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Part 1 01 Definition of the terminal difference: The difference between the temperature of saturated steam at the condenser pressure and the exit temperature of the condenser cooling water is called the terminal difference. 02 Factors affecting the terminal difference: For a given condenser, the magnitude of the terminal difference is related to the inlet temperature of the condenser’s cooling water, the steam load per unit area of the condenser, the surface cleanliness of the titanium tubes in the condenser, the amount of air that leaks into the condenser, and the flow velocity of the cooling water within the tubes. A clean condenser has a certain terminal difference value under specific conditions regarding circulating water temperature, circulating water volume, and unit steam load. Generally, as the circulating water volume increases, the outlet temperature of the cooling water decreases, resulting in a larger terminal difference; the opposite is true as well. Additionally, the higher the unit steam load, the greater the terminal difference, with the inverse relationship holding true as well. In actual operation, if the terminal temperature difference is much higher than the specified value, it indicates that the titanium tubes on the cooling surface of the condenser are dirty, resulting in deteriorated heat conduction conditions. Reasons for the increase in end difference: ① Scaling on the water side or steam side of the condenser’s titanium tubes ； ②Air leaks into the steam side of the condenser ； ③Cooling water pipe blocked ； ④Increased cooling water volume ； ⑤The unit steam load of the condenser increases. Part II 01 Measures for Addressing the Cold End of Turbines and Terminal Difference (1) When the terminal difference of the condenser exceeds the limits specified in the Group Company’s \"Technical Standards for Energy Conservation Monitoring in Thermal Power Plants,\" it is necessary to determine the cause by examining parameters such as the vacuum tightness of the condenser, the operating conditions of the vapor-side vacuum pumps (working water temperature, separator water level, and whether components such as air extraction/vacuum injection/pipeline check valves are functioning properly; if necessary, additional vacuum pumps can be used for evaluation), the water resistance of the condenser (circulation pump head), the condenser pressure, and the discharge temperature of the low-pressure cylinder, and then take appropriate measures. The installation locations of the vacuum and circulating water return temperature sensors used for calculating the terminal difference, as well as the accuracy of the instruments and transmitters, shall comply with DL/T1078 \"Test Procedures for Operating Performance of Surface Condensers\", in order to ensure the accuracy of the terminal difference data. 1. Reduce the heat load on the condenser. The heat load on the condenser has a significant impact on the vacuum level. The increase in the heat load of the condenser is mainly due to high-quality steam failing to do work, or other high-temperature fluids entering the condenser directly. This not only results in losses of energy and working fluid but also causes a drop in the condenser vacuum, which is a major factor affecting the thermal efficiency of the unit. The main factors affecting the heat load of the condenser are internal valve leaks, including leaks from the low-pressure bypass, cylinder drains, pipeline drains, emergency drains from the high-pressure heater, and drains from the low-pressure heater to the condenser. The main measure to reduce the heat load on the condenser is to improve the control of internal leakage in the valves; by comparing the temperatures before and after the valves, the leakage points can be identified, which can then be addressed through manual isolation or thorough repair during maintenance. 2. Improvement of vacuum system integrity: The integrity of the vacuum system has a significant impact on the cold end of the turbine as well as the temperature difference across it. It is necessary to optimize the condenser vacuum system and eliminate any leaks, so that the vacuum integrity meets the requirements specified in the \"Huaneng Standards for High-Performance, Energy-Efficient, and Environmentally Friendly Coal-Fired Power Plants\". (1) Locate the vacuum leakage points in the condenser; the main potential leakage points are: a) the shaft seal of the low-pressure cylinder ； b) Horizontal mid-plane of the low-pressure cylinder ； c) Low-pressure cylinder safety doors, manway doors ； d) Vacuum break valve and its piping ； e) Condenser manholes, reserved pipe openings and plug plates, steam-side drain valves, and body welds ； f) Shaft seal heater and feed pump seal water return water seal ； g) Connection between the low-pressure cylinder and the throat of the condenser ； h) Steam turbine shaft seal of the steam-driven feed water pump ； i) Flanges before and after the turbine exhaust butterfly valve of the steam-driven feedwater pump turbine ； j) Connection flange for the extraction pipe in the negative pressure section ； k) Low-pressure heater drain pipeline ； l) Pump from extractor to condenser pipeline ； m) Condensate pump gasket ； n) Low-pressure feedwater pump gasket ； o) Hot well drain valve ； p) Damage to cooling tubes or port leakage ； q) Low-pressure bypass isolation valve and flange ； r) Extraction steam pipe passing through the condenser joint surface ； s) Negative pressure zone heater exhaust, drain pipe flanges ； t) Steam feed pump turbine casing drain flange ； u) Steam feed pump turbine casing balance pipe flange ； v) Steam feed pump turbine casing and exhaust hood flange ； w) Other piping systems connected to the negative pressure area. (2) It is recommended that the shaft end seals of the turbine’s low-pressure cylinder and the feedwater pump turbines be replaced with contact-type seals such as the \"Wang Changchun\" ferritic seal. Before switching to contact-type seals, the steam supply pressure for the shaft seals can be increased appropriately; meanwhile, care should be taken to ensure that the vacuum applied to the shaft is not too high, so as not to affect the sealing performance of the low-pressure cylinder shaft seals. (3) Improvement of the shaft water seal or the return water seal for the feedwater pump. In some power plants, the water seal height is insufficient or its structure is incorrect, preventing it from performing its sealing function; as a result, the vacuum integrity is poor, and such leakage points are difficult to detect. This issue warrants sufficient attention. (4) The air release valve or water release valve of the negative pressure systemほとんど no function for releasing air or water, and there is a risk of vacuum leakage; it is recommended to remove them. 3. Optimization of the vacuum system: It is necessary to maintain optimal operating conditions for the vacuum pump on the steam side. For the control of the operating water temperature of vacuum pumps, refer to the requirements outlined in \"Improvements to the Vacuum Pump Cooling Water System\" within the \"Catalogue of Energy-Saving and Consumption-Reduction Technologies for Coal-Fired Power Plants\" ； Strengthen the operation and maintenance of the vapor-side vacuum pump to ensure normal water levels in the separator and proper functioning of all components of the pump. In addition, in the case of a double-back-pressure condenser arranged in series, due to the fact that the calculation of air flow resistance in the piping during the design phase does not reflect actual conditions, the high-pressure and low-pressure condensers interfere with each other, which can lead to uneven pumping volume and affect the heat exchange efficiency of the condensers. It is recommended to change the arrangement of the vacuum piping from series to parallel. The exhaust system of the double-backpressure condensers has been changed from a series arrangement to a parallel arrangement. In addition to the provisions specified in the \"Catalogue for the Promotion and Application of Energy-Saving and Consumption-Reduction Technologies in Coal-Fired Power Plants,\" control valves are installed on the parallel exhaust pipes of the double-backpressure condensers. When the vacuum integrity of the condensers is better than 100 Pa/min and the vapor-side vacuum pumps are operating properly, the opening degree of the control valve for exhaust air from the high-backpressure condenser is adjusted to maintain constant pressure on both sides of the condensers, thereby allowing a single vapor-side vacuum pump to continue operating.