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1. What are the auxiliary equipment of a steam turbine? Answer: In addition to the main unit, protection and control equipment, as well as oil supply equipment, turbine systems also have many important auxiliary devices. The main components include condensing equipment, regenerative heating equipment, deaerators, etc. 2. What devices make up the condensing equipment, and what are their functions? Answer: The condensing equipment of a steam turbine mainly consists of a condenser, a circulating water pump, an extractor, and a condensate water pump. The task of the condensing equipment is to: (1) establish and maintain a high vacuum at the exhaust port of the turbine. (2) The exhaust steam from the turbine is condensed into water, which is then pumped by a condensate pump to the deaerator, where it becomes feedwater for the boiler. (3) In addition, the condensing equipment also serves a certain role in vacuum deoxidation. 3. What are the various methods of condensing the steam exhaust from a turbine? Based on the different methods of condensing the steam exhaust from the turbine, condensers can be divided into (surface) condensers and (mixed) condensers. A condenser in which the turbine exhaust is directly mixed with cooling water for heat exchange is called a mixed-type condenser. The downside is that the condensate water cannot be recovered. A condenser in which the steam exhaust from the turbine and the cooling water exchange heat indirectly through the surface of copper tubes is called a surface-type condenser. 4. What is the working principle of a condenser? Answer: The formation of vacuum in the condenser is mainly due to the exhaust steam from the turbine being cooled into condensed water, which results in a sharp decrease in its specific volume. For example, at an absolute pressure of 4 kPa, the volume of steam is more than 30,000 times greater than that of water. When the exhaust vapor condenses into water, its volume decreases significantly, creating a high vacuum inside the condenser. Three conditions must be met for the formation and maintenance of vacuum in a condenser ； (1) The copper tubes of the condenser must be passed through a certain amount of cooling water. (2) The condensate pump must continuously remove the condensate to prevent the water level from rising, which could affect steam condensation. (3) The extraction pump must remove the air that has leaked in as well as other gases present in the exhaust steam. 5. What are the requirements for the condenser? (1) It has a high heat transfer coefficient and a reasonable tube bundle arrangement. (2) The condenser itself and the vacuum tube system must have a high degree of tightness. (3) The vapor resistance and condensate subcooling should be low. (4) The water resistance should be low. (5) The oxygen content in the condensate water should be low. (6) Facilitates cleaning of the cooling water pipes. (7) Easy to transport and install. 6. What components typically make up the structure of a surface condenser? Answer: The condenser is mainly composed of components such as the casing, water chamber, tube sheet, copper tubes, compensation devices connected to the turbine, and supports. The condenser has a circular (or square) shell, with cooling water chambers at each end. The cooling water pipes are fixed to the tube sheet; the water flows into the condenser through the inlet, passes through the tube bundle, and then exits through the outlet. The exhaust steam from the turbine enters the condenser through the steam inlet, where it comes into contact with the outer wall of the cooler water pipes at a lower temperature, releasing heat and condensing. The water condensed in the exhaust gas eventually collects in the hot water well, where it is pumped out by a condensate pump. The non-condensable gases flow through the air cooling zone and are then extracted from the air extraction port. The above is the working process of the condenser. 7. What is the cooling ratio of a condenser? Answer: The amount of cooling water required to condense 1 kg of exhaust steam is called the cooling ratio. Its value is the ratio of the amount of cooling water entering the condenser to the amount of turbine exhaust entering the condenser. Generally, 50–80 is used. 8. What is the ultimate vacuum of a condenser? Answer: During operation, measures should be taken from various aspects for condensing equipment to achieve a good vacuum level. However, increasing the vacuum level is not the better the higher; there is a limit to it. The limit of this vacuum is determined by the expansion limit at the outlet section of the last stage blade of the turbine. When the steam passing through the final stage of blades has reached its expansion limit, further increasing the vacuum will not yield economic benefits; instead, it will reduce them. Simply put, the vacuum corresponding to the point at which expansion of steam in the final stage blades reaches its limit is known as the ultimate vacuum; it is also referred to as the critical vacuum. This vacuum value is generally provided by the manufacturer. 9. What is the most favorable vacuum for a condenser? Answer: For a condenser with a fixed structure, at extreme vacuum and with constant steam parameters and flow rate, increasing the vacuum raises the available enthalpy drop of the steam in the turbine, which in turn increases the output power of the generator. However, while increasing the vacuum level, more cooling water must be supplied to the condenser, thereby increasing the power consumption of the circulating water pumps. The vacuum level at which the difference between the increased turbine power resulting from an elevated condenser vacuum and the additional power consumption of the circulation water pumps is at its maximum is known as the optimal vacuum for the condenser (i.e., the economic vacuum). The main factors affecting the optimal vacuum of the condenser include: the steam flow rate entering the condenser, the exhaust pressure of the turbine, the inlet temperature of the cooling water, the volume of circulation water (or the number of circulation water pumps in operation), changes in the turbine’s output, and changes in the power consumption of the circulation water pumps. In actual operation, the amount of cooling water required at the most favorable vacuum level is determined based on the condensate volume and the inlet temperature of the cooling water; in other words, the capacity and number of circulation water pumps are used in a rational manner. 10. What is the rated vacuum of a condenser? Answer: Generally, the vacuum corresponding to the absolute exhaust pressure indicated on a turbine’s nameplate is the rated vacuum of the condenser. This refers to the vacuum of the unit under design conditions, rated power, and design cooling water temperature. This value is not the ultimate vacuum value of the unit. 11. What are the methods for cleaning the copper tubes of a condenser? Answer: When the cooling water pipes of the condenser are scaled or blocked by debris, it disrupts the normal operation of the condenser. Reduce the vacuum. Therefore, the copper tubes must be cleaned to maintain a high level of cleanliness. Common cleaning methods include: (1) Mechanical cleaning. Mechanical cleaning involves using tools such as wire brushes and bristles to manually remove scale. The disadvantages are long time consumption and high labor intensity; this method is now rarely used. (2) Pickling. When hard scale forms in the condenser and the vacuum cannot be maintained, the unit should be shut down for acid cleaning. Use an acid solution to dissolve and remove hard water scale. While removing scale, appropriate measures must also be taken to prevent the copper pipes from corroding. (3) Adopt the drying method. When the condenser is covered with soft scale and sludge, the ventilation and drying method can be used for treatment. The principle behind this method is to crack the microorganisms and sludge inside the tubes, allowing water to flush them away. (4) Backwashing method. The soft scale in the condenser can also be removed by using cooling water to flow in the reverse direction through the copper tubes on a regular basis, via a backwashing method. The drawback of this method is that it requires additional investment in pipeline valves, and the system becomes more complex. (5) Continuous cleaning method with rubber balls. It involves introducing rubber balls with a density similar to that of water into the circulating water, and using these balls to pass through the cooling pipes in order to clean away the soft deposits inside the copper pipes. It is a good cleaning method, and it is currently widely used in power plants across China. (6) High-pressure water pump. (15–20 MPa). High-speed water flow shock washing method. 12. Briefly describe the composition of the condenser ball cleaning system and the cleaning process. Answer: There are two types of rubber balls used in continuous rubber ball cleaning systems: soft rubber balls and hard rubber balls. Their cleaning principles also differ. The diameter of the rubber ball is 1-2 mm smaller than the inner diameter of the copper tube; as it enters the copper tube with the cooling water, the rubber ball moves irregularly and collides with the inner wall of the tube. Together with the force of the flowing water, this helps to remove any deposits attached to the tube wall. Achieving the purpose of cleaning. The diameter of the soft rubber balls is 1-2 mm larger than that of the copper pipes. Once these soft, sponge-like balls enter the copper pipes along with the water, they are compressed and deformed to make full contact with the inner wall of the pipes, thereby removing the dirt from those walls. The automatic rubber ball cleaning device system consists of a rubber ball pump, a ball loading chamber, a ball collection net, etc. During cleaning, the sponge ball is placed in the ball chamber; the rubber ball pump is started, and the rubber balls are then carried by water flow at a pressure slightly higher than that of the circulating water, entering the copper tubes through the feed water chamber of the condenser for cleaning. Since the outlet of the rubber ball delivery tube faces downward, the rubber balls are distributed evenly in the circulating water, resulting in little difference in the rate at which they enter each copper tube. The rubber ball rubs the inner wall of the copper tube; as it flows out of the tube’s opening, its own elasticity causes it to return to its original shape. It then moves with the water flow toward the receiving mesh, where it is drawn into the pump by the negative pressure at the pump’s inlet. This process repeats itself, allowing for repeated cleaning. 13. What are the causes of leakage due to corrosion and damage of the condenser copper tubes? Answer: The corrosion of copper tubes in operating condensers can be roughly divided into three types. (1) Electrochemical corrosion ； Electrochemical corrosion occurs due to the quality of the copper tube material itself, leading to perforation of the tube and zinc loss corrosion. (2) Impact corrosion ； The presence of mechanical debris in the water creates vortices at the pipe outlet, leading to ulceration and erosive damage at the inlet end of the pipe. (3) Mechanical damage ； The main causes of mechanical damage are poor heat treatment of the copper material, cracks that occur in the tubes during expansion joining, and resonance during operation. The corrosion of condenser copper tubes mainly takes the form of zinc loss. The surface of the corroded area becomes spongy due to zinc loss, the pipe material becomes brittle, and its mechanical strength **decreases**. 14. Why does a condenser need a hot water well? What are the hazards of too high or too low water levels? Answer: The function of a hot water well is to collect condensate water, which facilitates the proper operation of the condensate pump. The hot water well stores a certain amount of condensate water to ensure that the condensate pump does not run out of water immediately when the load is reduced. The capacity of a hot water well is generally required to be equivalent to the flow rate of condensate water accumulated within about 0.5–1 minute under full load. Generally, the water level in a hot water well should be maintained between 1/3 and 2/3 of the well’s capacity. If the water level is too high, it will submerge part of the condenser tubes, reducing the space available for steam to condense as well as the heat exchange area. This leads to an increase in the exhaust steam temperature, a decrease in vacuum, and a decline in the efficiency of the unit. If the water level is too low, the condensate pump consumes less power, but it is prone to cavitation, which causes severe damage to the impeller and results in certain vibrations in the pump as well as fluctuations in the outlet pressure during operation. 15. What is the terminal difference of a condenser? What measures can be taken to reduce the terminal difference during operation? Answer ； The difference between the exhaust temperature of the turbine and the outlet temperature of the circulating cooling water in the condenser is called the terminal difference of the condenser. That is, the difference between the saturation temperature at the condenser pressure and the temperature of the condenser cooling water. It is called end difference. Measures to reduce the terminal difference of the condenser during operation include ； (1) Keep the heat transfer surfaces of the condenser as clean as possible. For example, during operation, a gel ball cleaning system is used; during maintenance, mechanical or hydraulic methods are employed to scrub and clean the heat transfer surfaces of the condenser, and acid cleaning is used when scaling is severe. (2) Add some chemicals to the cooling water to kill the microorganisms present in it, thereby reducing the attachment and proliferation of certain substances on the heat transfer surfaces ； Further treatment involves removing some salt substances from the water to reduce scaling. (3) Maintain the integrity of the vacuum system to reduce air leakage. When the vacuum tightness test fails, it is necessary to find and eliminate the air leakage points. (4) The exhaust pump should operate in a normal and efficient condition to keep the amount of air in the condenser as low as possible. (5) Reasons for the increase in end difference ； There is 1 ； Scaling on the water side or steam side of the condenser copper tubes ； 2 ； Air leaks into the steam side of the condenser ； 3 ； Cooling water pipe blocked ； 4 ； Reduction in cooling water volume, etc. 16. The following points should be noted when commissioning the condenser. Answer: It should be noted that: (1) Before commissioning, it is essential to ensure that the temporary supports used during the static hydrostatic test of the condenser have been removed, otherwise it will affect the expansion of the condenser. (2) After the condenser is evacuated and steam is introduced, it is necessary to check the temperature and expansion deformation of various parts of the condenser, and to monitor relevant parameters such as vacuum level, water level, exhaust steam temperature, as well as the pressure and temperature of the circulating water. (3) Before feeding circulating water into the cloud, it is prohibited to allow any hydrophobic substances to enter the condenser. Before evacuating the vacuum, it is necessary to control the amount of water entering the condenser. (4) It is strictly prohibited to activate the low-pressure bypass system when the vacuum is below the specified value. (5) Special attention should be paid to ； The outlet of the condenser must be open when starting the circulating water pump; otherwise, it will cause the end cover of the condenser to deform. Especially in tower-type cooling towers, the operations of pumping cooling water up and down the tower must be carried out in accordance with the operating procedures. 17. What are the effects of the presence of non-condensable gases in the condenser? Answer: It has the following adverse effects on the safe and economical operation of the condenser. (1) It affects the operating conditions of the condenser, increases the terminal difference of the condenser, and reduces the thermal efficiency of the unit. (2) The presence of air backpressure causes the steam to condense under its own pressure, resulting in supercooling of the condensed water. (3) The presence of air reduces the deoxygenation efficiency of the condenser, allowing some gases to dissolve in the condensate water. The presence of dissolved oxygen in the condensate water causes oxygen corrosion of the equipment and pipelines in the condensate water system, affecting the safe operation of the unit. (4) The presence of air directly reduces the vacuum in the condenser. 18. Daily operation and maintenance of the circulating water pump. Answer ； The circulating water pump should have the following operation and maintenance tasks carried out during operation ； (1) Regularly monitor the vibration, noise, and operation of the pump set; if any abnormalities are detected, the cause should be identified promptly and eliminated. (2) Regularly check the tightness of the packing gland; if too much water leaks from the packing gland or no water leaks at all, adjust the tightness of the packing gland ； When the packing is worn out, it should be replaced with new packing promptly. (3) Check the lubrication condition of the motor bearings; the oil level should be normal ； When oil deterioration is detected, it should be replaced with fresh oil, and the bearing shell temperature should not exceed 70°C. (4) Regularly monitor the motor current and the temperature of the core and windings. The current should not exceed the specified value, nor should it fluctuate ； The temperature of the core and windings should not exceed the specified values. (5) Regularly check that the pump outlet pressure and the lubrication water pressure for the rubber bearings are within the normal range. (6) Regularly check the water level in the pump suction tank and the inlet filter screen. The water level should be normal, and the filter screen should be kept clean to prevent clogging. (7) In addition to the tasks mentioned above, it is also necessary to keep proper operation logs and generate regular reports (recording parameters such as outlet pressure, current, voltage, and relevant temperatures), as well as to periodically measure and record the vibration of the pump set. 19. How to handle accidents involving the circulating water pump? Answer ； The pump should be shut down immediately in case of serious faults that pose a threat to human safety and equipment integrity, such as severe vibration of the pump, audible metal grinding sounds inside the pump, smoking or catching fire of the motor, or smoking or catching fire of the bearings. The general steps for emergency pump shutdown are as follows: (1) Press the emergency button for the faulty pump or disconnect the switch used to stop the pump. (2) Check that the standby pump should be activated automatically immediately to ensure normal water supply. If the backup pump fails to start automatically, it should be started manually immediately. (3) Check that the current of the faulty pump drops to zero; the outlet butterfly valve should close automatically, and the pump should not rotate in reverse. If this does not happen, the outlet butterfly valve must be closed manually. (4) Report to the relevant production supervisors in a timely manner and take necessary measures to prevent the accident from spreading to other systems and equipment. (5) After the fault has been resolved, detailed records should be kept to facilitate accident analysis. In the event of faults such as heating, smoking, or excessive water leakage from the pump’s packing, a bearing temperature reaching 80°C with a tendency to rise, the motor current exceeding the rated value or the motor temperature exceeding the specified limit, or bearing vibration exceeding the specified limits, the backup pump should be started first, followed by shutting down the faulty pump. This is because when a water pump fails, it does not cause severe damage to the equipment in the short term; such handling has a minimal impact on the operation of the system, which helps ensure the safe and stable operation of the main unit. How to deal with the situation where the butterfly valve at the outlet of the 20-cycle water pump cannot be opened? Answer: If it is found that the outlet butterfly valve of the circulation pump has dropped, a thorough inspection should be carried out and appropriate actions taken. If this is caused by a malfunctioning solenoid valve or internal leakage, the isolation valve in front of it should be closed or the outlet butterfly valve should be opened manually, and maintenance personnel should be contacted. 21. How should the circulating water pump be shut down in case of a fault? Answer: The following steps should be taken to shut down the circulating water pump due to a fault ； (1) Disengage the interlock switch and start the backup pump. (2) Shut down the faulty pump, paying attention to the coasting time. If reversed, close the outlet door or the inlet door. (3) If there is no backup pump or the backup pump cannot be started, the faulty pump should be shut down after seeking approval from higher authorities. (4) Check the operation of the standby pump after it starts. 22. Indicators and handling of circulating water pump tripping. Answer: The indicators of a circulating water pump tripping include ； (1) The current indication reaches “0”; the green light flashes, the red light goes out, and the alarm bell sounds. (2) The motor speed decreases. (3) The discharge pressure of the water pump decreases. (4) The standby pump should operate in conjunction. 23. In the event of a trip of the circulating water pump, the following actions should be taken: Answer: (1) Close the interlocked pump operation switch, and pull the trip switch. (2) Switch the interlock switch. (3) Quickly check whether the trip pump is running in reverse; if so, close the outlet valve immediately. (4) Check the operation of the coupling pump. (5) If the standby pump does not start automatically, it should be started promptly. (6) If there is no backup pump or the backup pump trips again after being activated, the shift leader and station master should be informed immediately. (7) Contact the electrical personnel to check the cause of the trip. (8) In the event of a drop in vacuum, it shall be handled in accordance with the regulations for such drops.