Detailed explanation of the importance of the type

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Detailed explanation of the importance of regulating valve selection

Abstract: this lecture analyzes the importance of regulating valve selection with a large number of practical application examples. The author believes that the quality of the regulating valve, as the actuator in the automatic control system, is closely related to the Design Institute, manufacturer and users. Quality is not only the problem of the manufacturer, but also the problem of system designers, manufacturers and users. It is a broad concept. Therefore, improving the application quality of regulating valve should be considered from the whole process, especially the selection quality. In order to improve the quality of regulating valve selection, we must improve the knowledge and application level of regulating valve practitioners, which is also the purpose of this lecture

the regulating valve is the actuator in the automatic control system, Its application quality is reflected in the regulation quality in the system. He said: "we need those highly specialized materials to keep pace with our progress. The application quality of the regulation valve is related to three aspects:

(1) correct selection (including calculation) - system designer;

(2) product quality - manufacturer;

(3) Correct installation, use and maintenance - users

therefore, we say that quality is not only a problem of the manufacturer, it is a broad concept, including system designers, manufacturers and users. The following is a list of common application problems. If these problems can be handled well, it can be said that you will not have major quality accidents when selecting valves

The error value usually follows a constant law and has the highest value

(1) caliber calculation - it cannot meet Qmax when it is small, it works when it is large and the opening is small, the adjustment performance is poor, and the service life is short

(2) check the △ P when it is closed -- some are not checked at all, resulting in the valve can not be closed and opened

(3) check that the adjustable ratio R - R is too small to meet the flow change range

(4) determine the spring range - involving spring range, starting working pressure, output force, stability, adjustment, etc

(5) material and structure - here is the most learned. An excellent engineering designer should choose the valve structure and material on the premise of meeting the use function, and get a simple structure and the lowest price (relatively speaking). On the contrary, it is still not good to spend a lot of money, even to introduce products. This kind of cost can be 20 ~ 30 times worse. The impact of poor use is even greater, with start-up and stop-up, resulting in economic losses and production decline, and some even cannot be put into use. Therefore, an experienced system designer knows the importance of valves on site, pays attention to the correct selection of valves from the beginning, and works closely with us

(6) Annex - guarantee to the subject and intentional compensation as long as performance 228

there are also many successful examples, and success first lies in their correct selection. These examples are the author's personal experience:

(1) the selected hydrochloric acid resistant regulating valve of the eighth Chemical Research Institute has been used for more than two years due to the appropriate valve type and material

(2) the sixth Chemical Research Institute and Shashi pesticide factory - fine chemical engineering, a strong corrosive medium mixed with a variety of substances, the valve has been in normal operation since 1993

(3) the fourth Institute of chemical engineering selects the special valve for caustic soda, which overcomes the problems of high temperature concentrated alkali corrosion and blockage in the caustic soda evaporation system

(4) in the past, rubber lined butterfly valves or diaphragm valves were used in the water treatment (desalted water) system of the eighth Institute of chemical industry and Inner Mongolia Jilantai chemical project, regardless of domestic and foreign devices, and the valves have not been used well. After the factory changed the diaphragm valve into a water treatment valve specially designed by us, the valve has been in operation for more than two years. Similar to Yunnan nitrogen fertilizer plant

(5) Nuclear Power Design Institute - high temperature and high pressure, 0.2 second emergency action valve is selected to ensure the operation of the test device

(6) Chengdu Chemical Plant - wet chlorine regulation, originally an American valve, has been localized after selecting a special valve for chlorine

(7) the special valve for ammonium phosphate was selected for Shifang chemical plant - 346 project, which was normal after more than two years of operation

(8) Hongguang Chemical Plant - 98% concentrated nitric acid, using all tetrafluoro corrosion-resistant valve, has been operating normally since 1992

(9) Yunnan nitrogen fertilizer plant - phosphoric acid and mixed media, choose corrosion-resistant ball valve to replace the products prepared for import in advance. The products have operated normally since 1992, and more than 100000 US dollars have been saved

(10) WISCO selects micro pressure self operated valve for technical transformation, which solves the problem of ultra-low pressure stability of furnace 50mmhz in terms of tax burden

the problems involved and successful examples are aimed at proving the importance of model selection and the value of technical treatment, so as to attract enough attention to the model selection of regulating valve

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