1. What equipment mainly constitutes the condensing system of a steam turbine?
Answer: The main components include the condenser, circulating water pump, air ejector, and condensate pump. After steam has worked in the turbine, it enters the condenser, where it is cooled and condensed into water by the cooling water pumped in by the circulating water pump. The condensate is then extracted by the condensate pump and sent to the shaft seal heater, where it absorbs the heat released by the shaft seal steam before being sent to the low-pressure heater. To prevent air leaking into the condenser from accumulating and affecting heat transfer efficiency, thus reducing the vacuum, the system is equipped with steam jet ejectors that promptly remove any air that leaks into the condenser to maintain its vacuum. The shaft seal heater condenses the steam leaking from the shaft seal into water and sends it into the condenser.
2. What are the principles of accident handling?
Answer: 1) First, eliminate threats to personnel and equipment; if necessary, immediately disable or shut down faulty equipment. 2) Quickly identify the nature, cause, location, and extent of the damage, and actively eliminate the fault as soon as possible according to regulations. 3) At every stage of fault elimination, report to the duty chief and department leaders as quickly as possible to take correct countermeasures, facilitate rapid accident mitigation, and prevent the spread of the incident. 4) During the accident handling process, operating personnel must remain at their posts.
3. What is the function of the condensate pump outlet recirculation pipe?
Answer: It is to ensure that the condensate pump has a certain flow rate under any operating condition, to provide sufficient cooling water for the steam jet ejector and shaft seal heater, and to prevent cavitation of the condensate pump when operating under low load due to too small a flow.
4. What are the hazards of condensate overcooling?
Answer: It makes the condensate easily absorb air, which results in an increased oxygen content in the condensate, accelerating corrosion in the equipment piping system and reducing the safety and reliability of the equipment.
5. What is the function of the air ejector? How do the functions of the main and auxiliary air ejectors differ?
Answer: The function of the air ejector is to continuously remove non-condensable gases from the condenser, facilitating the condensation of steam into water. The auxiliary air ejector is generally used before the turbine starts to remove air from the condenser and the turbine itself, quickly establishing a vacuum to shorten the start-up time, whereas the main air ejector maintains the vacuum during normal turbine operation.
6. What is the function of the deaerator?
Answer: The function of the deaerator is to remove oxygen and other gases from the boiler feedwater, ensuring the quality of the feedwater. At the same time, it also serves as a mixed-type heater in the regenerative system, playing a role in heating the feedwater.
7. What are the signs of cavitation at the inlet of a feedwater pump during operation?
Answer: The signs of cavitation at the inlet of a feedwater pump during operation include drastic fluctuations in pump current, outlet pressure, inlet pressure, and flow rate, accompanied by noise and vibration within the pump.
8. Why must you wait until the condenser temperature drops below 50°C before resuming water supply to the condenser after a prolonged interruption of circulating water?
Answer: When the circulating water is interrupted, the exhaust steam temperature will rise rapidly, causing lateral expansion of the condenser supports, low-pressure cylinder, and copper tubes. If circulating water is supplied at this time, the copper tubes will first be cooled, but the supports of the low-pressure cylinder condenser will not be cooled. As the copper tubes contract while the supports do not, a significant tensile stress develops in the copper tubes. This tensile stress can pull the ends of the copper tubes loose, resulting in condenser tube leakage. Therefore, after a prolonged interruption of circulating water, it is necessary to wait until the condenser temperature drops below 50°C before resuming water supply to the condenser.
9. What is the function of the shaft seal heater?
Answer: It is used to heat the condensate water and recover the steam leaking from the shaft seal, thereby reducing shaft seal steam leakage and heat loss, and improving the working environment of the workshop. The amount of air that enters along with the shaft seal steam leakage is usually guided by a connecting pipe to the ejector diffuser duct, where it is drawn out by the negative pressure of the latter, or a dedicated exhaust fan is installed, ensuring the micro-vacuum state of the shaft seal heater.
10. If the main steam pressure remains unchanged, what are the hazards of a decrease in main steam temperature?
Answer: (1) The decrease in steam temperature increases steam consumption, resulting in poor economy. (2) It increases the moisture content in the last stages of steam, accelerating erosion of the last-stage blades and shortening their service life. (3) When the steam temperature drops sharply, high-temperature components such as cylinders can experience significant thermal stress and thermal deformation, which in severe cases may cause wear between moving and stationary parts. (4) A decrease in steam temperature also increases axial thrust. (5) It can easily cause steam turbine water hammer.
