Device for improving tightness of steam turbine vacuum system

Abstract

The invention provides a device for improving the tightness of a steam turbine vacuum system. The device comprises steam pump sealing water return pipes, a water return main pipe, shaft steam-adding side return pipe, a water seal device, a water outlet pipe, a stop valve and a condenser, wherein the water seal device comprises a case body, a liquid level float and a case lid; two sides of the casebody are equipped with a water inlet and a water outlet separately; the case body is partitioned by a separator into a water inlet trough and a water outlet trough; the separator is provided with anoverflow port; the liquid level float is disposed inside the water inlet trough of the case body; the steam pump sealing water return pipes communicates with the water return main pipe; the water return main pipe and the shaft steam-adding side return pipe enter into the water inlet trough through the water inlet of the case body; one end of the water outlet pipe enters into the water outlet trough through the water outlet of the case body while the other end is connected with the condenser; and the stop valve is arranged on the water outlet pipe. With adoption of the device, the vacuum tightness of a steam turbine can be effectively raised, the reliability of a unit can be improved, the unit becomes economical, and working loads of operation and maintenance personnel can be reduced.

Description

technical field [0001] 本发明属于汽轮机真空系统技术领域,具体涉及一种提高汽轮机真空系统严密性的装置。 Background technique [0002] 汽轮机组的真空严密性能差,是一个长期困扰电厂机组经济性的重要参数之一,机组严密性差必将导致凝汽器真空低,真空低会使蒸汽在末级膨胀做功达不到设定值,使机组出力受限制,经济性必然降低,机组轴向位移会增加,影响机组安全运行。机组严密性差必将导致凝结水含氧量超标,会对凝结水管路和设备造成腐蚀,因此,要获得最有利的真空,降低厂用电率,降低供电煤耗,提高机组安全运行,提高经济效益。正因如此,在机组运行中都将真空系统严密性作为重要的考核指标之一。然而,300 MW 及以上大型机组真空系统庞大而复杂, 真空系统严密性的影响因素较多, 提高该型机机组真空系统严密性一直是大多数电厂的难题。 [0003] 大唐西安热电厂2号机组为哈尔滨汽轮机厂生产的300MW亚临界、一次中间再热凝汽式汽轮机。2017年3月14日,该机组在运行中进行真空严密性试验时发现真空值3分钟内下降3Kpa,严重超出国家规定的最低标准0.399Kpa / min。检修人员多次在线进行真空查漏、黄油封堵、加装堵板等方法均无明显效果。 [0004] 该机组于2017年5月停机检修时实行了灌凝汽器水查漏,将凝汽器汽侧高位灌水至低压缸凹洼窝处,多次检查运转层以下真空系统的法兰、结合面、焊缝等处容易发生泄漏空气的部位。对发现的泄漏部位通过更换密封垫、拧紧法兰螺栓、填压密封胶等手段进行了处理,然而在机组6月26日启动后,真空泄漏量仍有扩大趋势,严密性试验中1分钟内真空下降3Kpa,需联启备用真空泵方能维持机组正常运行。2017年7月对采用氦质谱检漏仪对2号汽轮机真空系统进行了真空查漏,试验中发现汽泵密封水回水及轴加疏水至凝汽器多级水封走空,空气由此处进入导致凝汽器真空变差。 [0005] 目前,各火电厂真空系统的汽泵密封水回水及轴加疏水均是连接至凝汽器,在接入凝汽器前装设有U型水封,汽泵密封水疏水装设六级水封,轴加回水装设五级水封,其系统见 figure 1 . 由于U型水封整体为密闭式结构,水位在运行中不便于监测,需要定期进行注水,一旦发生水封走空,就会影响机组真空。 Contents of the inv...

AI Technical Summary

Problems solved by technology

In July 2017, a helium mass spectrometer leak detector was used to conduct a vacuum leak check on the vacuum system of the No. 2 steam turbine. During the test, it was found that the seal water of the steam pump was backwater and the shaft was drained until the multi-stage water seal of the condenser was empty, and the air was thus The entry of the place causes the vacuum of the condenser to deteriorate

Since the U-shaped water seal is a closed structure as a whole, the water level is not easy to monitor during operation, and regular water injection is required. Once the water seal is empty, it will affect the vacuum of the unit

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