Product Introduction Steam Turbine Vacuum System Introduction Fu Yongyu (Zhejiang Electric Power Construction Corporation, Ningbo 315010, Zhejiang, China) 1 System Components The steam pumping vacuum system is mainly cooled by a water ring vacuum pump, gas-water separator, seal water recirculation pump and seal water. And other components. The vacuum pump is installed horizontally, with two stages and water ring type. It is driven by the AC motor and the flexible coupling is used between the motor and the pump. Each vacuum pump is mounted on a common frame with its air-water separator unit, seal water recirculation pump, and cooler. The vacuum system is equipped with a total of two water ring vacuum pumps, one for operation and the other for standby. When the turbine starts, the two pumps work simultaneously to quickly reach the specified vacuum.

2 system flow The vacuum system flow sees. The gas and steam mixture extracted from the condenser air cooling zone passes through the air-controlled inlet valve XV001 (XV004) linked with the vacuum pump and enters the water ring vacuum pump PU001 (PU002). The air-water mixture discharged from the vacuum pump is in the separator SR001 (SR002). In the separation, the separated air is discharged to the atmosphere through the exhaust valve NV007 (NV010). When measuring the vacuum system exhaust volume, you can close the exhaust valve NV007 (NV010), open the inlet and outlet valve HV008, HV009 (HV011, HV012), then the dry air flow meter FI011 (FI022) will be displayed The amount of air (which also includes some uncondensed steam) is divided into two parts after the water separated in the separator passes through seal water recirculation pump PU003 (PU004) and seawater-cooled plate heat exchanger EX001 (EX002). The spray nozzle is injected into the vacuum pump through the atomizing nozzle and the inlet pipe is used to cool the gas-steam mixture therein, so that steam in the gas-steam mixture is condensed into water as much as possible to improve the performance of the vacuum pump and prevent the steam condensation time from being delayed due to this part. Interfering with the precise control of the sealing water volume of the vacuum pump; the other sealing water ring entering the vacuum pump. Since the sealing water volume and the water temperature all affect the performance of the vacuum system, the system sets up a complete automatic control system for the water level and water temperature of the sealed tank.

Vacuum system flow diagram The water level of the water separator is indicated by the water level indicator, and a water level indicator switch provides the low water level signal to the plant control system. The replenishment is to provide cooling water to the separator through the float-type water supply valve LCV041 (LCV042) in the tank. When the water level exceeds the upper limit, the overflow pipe will automatically drain the excess water.

In addition, in order to prevent cavitation damage of vacuum pump internal components under high vacuum conditions, from the gas side of the sealed water gas water separator, a pipe is introduced to the inlet of the vacuum pump. When the vacuum is high to a certain degree, the control valve HV013CHV016 is opened to lower Vacuum pump inlet vacuum to prevent cavitation damage.

The continuous operation of the vacuum system ensures the normal vacuum value of the system. When the system pressure drops to 5X103Pa (absolute), one pump can be stopped and only one vacuum pump can be operated, and when the unit is running normally, the throttle water cooler can be throttled slightly to reduce the operating noise and power consumption of the plant. Outlet valve HV024 (HV028).

3 system components production, model: HR2950; design capacity: 25.5kg/h air and 56.1kg/h steam; pump speed: 980r/min; motor power: 45kW; sealed water volume: 14m3/h; sealed water temperature: 22*C. The casing of the pump is made of carbon steel. The fixed parts of the pump are composed of two end caps, two center rings, a center baffle, and a two-stage center shell. The above parts are connected together by six tension bolts. In the center of the end cap, a flexible mechanical seal is installed to prevent water leakage from the dynamic and static joint surfaces. Bearing supports are installed on the outer sides of the end caps on both sides, and the bearings are double-volume roller bearings. The rotor consists of a shaft (made of carbon steel) impeller (made of stainless steel), two end and intermediate spacer sleeves (made of stainless steel), two end tension nuts, bearing inner rings and other components, when the two ends are tightened The entire rotor becomes a rigid body. There is a certain eccentricity between the center of the rotor and the center of the stator, which is the key to pumping the pump.

Water ring vacuum pump outline drawing, single-suction centrifugal pump with mechanical seal, type NOBL40/60/165, design flow 14m3/h, design pressure head 7m, design NPSH (pump suction head) 1.5m, speed 1450r /min, driving motor power 1.1kW, impeller and casing are cast iron, the shaft is chrome steel.

As a gas-water separation device for the water ring vacuum pump exhaust, the structure is a cylindrical body, a diameter of 450mm, a height of 1450mm, the upper neck is a one-dimensional body, shrinking from 450mm diameter to 200mm, and connected with the air exhaust outlet . The container is made entirely of carbon steel and galvanized.

The inlet of the gas-water mixture is tangential to the outer diameter of the separator cylinder, so that the gas-water mixture enters the cylinder and undergoes a rotational movement, so that better separation can take place. The separator is also equipped with an overflow pipe, water level alarm probe interface, water ring vacuum pump body drain interface, replenishment interface, water ring vacuum pump middle level air replenishment interface (this interface is on the top of the separator, in order to prevent the vacuum pump from generating steam during high vacuum. Erosion) and air flow meter cone interface, etc.

The sealed water cooler is a standard plate heat exchanger manufactured by Sondex, UK, model S1SIG. It consists of two steel end caps and 37 titanium plates with nitrile rubber gaskets and compression bolts. The total area is 5.7m2, the sealing water volume is 14m3/h (the temperature is between 22C~26.5C), the cooling water volume is 22.6m3/h (seawater, the temperature is between 20*C~22.8*C), and the cooling water pressure loss is 5X104Pa. The device is a seawater-cooled, double-stroke, surface-type condenser manufactured by the American Ecolaire Company. The condenser has an effective condensing area of ​​8710 m2, a design cooling water inlet temperature of 21°C, a flow rate of 33.22*C for the exhaust gas, and a pressure of 5.IX103 Pa (absolute).

4 Commissioning and operating conditions When the vacuum system was commissioned in July 1998 (shaft seal was not cast), a single vacuum pump was operated to test vacuum, the vacuum had reached 0.037 MPa (absolute), and when the two vacuum pumps were simultaneously operated, the vacuum reached 0. 024 MPa ( absolute). In October 1998, in the case of shaft-seal steam injection, two vacuum pumps were turned on at the same time. After about twenty minutes, the condenser vacuum reached 0.01 MPa (absolute). At this time, one vacuum pump was automatically shut down and the other was stopped. Keep running and maintain the vacuum at 0. (absolute).

(Rated load 100MW) The vacuum pumping system operates normally and the condenser vacuum is stabilized at 0.0017 MPa (absolute). When the steam turbine was operating at full capacity in April 1999, the condenser vacuum was stable at 0. Afterwards, when the turbine is loaded with 87MW of stable operation (regulation requirement is greater than 80MW), the condenser is closed in place to the manual isolation valve of the vacuum system, the condenser vacuum value is recorded for 8 minutes continuously, the test is stopped after 8 minutes, and the system is restored to the test In the previous working condition, the vacuum reduction rate within 5 minutes after calculation was 0.044 kPa/min, less than the specified value of 0.4 kPa/min, and the vacuum tightness test of the condenser passed smoothly.

Announcement of the 2004 Academic Symposium of the Chinese Turbomachinery Technical Committee (12th) The 2003 Academic Conference of the 11th Turbo Special Committee of the China Power Engineering Society was successfully held in Beijing in mid-September 2003 . According to the spirit and decision of the conference, the 2004 China Turbomachinery Society Academic Symposium will be held in September 2004 at the Qingdao Jieneng Steam Turbine Works together with the General Engineer Engineering Workshop for the turbine industry. In order to strengthen academic exchanges and promote information sharing to jointly promote the prosperity of China's turbine manufacturing industry, the academic seminar will widely recruit academic papers and deep review articles from domestic steam turbine industry professionals. Specific requirements are as follows: Theme content: As the seminar was held at the Jade Bird Jet Power Plant, it will focus on the status quo of small and medium sized steam turbines and drive the development of small and medium-sized heat and power turbines to drive feed pumps, turbines for fans, small and medium-sized combined cycle steam turbines, waste power station steam turbines, Small and medium-sized air-cooled steam turbines and other topics are specially drafted.

Requirements: The submission must be an original paper. Publications already published in public journals are not candidates for this submission; the paper must be clearly illustrated and the format should be based on the formal publication requirements. Manuscripts should be processed in four copies. Please mark the envelope on the envelope. The special committee called for "".

After the 2004 symposium was held, it was proposed that the papers presented at the conference be published in the form of albums or selected albums in the publication “Thermo Turbo”, which was jointly sponsored by the Turbo Special Committee.

Send address: No. 333, Jiangchuan Road, Minhang District, Shanghai, China Postcode: 200240 Chief Engineer Office of Shanghai Steam Turbine Co., Ltd. Secretariat of the Turbine Committee of the China Power Engineering Society Zhao Yan, Lu Jinzhong Received the secretariat of the Turbine Committee of the China Institute of Power Engineering

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