A clever choice of regulating valve, this paper referred to 7 points. In this section, the summary and analysis of matters need to pay attention to regulating the correct selection of the valve, according to the control valve, actuator, material, flow characteristics, mode of action, spring range, flowing, packing, annex summarizes nine aspects of control valve selection of experience and attention, for regulating valve practitioners understand selection knowledge regulation valve, there are more helpful to improve the selection level, but due to the limited level of the author, there are many problems and defects, welcome the masses of readers criticism.
Valve type selection:
(1) to determine the nominal pressure, not to cover with Pmax PN, but by the temperature, pressure, material three conditions from the table to find the corresponding PN and to meet the selected valve of the PN values.
(2) to determine the valve type, the leakage rate to meet the technological requirements.
(3) to determine the valve type, its working pressure should be less than the permissible differential pressure valve, such as not, shall be considered or choose it from the special angle valve.
(4) the medium temperature in the valve's operating temperature range, the ambient temperature to meet the requirements.
(5) according to the medium considered not clean the valve attempts to prevent the problem.
(6) according to the media to consider the chemical properties of corrosion resistant valves.
(7) according to the media pressure and with a hard object, consider the valve problems of erosion and abrasion.
(8) the price performance, consider the overall economic effect of. Need to consider three questions: A. simple structure (more simple and higher reliability, convenient maintenance, spare parts); the service life of the B.; C. price.
(9) preferred order.
Butterfly valve - single-seat valve - two-seat valve, sleeve valve, angle valve - valve - valve, eccentric rotary valve, diaphragm valve.
The choice of implementing agencies:
(1) the simplest is the pneumatic membrane, followed by the piston, and finally electric.
(2) the main advantage of electric actuators is the driving source (power) is convenient, but high price, reliability, water proof as pneumatic actuator, it should be preferred pneumatic.
(3) the old heavy electric actuator, electric actuator we have electronic fine small high reliability (corresponding high prices).
(4) ZMA, ZMB thin film actuator can be eliminated by the old, multi-spring actuators on behalf of light (performance, weight, height decreased by about 30%.).
(5) the piston executive body more varieties of different specifications, the old, big, stupid proposal no longer use, and use the new structure of light.
The choice of materials:
(1) valve pressure rating, temperature and corrosion resistance should not be less than the process required to connect the pipeline, and factory styling products should be preferred.
(2) steam or water more wet gas and explosive media, should not use cast iron valve.
(3) the environment temperature is lower than -20 ℃ (especially the North), should not use cast iron valve. L good, good.
(4) on the cavitation, erosion medium temperature is more serious and pressure difference formed in rectangular coordinates, the temperature is 300 ℃, pressure difference is 1.5MPa straight line area, on the throttle sealing surface should be made of abrasion resistant material, such as cobalt base alloy or surfacing division Terai alloy etc..
(5) of the corrosive medium, corrosion resistant alloy selection must be based on media type, concentration, temperature, pressure difference, choose a suitable corrosion-resistant materials.
(6) the valve and throttle parts separately, the inner wall of the valve body and throttle speed small to allow a certain degree of corrosion, the corrosion rate in LMM / year; throttle by high-speed erosion, corrosion will bow [leakage increased, the corrosion rate should be less than 0.1mm per year.
(7) on the lining materials (rubber, plastic) temperature, pressure, concentration of the choice of the working medium must meet the use of the material, and consider it when the valve moves the physical, mechanical damage (such as shear failure).
(8) vacuum valves lining body should not use rubber, plastic structure.
(9) water treatment system of the two shut-off valve should not use rubber lining material.
(10) select the typical medium typical corrosion resistant alloy materials: A. sulfuric acid: 316L, Hastelloy alloy, 20 alloy. B.: aluminum nitrate, C4 steel, C6 steel. C. hydrochloric acid: Hastelloy B. D. hydrofluoric acid: monel. Acetic acid: e., 316L, Hastelloy alloy. F.: because of nickel, phosphate, Hastelloy alloy. G. urea: 316L. H. caustic soda: monel. I. chlorine: Hastelloy C. J. seawater: due to nickel, 316L.
(11) so far, the most versatile corrosion-resistant material is PTFE, known as the "king of corrosion". Therefore, we should choose the PTFE corrosion valve, no circumstances (such as the temperature of >180 ℃, PN > 1.6) the alloy. The flow characteristics of the choice: here is a preliminary selection, detailed selection see specialized information: content from dedecms
(1) S > 0.6 the number of features selected.
(2) the work of a small opening, unbalanced force changes when the number of features selected.
(3) the request parameters are adjusted to reflect the speed when the selected line, slow when selecting the right number.
(4) straight line features optional pressure regulating system.
(5) the level control system features an optional line.
Mode of selection:
(1) abroad on or off under the common failure to express, that the failure to open, fault off, and the opening of China's gas, gas said closing the contrary, the failure to open the corresponding gas valve closed, the corresponding failure related to open the gas valve.
(2) the new light valve, fine small valve has not emphasized the positive role of execution, mechanical, and therefore must be marked in the endnotes.
B (gas closed) K (open air)
Spring range of options:
(1) is the first select the spring range, but also to determine the scope of the work of spring.
(2) to determine the scope of the work of the spring to calculate output force to overcome the imbalance force. If you have difficulties, should the conditions (mainly when the pressure valve closed) to tell the factory, to help calculate and adjust the springs and scope of work factory (currently, many manufacturers simply do not calculate).
The choice of the flow:
(1) in the throttle, valve open against the direction of media flow away, to the direction of flow streams closed off.
(2) the choice of the flow of the single seal type valve, a single-seat valve, angle valve, single-sleeve valve seals three categories. Its provisions to (such as two-seat valve, V ball) and arbitrary flow (such as O). Dedecms
(3) when DG > 15, usually open flow, when the small caliber valve DG ≤ 15, especially high pressure valve optional flow close, in order to improve the life.
(4) two optional flow switch valve closed.
(5) if the current closed-type valve to oscillate, change over, flow type can be removed.
The choice of packing:
(1) is commonly used PTFE valve "V" - shaped packing and graphite "O" - shaped filler.
(2) PTFE packing friction is small, but the temperature difference, short life; graphite packing friction, but the temperature is good, long life; high temperature and with a locator the proposed election of graphite valve packing.
(3) if the PTFE packing often change, you can consider the use of graphite packing.
The selection of accessories:
(1) the annex to the main control valve: locator, converter, relay, pressure valve, valve, valve, filters, oil mist device, a travel switch, position transmitter, electromagnetic valve, hand wheel mechanism.
(2) features and accessories to complement the role to ensure that valve operation. Necessary to increase, not to increase unnecessarily. It is not necessary to increase the attachment will raise prices and reduce reliability.
(3) locator main function is to increase the output force and movement speed, does not need these functions, can not take, not with a locator.
(4) for the rapid response system, do not move fast valve, optional converter.
(5) and explosion-proof occasions, strict optional: electrical converter + pneumatic positioner.
(6) solenoid valve should choose a reliable product, its action should not prevent action. Content from dedecms
(7) suggest an important occasion not hand wheel mechanism, action to prevent human error.
(8) provided by the manufacturer and the best assembly of the valve on the supply, to ensure the reliability of the connection and assembly system.
(9) order, provide attachment name, type, specifications, input signal, the output signal.
(10) reiterate the importance: Please note that these "little things", especially the reliability, if necessary, can be matched with pneumatic components, such as solenoid valves.
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