Power station safety valve verification standards related to the provisions of the State Quality Supervision Bureau Boiler and Pressure Vessel Inspection Bureau promulgated the "steam boiler safety technology supervision regulations:" in the boiler safety valve should be checked at least once a year ";" power boiler pressure (DL612-1996) 9.1.13) stipulates: "After the installation and overhaul of the boiler and the safety valve shall be checked, the pressure of the safety valve shall be checked" (and clearly stipulates the scope of the regulation: f) Thermal system pressure vessels: high and low pressure heaters, deaerators, various types of expansion vessels, etc. "The State Power Corporation promulgated the" 25 key requirements for preventing major accidents in power generation "states:" All kinds of pressure vessels Safety valve should be regularly checked and discharge test. " These provisions are very clear on the regular inspection of power station safety valve. Electricity Industry Standard Electric Power Industry Boiler and Pressure Vessel Supervision Order (DL612-1996) 9.1.13 There are clear provisions on the safety valve of the instrument calibration: "The pure mechanical spring-type safety valve can be calibrated and adjusted by the hydraulic device, generally at 75% ~ 80% of the rated pressure.After adjusting the hydraulic valve safety valve, at least the minimum starting value of the safety valve from the actual seat review. "1 Safety valve testing methods At present, the power system safety valve calibration is generally The methods used are offline measurement and online measurement of two. Off-line measurement requires the removal of the safety valve to the test bench when the equipment is stopped, which is time-consuming and laborious. And this kind of measurement method can not solve the influence of temperature on the safety valve opening pressure, but for some non-removable safety valves Valve, etc.) is powerless. Online measurement is divided into real jump measurement and measurement of two instruments. The actual jump measurement will cause unnecessary damage to the safety valve, and noise pollution and safety issues at the time of measurement have drawn more and more attention. On July 9, 1999, Liaoning Province, Jinzhou Power Plant in the safety valve school Five traumatic experience of tragedies should not be forgotten. Instrument measurement methods are currently more advanced and commonly used methods, such as the British FURMANITE company in the eighties developed TREVITEST practical products. The instrument uses a hydraulic motor driven hydraulic pump as the power source, using two-channel pen recorder with the sensor as a measurement recording unit. The recorded safety valve opening process of the force curve, the operator manually determine the feature points, by hand to calculate the final result of the entire measurement process need to be involved, so the consistency of the measurement results are greatly affected by human factors, the measurement accuracy can not Guarantee. In addition, the high cost of such instruments (quoted in 2000 amounted to 1.25 million) is difficult to promote in the country. Safety valve manufacturers in Japan, the United States and other countries also developed similar products in succession in the 1990s, but such products can only be used in safety valves manufactured by their own manufacturers, which are powerless to domestic and other manufacturers' safety valves. Since the nineties, there have been some imitations in China, and there is not much breakthrough in technology. There are still some shortcomings of poor measurement consistency and low measurement accuracy. NSH series of on-line pressure relief valve safety valve system by the Beijing State Mechanical and Electrical Technology Co., Ltd. and Beijing Labor Safety Technology and Equipment Center developed a new type of portable instruments, the basic working principle is the same as the British FURMANITE TREVITEST safety valve detection system, and in the design process There are major breakthroughs. NSH safety valve on-line constant pressure meter is a new type of patented product to check the safety valve of power station, Boiler & Pressure Vessel Bureau of Labor Ministry, Recommended Products of Power Station Valve Standard Committee. This product has passed the test of China Academy of Metrology. At present, the instrument has been in the country more than 50 power plant safety valve calibration application, the practice proved that this instrument set NSH safety valve on-line calibrator can be stopped or running in the case of the unit, only 2-5 Sec open time to complete on-line performance testing of safety valves and operating parameters of the test, but also failed to detect the safety valve on-line setting can measure and record the safety valve opening pressure and the safety valve where the system media pressure and other parameters . 2 Design Principle Spring safety valve opening and closing action is dependent on the pressure changes at the inlet of the media and spring preload to make the valve automatically open and close. When the medium pressure (internal pressure) rises to enhance the lifting force than the spring preload force, the valve spring to open automatically against the spring preload to release excess media, so that the pressure drop, but also due to the spring force, Pressure drop to safety, the valve automatically shut down, stop bleeding. According to this principle, it is conceivable that when an on-line (also known as hot) measurement or adjustment safety valve provides an upward additional force from the outside, when the sum of the medium pressure and this additional force just overcomes the spring preload, the valve The core will also be opened, even in the absence of medium effect offline (also known as cold) conditions, alone by the external force to overcome spring preload, the valve core can also be opened, a clearly shows that the force Balance the relationship. Obviously, we can see that the spool open condition is: FT = FW + PL × S Where: FT - spring preload FW - external additional force PL - medium pressure S - safety valve sealing surface area The opening pressure P is: P = PL + FW / S When cold, P = FW / S Obviously, if the additional external force FW can be accurately measured, it can be easily calculated based on the known spool area S and system operating pressure The safety valve opening pressure P. This is the safety valve on-line test technology design basis and principle. 3 Technical Basis According to the analysis of the spring safety valve opening action characteristics, we can draw: Under the action of external force FW, a safety valve from closed to open, and then from open to close the whole process, the external force FW changes Law, when the additional force increases gradually from zero, and the internal pressure PL × S just happens to spring preload, the valve micro-Kai, increasing the role of medium area S, so that the spring pressure to overcome the internal pressure of the role of preload The force increases dramatically, which results in an instant reduction in external appendages. The first characteristic peak A appears. When the external additive force decreases to reach the close point, the external force will appear instantaneous rebound due to the sudden decrease of the medium acting area in order to maintain the balance of force. The above two characteristic peaks A and B are the technical basis for detecting the opening pressure of the safety valve and the pressure of the seatback under the on-line condition. When the valve is not open, the external force to overcome the static rigidity of the valve core, when it reaches the opening point, the external force to overcome the spring elastic force, the slope of the two changes over time, resulting in the first inflection point C, The same situation, the valve is closed, there will be another inflection point D. The two inflection points corresponding to the valve opening and back seat, it is cold test valve open, back seat pressure technical basis. From the above analysis is not difficult to see that the key to safety valve on-line test technology is how to quickly and correctly find the corresponding open feature points. 4 System Configuration Online testing system consists of mechanical fixtures, hydraulic power unit and data acquisition and processing unit composed of three parts, relatively independent of each other by two 10-meter-long hydraulic hose and two 10-meter long five-core shielded cable interconnection Into a complete safety valve test system. It has small size, light weight, modular components, equipment, computerized, simple operation, stable and reliable, and other notable features, performance in many ways than the same level of foreign instruments. 4.1 Fixture: to ensure that the measured safety valve clamping position, for the hydraulic power unit to provide external force to the environment, the modular structure, demolition is very convenient. (See Figure 3) 4.2 Hydraulic power unit: Provides adjustable hydraulic output and flow, the maximum output 10MPa, the maximum lifting force of 50KN, used to control the additional lifting force and speed. 4.3 data processing unit: it is the heart of the test system, directly determine the reliability and accuracy of the system. Among them, the force sensor with spoke structure, high sensitivity, accuracy can reach 0.05%, the pressure sensor using high temperature sensor, the working temperature up to 200 ~ 250 degrees. Both sensors are high-output, built-in amplifier, its linearity, repeatability and anti-interference ability. The test system uses two channels of low gain and high precision amplification circuit, intelligent A / D conversion and data acquisition circuit, which can simultaneously collect two parameters of force and pressure. The core part selects the advanced notebook PC (CPU PⅢ600) currently on the market, Can draw curves and print the test results, with Chinese character of man-machine dialogue, the data of each measurement channel can be displayed on the screen, in the case of over-range, to ensure the safety of the system and safety valve, all the hardware modular structure , Easy to repair and debug. In addition, in order to ensure that the host can work normally and continuously under the high temperature environment of 50 ℃, specially designed ancillary equipment - computer low temperature workbench. Operation steps The operation steps are as follows: See Figure 4, select the tested safety valve, according to the system installation diagram can be easily completed NSH parts installation and connection; in the computer control window, click "load parameters" selected measured safety valve (See Figure 5) Select the pressure sensor measurement method, enter the basic pressure value; check the correct, click "re-line pressure", then the system prompts: "Testing! Please wait!" Open the hydraulic unit power switch to " Open "position, adjust the" system pressure adjustment "knob to the computer indicates the" required hydraulic pressure "value; the commutation control knob to the" lift "position, so that the cylinder piston valve rod driven by the valve to move up; After the valve is turned on, turn the reversing control knob back to the "reset" position to turn off the power; the computer will automatically enter the result display window (see Figure 6) to display the test curve and the test time , Open the pressure, adjust the height and other parameters; according to the computer prompted to adjust the height, adjust the pressure nut; click "Exit" button to restart Test procedures, draw new test curves and results. Repeat the above steps until the opening pressure and setting pressure difference is not greater than "measurement tolerance", then the computer displays "adjusted", said the end of the measurement. 5 Error Analysis According to the selection of MSC-5101 sampler, the accuracy of the sensor and amplifier design accuracy, test system to open the pressure measurement error analysis is as follows. Among them: f - Physical quantity (force, pressure) V1V2 - Intermediate electricity quantity N - Digital quantity (force, pressure) K1, K2, K3-- The conversion coefficient of all levels is:;;; So: According to the error transmission theory, the absolute error And relative errors are: Substitute Actual Deviation: (Force Sensor Maximum Error) Accuracy 0.05% (Pressure Sensor Maximum Error) Accuracy 0.2% (Amplifier Error) (A / D Converter Maximum Error) Thus, The relative error of the pressure is: According to the opening pressure formula: Where: P - opening pressure PL - system pressure A - valve sealing area f - additional external force which can be derived from the opening pressure of the relative error: From It can be seen that the relative error of cracking pressure is not only related to the additional force and system internal pressure but also to the sealing area. Generally speaking, the sealing area of ​​the safety valve is 20 ~ 125cm2. Through the calculation and analysis, we can draw: 6 Software Design Features and Features The test system uses a powerful notebook computer for For the data processor, after nearly six years before and after more than six thousand tests, modify, the system is equipped with a set of powerful software systems. Its main functions and features: 6.1 preset working parameters and instrument detection status, the entire pre-process are Chinese man-machine dialogue form, fast and convenient, and according to the working conditions of the valve under test to calculate the system should provide hydraulic Enhance the force to ensure the valve under test. 6.2 Data acquisition and digital filtering function, data acquisition software allows users to select different sampling times according to different valves and different working conditions to reduce the spurious signal interference and ensure the test curve smooth and intact. 6.3 draw the test curve, according to the test force, pressure in a variety of different colors to draw the curve of the entire test process. 6.4 According to the processing and result printing, according to the measured valve process parameters and working conditions, the corresponding calculation method is automatically selected to calculate the opening pressure, back seat pressure, open height measurement results, and can automatically make a variety of amendments. Such as: the pressure changes on the amendment, the amendment of the low-pressure state, the micro-valve correction. According to the opening height and internal pressure value of the back seat pressure correction, etc., the final form of Chinese characters print out the test results. 6.5 Valve setting pressure adjustment method Prompt software, you can prompt the user to adjust the unit increment first, and then according to the measured value changes by logic and linear processing to Chinese characters to indicate the user to adjust the fixed pressure nut quantitative, after adjustment measured again , The second approximation and after processing instructions to accurately adjust the value until the set pressure value is met. 7 Application: NSH safety valve on-line constant pressure meter since 1996 into the power system, has Qinshan Nuclear Power Co., Ltd., China Huadian Corporation Tieling Power Plant in Liaoning Province, North China Power Group Qinhuangdao Power Plant in Hebei Province, Henan Jiaozuo love by Swanfang Power Plant, Shanxi Yangquan Second Power Plant, China Datang Corporation Huainan Tianjia'an Power Plant, Huaneng Power International Corporation Dandong Power Plant, China Datang Corporation Hebei Zhangjiakou Power Plant, Huaneng Power International Corp. Dezhou Power Plant, China Power Investment Corporation Henan Yao Meng Power Plant, Meixian Power Plant in Guangdong Province, Heze Power Plant in Shandong Province, China Guodian Corporation Jianbi Power Plant in Jiangsu Province, China Huadian Corporation Hubei Qingshan Power Plant, Hubei Hanchuan Power Generation Guangzhou Zhujiang Power Plant in Guangzhou, Shenzhen Mawan Power Plant, Huaneng Power International Co., Ltd. Chongqing Luohuang Power Plant, Guangzhou Hengyun Power Plant in Guangdong, China Minhang Power Plant in China Power Investment Corporation, Guangdong Shaoguan Power Plant, Huaneng Power International Company Dalian Power Plant, Wuhan Huaneng Huazhong Yangluo Power Plant, Hubei Xiangfan Power Plant, Guangdong Yunfu Power Plant, Huaneng Power International Corporation Shidongkou Power Plant, Shanghai Nengtang Second Power Generation Co., Ltd., Jiangsu Nantong Tianshenggang Power Plant, Guangdong Zhanjiang Power Plant, Henan Jiaozuo Power Plant, Huaneng Daqing Xinhua Power Plant, China Datang Corporation Xinyang Huayu Power Plant in Henan Province, Shandong Jinan Suburb Thermal Power Plant, Huaneng Power International Corporation Fuzhou Power Plant, Henan Yu Gong Gongyi Power Plant, Henan Yichuan Yu Gang Power Plant, China Power Investment Group Jiangxi Guixi Thermal Power Plant, Hunan Huayin Zhuzhou Power Plant, Henan China Resources Dengfeng Power Plant, Guangdong Yuehua Power Generation Co., Ltd. (Huangpu Power Plant), China Guodian Corporation Jiangxi Jiujiang Power Plant, Jiangsu Taicang Environmental Power Plant, Jiangsu LiGang Power Plant , Shaanxi Baoji II Power Plant, Jiangsu Xiaogang Power Plant, China Guodian Corporation Guizhou Carey Power Plant, Yunnan Electric Power Research Institute, Beijing Guohua Power Co., Ltd. Beijing Sanhe Power Plant, Shaanxi Huadian Pucheng Power Plant, Huaneng Shandong Jining Power Plant, Huaneng Weihai Power plant, Shandong Power plants such as Canal Power Plant, Anhui Tongling Power Plant and Henan Shangqiu Yu Tung Power Plant have purchased on-line constant pressure gauges using NSH safety valves; Guangdong Daya Bay Nuclear Power Station, Xiamen Huaxia International Power Co., Ltd. Songyu Power Plant, Tianjin Dagang Power Plant, Shanshan Power Plant, State Power Changyuan Electric Power Co., Ltd. Ezhou Power Plant in Hubei Province, Shajiao A Power Plant in Guangdong YUDEAN Power Company, Shajiao Power Plant B in Guangdong Energy Company, Shajiao C Power Plant in Guangdong Yudean Company, Guangdong Daya Bay Nuclear Power Station, Yang Power Co., Ltd., Hunan Yiyang Power Plant, Jiangsu Wangting Power Plant, Henan Pushan Power Plant, Jiangxi Huaneng Jinggangshan Power Plant, Huaneng Shanghai Huaneng Shidongkou No.2 Plant, Shanghai Baoshan Iron & Steel Co. Ltd. Power Plant, Wuhan Iron and Steel Company Power Plant, Huadian Fujian Meizhouwan Power Plant, Guizhou Xiushui Power Plant, Niagong Guizhou Power Plant, Anhui Tongling Power Plant, Henan Duhekou Power Plant, Datang Henan Yuzhou Longgang Power Plant, Shaanxi Weihe Power Plant, Jiangsu Huaneng Taicang Power Plant, Guangdong Yudean Zhuhai Power Plant , Jiangsu Changshu Power Plant, Fujian Houshi Power Plant, Anhui Wuhu Power , Shanxi International Yangcheng Power Plant, China Aluminum Co., Ltd. Zhongzhou Branch Thermal Power Plant, Henan Jiaozuo China Resources Thermal Power Co., Ltd. and more than a dozen other thermal power plants or nuclear power plants put into use, involving generating units 100 MW ~ 1000MW, covering the current Power station boilers all safety valves, such as the United States DRESSER, CROSBY, Japan East Asia, Japan Okano production of full-scale safety valves and other valve manufacturers at home and abroad. Proved by practice, this instrument has outstanding advantages in terms of design principle, instrument structure, measurement accuracy, safety and convenience of use. In summary, "NSH safety valve on-line constant pressure instrument in the design principles, measurement accuracy, degree of automation and methods of operation in the world's leading level, especially the instrument using computer systems and Chinese characterization of the test software more similar Instrument of the first. " (2001 "China Power" magazine No. 5 "power plant boiler safety valve calibration of new technologies"). 8 Conclusion In summary, "NSH safety valve on-line constant pressure meter in the design principles, measurement accuracy, degree of automation and methods of operation in the world's leading level, in particular, the instrument using computer systems and Chinese character test software more domestic Foreign similar instrument's first. "
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