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I. Introduction to condensing steam turbines: A steam turbine, also known as a steam turbine engine, is an energy conversion device that uses steam as the working medium; it utilizes high-speed airflow to drive the rotor, thereby converting the thermal energy of steam into mechanical energy. 1. Composition of the steam turbine: rotor (including the main shaft, impeller, and blades), stator (including the cylinder, nozzles, and diaphragms), speed control system, and safety system. 2. Working principle of the turbine: High-pressure steam is ejected from nozzles mounted on the cylinder; as it expands and its pressure drops, it forms a high-speed airflow. This high-speed airflow strikes the blades surrounding the rotor, thereby causing the rotor to rotate and completing the conversion of steam’s thermal energy into mechanical energy. During this process, both the temperature and pressure of the steam released decrease, which is why it is called waste steam. 3. Types of steam turbines: Classified thermodynamically, they are mainly divided into back-pressure type, extraction type, and condensing type. Our plant uses a condensing turbine; after doing work in the turbine, the steam is entirely discharged into the condenser, where it condenses into water under vacuum conditions with pressure lower than atmospheric. 4. Auxiliary systems of condensing steam turbines: A. Steam inlet system, including the main steam valve and the governor valve. The main steam valve is the passage through which steam enters the system ； The governor valve can automatically adjust the steam inflow based on the signals from the governor in order to maintain a constant speed. The governor allows for manual setting of the speed, or it can be connected to other systems to keep a certain parameter constant. B. Condensation system: It includes surface coolers (recondensers) and condensate pumps (rewater pumps), and is specialized equipment for condensing turbines. An air cooler is a type of water cooler; by passing cooling water through it for heat exchange, it enables the exhausted steam after work to be condensed into water. This water is then pumped by a condensate pump to the steam extraction condenser to be used as cooling water. Part of this water returns to the air cooler to maintain a certain liquid level, while another portion is sent to the deoxygenation tank for reuse. A negative pressure is generated during the cooling process, resulting in instantaneous cooling and a rapid contraction of volume, which facilitates further work extraction from the waste steam and creates a certain degree of vacuum. C. Vacuum system: The function of the vacuum system is to maintain the vacuum level in the exhaust gas of the condensing turbine, while also recovering and reusing the condensate. The main equipment includes steam extraction condensers, startup extractors, and primary and secondary extractors (extractors are also known as air extractors or steam ejectors). Working principle of the extractor: Working steam is ejected from a nozzle at high pressure and high velocity. During this ejection process, the static pressure energy of the steam is converted into kinetic energy, creating a low pressure that draws in gases. The gases drawn in mix with the steam and enter the diffuser, where their velocity gradually decreases and the pressure rises, before being discharged from the pressure outlet. After the steam condenses, the accumulated non-condensable gases are removed through two series-connected steam ejectors. With each draw, the pressure increases slightly, and more water condenses; this condensed water can be returned to the system, while the non-condensable gases are finally released into the atmosphere. The factors that affect vacuum level are as follows: First, the temperature of the cooling water rises. Second, scaling occurs on the tube wall of the surface cooler (the side where water flows) ； Third, the steam injector is clogged, or there is insufficient steam supply ； Fourth, the pipeline or equipment is leaking. D. Atmospheric safety valve 1. Function: When a fault occurs and the vacuum is broken, this valve opens to release air, thereby quickly breaking the vacuum and causing the rotor to stop rotating as soon as possible, in order to prevent the accident from worsening. 2. Key operating points: First, to prevent air leakage due to a faulty safety valve, the exhaust safety valve must be sealed with water, with sealing water being introduced to maintain the vacuum. Second, if the exhaust safety valve does not activate when a positive pressure of 0.02 Mpa is reached, the valve can be opened manually immediately; if it still cannot be opened, an emergency shutdown must be carried out. E. Sealing steam function: Creates a seal at both ends of the shaft. Prevent the gas inside the cylinder from escaping into the atmosphere (the high-pressure side, i.e., the steam inlet side) ； Or air may leak into the cylinder block (on the low-pressure side, that is, the side with the exhausted steam after work is done), affecting the vacuum of the surface cooler. F. Speed control system: Its main component is the governor, which controls the amount of steam supplied by means of oil pressure, thereby regulating the speed of the turbine. G. Emergency safety system: When the rotational speed exceeds the design limit, it can automatically release the pressure in the governor oil system, quickly close the valves, and cut off the steam supply. Interlocks such as low oil pressure and high vibration can also cause the governor’s oil pressure to drop, leading to shutdown. Function: It is a protective device designed to prevent the engine from spinning at excessive speeds and causing a runaway situation.