Matters needing attention in the selection of Shanghai regulating valve

by:Lianke Valve     2022-08-01
Selection of valve type of pneumatic control valve/electric control valve: (1) To determine the nominal pressure, not to use Pmax to cover PN, but to find the corresponding PN from the table according to the three conditions of temperature, pressure and material and satisfy the selected The PN value of the valve. (2) The determined valve type, its leakage meets the process requirements. (3) The working pressure difference of the determined valve type should be less than the allowable pressure difference of the valve. If not, it must be considered from a special angle or another valve should be selected. (4) The temperature of the medium is within the working temperature range of the valve, and the ambient temperature meets the requirements. (5) Consider the anti-blocking problem of the valve according to the unclean condition of the medium. (6) Consider the corrosion resistance of the valve according to the chemical properties of the medium. (7) Consider the erosion and wear resistance of the valve according to the pressure difference and the medium containing hard objects. (8) The performance and price ratio considering the comprehensive economic effect. (9) Optimal order. Butterfly valve-single-seat control valve-double-seat control valve-sleeve control valve-angle valve-three-way control valve-ball valve-eccentric rotary valve-diaphragm control valve. The choice of regulating valve actuator: (1) The simplest is the pneumatic film type, followed by the piston type, and finally the electric type. (2) The main advantage of the electric actuator is that the driving source (power supply) is convenient, but the price is high, the reliability, waterproof and explosion-proof are not as good as the pneumatic actuator, so the pneumatic type should be preferred. (3) The old electric actuators are heavy and heavy, and we have already provided electronic, small and highly reliable electric actuators (the price is correspondingly high). (4) The old ZMA and ZMB thin-film actuators can be eliminated and replaced by multi-spring light actuators (the performance is improved, and the weight and height are reduced by about 30%). (5) There are many varieties and specifications of piston actuators, and the old, big and stupid ones are no longer recommended, but a new light structure is selected. Selection of control valve materials: (1) The pressure resistance level, operating temperature and corrosion resistance of the valve body should not be lower than the requirements of the process connection pipeline, and the manufacturer's stereotyped products should be preferred. (2) Cast iron valves are not suitable for water vapor or wet gas with more water and flammable and explosive media. (3) When the ambient temperature is lower than -20°C (especially in the north), cast iron valves should not be used. (4) In the Cartesian coordinates formed by the medium temperature and pressure difference with serious cavitation and erosion, when the temperature is 300°C and the pressure difference is 1.5MPa in the area beyond the line connecting the two points, the throttling sealing surface should be Choose wear-resistant materials, such as cobalt-based alloys or surface surfacing Stellite alloys. (5) For strong corrosive media, the selection of corrosion-resistant alloys must be based on the type, concentration, temperature and pressure of the medium, and appropriate corrosion-resistant materials must be selected. (6) The valve body and the throttling part are treated separately. The throttling speed of the valve body wall is small and a certain degree of corrosion is allowed. The corrosion rate can be about 1mm/year; the throttling part is eroded by high speed and corroded, which will cause leakage and increase. If it is large, the corrosion rate should be less than 0.1mm/year. (7) When selecting the lining material (rubber, plastic), the temperature, pressure and concentration of the working medium must meet the use range of the material, and consider the physical and mechanical damage (such as shear damage) of the valve when it acts. . (8) The vacuum valve should not be lined with rubber or plastic in the valve body. (9) The two-position shut-off valve of the water treatment system should not be made of rubber-lined materials. (10) Typical corrosion-resistant alloy material selection for typical media: a. Sulfuric acid: 316L, Hastelloy, Alloy 20. b. Nitric acid: aluminum, C4 steel, C6 steel. c. Hydrochloric acid: Hastelloy B. d. Hydrofluoric acid: Monel. e. Acetic acid, formic acid: 316L, Hastelloy. f. Phosphoric acid: Inconel, Hastelloy. g. Urea: 316L. h. Caustic soda: Monel. i. Chlorine: Hastelloy C. j. Seawater: Inconel, 316L. (11) So far, the most versatile corrosion-resistant material is tetrafluoroethylene, which is called 'corrosion-resistant king'. Therefore, the all-tetrafluoro-corrosion-resistant valve (the patented product of Hualin) should be selected first.>180 ℃, PN> 1.6) only select the alloy. Selection of flow characteristics of the regulating valve: The following is the preliminary selection, and the detailed selection is shown in the special information: (1) When S>0.6, logarithmic characteristics are selected. (2) The logarithmic characteristic is selected when working with small opening and when the unbalanced force changes greatly. (3) The required adjusted parameter reflects the straight line when the speed is fast, and the logarithm when it is slow. (4) The linear characteristic of the pressure regulation system is optional. (5) The linear characteristic of the liquid level adjustment system is optional. Selection of the action mode of the regulating valve: (1) It is commonly used abroad to indicate that it is open or closed under fault, that is, fault open and fault close, which is exactly the opposite of the air open and air closed in my country. valve. (2) The new light valve and fine small valve no longer emphasize the positive and negative effects of the execution machinery, so they must be marked on the endnote. B (air closed) K (air open) (1) First, select the spring range, and also determine the working spring range. (2) Determining the working spring range involves calculating the output force to overcome the unbalanced force. If there is any difficulty, the conditions (mainly the pressure difference when the valve is closed) should be told to the manufacturer to assist in the calculation and adjustment of the spring and the working range before leaving the factory (at present, many manufacturers do not do the calculation at all). Selection of the flow direction of the regulating valve: (1) At the throttling port, the flow of the medium in the opening direction of the valve core is flow open, and the flow in the closing direction is flow closed. (2) The choice of flow direction is mainly single-sealed regulating valve, which includes three categories: single-seat valve, angle valve, and single-sealed sleeve valve. It is based on the specified flow direction (such as double seat valve, V ball) and arbitrary flow (such as O ball). (3) When dg>15, the flow is usually selected to be open. When dg≤15, the small-diameter valve, especially the high-pressure valve, can be selected to be closed to improve the service life. (4) Optional flow and close for the two-position switch valve. (5) If the flow-closed valve oscillates, change it and the flow-open type can be eliminated. Selection of regulating valve packing: (1) PTFE 'V'-shaped packing and graphite 'O'-shaped packing are commonly used in regulating valve. (2) The tetrafluoro packing has small friction, but has a short temperature difference and short life; the graphite packing has large friction, but has good temperature resistance and long life; it is recommended to choose graphite packing under high temperature and for valves with positioners. (3) If the tetrafluoro packing is often replaced, graphite packing can be considered.
Lianke Valve Co.,Ltd. have now decided to extend our company in other countries.
Helping our customers manage document workflow and increase efficiency through best-in-class valve application and services. Fostering the growth and development of our employees.
Visit Lianke Valve to find recent dynamics of valve application and contact Lianke Valve Co.,Ltd. for the latest and most capable in global market.
Rewards and discount programs give customers more reason to come back for valve application again, especially in the competitive retail and services markets.
There are many advantages associated with .
Custom message
Chat Online 编辑模式下无法使用
Chat Online inputting...