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Key words: nuclear power project; valve; manufacturing; quality control CLC number: TM623 Document code: A Article ID:1004-7344(2018)18-0067-02
Introduction With the rapid development of China's economy, the energy gap is becoming more and more serious. Nuclear power has become an important means and an inevitable choice for the adjustment of power energy structure. Whether a nuclear power plant can operate safely is directly affected by the operational stability of each component. However, nuclear power equipment generally has the characteristics of complex structure, difficult manufacturing, and high technical requirements. Therefore, it is the key and difficult point in the manufacturing process to do a good job in quality supervision and control of nuclear power equipment. Nuclear power plant valves have the important function of changing the flow direction of the medium, cutting off or turning on the flow of the medium in the pipeline, and also regulating the flow and pressure of the medium to ensure that the equipment and pipelines operate under normal conditions. Manufacturers often have insufficient understanding of the importance of quality control in the valve manufacturing process, and the measures are not strict enough, causing many quality problems. Therefore, the relevant manufacturing enterprises must effectively control and improve the manufacturing quality of the valves, thus ensuring the safe operation of the power station equipment.
1 Introduction to Nuclear Power Project Valves 1.1 Basic Structure Valves are the basic guarantee for reliable operation of nuclear power plants. The main components include valve body, valve cover, valve shaft, valve seat, valve disc, drive structure, mating flange, packing, gasket, and fastening. Parts, etc., depending on the type of valve, the number of parts is not the same. The specific function of the nuclear power plant valve is to control the flow of fluid (liquid, gas, suspension) in the pipeline or other container during the operation of the equipment, mainly through the opening and closing member to open or close or partially block the opening in the passage, and connect the numerous nuclear power plants. The system has functions such as cut-off, regulation, diversion, anti-backflow, voltage regulation, shunt or overflow relief.
1.2 Valve classification valves are distributed in various systems and rooms of nuclear power plants, with many types and large numbers. The valve grade is divided into nuclear 1/2/3/NC grade, which can be divided into stop valve, gate valve, safety valve, regulating valve, pressure reducing valve, butterfly valve, ball valve, diaphragm valve, etc. according to the type; For electric, pneumatic, manual; by caliber, from DN8-DN3600 are different. Some valves work automatically, for example check valves or check valves are automatic and only allow fluid to flow in one direction. The safety valve is opened at a predetermined pressure, and the opening and closing member is pressed against the valve seat by a gravity lever or a spring spring having a sufficiently strong spring force to close the valve until the pressure reaches a certain pressure. The working environment of nuclear power plant equipment gates is relatively sinister, and the safety standards for temperature are also very high when transmitting media. The so-called "medium" here refers to a variety of fluid media, so as to improve the environment of nuclear power plant equipment gates. adaptability.
2 Quality control measures in the valve manufacturing process of nuclear power projects 2.1 Strengthening raw material quality control Nuclear power projects In the valve manufacturing process, it is necessary to strengthen the control and inspection of raw materials procurement, and do product quality control from the source. The supervisory personnel should carefully review the quality and specifications of the manufactured materials, confirm whether the test results are consistent with the technical terms and agreements of the equipment procurement contract, and strictly review the supplier's qualification certificate to ensure the standardization and validity of the raw material quality certification documents. . Review the material grades and specifications used for the valve to ensure that all raw materials used meet the requirements of the contract or technical agreement. On-site equipment supervision shall check the appearance quality of the valve components through visual inspection during the inspection, the overall appearance quality is better, and the appearance quality is unqualified, and timely rectification shall be carried out. The testing of materials should pay attention to chemical composition retest, room temperature stretching, room temperature impact, high temperature stretching, grain size, corrosion resistance test, etc. In the raw material test, if the tensile and impact are not qualified once, the double sample can be further tested. If the double sample is qualified, it can be judged as qualified; if the grain size and intergranular corrosion test are not acceptable, the double sample test is not allowed.
2.2 Strict control of process heat treatment process is an important process to improve valve manufacturing quality and improve material performance. The main problems are: heat treatment process fails to meet the corresponding standards and requirements; parameter control does not comply with relevant regulations; The workpiece is heat treated. Effective ways to solve these problems need to start with the process documentation, control the process documentation, review and approval, and ensure the quality of valve manufacturing.
Welding is also an indispensable process in the manufacture of valves, which directly affects the sealing performance of the valve! . Before the welding, the supervisors need to check whether the welding salary range covers the used process, check whether the welding process has passed the process evaluation, check whether the specific requirements of the welding procedure are implemented, and pay attention to the welding consumables, preheating temperature, interlayer temperature, Welding current, welding speed, post-weld heat treatment, etc. The most probable problem is that the welder is easy to weld and increase the welding current. The high current easily leads to burn through and undercut, which will lead to more burning of alloying elements, and the overheating of the joint will affect the mechanical properties of the joint heat affected zone. In the supervision, we need to pay attention to and eliminate it. Before welding, the qualifications of personnel, the welding process, welding consumables, etc. should be strictly checked. It should be noted that suitable interlayer temperature and welding consumables should be used for different welding layers.
2.3 Do a good job of leak test and hydrostatic test The water pressure test is the most intuitive means to judge whether the function is satisfied after the valve is manufactured. The hydraulic test generally includes shell pressure test, valve strength test, inverted seal test, seat seal test, packing seal test, and action test. When supervising, it is necessary to pay attention to whether the test water quality requirements are met; the tightening torque of the fasteners must meet the technical requirements; when the shell strength test is carried out, the inverted seals must not be in contact, and the packings are allowed to leak, but if the filler leaks, the pressure will be maintained. To reduce and affect the leakage judgment, it is necessary to minimize the leakage at the packing or make timely pressure compensation. If necessary, use the process packing; when leaking the test, pay attention to the use of effective collection and metering leakage methods to accurately measure the leakage amount to ensure that the sealing requirements of the valve are met.
When conducting leak inspection work, the staff needs to use a variety of advanced technologies to timely check whether helium, Freon and other gases are leaking. Sensitive detection of cracks in the gates of nuclear power plant equipment, doing on-site recording work, and setting new standards in combination with test results. And to ensure that the nuclear power plant equipment gate manufacturing can reach the standard. During the hydrostatic test, the staff should verify the hydrostatic test results in accordance with the latest technical agreements, test procedures and codes of practice; strictly review the qualification of the water supply room; before the test, the water pressure gauge and all instruments should be strictly tested; Record the results of each test step in time, supervise and inspect the project, record the withstand voltage time, strictly check the number and quality of the bolt fittings of the nuclear power plant equipment gates, and strengthen the review of the hydrostatic test report.
2.4 Conducting prevention and experience feedback In the process of nuclear power equipment manufacturing, prevention and experience feedback can be used for quality control. Prevention and feedback are an important way of quality control, and there is a lot of room for improvement. Actively carry out prevention and experience feedback, learn from the production experience and quality management experience of the previous projects, effectively realize problems in advance, deal with problems in advance, improve efficiency, save costs, and ensure progress on the manufacturing progress and quality of the entire equipment. Etc. From the perspective of quality control, quality supervision should not only focus on discovering and dealing with problems, but also focus on the future. Positive preventive measures and good experience feedback can save a lot of time and cost and avoid quality problems or Repeatedly.
2.5 Quality control of the packaging delivery phase Packaging shipment is the last control process before the valve leaves the factory. Valves are batch equipment, not shipped one by one, but in batches, ranging from a dozen or more, to seven or eight hundred, and also shipped fasteners, spare parts, special tools, etc., therefore, compare It is easy to be affected by external factors and cause quality problems. For example, the valve is not securely fixed in the box, the valve is scratched and scratched; the number of fasteners is wrong; the small parts of the individual package are missing the mark; the format of the box is inconsistent with the program; the box list does not match the actual object. Therefore, check carefully before shipment, such as bill of lading, quantity, identification, etc. The supervisory engineer should have sufficient patience and strong sense of responsibility to ensure that the equipment is last closed before leaving the factory.
3 Conclusion In summary, under the situation of achieving low carbon, environmental protection, green and sustainable development and actively developing clean and efficient energy such as nuclear power, nuclear power plant valve manufacturers are usually at full load or overload, so the quality control of nuclear power valves is controlled. Play a vital role. Valve equipment manufacturers and purchasers should strengthen their understanding of the importance of quality control, and take measures to strengthen the quality control of nuclear power valve manufacturing from the aspects of technology, talents, policies, software, hardware and management, to avoid causing valve quality problems, and to be nuclear power. The equipment provides high quality, safe and reliable valves.
References [1] Zhang Yong, Jiang Zhiyuan. Analysis on Quality Control of Nuclear Power Valve Manufacturing[J]. Equipment Supervision, 2014(02): 57~60.
[2] Zhang Yifang, Zhang Qingshuang, Wang Jianxin. Preliminary study on valve green manufacturing technology [J]. Valve, 2013 (05): 20 ~ 22.
[3] Guo Depeng, Cai Hongwei, Yan Xiaohong, Li Maolin, Li Zen. Analysis and countermeasures of main problems in valve manufacturing of nuclear power projects[J]. Nuclear Standards Measurement & Quality, 2013(02): 48~52.
Received date: 2018-5-17
It is one of the low-value consumables with high usage rate. It is generally installed on a dry foam rack with the package or in bulk. When used, it is taken out by the operator and placed on the plastic centrifuge tube rack in the ultra-clean workbench. The common centrifuge tube rack can only make the centrifuge tube stand upright. When transferring liquid or needing centrifugation, the operator should hold the centrifuge tube in the left and the night gun or aspirator in the right. If it is necessary to transfer a large amount of liquid reagents or perform gradient centrifugation operations, such as density gradient centrifugation to separate mononuclear cells, the operator needs to hold the centrifuge tube with the right hand for a long time and tilt the centrifuge tube, which often causes the operator's wrist joint pain. At the same time, it will also affect the liquid superposition effect, which will easily lead to the mixing of liquids of different densities, resulting in the failure of the experiment.
Quality control in the manufacture of valves for nuclear power projects
Abstract: Valves are a very important basic component in nuclear power projects. They are very diverse and different valves have different structural forms, which puts high demands on manufacturing quality. The quality control of the power plant valve manufacturing process is a systematic project. The quality of the control valve manufacturing must be highly concerned and considered by the owners and the relevant personnel of the manufacturing plant to ensure the safe operation of the power station equipment. This paper makes a simple analysis of the structure and type of nuclear power project valves, and discusses the quality control strategy in the valve manufacturing process of nuclear power projects.