Key words: pneumatic valve diagnostic device; heavy water reactor nuclear power plant; Application 1 Overview Nuclear power plants have a large number of pneumatic valves, these pneumatic valves as the flow control of the final equipment in the operation of nuclear power plant plays a very important control, regulation, valve performance The quality is directly related to the safe and economic operation of nuclear power plants, especially if the pneumatic valve on the first nuclear island of the nuclear island fails, it may cause serious economic losses and nuclear accidents. The right maintenance strategy, effective maintenance methods can improve the safety performance of the valve, the early concept of valve maintenance is to allow the valve as long as possible work, once found fault, immediately repair the valve to restore the original state, which needs to be demolished and Opened the valve, repair or replacement of worn or damaged parts, this passive maintenance is due to the lack of diagnostic technology caused not only a waste of time, but also result in the cost of waste.
Pneumatic valve calibration routine means that the standard current signal source, standard pressure gauge, dial indicator and other basic measuring instruments to measure valve stroke, cylinder pressure and electrical converter output, due to the accuracy of the measuring instruments used, according to the measurement data It is difficult to achieve accurate calibration, and conventional measures can not measure the valve stem during the action torque, friction and valve opening and closing time and other important parameters, it can not be on the valve performance and dynamic response characteristics of the analysis , The valve is not clear the specific problems exist, overhaul can not be targeted; put into operation during the normal operation of the valve can run heartless bottom; also in the unit overhaul when a large number of pneumatic valve needs maintenance, repair costs and maintenance personnel a higher dose . Based on this, the Qinshan Third Nuclear Power Plant introduced a pneumatic valve diagnostic technology.
2 pneumatic valve diagnostic device features pneumatic valve diagnostic device is the United States CRANE NUCLEAR produced specifically for the pneumatic valve calibration and testing of portable data acquisition system is mainly used to measure the pneumatic valve pneumatic and mechanical parts of the various parameters, And analyze the collected data to find out the cause of the valve failure, the right medicine, guiding maintenance activities, pneumatic valve overhaul more targeted, cost savings, improve efficiency, and maintenance technicians on the health of the valve in the Chest, the valve repair activities have data available, but also according to the valve data to develop a reliable preventive maintenance program pneumatic valve.
Pneumatic valve diagnostic device consists of sensors, multi-channel signal acquisition module and a portable computer composed of three parts.
The Signature Software for Pneumatic Valve Diagnostics is based on the Microsoft Windows platform and provides an easy-to-use, human-machine interface. Maintenance personnel can according to different measurement needs, choose different sensors and signal acquisition module, the measurement data into electrical signals, and then data lines into the portable computer Signature Software software, through the analysis of these signals and processing, and ultimately Pneumatic valve to get the performance of the data and curve, shown in Figure 2.
3 valve diagnostic device in the actuator diaphragm replacement work Qinshan Third Nuclear Power Plant main heat transfer system uses an important regulator are the United States DRESSER nuclear first-class valves, the model nuclear-level valve actuator ( 110 kg), diaphragm size (160in2), the actuator diaphragm replacement for the instrument control staff is a very difficult task. Diaphragm replacement is good or bad, is directly related to whether the unit can operate normally. According to CANDU owners Federation statistics, other similar types of power plants have occurred after the replacement of the diaphragm assembly is not in place caused the shutdown event. Therefore, in addition to operating staff in strict accordance with the rules of the diaphragm replacement operation, the most important is the use of pneumatic valve diagnostic device on the valve data collection and comparison, according to changes in parameters to determine the success of the diaphragm replacement. In the overhaul of 205 Qinshan No. 3 nuclear power plant, according to the requirements of the preventive program, the actuator diaphragm of 2-63341-HCV22 needs to be replaced. In the maintenance before the pneumatic valve diagnostic device for the original data acquisition valve, the replacement of the actuator diaphragm and valve accessories, the valve re-data acquisition, the main data in Table 1 can be seen in contrast, 2-63341-HCV22 trip A slight decrease from 0.844 inch before replacement, all meeting the 0.8 + 0.125 inch requirement. Actuator spring rate also did not change much, but the output voltage range of the converter is not correct, only 1.1 ~ 11.9 psi, check the electrical converter monomer calibration data to confirm the value measured by the instrument is not on the line suspected Leaky place, check the connecting lines of the electrical converter and the locator with the leak detection liquid, and find that there is a clear leakage phenomenon at the connecting connector with the locator, re-measure the tightening of the connector, Output restored to 2.9 ~ 14.4psi, to meet the requirements. Thus determine the valve diaphragm replacement work is completed, the diaphragm replacement success, the data shown in Table 1.
From the overhaul of Qinshan Third NPP 103, Pneumatic valve diagnostic equipment was used to evaluate the replacement of diaphragms in the diaphragm replacement work of important valves in the main heat transfer system of the heavy water reactor nuclear power plant. So far, two Qinshan Third Nuclear Power Plant The unit has replaced the 34 valve diaphragm, diaphragm replacement success rate of 100%.
4 Pneumatic valve diagnostic device in the valve disassembly work 63332-PCV5 / 6 pressure regulator system is the pressure control valve , under normal circumstances, the valve is fully closed when the regulator pressure rises to Take-off value (9.931MPa), the valve began to slowly open the pressure relief, because the medium is a mixture of steam and water, and the valve pressure before and after large, each overhaul cycle, there will be different degrees of valve cavitation, overhaul must be replaced spool and The valve seat and the pneumatic valve diagnostic device play an important role in the mechanical disassembly of the valve. By using the pneumatic valve diagnostic device to collect the valve data, it is possible to timely find out whether the valve back-up is in place or whether the valve closing force is sufficient , Easy to promptly notify the mechanical staff need to be repaired.
During the overhaul of the Qinshan No. 3 NPP, the mechanics completed the disassembly and inspection of 1-63332-PCV5. We tested the valve with the pneumatic valve diagnostic device and found that the values of "BENCHSET MIN" and "BENCHSET MAX" of the valve were too large. " BENCHSET MIN "reached 34.6 psig and" BENCHSET MAX "reached 50.8 psig. If these two values are too large, then the valve start value will be too large, the valve moves slowly, and most likely the valve will not be fully open. The final release of the 1-63332-PCV5, the valve's "BENCHSET MIN" and "BENCHSET MAX" values were reduced to 29.6 psig by unmanaging the valve stem block, shortening the stem length adjustment block, and reconnecting , And 45.0 psig, to meet the valve action requirements. Check the data curve through the valve action shown in Figure 3, the valve stem from the stress curve shows that the valve in the closed position, the valve stem and the actuator spring is squeezed, the valve stem In an outwardly swollen condition, the valve stem begins to deform as soon as the actuator begins air intake and overcomes the spring preload, which is shown in the figure as the curve falls rapidly. In the valve opening process, the valve stem stress no significant change, shown as a straight line. Judging from this, the valve can be closed in place.
5 Conclusion Pneumatic valve diagnostic technology not only greatly improve the quality of maintenance, improve the accuracy of the valve calibration, but also to determine the valve failure provides an important means of detection, pneumatic valve diagnostic device through the use of greatly shortened the valve Maintenance period, reducing the radiation dose of personnel. After years of use, the device is widely used in the main heat transfer system, moderator system, liquid poison injection system and liquid area control system of Qinshan No.3 nuclear power plant as an important maintenance equipment, and has set up a set of pneumatic valves More complete valve database. For the stable operation of the unit provides a strong guarantee.
References [1] Lu Peiwen practical valve design manual [M] Beijing: Mechanical Industry Press, 2002.
[2] AOV Data Acquisition and Basic Analysis [Z]. CRANE NUCLEAR, INC, 2001.
[3] DRESSER MAUNUAL IOM-108253 (98-30835-9024-1-MM-A) [Z].
[4] Liquid Injection Shutdown System Design Manual (98-34700-DM-000).
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