Analysis and Treatment of Common Problems in Generator Hydrogen Cooling System
6×350MW ，发电机为德国西门子公司设计 生产。 The first-phase installed capacity of a power plant is 6 × 350MW , and the generator is designed and produced by German Siemens . 直接气体冷却。 The cooling form is full hydrogen cooling, that is, the rotor winding, stator winding, three-phase outlet and bushing are directly cooled by gas. 杂散损耗等均通过氢气散失。 Other heat generated by the normal operation of the generator, such as iron loss, wind resistance loss, and stray loss, are all lost through hydrogen.
H 2 1 H 2 Cooling characteristics
Hydrogen is the element with the smallest atomic mass. H 2 的密度只有空气的 1/14 ，因此用 H 2 冷却发电机，其通风损耗最小，提高了发电机效率， 减少了发电机噪音。 Under standard conditions, the density of H 2 is only 1/14 of that of air . Therefore, cooling the generator with H 2 has the smallest ventilation loss, which improves the efficiency of the generator and reduces the noise of the generator. H 2 Secondly, H 2 8.4 倍， 在相同温差下所吸收的热量更多，换热效率更高，当单机容量一定时， 缩小了发电机的体积，减少了材料使用。 Strong thermal conductivity, its thermal conductivity is 8.4 times that of air , more heat is absorbed at the same temperature difference, and higher heat exchange efficiency. When the capacity of a single machine is constant, the volume of the generator is reduced and the use of materials is reduced. H 2 比较稳定，可保护 发电机的绝缘。 In addition, H 2 is relatively stable and can protect the insulation of the generator. H 2 是一种易燃易爆气体，扩散性强，安全要求高。 However, H 2 is a flammable and explosive gas with strong diffusivity and high safety requirements.
氢冷系统的构成 Structure of 2 hydrogen cooling system
气体系统 2.1 Gas system
H 2 供给装置、 CO 2 供给装置、压缩空气供给装置、 H 2 干燥器等组成。 The gas system consists of an H 2 supply device, a CO 2 supply device, a compressed air supply device, an H 2 dryer, and the like. 2 正常由氢站供给， H 2 瓶作为气源备用。 The H 2 is normally supplied by the hydrogen station, and the H 2 bottle is used as a gas source for backup. 2 供给装置包括贮存液态 CO 2 的钢瓶、 CO 2 气化风机、换热器和风扇等。 The CO 2 supply device includes a steel cylinder storing liquid CO 2 , a CO 2 gasification fan, a heat exchanger, and a fan. The compressed air supply device consists of a compressed air chamber, an air filter, and a gas dryer. CO 2 是作为发电机在充、排氢其间，防止 H 2 爆炸的一个重要安全措施。 Inert gas CO 2 is an important safety measure to prevent H 2 explosion during charging and discharging of hydrogen as a generator .
密封油系统 2.2 Sealing oil system
过滤器、冷油器、差压调节阀等组成。 The sealing oil system consists of a sealed oil pump, a sealed oil tank, an intermediate oil tank, an oil storage tank, a vacuum pump, a filter, a oil cooler, and a differential pressure regulating valve. 环之的间隙形成轴封，防止了 H 2 的泄漏。 The sealing oil system drives oil into the gap between the shaft and the seal ring to form a shaft seal, preventing H 2 leakage. 闭回路供给密封环，保证了可靠的密封效果。 The sealing oil pressure is higher than the hydrogen pressure, and the sealing ring is supplied through a closed circuit to ensure a reliable sealing effect.
冷却系统 2.3 Cooling system
The cooling system consists of a hydrogen cooler, a multi-stage axial fan, and a cooling channel. H 2 送入氢冷器，由闭式水进行冷却。 The multi-stage axial flow fan is located at the end of the rotor near the steam turbine side. It extracts high temperature H 2 from the cooling channel inside the generator and sends it to the hydrogen cooler, which is cooled by closed water. H 2 有选择性地带走发电机内各部热量，最大限度的消除了局部过热，减小了导体间的机械应力。 The precise arrangement of the cooling channels enables H 2 to selectively remove heat from all parts of the generator, which minimizes local overheating and reduces mechanical stress between the conductors.
常见问题及处理 3Common problems and treatment
漏氢或氢压低 3.1 Hydrogen leakage or low hydrogen pressure
There are two ways to leak hydrogen. One is to leak into the atmosphere through the generator casing, or leak into the female casing through the outlet sleeve. In addition, there are also inadequate end caps, hydrogen coolers, and gas pipelines. Give way. In this case, the gas is not easy to accumulate, the danger is not large, and it is not difficult to handle. H 2 进入到发电机的油系统中，甚至汽机 蒸汽系统中。 Second, due to the abnormality of the sealing system, H 2 enters the oil system of the generator, and even the steam system of the turbine. The hydrogen side of the generator returns oil to the intermediate tank, which is connected to the sealed tank and then enters the main tank. 聚，在一定条件下发生爆炸。 Due to improper pressure control, the leaked hydrogen eventually condensed in the main fuel tank and exploded under certain conditions. 0.35MPa， 油氢差压在 0.2 ～ 0.25 MPa 之间。 Therefore , the hydrogen pressure in the generator should be strictly maintained at 0.35MPa, and the oil-hydrogen differential pressure should be between 0.2 and 0.25 MPa. 常，并定期检测油箱内含氢量。 It is also necessary to ensure that the exhaust fan of the fuel tank of the main engine is normally discharged , and the hydrogen content in the fuel tank is regularly checked. H 2 随主机油进入汽机蒸汽系统， 将使汽机叶片受力不均而受到损害。 If H 2 enters the steam system of the steam engine with the main oil, it will cause uneven stress on the steam turbine blades and cause damage. H 2 漏入氢冷器内的闭式水时， 将破环氢冷器的冷却效果，引起氢温高。 When H 2 leaks into the closed water in the hydrogen cooler, it will break the cooling effect of the hydrogen cooler and cause the hydrogen temperature to be high. 耗时较长。 These leaks are hidden, difficult to find, and take a long time. In the process of shutdown and maintenance, we must control the quality, do a good test on the rotor air tightness of the generator, and perform a hydrostatic test on the hydrogen cooler.
氢温高 3.2 High hydrogen temperature
High hydrogen temperature is divided into high cold hydrogen temperature or high hot hydrogen temperature. High cold hydrogen temperature is generally due to the heat conduction failure of the hydrogen cooler, or the closed water temperature inside it is high. Closed water supervision should be strengthened to ensure the quality of closed water and prevent the hydrogen cooler from being dirty. 43℃，闭式水因故停运时，满负荷下，冷氢温度达到机组跳闸值53℃只需短短几分钟。 The hydrogen cooler maintains the normal cold hydrogen temperature at 43 ° C. When the closed water is shut down for some reason, it takes only a few minutes for the cold hydrogen temperature to reach the unit's trip value of 53 ° C under full load. The abnormal temperature of hot hydrogen is usually accompanied by internal faults of the generator, such as insulation damage or short circuit.
H 2 3.3 H 2 Humidity does not meet standards
2 H 2 受力不均而产生裂纹 ; H 2 湿度过低，会影响定子端部垫块的收缩或使 支撑环产生裂纹。 If the humidity is too high, the insulation strength of the generator winding will be reduced, and even the rotor guard ring will crack due to uneven force . H 2 According to the national industry standard "hydrogen-cooled generator H 2 规定，已建电厂 ( 站) H 2 Technical Requirements for Humidity " stipulates that the power plant (station) H 2 has been built ≥ -25℃，绝对湿度＜ 4.75g/m³， 容量在 300MW 及以上的发电机应连续监测 H 2 Dew point temperature should be ≥ -25 ° C, absolute humidity <4.75g / m³, and generators with a capacity of 300MW and above should continuously monitor H 2 humidity. H 2 干燥器对 H 2 The H 2 dryer should be started regularly for H 2 H 2 For dry regeneration, or H 2 H 2 When the dew point temperature and absolute humidity are not in the normal range, H 2 should also be handled. regeneration.
H 2 3.4 H 2 Purity does not meet standards
2 纯度应在在 96% 以上。 H 2 purity should be above 96%. 2 系统，使 H 2 纯度降低。 When the sealed oil differential pressure valve is improperly adjusted, the air-side oil pressure is much higher than the hydrogen-side oil pressure, and air enters the generator H 2 system, which reduces the purity of H 2 . In addition, in the rainy season, water vapor is easily mixed into hydrogen. H 2 中，既影响纯度又影响湿度。 The reason is that the water content in the oil system is relatively high. In a relatively high temperature and high pressure hydrogen-side sealed oil, water vapor passes into the relatively low pressure H 2 through evaporation , which affects both purity and humidity. H 2 干燥周期。 Therefore, the monitoring of the oil-hydrogen differential pressure and the maintenance of the exhaust fan of the oil system should be increased at this time, and the H 2 drying cycle should be shortened .
检修注意事项 4 Maintenance precautions
充、排氢 4.1 Charge and discharge hydrogen
Gas replacement in a generator is generally performed with the rotor stationary. Before replacement, confirm that the gas detector is reliable and that the sealing oil system is operating normally. 0.08 ～ 0.1MPa。 Throughout the replacement process, the internal pressure of the generator was strictly maintained at 0.08 to 0.1 MPa. 2 的置换时，应缓慢进行，防止 H 2 流摩擦过热发生爆炸。 When H 2 replacement is involved , it should be performed slowly to prevent the H 2 flow from frictional overheating and explosion. 100 ～ 150ml/min ，使被置换气体逐层排出，防止两种气体互窜，影响纯度。 Control the flow rate at 100 ~ 150ml / min to discharge the replaced gas layer by layer to prevent the two gases from channeling each other and affect the purity. CO 2 排出发 电机内的空气，再由 H 2 排出 CO 2 ，排氢过程与此相反。 During hydrogen charging, CO 2 is used to exhaust the air in the generator, and then H 2 is used to exhaust CO 2. The process of hydrogen removal is the opposite. H 2 密度小， 为保证取样点准确性和防止油污染， H 2 纯度测点一般位于发电机本体 底部高约 15cm 的位置。 Because the density of H 2 is small, in order to ensure the accuracy of the sampling point and prevent oil pollution, the H 2 purity measurement point is generally located at a height of about 15 cm at the bottom of the generator body . H 2 干燥器或其进、 出口管道等较低部位，在充氢过程中，将以下操作重复至少 20 次： In order to prevent the denser gas from staying in the lower part of the H 2 dryer or its inlet and outlet pipes, the following operations are repeated at least 20 times during the hydrogen charging process :
2 干燥器由干燥位切至中间位； ②干燥器内气体压力到零并维持10 秒；③ 再切至干燥位对干燥器充压。 ① Cut the H 2 dryer from the drying position to the middle position; ② The gas pressure in the dryer reaches zero and maintain it for 10 seconds; ③ Cut to the drying position to charge the dryer. 2 在发电机内停留不超 24 小时，宜在6 小时内排出，防止时间过长而凝露。 It is stipulated that CO 2 stays in the generator for no more than 24 hours and should be discharged within 6 hours to prevent condensation for too long. After the replacement of a gas is completed, the local record shows that the purity is acceptable and stable, and then manual sampling is performed. The sampling points are different at different stages. 2 置换 H 2 时， CO 2 置密度远大于 H 2 密度， CO 2 在下， H 2 在上，上部 CO 2 纯度必须合格，故取样点在上部。 When H 2 is replaced by CO 2 , the density of CO 2 is much greater than the density of H 2 , CO 2 is below , H 2 is above, and the purity of the upper CO 2 must be qualified, so the sampling point is at the upper part. CO 2 时，取样点在下部。 Similarly, when CO 2 is replaced by air , the sampling point is in the lower part.
风压试验 4.2 Wind pressure test
The wind pressure test is used to check the sealing performance of the generator. 压的压缩空气，记录其 24 小时内每小时压力、大气压、温度等变化数据， 来折算一天内的漏氢量。 The wind pressure test is usually filled with compressed air of rated hydrogen pressure, and records changes in pressure, atmospheric pressure, temperature and other changes within 24 hours to calculate the amount of hydrogen leakage in a day. During the wind pressure test, the shut-off door of the gas analyzer should be closed to prevent damage to the gas analyzer. When checking for leaks, first use a soapy water foaming method to make a rough check. If you can't find a leak, you can fill in an appropriate amount of Freon to check it. After checking, wipe the soapy water with a clean cotton cloth
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Works normally in harsh environments. Mechanical equipment works in harsh environments for a long time, and different locations in different climates will directly affect the working time and capacity of mechanical equipment. If the working conditions of the mechanical equipment are harsh, protective equipment should be prepared in advance to protect the mechanical equipment from being affected by the harsh environment. The structure of mechanical equipment is complex, and sometimes some sand particles may cause mechanical equipment failure. The need for protection is particularly important. Assuming no protection, the maintenance cost of machine failure will be higher, and the economic benefits and human resources will be lost. Waste is inevitable. Each mechanical equipment has corresponding professional protective measures. The experience of maintenance personnel is particularly important to avoid accidental failure of the machine due to improper operation.
Commissioning and maintenance of equipment
比如油温，油压，水温等是否处于正常范围，应由专业的维修人员检查机器的外观是否完整，杆件等复杂结构是否有杂物，如果有就要及时清理。 At the end of each use of the equipment, the time of use of the equipment should be recorded, and some parameters of the equipment, such as oil temperature, oil pressure, water temperature, etc. are in the normal range. Professional maintenance personnel should check whether the appearance of the machine is complete, and the complex structures such as rods If there are any debris, clean up in time. At the beginning of the normal operation of the equipment, you should first observe whether the running machine is abnormal, and if so, stop the operation immediately to eliminate the fault. The maintenance and operation rules of the machine must be carried out by professional maintenance personnel. Irrelevant personnel must not be contacted. Strictly implement the maintenance system and enforce regular maintenance. Low-level maintenance can be handled by the operator, while high-level maintenance must be handled by the maintenance personnel, so as to reduce the cost of repairs and maintenance, thereby maximizing the savings of manpower and equipment maintenance funds.
Parts of mechanical equipment
 。 Machine failure is inevitable in the process of machinery production. If the machine has a temporary failure, it may cause the entire production line to stop operating. To a certain extent, the efficiency of machine production will be reduced. When maintenance personnel are performing machine maintenance, The faulty parts will be replaced. At this time, the preparation of the parts is very important. The replacement time will affect the production efficiency and work cycle of the entire enterprise. Especially for some special parts, spare parts should be purchased in advance to make the machine. Get reasonable maintenance in the shortest time to continue normal operation  .
The operation of machinery and equipment is always around the clock, and human energy is limited. At this time, handover work is required. 查，确定机器是否能够正常的运作，检查各个零件是否出现瑕疵等等。 The process of the handover shift also indirectly affects whether the machine can run effectively for a long time. A reasonable handover shift system should be formulated. The handover personnel must communicate effectively during the handover process. The problems generated by the machine should be timely transmitted to another A handover person, in the process of handover, two people must jointly inspect the machine to determine whether the machine can operate normally, check whether each part has defects, and so on. 如果检查之后发现一切正常，需要在机器的记录本上签名，完成交接。 If there is a problem with the equipment during the inspection, the handover personnel should deal with it as soon as possible . If everything is found to be normal after the inspection , you need to sign the machine's logbook to complete the handover.
3.2 Problems in the performance of mechanical equipment
There are various problems in the use of machinery and equipment, and we will divide them into four points to explain below.
First, use mechanical equipment at will. The use of machinery and equipment without permission or in accordance with relevant regulations makes the machinery and equipment perform long-term work, and the performance and efficiency of machinery and equipment will inevitably be affected. Some workers are working on-site
When not paying attention to the harsh environment of the site, directly using machinery and equipment, causing frequent failures of the machine, which increased the cost of repairs and maintenance.
Secondly, before the mechanical equipment is used, if the mechanical equipment has failed and is not repaired in time, but the faulty mechanical equipment is directly used for work, the life of the mechanical equipment will be greatly reduced. 重要的作用。 At the same time, the role of lubricants will also have a vital effect on the machine . 才能大幅度降低机器的磨损和损耗，延长机器的使用寿命。 According to the different types of machinery and equipment, the use of reasonable lubricants can greatly reduce the wear and tear of the machine and extend the service life of the machine.
Third, in the environment in which machinery and equipment work, the unpredictability of temperature must exist. Assume that the temperature at the work site is too low, and the loss of mechanical equipment will increase; if the temperature at the work site is too high, it will directly affect the work efficiency of the mechanical equipment. 下也会增加机械设备的损耗，甚至能够将机械设备烧坏无法正常运行， 使得维修的成本巨大。 At the same time , the loss of mechanical equipment will increase under high temperature conditions , and even the mechanical equipment can be burned out and cannot operate normally, which makes the maintenance cost huge.
The fourth point is that after the project is completed, the machinery and equipment must be sealed. Before the next new project is carried out, a long period of time must pass. During this time, it is not that the machine is not working and does not need to be repaired and maintained. Mechanical parts have a life span. The influence of air will cause wear and corrosion on parts, even rust. If not handled in time, it will directly affect the performance and working efficiency of mechanical equipment. If such mechanical equipment is directly affected, Put into use, the probability of failure will greatly increase, increasing the cost of mechanical equipment repair and maintenance.
总结 4 Summary
The maintenance and maintenance of machinery and equipment is not static to a certain extent, but the establishment of a repair and maintenance system is necessary. Our goal is to allow machinery and equipment to operate normally and efficiently within the range it bears, so that the machinery has a good and Maintain superior performance in order to meet the normal needs of businesses and people. In the process of mechanical equipment repair and maintenance, we must pay enough attention to avoid the same problems repeating the same mistakes. Maintenance personnel should improve their professional accomplishment and sense of responsibility, ensure the best repair quality, improve the performance of the machine, and drive the company's overall efficiency To contribute to the development of China's economy.