ã€Abstract】 The working principle and performance test of the inlet valve of M310 steam turbine in a nuclear power plant in China are introduced. Combined with the main failure modes of steam turbine inlet valve, the improvement scheme of the on-line performance test of steam turbine inlet valve is proposed. The diagnostic technology is applied to the fault diagnosis, analysis, accident prevention, performance re-qualification and preventive maintenance activities of steam turbine inlet valves, and promotes the optimization of the preventive maintenance strategy of steam turbine inlet valves to improve the safe operation reliability of nuclear power plant steam turbine generator sets.
Key words: steam turbine; main steam valve; preventive maintenance CLC number: TK264.9 Document code: A Article ID: 2095-2457(2018)14-0049-002
DOI: 10.19694/j.cnki.issn2095-2457.2018.14.021
Diagnosis practice and improvement of the performance of nuclear steam turbine valve
WU Song-lin CHEN Zhan-yang
(Fuqing Nuclear Power Plant, Fuqing Fujian 350318, China)
Abstract paper introduces the working principle and performance test status of the steam inlet valve of M310 steam turbine in a nuclear power station in our country. Combined with the main fault mode of the steam turbine inlet valve, an improved scheme for the on -line performance testing of the current steam turbine inlet valve is put forward, and the advanced valve diagnosis technology is applied to the steam turbine inlet valve. In order to improve the safety operation reliability of steam turbine generator set in nuclear power plant, the preventive Maintenance strategy of steam turbine inlet valve is promoted in the activities of obstacle diagnosis, analysis, accident prevention, performance re identification and preventive maintenance.
[Key words] Steam turbine; Main steam valve; Preventive maintenance
0 Introduction During the operation of the steam turbine, the steam turbine regulating system controls the dynamic indexes such as the rotational speed, power, frequency and pressure of the steam turbine generator set by adjusting the opening degree of the steam inlet valve of the steam turbine, and the speed limit and speed acceleration of the unit are exceeded. Limitations such as overrun, load change rate, and steam demand. Turbine inlet valve is the actuator for steam turbine control and regulation. Its working performance must be reliable enough to ensure safe, reliable and reliable operation of the generator set. Therefore, the performance test and identification of steam turbine inlet valve is particularly important. There are many types of failures of steam turbine inlet valves. The discovery, diagnosis, resolution and prevention of faults often require a lot of research work. In the course of practice, various aspects of experience are summarized, and some improvements are made to improve steam turbine intake. The reliability of the valve work.
1 Introduction to the working principle of the main steam valve of the steam turbine In the control of the steam turbine regulating system, the steam turbine load control logic calculates the valve opening command through the target load. The control system outputs the valve opening command current signal to the servo amplifier card through the analog output card. The amplifier is operated on the proportional valve pilot valve according to the main steam valve opening command received from the upstream and the received feedback signal from the main valve position, the proportional valve pilot position feedback signal, and the proportional valve main valve position feedback signal. The opening command signal, the position feedback of the proportional directional valve main valve determines the oil inlet of the main regulating valve, thereby controlling the opening degree of the steam turbine valve. Therefore, the proportional valve used for the main control valve control of the steam turbine is a two-pole amplified proportional valve. The primary valve is a pilot solenoid valve and the secondary valve is a spool valve system. The primary valve is a proportional valve. The main components are proportional electromagnets and spool valves. The electrical signals are converted into linear reciprocating motions of the spool valves by proportional electromagnets, which convert electrical signals into hydraulic signals. The secondary is the main spool valve system. The hydraulic signals outputted by the spools A and B respectively control the control oil pressure at both ends of the main spool valve, thereby controlling the position of the main spool, thereby controlling the oil pressure of the main spools A and B. Both the main spool and the pilot valve have an electrical feedback sensor that converts the position signal of the spool into a 4-20 mA current signal.
2 Turbine inlet valve performance test practice and thinking In the initial stage of commissioning, the steam turbine inlet valve performance test uses a set of on-site offline valve commissioning and installation tool device developed by the valve manufacturer, which needs to be the servo amplifier card in the control system. The parts are removed and installed on the test device. The signal cables of the main valve of the steam turbine are connected and the valve signal interface is connected to the test device through a dedicated cable to debug the performance and control of the valve at the valve installation site. The test device is only suitable for the initial installation and commissioning of the valve. It has a single function and only supplies power to the sensor on the valve body, provides a mounting carrier for the valve servo amplifier, provides an interface for each signal cable, etc. There are many working conditions, low work efficiency, low convenience, and additional signal generation and acquisition equipment. Another feature of the test device is that it can only perform off-line performance testing of the valve. It is not feasible to use the device after the unit is operated.
During the operation of the steam turbine, since the steam inlet valve of the steam turbine has been in working state, it is impossible to conduct long-term offline action test on the valve. The valve action will have a direct impact on the output power of the steam turbine generator, and the process has high risk characteristics. . The operational reliability of the steam turbine inlet valve needs to be fully tested and verified. The above test device cannot meet the requirements of the actual valve performance test. For this purpose, the performance of the valve needs to be tested online. For this purpose, a set of online action test logic is designed for the turbine governing system. According to the test logic, the control of the steam turbine regulating valve is switched to the test state by the automatic control logic test program. The opening command of the valve is issued by the test program, and the steam turbine regulating valve in the test state is slowly opened according to the test logic instruction, and then the corresponding switch is fully closed. The steam inlet steam valve of the steam inlet circuit makes the turbine inlet steam regulating valve of other working states slowly open to maintain the total steam inlet steam stability, so as to avoid excessive power disturbance. Through the sequential control command valve can normally switch and operate in the expected time, the valve feedback can complete the test, and the control logic automatically generates the test qualified signal feedback. The main feature of the valve performance test method is that it can perform online performance test. It has the characteristics of fast and convenient, high degree of automation, but there is a high risk, which will affect the power of the steam turbine unit, cause power fluctuations, and will also operate the unit safely. Have a certain adverse effect. In addition, the test data obtained by this method only includes the valve position action curve, which can only reflect whether the valve's active performance is normal, and can not meet the data requirements for abnormal cause analysis under the test failure condition, and even if the valve is abnormal, it is often at a loss. The valve performance test method of the above system under the online condition can not meet the requirements of the performance test and abnormal cause diagnosis of the steam turbine inlet valve. For this reason, a steam turbine regulation system under the power operation condition of the unit is proposed. The inlet steam regulating valve performance test method is supplemented to meet the performance test of the turbine inlet steam regulating valve under the development trend of the nuclear power unit long maintenance cycle. The following is an overview of the situation of this method:
By collecting the main valve position feedback signal of the steam turbine inlet valve, the proportional pilot valve position feedback signal, the proportional valve control command signal, the oil pressure pressure signal by accessing the signal acquisition device in the steam turbine regulating system, The input command in the engineer station of the steam turbine control system slowly reduces the opening degree of the regulating valve to the fully closed position, and then sets the main steam valve of the corresponding loop to the fully closed state. In this way, the steam turbine regulating valve is placed in a safe state that can operate without affecting the power of the steam turbine, and the dynamic action data of the valve is obtained by outputting different valve action commands, thereby providing sufficient basis for fault diagnosis. This method has successfully completed the analysis of the causes of multiple valve action anomalies, resulting in a good practical application effect.
In the above-mentioned steam turbine inlet valve performance test activities, in the face of the type of steam turbine valve failure, the flashing abnormal action type fault is often more difficult to locate the fault cause, after the abnormal action caused by the non-upstream control command of the valve It is necessary to install a temporary data acquisition device. The retention time of the connection between the acquisition device and the turbine control system often needs to wait for the fault to flash again before it can be removed. The fault cannot be eliminated in time, leaving a hidden danger for the safe, economic and stable operation of the unit.
3 Turbine inlet valve performance test improvement direction research After the previous section on the steam turbine inlet valve performance test practice and thinking, we can easily conclude that the current steam turbine inlet valve performance test work has many shortcomings:
(1) Off-line performance test of steam turbine inlet valve can not meet the requirements of nuclear power plant reliability test of valve performance, especially now that nuclear power plant is facing the development of long maintenance cycle, it is only suitable for installation and debugging of equipment, and work efficiency is better. Low, single function.
(2) The data obtained by the performance test of the steam inlet valve of the steam turbine under load is too small, which is insufficient to meet the data requirements for abnormal diagnosis and cause analysis of the valve.
(3) The data collected by the technical personnel intervention control system adopted in the current practice has the problems of large amount of repeated labor, low data accuracy, difficult data analysis application, low data collection frequency, low automation, and untimely data acquisition.
Combined with the practice and thinking of the performance test of the turbine inlet valve in Section 2, we can improve the integration of various performance test methods in a series of improvements, and improve the automation performance test of the steam turbine inlet valve of the power station. The main valve position feedback signal of the steam valve, the proportional pilot valve position feedback signal, the proportional main valve position feedback signal, the proportional valve control command signal, and the oil pressure signal are collected in real time, and connected to the real-time monitoring system of the power station for monitoring. The turbine control system itself tests the performance of the steam turbine inlet valve, eliminating the need for a large amount of data acquisition by manual valve performance testing, and also providing sufficient analytical data for abnormal conditions in the valve operating state.
4 Turbine inlet valve common action abnormal cause identification The following table is based on the nuclear power plant steam inlet valve maintenance history data summary of the common valve action abnormality analysis and troubleshooting methods. The analysis is based on the main control valve control command, valve position feedback, control oil pressure, and control oil pressure. Therefore, the control command, valve position feedback, control oil pressure, and control oil pressure characteristic curve are mastered. The specific reason for abnormal valve action can be quickly determined by feature extraction of data from previous failures.
5 Development and Prospect of Steam Turbine Inlet Valve Performance Test The current valve diagnostic technology has been developed for many years in the operation and maintenance of intelligent pneumatic valves. The application has been extensive, but due to the special characteristics of each valve manufacturer and the special working principle of steam turbine inlet valves. Sex, the valve diagnostic technology applied to the steam inlet valve of the turbine is less research equipment and software.
Further research and improvement is to apply advanced valve diagnostic technology to the fault diagnosis and preventive maintenance activities of steam turbine inlet valves. The valve diagnosis technology can accurately find the cause of the fault without disassembling the valve, thus reducing the turbine. The maintenance cost of the preventive maintenance of the inlet valve is high, the maintenance period is long, the spare parts replacement is large, the frequency of preventive maintenance is small, the abnormal diagnosis is completely dependent on personal experience, the valve abnormality cannot be found in time, etc., and the turbine operation of the nuclear power unit is improved. Reliability.
ã€references】
[1] Wang Shuhong. Application of valve diagnostic technology and prospects for localization of diagnostic equipment [D]. Huadian Technology, 2015.
[2]Ban Zhiwei. Probe and maintenance strategy for DEH system fault of 600MW unit[D].North China Electric Power Technology,2009.
[3] Sun Weidong. Test method for automatic valve activity of 600MW steam turbine [D]. North China Electric Power Technology, 2010.
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