Datang Wushan Power Plant due to a longer period of high load each year, so the steam turbine condenser water ring vacuum pump long-term operation in high vacuum conditions, especially the summer conditions even worse, the vacuum pump rotor blade material on the anti-cavitation Reach the limit, so that its service life is affected to some extent. After investigation, the installation of atmospheric ejector effectively avoids the influence of cavitation on the vacuum pump rotor and prolongs the service life of the vacuum pump. 1, a brief analysis of the causes of water ring vacuum pump cavitation Wushan power plant steam turbine water ring vacuum pump size is based on the design of the generator set operating conditions identified, when the operation within the design range , The vacuum pump can be normal operation, such as related reasons, such as: long-term operation of the unit at full capacity; summer cooling water temperature is too high or cooling water flow is too small, resulting in poor cooling effect of vacuum pump heat exchanger, vacuum pump will run under high vacuum, Close to or in a suffocating state of operation, due to the inherent physical phenomena, under certain water temperature conditions, the higher the vacuum, the water temperature is higher, the water in the pump is close to boiling and will produce a large number of bubbles, bubble generation and rupture will Cause cavitation damage to the impeller, destroy the dynamic balance of the impeller, cause strong vibration of the pump body, vibrate the ancillary equipment of vacuum pump (pressure vacuum gauge, pressure switch, feedback device of inlet pneumatic door, etc.), and will emit very large steam Noise erosion, these conditions have seriously affected the safe operation of the vacuum pump group and the safe operation of the turbine generator set. 2, the basis for technical transformation programs and detailed instructions If you want to solve the problem of cavitation of vacuum pumps, reduce the cost of water temperature larger, reducing the vacuum is so that the condenser back pressure rise is even more unlikely, which will seriously affect the load with the unit Capacity, the ideal approach is to solve the cavitation generated in the original water temperature, the system vacuum unchanged, the best option is to install the vacuum ejector to the vacuum pump, the whole vacuum pump group will be better extraction performance, so condensate Steam still can guarantee the current level of vacuum or higher, but the vacuum within the vacuum pump body only 12Kpa (this time the system vacuum within the 3-8Kpa range), which can effectively prevent cavitation. Atmospheric jet pump by: nozzle, suction chamber, and diffuser composition, the exhaust port and water ring pump inlet connected. Atmospheric ejector principle Introduction: First, start the water ring vacuum pump, the nozzle inlet and exhaust pressure difference between the formation of the atmosphere from the nozzle into the pump, when the pressure difference is the atmospheric pressure of 1/2, the air medium by The nozzle contraction section is accelerated to the larynx when the speed of sound can be reached, to expand the section can be further accelerated to the speed of sound, the diffuser to form a high-speed jet, and the resulting pressure in the suction chamber is lower than the pressure inside the container being evacuated, Inhaled into the room, due to the mixing of the two air-suction chambers, the loss of momentum exchange slows down the air flow rate and falls below the speed of sound as it enters the throat of the diffuser, further reducing the pressure through the diffuser expansion and increasing the pressure To achieve the exhaust pressure of the air ejector, that is, the suction pressure of the water ring pump, the water ring pump sucked into the gas and then discharged from the pump, the completion of the suction, exhaust process. 3, the technical transformation of the specific steps and detailed description 3.1, mechanical transformation part can know the modified intake pipe than the original pump group pipe length of about 700mm, the increase in the parts have been marked on the map, if the location is not enough The pipeline valve on the pipeline installed on the vertical, so there is room to cut off the 700mm pipeline. 3.2, the pump control part of the change (see Figure 3) increase the pressure switch 47a (double contact 47a1, 47a2) its role is to control the intake tee and ejector tee butterfly valve (16b) and between the injector On the pneumatic butterfly valve (19a) on and off, thereby controlling the injector into and out. 3.2.1. When a main pump is running, the pressure switch detects the pressure is less than 10kpa (can be set specifically), the atmosphere ejector switching valve [16b] is closed, while the atmosphere ejector drives the gas valve [19a] After the above two valve action is completed, the atmospheric ejector is put into the state. 3.2.2 When a main pump is running, the pressure switch [47a2] measured pressure greater than 14Kpa (this value can be set by yourself), the atmosphere ejector drives the gas valve [19a] to close, and the atmosphere ejector switches the valve [ 16b] open, when the two valve action is completed, the atmosphere ejector is in an exit state. 3.2.3, the original unit pressure switch and pressure switch settings do not need to change. 4, after the transformation of the advantages and transformation before and after the performance and economic comparison 4.1, after the transformation of the advantages: â‘ most important to ensure that the vacuum pump does not occur cavitation, noise and vibration will be substantially reduced, the life of the vacuum pump will be Improvement, has been the transformation of the No. 3 machine A vacuum pump since August 2008 installation of atmospheric ejector noise and vibration will be greatly reduced, never seen the impeller rupture, excessive vibration damage to thermal control equipment phenomenon. â‘¡ Because of the tightness of the condenser of this unit, the pumping performance of the pump equipped with atmospheric ejector in the high vacuum stage is better than that of the single pump, meanwhile, the condenser vacuum is always maintained at the ideal level of 5-6Kpa, Improve the unit with the load rate to create a good condition. 4.2, before and after the transformation of the performance, economic contrast â‘ installed before the atmospheric ejector, the vacuum within the vacuum pump to maintain about 6Kpa, after the installation of atmospheric ejector, the vacuum within the vacuum pump to maintain about 12Kpa, vacuum pump power curve reference, at 12Kpa , The shaft power of 113KW, as the condenser vacuum is constantly changing, so the vacuum pump vacuum evacuation is also changing, it can not be very specific about how much the shaft power increase, the general we press 6Kpa (power is 99KW ) And 12Kpa (power is 113KW), which means that after the installation of the air ejector its power will increase about 14KW. (2) After the installation of the air ejector, the pumping performance of the water ring vacuum pump is improved. According to our observation and DCS PC history curve, the condenser condenser vacuum is more stable and the vacuum energy can be increased compared with the original condition 1Kpa or so, and there is a trend towards higher vacuum.
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