles appear, it indicates that this oil cooler is leaking. Report the above situation to the shift supervisor and the captain, and make preparations to disconnect the cold oil cooler. Upon receiving the captain’s order, began removing the cold oil cooler. The inspector releases the handwheel used to compress the switch valve, slowly turns the handle of the switch valve to activate the cold oil cooler, and at the same time gradually closes the outlet valve of the cold oil cooler. When the switch valve handle is turned to the cold oil cooler operation mode, close the inlet and outlet valves of the cold oil cooler. Close the cold oil cooler oil injection valve. Adjust the outlet oil temperature of the operating cold oil cooler to 40–45°C, check that the automatic oil temperature regulation functions properly, and maintain stable oil temperature. The captain instructed the maintenance crew to go to the site as soon as possible to address the leak in the cold oil cooler. 4 Generator oil supply – Check whether the thermal alarm signal related to the seal oil tank level is abnormal. If the inspector detects an abnormal level in the seal oil tank, he/she shall report to the captain, who will then inform the thermal control crew to check whether the solenoid valve for filling and draining the seal oil tank is functioning properly. If the thermal inspection is caused by an abnormality in the make-up and drain oil solenoid valve, the automatic mode of the solenoid valve should be disabled immediately, allowing the inspector to use manual make-up and drain oil operation; at the same time, it is necessary to check whether the local oil level indication matches the actual level. If it is caused by an abnormal signal, immediately disable automatic refueling ； If it is not caused by a fault in the sealed fuel tank, the inspector should immediately go to the top of the main fuel tank to check its fuel level, and promptly contact the co-pilot and captain to prevent the tank from becoming full. If the generator’s oil-water relay indicates full oil level, oil will be supplied to the generator. Drain the oil through the oil-water relay until it is normal. And monitor the generator hydrogen pressure. 5 The fuel level in the tank is dropping slowly — the captain immediately instructed the maintenance crew to top up the main fuel tank, and assigned someone to monitor the changes in the fuel level of the main tank on site. Adjust the tank negative pressure to within the specified range if necessary. 20 Plans for Addressing High Lubricating Oil Temperature and Vibration in the Host Machine I. System Overview: The reliability of the lubricating oil system in steam turbine generator sets is of great importance for the proper operation of these units. Any abnormal changes in oil pressure or oil temperature, even if they are brief, can have serious consequences for the unit. Therefore, during operation, we should strengthen monitoring and inspection, and take measures to prevent and handle various emergencies. II. High lubricating oil temperature and oscillation of the main engine: 1. The lubricating oil temperature indicated on the OS screen is high or keeps rising, triggering an alarm for high lubricating oil temperature. 2. The return oil temperature of each bearing bush increases and an alarm is triggered; the metal temperature of each bearing is high and an alarm is triggered as well. 3. The temperature of the thrust bearing pads rises and an alarm is triggered; the temperature of the oil returning to the thrust bearing also rises and an alarm is triggered. 4. The lubricating oil pressure decreases, the temperature of the seal oil on the air side rises, and there may be accident alarm signals such as \"severe bearing vibration\". III. Reasons for high lubricating oil temperature and oscillation in the main engine: 1. The control valve of the main engine’s cold oil cooler is stuck or closed by mistake. 2. Water leakage in the oil cooler. 3. Low industrial water pressure, clogged rotating screens, or a low water level in the forebay, resulting in the intake of large amounts of air. 4. The unit experiences high vibration. 5. Fire in the oil system. 6. Deterioration of lubricant quality. IV. Handling of high lubricating oil temperature and oscillation in the main engine: When the lubricating oil temperature rises abnormally, it is necessary to inform the captain and the shift supervisor, and alert the engine and boiler teams as well as the thermal control staff to arrive at the site to assist in handling the situation. Send someone to conduct on-site inspections, analyze the causes, and take appropriate actions based on the situation. 1. Main engine cold oil cooler door jam: (1) Quickly go to the site and open the manual bypass door next to the cold oil cooler control valve in order to adjust the oil temperature; during this adjustment, care must be taken to prevent the control valve from moving suddenly, which could cause the oil temperature of the main engine to drop too much. (2) On the furnace side, the unit load can be reduced based on the rate of increase in oil temperature. (3) After maintenance is completed, automatic control of oil temperature is activated, the manual bypass valve is closed, and the unit resumes normal operation. 2. To deal with water ingress into the main engine’s cold oil cooler, increase the cooling water pressure by opening the inlet valve wider and closing the outlet valve. Also, open the air release valve on the water side to remove any air present, thereby restoring the cooling water pressure. 3. Low pressure of industrial water: (1) If the control valve has been opened to its maximum, the outlet valve of the cold oil cooler can be increased slightly, but care must be taken to prevent water from leaking out. (2) When the filter screen of low-pressure industrial water is clogged, the screen can be rotated to open the drain valve for cleaning, or a bypass can be used; in such cases, maintenance personnel should be notified to clean the filter screen. (3) Strengthen air removal on the water side of the cold oil cooler. 4. Fire in the oil system: (1) Strengthen oil temperature regulation; (2) Organize fire-fighting efforts and handle the situation in accordance with the “Emergency Plan for Fires in the Oil System”. 5. Deterioration of oil quality leads to an increase in oil temperature. (1) Strengthen oil temperature control. (2) Request to shut down the unit. 6. Excessive vibration of the unit results in damage to the oil film, leading to an increase in oil temperature. (1) Take measures appropriate for excessive unit vibration. (2) Strengthen oil temperature control. During accident handling, once any condition triggers an emergency shutdown, the relevant emergency shutdown procedures must be strictly followed. V. Accident handling plan: When the lubricating oil temperature rises, an alarm appears on the OS screen. The assistant engineer in charge of the steam turbine notices that the indicator for the return temperature of the lubricating oil on the OS screen turns yellow, indicating an alarm as well as an increase in the lubricating oil temperature; he immediately reports this to the shift supervisor and the chief engineer. The shift supervisor arranges for the adjustment of unit load and makes provisions for an emergency shutdown of the unit. The captain sent an inspector to the site promptly to check the operation of the main engine’s oil cooler, while ordering other inspectors to prepare their walkie-talkies in order to maintain timely communication with the inspector on site. The captain and first officer closely monitor the OS screen displays showing the temperature of tungsten gold, the temperature of the return oil, and the temperature of the lubricating oil. When the return oil temperature exceeds 82 degrees or the temperature of the bearing in question surpasses 112 degrees – which trigger the emergency shutdown conditions – they shall strictly follow the emergency shutdown procedures under the unified command of the shift supervisor. The turbine inspector rushed to the site promptly to check the opening degree of the cooling water valves as well as the pressure readings at the inlet and outlet of the cooling water for the two oil coolers, and reported the findings to the shift supervisor and the captain in a timely manner. If necessary, the assistant chief engineer of the steam turbine also goes to the site to assist the inspector with operational adjustments. If it is found that the throttle valve has closed abnormally, quickly open the cooling water bypass valve, and check whether the local temperature indicator returns to normal. If the valve is opened to a certain degree and the pressure readings at the cooling water inlet and outlet are low, the inspector can release air from the water side of the oil cooler, adjust the opening degree of the cooling water outlet valve, and closely monitor whether the local temperature drops. The assistant captain of the steam turbine promptly reports the situation on site to the captain and the shift supervisor via walkie-talkie. Based on the report, the captain promptly informed the thermal engineers or other relevant maintenance personnel to go to the site to restore the control valve. Check whether the door post has fallen off or anything similar. When the oil temperature drops to normal levels, gradually adjust the opening degree of the bypass valve to stabilize the temperature. Once the thermal control personnel arrive at the site and confirm that the throttle is correct, it is switched to automatic mode. The inspector slowly moved toward the bypass door next to the small gate, paying attention to the door gradually opening. It is necessary to ensure that the oil temperature remains normal during this time. After the bypass valve is fully closed, adjust the opening degree of the cooling water outlet valve as appropriate based on the opening degree of the control valve, in order to keep the oil temperature at the outlet of the operating cooler between 40–45°C. Emergency response plan for high vibration of Unit 21 I. Symptoms of high unit vibration: 1. An alarm is triggered when the vibration level of the unit increases. 2. The noise generated by the unit during operation increases. II. Dangers associated with high vibration of the bearing shells: 1. Friction between the moving and stationary parts. Friction between the moving and stationary parts not only directly causes damage to the flow-through components, reducing the economic efficiency of unit operation, but it also leads to an increase in axial thrust, raising the temperature of the thrust bearings and even causing damage to them. Depending on the location where friction occurs, it can cause damage to the steam seal and blades, deformation of the impeller and diaphragm, as well as bending of the main shaft. 2. Accelerate the wear of other components. It mainly includes bearing shells, shaft journals, generator rotor slip rings, and exciter rectifiers, etc. 3. Accelerate the damage of other components. Damage to vibrating components usually requires a prolonged time process, but as the alternating stress on these components increases, this time period is significantly reduced; as a result, even intense vibrations over a short period of time can cause fatigue damage to certain components. For example, the bearing surfaces can develop surface fatigue cracks due to intense vibration impacts over a short time, leading to flaking, delamination, and fragmentation. 4. Fracture and loosening of fasteners: Excessive vibration can cause the bolts securing the bearing housings to fracture, the foundation and platform to become loose, and the secondary grout to crack, thereby reducing the stiffness of the bearings and increasing their vibration levels further; in some cases, this can also cause cracks in the foundation and surrounding buildings. 5. Causing major equipment accidents, directly or indirectly. Excessive vibration can cause the turbine protection systems to malfunction, lead to damage to the generator’s insulation, and result in the rupture of the water cooling pipes of the generator. Excessive vibration can also cause damage to the shafting system, leading to machine failure and even loss of life. III. Reasons for excessive vibration of the bearing shells: 1. Low oil pressure in the bearings, as well as excessively high or low oil temperatures, lead to instability of the oil film, resulting in oil film oscillations. 2. During startup, the warming-up is inadequate, expansion is uneven, and the rotor center shifts. 3. Dynamic and static friction occurs in the steam turbine unit. 4. Water hammer occurs in the steam turbine. 5. A sudden drop in vacuum causes the temperature of the exhaust casing to rise, leading to changes in the rotor center. 6. Damage to the turbine blades or detachment of internal components can cause an imbalance in the rotor’s mass. 7. The bearing shells are loose or the gap has increased. 8. A malfunction in the shaft sealing system of the main engine causes significant fluctuations in the shaft seal temperature. 9. The components of the generator exciter are loose. 10. Sudden changes in ambient temperature cause an increase in vibration in unit #7. IV. Measures to address high vibration in the unit: 1. When the vibration level of the unit reaches 0.125 mm during normal operation, the load should be reduced appropriately; the cause should be identified and addressed, and the situation reported to the shift supervisor. 2. Check whether the lubricating oil pressure and temperature of the unit are normal. If any abnormalities occur, make adjustments promptly. 3. Check the operation of the shaft seal system. If any abnormalities occur, make adjustments promptly. 4. In the case of vibration in the unit caused by other reasons, it is necessary to stabilize the load and parameters of the steam supply. At the same time, check the thermal expansion of the cylinders, the expansion difference, axial displacement, changes in temperature differences between the upper and lower cylinders, as well as to ensure that there is no jamming in the slip system. 5. When the conditions for vibration protection activation are met, the turbine equipped with this protection should trip; otherwise, an emergency shutdown should be initiated by breaking the vacuum. 6. If water hammer occurs in the turbine, it shall be handled as a water hammer accident. After tripping the turbine, pay attention to its coastdown time and listen for any sounds coming from inside the turbine. Check that all meters show no abnormalities; once the shaft vibration readings decrease and stabilize, eliminate the cause of the fault, and restore normal operation after confirming there are no issues. The crew checks whether the main engine lubrication pump starts automatically; if not, it is started manually. Check that the generator has been disconnected, and the automatic switchover to station power has been completed. The boiler has been disconnected. Check the equipment on the furnace side; those that need to be shut down have already been turned off. The machine-side body and pipeline drain valves are open, the extraction steam electric valve and check valve are closed, and the drain valves have been interconnected. Manually start two small machines to simultaneously activate the electric pumps, maintaining the drum water level. The steam supply for the shaft seal and the steam source for the deaerator are switched to the auxiliary steam supply, in order to maintain normal water levels in the exhaust steam system and the deaerator. After extinguishing the fire on the furnace side, maintain the secondary air flow for 5 minutes before shutting down the fan. Keep the air preheater rotating continuously. With the unit speed at 600 RPM, the top shaft oil pump is started; once the unit speed reaches zero, the steam supply to the shaft seal is cut off, and the crankshaft turning device is activated. Adjust the cooling water of the main oil cooler according to the unit’s oil temperature to keep it within the normal range. During the shutdown of the unit, if the vacuum has been lost, the drain valves leading to the exhaust devices should be closed as soon as possible, and the main engine’s atmospheric drain valve should be opened. After the unit is put into cranking mode, the cause of vibration in the unit must be identified, and it must be cranked continuously for four hours before it can be restarted. 7. Due to drastic changes in ambient temperature, vibration level at unit #7 increases; measures such as adjusting the temperature difference on the steam side and drive side of the hydrogen cooler, raising the temperature of the seal oil, lowering the set value for vacuum, and reducing the load of the unit can be taken. 5. Precautions: 1. Once the vibration level of the unit increases, it is necessary to closely monitor its development, and appropriate actions such as reducing the load or closing valves can be taken. However, if the unit vibration has exceeded the limits, it is absolutely not permissible to reduce the load even if the protection systems have not activated; an emergency shutdown by breaking the vacuum must be carried out immediately. 2. After shutting down, remember that the high-pressure bypass valve has already opened; it must be closed manually. Especially for cooling water valve 3, due to vibration-induced shutdown, it is not allowed to apply the brake during the speed reduction process; one must wait until the machine has come to a complete stop and then rotate the shaft for 4 hours before restarting it. 4. After the unit starts rotating the shaft, the bending degree of the main shaft should be measured; if any significant abnormalities are detected, the rotation time should be increased. Record the barring current and compare it with previous values; there is no significant change. 5. On the furnace side, after the unit is shut down, it is first purged, and then the air and flue gas systems are closed to prevent heat loss from the furnace, keeping it ready for startup at any time. 22 Emergency Plan for Turbine Overspeed Incidents I. Turbine overspeed (normal operation of the overspeed protection) (I) Symptoms: 1. The message “Turbine overspeed” is displayed. 2. The “turbine tripped” signal is issued. 3. The turbine speed starts to drop after rising. (II) Handling: 1. Confirm that the shutdown protection has activated ； 2. Check that the high and medium pressure main steam valves, throttle valves, extraction check valves, and high-pressure exhaust check valves are closed ； 3. Check that the turbine begins to drop normally, verify that the high and low bypass systems are activated, and make manual adjustments ； 4. Manual MFT on the furnace side ； 5. Check that the switch to plant power supply is normal on the electrical side. 6. When the speed drops to 2900 RPM, start the main machine’s AC lubricating oil pump; at 600 RPM, start the jacking oil pump to maintain normal jacking oil pressure. 7. For other operations, refer to the emergency shutdown procedures. 8. Identify the cause of the turbine overspeed and inform the relevant departments to handle it. II. Turbine overspeed (overspeed protection not activated) (I) Symptoms: 1. The “Turbine Overspeed” indicator light comes on. 2. Sudden increase in turbine speed. (II) Handling: 1. Immediately perform a manual shutdown to break the vacuum and trigger an emergency stop. 2. Send someone to manually operate the shutdown switch on site. 3. If the unit still has not tripped, manually stop the fire-resistant fuel pump on-site (disable the standby pump interlock). 4. Perform a manual MFT from the furnace side, close the steam inlet isolation valve of the turbine, open the PCV valve to relieve pressure, and activate the drain valves of the superheater and reheater to assist in pressure relief. Manually activate the low-pressure bypass for pressure relief. 5. Check that the high and medium pressure main steam valves, throttle valves, extraction check valves, and high-pressure exhaust check valves are closed; the unit’s speed begins to decrease. 6. When the unit’s speed is 2900 RPM, start the AC lubricating oil pump; at 600 RPM, start the top shaft oil pump. Observe the way the unit operates in its idle state, listen for any noises on site, and conduct a chemical analysis to determine the hardness of the condensate water. 7. Switch the plant power on the electrical side to the standby transformer. 8. Check the cause of the unit’s overspeed and inform the relevant personnel to conduct an inspection. 23 Emergency Plan for Sudden Tripping During Turbine Operation I. Operating condition before the accident: The unit was operating stably under normal load, all protections of the steam turbine generator set were active, and there were no alarm signals or protection actions on the indicator panel. II. Phenomena of sudden tripping during turbine operation: 1. Decrease in turbine speed (it may first increase and then decrease). 2. Optical signals indicating protection actions related to the turbine and generator are generated. 3. When the main steam pressure rises, the bypass valve opens quickly. 4. Shut down the furnace, disconnect and de-excite the generator, and switch to plant power. III. Procedures for dealing with sudden tripping of the turbine during operation: 1. After an accident occurs, promptly start the main AC lubricating oil pump and closely monitor the decline in the turbine’s speed. 2. Assign a dedicated person to record any alarm signals related to protection actions, and quickly notify the relevant maintenance teams to arrive and determine the cause of the accident as well as assist in restoring normal operation as soon as possible. 3. Determine as quickly as possible the type of protection action taken and whether it was correct, so that normal operation can be restored sooner. Several possibilities exist: 1) Turbine protection action: ① Human error: If this is the case, it is necessary to report immediately to the shift supervisor; restart the hydrogen seal standby oil pump to restart the turbine (being careful to avoid reaching critical speed), and quickly connect the generator to the system. ② False protection action: If an alarm is triggered and the turbine trips, but all parameters of the turbine are within normal ranges and no abnormalities are found upon on-site inspection, then notify the thermal engineering team to check and calibrate the protection circuit. If it cannot be repaired immediately, report to the shift supervisor and relevant management, develop appropriate measures, and restore the unit’s operation at 3000 RPM as soon as possible. ③ Correct action: It is necessary to conduct thorough inspections and analyses of the turbine itself and all monitoring parameters. At the same time, notify the boiler and turbine maintenance teams to verify that the protection action was correct; thereafter, shut down the unit safely in accordance with procedural requirements, waiting for maintenance work to be carried out or for further instructions. During shutdown, it is necessary to conduct internal sound inspections of the turbine and plot an analysis of the rotor’s coasting curve, so as to promptly identify the actual problems existing in the unit and formulate targeted preventive measures. 2) Generator protection activation: ① False protection activation: If a visual alarm is triggered and the protection activates, resulting in full shutdown I, full shutdown II, or a programmed trip that causes the turbine to stop, but all parameters of the generator remain within normal ranges with no abnormal changes, and once the alarms disappear on the protection panel after it returns to normal, it can be determined that this was a false protection activation. The situation should be reported to the shift supervisor immediately, and the backup hydrogen seal oil pump should be started promptly to restart the turbine. At the same time, the electrical department should be notified; once confirmed, the issue should be resolved as soon as possible so that the unit can be reconnected to the system. ② Proper protection activation: If, along with the visual alarm and protection activation, there are sudden changes in the parameters of the generator’s stator and rotor that exceed the specified limits, or if there is an obvious short circuit, explosion, smoking, or fire in the generator itself or its primary/secondary connections, it can be determined that this was a proper protection activation. In such cases, it is necessary to monitor the decrease in turbine speed, start the thrust oil pump promptly to ensure the safe shutdown of the unit, and engage the barring gear ； At the same time, notify the electrical maintenance team immediately to conduct an inspection in order to determine the extent of the fault and decide whether it is possible to restart the unit. If it is possible, the unit should be started up, brought to operating speed, and connected to the grid as soon as possible after the electrical technicians have taken the necessary safety measures, so as to restore normal operation promptly; otherwise, safety isolation measures should be implemented as advised by the electrical technicians, and waiting until the issue is resolved before attempting to restart the unit. 24 Steam Turbine Water Hammer Accident Plan I. Operating conditions prior to the accident: The unit was operating stably under normal load, all protections of the steam turbine generator set were active, and there were no alarm signals or protection actions on the alarm panel. II. Phenomena of turbine water hammer accidents: 1. The temperatures of main steam and reheat steam drop sharply, the superheat decreases, and the load falls suddenly. 2. White steam is coming from the high and medium pressure main steam valves as well as the high and medium pressure control valves. 3. Vibration in the steam pipeline, with water impact sounds inside the pipe. 4. The axial displacement increases, and the temperature of the thrust bearings rises sharply. 5. The differential gauge indicates a significant change. 6. The temperature difference between the upper and lower cylinders of the turbine increases. 7. The temperature difference between the upper and lower parts of the steam pipe increases. 8. If it is caused by the heater being filled with water, the steam extraction pipeline experiences significant vibration, and the water-intrusion thermocouple triggers an alarm. 9. The vibration of the turbine suddenly increases; the sound of the unit is abnormal, accompanied by water impact or metal friction sounds. 10. Sparks are generated due to friction at the shaft seal and oil baffle. 11. During shaft turning, the current of the shaft turning motor increases or the shutdown mechanism for shaft turning activates. III. Causes of steam turbine water hammer: 1. Overfilling of the boiler, or a sudden drop in the temperature of the main steam or reheated steam, or the presence of water in the main steam or reheated steam. 2. The deaerator and heaters are filled with water. 3. The drainage in the main steam pipeline or reheat steam pipeline is not proper before startup. 4. The control valve for the main steam desuperheating water or reheat steam desuperheating water is malfunctioning. 5. Poor drainage in the steam supply or waste heat recovery steam pipelines for shaft seals, resulting in water accumulation or drainage entering the cylinder. IV. Handling of steam turbine water hammer accidents: 1. If the temperature of the main and reheat steam drops suddenly by more than the specified value during operation, the vacuum should be broken immediately to stop the turbine. 2. Open all drain valves on the steam pipes and the turbine itself. 3. If steam enters the turbine due to a leak on the water side of the heater, that heater should be shut down. 4. Record the idling time of the unit and check for any abnormal noises inside it. 5. With the rotor at rest, start the barring gear and check for eccentricity, axial displacement, differential expansion, and changes in the temperature difference between the upper and lower parts of the cylinder. 6. Once the cause of the accident has been eliminated, if the eccentricity of the main shaft measured is within 0.03 mm of the original value, the unit can be restarted. However, it is necessary to improve drainage, listen carefully for any abnormal sounds, and stop the machine immediately if vibrations are detected. 7. If water ingress is detected during shaft turning, it is necessary to continue the shaft turning process until the temperature difference between the upper and lower cylinders returns to normal. At the same time, strengthen the monitoring of internal sound levels, turning current, and rotor eccentricity. 8. During operation, when an alarm is triggered due to the risk of water ingress into the turbine, the cause must be identified and eliminated immediately. If the variations in vibration, thermal expansion difference, and temperature difference between the upper and lower cylinders exceed the specified limits, the machine should be stopped immediately. V. Accident prevention measures: 1. The turbine’s water ingress detection system must be in proper working condition. 2. When the unit starts up, the main and reheat steam pipelines, as well as the shaft seal steam supply pipelines, should be thoroughly drained of water. Ensure the system remains unobstructed when the hydrophobic system is put into use. 3. When the heater is put into operation, the water-side protection and interlocks should be tested to ensure they function properly and can be activated reliably. At the start of each shift, it should be checked that the local water level of the heater matches the indications in the control room as well as those provided by the transmitter. 4. When the unit is shut down, extra attention should be paid to changes in cylinder temperature to prevent cold steam and cold water from entering the cylinders. 5. During shutdown, record the temperature difference between the upper and lower cylinders at regular intervals; if this difference increases, the cause should be identified promptly, and the cold air and cold water supply systems should be shut off. 6. After shutting down, carefully monitor the water levels in the condensate tank, heater, and deaerator. 7. When the turbine is at operating temperature, if the main and reheat steam systems cannot be reliably isolated, the boiler shall not undergo a hydrostatic test. 8. During startup and at low load, the reheat steam desuperheating water system shall not be activated; when the boiler shuts down or the unit loses load, the desuperheating water supply must be cut off promptly. 25 Emergency Response Plan for Complete Shutdown of Auxiliary Cooling Pumps I. Operating conditions prior to the accident: The unit was operating normally, the auxiliary equipment was functioning properly, and the plant power supply system was also in normal operation. II. Symptoms of a complete shutdown of the auxiliary cooling pump: 1. An alarm for low industrial water pressure is triggered ； 2. An alarm is triggered when the auxiliary cooling pump stops operating; the current of the auxiliary cooling pump motor is 0 ； 3. The backup auxiliary cooling pump was not started, or the start attempt failed ； 4. Alarm for low cooling water pressure of the condensate pump bearing is triggered ； 5. The temperatures of the bearings in the electric pump, condensate pump, coal grinder, primary fan, supply fan, exhaust fan, and steam turbine increase; the temperature of the oil returning to the steam turbine rises, as does the temperature of the fire-resistant fuel. The temperatures of the hydrogen cooler and the stator cooling water in the generator increase, as well as the temperature of the working fluid in the water ring pump. The exhaust temperatures of the first and second stages of the air compressor, as well as those of the rear cylinder, also increase. III. The handling process is carried out according to the following three scenarios: (1) In winter, two auxiliary cooling pumps are in operation; after one of them stops working, attempting to start the other fails or it does not start automatically, but it can be started manually successfully. (2) During summer, two auxiliary cooling pumps are in operation; after one of them shuts down, attempting to start the other fails or it does not start automatically, but it can be started manually successfully. IV. Handling of the incident where both auxiliary cooling pumps stop operating: (I) In winter, two auxiliary cooling pumps are in operation; after one of them stops working, attempting to start the other fails or it does not start automatically, but it can be started manually successfully. 1. Report to the shift supervisor immediately; the supervisor will request the dispatch team to have the two units reduce their load rapidly. 2. Increase the rotational speed of the mechanical ventilation tower to reduce the temperature at the outlet of the industrial water. 3. Immediately dispatch an aircraft for on-site inspection to verify that the auxiliary cooling pump is operating normally. 4. Notify the mechanical and electrical crew to arrive and investigate the cause. 5. Notify the instrumentation and electrical system that the bearing cooling water pressure of the forced condensate pump is low, triggering pump protection. 6. Send inspectors to close the manual doors for the cooling water supply of standby equipment, such as standby electric pumps and standby coal grinding units, in order to increase the pressure of the industrial water. 8. Closely monitor the temperatures of the bearings in the electric pumps, condensate pumps, coal mills, primary fans, supply fans, exhaust fans, and steam turbines; as well as the temperature of the oil returning to the steam turbine, the temperature of the fire-resistant fuel, the temperature of the hydrogen coolers in the generators, the temperature of the cooling water, the temperature of the working fluid in the water ring pump, and the exhaust temperatures of the first and second stages of the air compressor as well as the rear cylinder. Stop the operation of the equipment when a hard stop is reached. 9. Cooperate with the maintenance personnel to investigate the cause of the auxiliary cooling pump shutting down; restart it once the fault is resolved. After confirming that everything is normal, restore the auxiliary cooling pump to its normal operating mode. Measures taken to restore the operation of a backup cooling pump. (II) During summer, two auxiliary cooling pumps are in operation; after one of them shuts down, attempting to start the other fails or it does not start automatically, but it can be started manually successfully. 1. Report to the shift supervisor immediately; the supervisor shall request that unit 1# have its load reduced rapidly, while unit 2# should be shut down immediately. 2. Increase the rotation speed of the mechanical ventilation tower to reduce the temperature at the industrial water outlet. 3. Immediately dispatch an inspector to the site to check that the auxiliary cooling pump is operating properly. 4. Notify the mechanical and electrical maintenance team to arrive and determine the cause of the problem. 5. Inform the mechanical and electrical team to activate the protection mechanism due to the low pressure of the cooling water for the condenser pump bearings. 6. Send an inspector to close the manual valves for the cooling water supply to the standby equipment of Unit 1, such as standby electric pumps and standby coal grinding mills. At the same time, close the manual valves for other industrial water users in Unit 2, except those related to the lubrication of the main engine, in order to increase the pressure of the industrial water. 7. Closely monitor the temperatures of the bearings of the electric pump, condenser pump, coal grinding mills, primary fan, supply fan, exhaust fan, and turbine in Unit 1, as well as the temperature of the turbine return oil, the temperature of the fire-resistant fuel, the temperatures of the hydrogen coolers and constant-temperature coolers in the generator, the temperature of the working fluid in the water ring pump, and the exhaust temperatures of the first and second stages of the air compressor as well as the rear cylinder. Stop the operation of the equipment when a hard stop is reached. 8. Cooperate with the maintenance personnel to investigate the reason for the shutdown of the auxiliary cooling pump; restart it once the fault is resolved. After confirming that everything is functioning normally, restore the auxiliary cooling pump to its normal operating mode. Measures taken by Unit 1 when restoring one auxiliary cooling pump to operation. 9. Unit 2 was restarted and brought back online. 26 Contingency Plan for Treatment Failures in Condensate Polishing I. Failure in Condensate Polishing – 1: (I) Symptoms: 1. The water level in the deaerator drops rapidly, and the flow rate of water supplied to the deaerator decreases sharply. 2. The pressure at the outlet of the condensate pump and the pressure after fine treatment decreases, which may lead to the startup of the standby condensate pump. 3. The water level in the exhaust device drops rapidly, and an alarm for low water level in the exhaust device may be triggered. (II) Cause: The drain valve for fine treatment was opened accidentally. (III) Handling: 1. Notify the auxiliary control system to immediately switch the fine treatment mode to bypass operation. 2. The unit should reduce its load rapidly in order to slow down the rate of drop in the deaerator water level. 3. Notify the chemistry department to start the standby pump for demineralized water, fully open the water supply valve of the venting device, and increase the water supply volume to the venting device. 4. Once water is being supplied to the deaerator properly, raise the level in the deaerator to its normal level; if a standby condensate pump starts up automatically, stop operating that standby pump. 5. After the fine treatment fault is resolved, start up the fine treatment process. II. Faults in the fine treatment of condensate water II: (1) Phenomenon: The differential pressure across the filter screen of the pump ahead of the electric pump increases abnormally, exceeding that across the filter screen of the main pump of the electric pump. (2) Cause: The dialysis membrane used in the fine treatment process is damaged, and as a result, it ends up in the deaerator along with the condensate water. (III) Handling: 1. Notify the auxiliary control system to immediately switch the fine treatment mode to bypass operation. 2. Reduce the unit load based on the magnitude and rising trend of the differential pressure across the filter screen of the pre-pump of the viscometer pump. 3. If the differential pressure across the filter screen of the pump ahead of the electric pump rises rapidly, start the backup electric pump to take over the load. 4. Slightly open the water discharge valve on the filter screen of the electric pump’s pre-pump to remove debris. 5. Inform the maintenance staff to clean the filter screen. 27 Plan for Handling Failure of the Crankshaft Rotation Mechanism I. Symptoms of failure in the crankshaft rotation mechanism: 1. The current supplied to the local crankshaft rotation mechanism drops to 0. 2. The main shaft stops rotating. 3. The signal indicating crankshaft rotation disappears from the display. 4. The indication of the main shaft’s eccentricity remains unchanged, and it is shown as a low value. II. Causes of failure in the crankshaft rotation mechanism: 1. Failure of the jacking oil pump. 2. Fault in the crankshaft rotation motor. 3. Activation of the thermocouple in the crankshaft rotation motor, resulting in the disconnection of the contactor. III. Procedures for dealing with failure in the crankshaft rotation mechanism: 1. After the jacking oil pump fails, identify the cause, quickly restore its operation, reconnect the crankshaft rotation mechanism, and start it up again. 2. Measure the insulation of the turning motor; if the insulation is not up to standard, arrange for personnel to turn the machine manually. 3. When the thermocouple of the turning motor activates and the contactor trips, after verifying that the insulation of the turning motor is satisfactory, reconnect the turning mechanism and start it. Observe whether there are any significant fluctuations in the current drawn by the turning motor; if such fluctuations occur, identify the cause and keep the turning mechanism running. 4. In the event of a barring gear failure: (1) After the barring gear stops, mark the rotor’s position, record the time of stoppage, activate the main shaft deflection meter, and adjust the marker to the “0” position. Before resuming the operation of the turning gear, rotate it 180 degrees first; once the rotor’s wobble returns to a level of “0”, resume continuous rotation. ⑵ If a fault in the turning gear motor prevents electric rotation, the cause must be identified and resolved as soon as possible, and efforts should be made to manually rotate the gear 180 degrees every 30 minutes. If the gear cannot be rotated for some other reason, it is prohibited to use mechanical means to force it to rotate or to start it forcibly. 28 Emergency Plan for Hydrogen System Leaks in Generators I. Symptoms of hydrogen system leaks in generators: 1. Rapid drop in hydrogen pressure, with an alarm being triggered when the pressure falls below a certain level. 2. An alarm from the hydrogen leakage detector may sound. 3. When there is a large leak in the hydrogen system, the hydrogen pressure cannot be maintained. II. Causes of hydrogen system leakage in the generator: There are leakage points in the hydrogen system. III. Handling of hydrogen system leaks in generators: 1. Verify that the hydrogen pressure reading is correct. 2. Adjust the seal oil pressure on the air and hydrogen sides to the normal range. 3. Check that the refilling and draining of oil in the hydrogen seal oil tank are functioning properly. 4. Recharge hydrogen to the generator to the normal level. 5. Check that all drain valves and exhaust valves are tightly closed, identify any leakage points in the hydrogen system, and eliminate them. 6. If there is a severe leak in the hydrogen system and continuous hydrogen supply is insufficient to maintain the hydrogen pressure, it is necessary to request the shift supervisor to reduce the load appropriately in order to keep the temperatures inside the generator within normal ranges. Improve ventilation in the server room, and prohibit any welding or electrical work inside it. 7. If the hydrogen pressure is approaching the lower limit of 0.2 MPa and continues to drop, a shutdown request should be submitted. If the fault cannot be repaired immediately, accident hydrogen discharge should be carried out. 29 Plan for dealing with water overflow in the shaft seal heater I. Phenomenon of water overflow in the shaft seal heater: 1. The local level gauge of the shaft seal heater indicates full capacity. 2. An alarm for high water level is issued on the screen axis. 3. The shaft exhaust fan may trip. 4. The temperature of the shaft seal steam may drop, and the temperature difference between the upper and lower walls of the cylinder may increase. II. Reasons for the shaft seal heater becoming filled with water: 1. High load combined with low vacuum in the exhaust system leads to poor drainage of water from the shaft exhaust system. 2. The opening of the drain valve on the shaft heating fan is too large, which increases the drainage resistance of the shaft heating system and leads to poor drainage. 3. Leakage on the water inlet side of the shaft. 4. Severe flooding can cause water to enter the shaft seal system. III. Treatment of water accumulation in the shaft seal heater: 1. Slightly open the shaft seal drain to the drain valve before the multi-stage water seal in order to lower the water level in the shaft seal heater. 2. Close the small shaft and the fan drainage valve. 3. Isolate the shaft and divert the condensate; notify maintenance for handling. 4. Open the shaft seal steam trap electric valve and the low-pressure shaft seal strainer drain valve to allow drainage. Open the steam trap discharge valve leading to the multi-pole water seal, and activate the cylinder’s own steam trap until the temperature difference between the upper and lower walls of the cylinders returns to normal. 5. Closely monitor important parameters such as the vibration of the main engine; if conditions for an emergency stop are met, carry out the emergency stop immediately. 30 Winter Plans for Dealing with Freezing of Air-Cooled Condensers I. Phenomenon of freezing in air-cooled condensers during winter: 1. Low temperature of the return water from the air-cooled condenser and a large difference between this temperature and the exhaust steam temperature. 2. The air-cooled exhaust temperature is low, and there is a large deviation from the steam discharge temperature. 3. The water supply volume to the exhaust steam device is abnormally high. II. Reasons for freezing of winter air-cooled condensers: 1. Low ambient temperature, excessively high vacuum setting, and high fan output lead to localized freezing in the air-cooling system. 2. During startup and shutdown in winter, the low steam flow rate persists for an extended period of time. 3. There are leakage points in the air cooling system. III. Handling of freezing in winter air-cooled condensers: 1. Do not set the vacuum level too high. When the temperature drops, stop some of the air-cooling fans manually as specified in the guidelines; if the anti-freezing procedure for air cooling cannot be carried out properly, it should be done manually. 2. Multiple water-ring vacuum pumps can be used to operate. 3. Winter is the period when the air-cooling system is most prone to freezing; during short shutdowns in winter, it is possible to avoid breaking the vacuum, or maintain the operation of the water ring vacuum pump for a while after the vacuum is broken, in order to remove all the steam from within the air-cooling island. 4. When starting the machine in winter, due to the rapid start-up process, try not to remain in a low steam condition for long periods. It is possible to close the steam valves for street 1 and street 6 while starting the machine, thereby increasing the steam flow to the other streets; also, try to maintain a low vacuum level whenever possible. 5. Locate the leak point and eliminate it.