discount 70% in 2018-09-19 to 2018-09-21
price: USD$ 2499.00
freight :USD$7.00,(Postal parcel)
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0123456789Selection of valve type
(1) determine the nominal pressure, not with Pmax to set PN, but by temperature, pressure, material three conditions from the table to find the corresponding PN, and meet the selected valve PN value.
(2) determine the valve type, the leakage to meet the process requirements.
(3) determine the valve type, its working pressure difference should be less than the allowable pressure of the valve, if not, you must consider or select the valve from a special point of view.
(4) the temperature of the medium is within the working temperature range of the valve, and the ambient temperature meets the requirements.
(5) the anti blocking problem of the valve is taken into account according to the non clean condition of the medium.
(6) according to the chemical properties of the medium, the corrosion resistance of the valve is considered.
(7) according to the pressure difference and hard material medium, the erosion and wear resistance of the valve are taken into account.
(8) performance and price ratio considered by comprehensive economic effect. Three issues need to be considered:
A. structure is simple (simpler, higher reliability), easy maintenance, spare parts have source;
Service life of b.;
(9) optimizing order.
Butterfly valve single seat valve, two seat valve, sleeve valve, angle valve, three-way valve, ball valve eccentric rotary valve diaphragm valve.
Selection of executive body
(1) the simplest is the pneumatic membrane 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 actuator is bulky, we have electronic fine, small, high reliability electric actuator to provide (the price is higher).
(4) the old ZMA and ZMB film actuators can be eliminated and replaced by multi spring lightweight actuators (performance improvement, weight, height drop about 30%).
(5) the piston actuator has many varieties and specifications, and the old, big and stupid suggestions are no longer used, but choose the light new structure.
(1) control valve body pressure level, use temperature and corrosion resistance, etc. should be not less than the process of connecting pipe requirements, and should be preferred manufacturer stereotypes products.
(2) cast iron valves should not be chosen for steam or water containing wet gas and flammable and explosive media.
(3) when the ambient temperature is below from-20 DEG (especially the North), should not use cast iron valve.
(4) on the cavitation erosion medium temperature, the more serious pressure difference and the Cartesian coordinate, the temperature is 300 DEG C, the pressure difference for two points outside the 1.5MPa area, the throttle sealing surface should be used wear-resistant materials, such as cobalt based alloy or alloy surfacing for taylor.
(5) the choice of corrosion resistant alloy must be based on the type, concentration, temperature and pressure of the medium.
(6) the valve body and throttle parts are treated separately, the throttle speed of the inner wall of the valve body is small and allowed to have certain corrosion, its corrosion rate can be about LMM / year; the throttle parts will be corroded by high-speed erosion, corrosion will bow, the leakage will increase, and the corrosion rate should be less than 0.1mm / year.
(7) when choosing the lining material (rubber, plastic), the temperature, pressure and concentration of the working medium must meet the application range of the material, and consider the physical and mechanical damage (such as shear failure) when the valve acts.
(8) vacuum valve should not use rubber and plastic structure of valve body lining.
(9) lining rubber material should not be chosen for two position shut-off valve of water treatment system.
(10) selection of typical corrosion resistant alloy materials for typical media:
A. sulfuric acid: 316L, Hastelloy, alloy 20.
B. nitric acid: aluminum, C4 steel, C6 steel.
C. hydrochloric acid: Ha's B.
D. hydrofluoric acid: monel.
E. acetic acid, formic acid: 316L, hastelloy.
F. phosphoric acid: because of Hastelloy and hastelloy.
G. urea: 316L.
Caustic soda: Monel h..
I. chlorine: Hastelloy C.
J. seawater: due to Ni Er, 316L.
(11) up to now, the most universal corrosion resistant material is PTFE, which is called "corrosion resistant king"". Therefore, the corrosion resistance valve should be selected first, and the alloy can be used only under the condition of no temperature (such as temperature >180, PN>1.6).
Selection of flow characteristics
The following is a preliminary choice, the detailed choice of special information:
(1) logarithmic characteristic when S > 0.6.
(2) the work of a small opening, the unbalanced force changes when the number of features selected.
(3) the required parameters are used to select the straight line when the speed is fast, and the logarithm is chosen when the speed is slow.
(4) optional linear characteristics of the pressure regulating system.
(5) optional linear characteristic of liquid level regulating system.
Mode of action selection
(1) the common failures under the opening or closing to express, that is, fault opening, failure, and China's gas open, gas closed, the opposite is true, the fault corresponding to the gas closed valve, fault corresponding to the gas open valve.
(2) the new light valve, fine small valve has not emphasized the positive role, the implementation of the anti machine, so it must be marked in the endnotes. B (gas closed) K (air opening)
Selection of spring range
(1) first, the spring range is selected, and the working spring range is also determined.
(2) determine the spring range of the work involved in calculating the output force to overcome the unbalanced force. If there is any difficulty, the condition (mainly the pressure difference when the valve is closed) should be told to the manufacturer, and the calculation and adjustment of the spring and working range will be carried out.
The choice of flow direction
(1) at the throttle orifice, the flow direction of the medium toward the valve core is opened, and the flow in the direction of the closure is closed.
(2) the selection of flow direction is mainly single seal type control valve, there are three categories: single seat valve, angle valve, single seal sleeve valve. Based on the specified flow direction (such as two seat valve, V ball) and arbitrary flow (such as O ball).
(3) when DG > 15, usually open flow, when the small caliber valve DG is less than or equal to 15, especially high pressure valve optional flow closed, in order to improve the life.
(4) optional flow closure for two bit switching valve.
(5) if the flow closed valve produces oscillation, it can be eliminated by flow opening.
Selection of packing
(1) the control valve is commonly used PTFE "V" shaped filler and graphite "O" shaped filler.
(2) PTFE packing has small friction, but it is resistant to temperature difference and short life; graphite packing has large friction, but good temperature resistance and long service life; at high temperature and graphite valve with positioner, it is recommended to choose graphite packing.
(3) if the PTFE packing is often changed, graphite packing can be considered.
(1) the main accessories of the control valve are: positioner, converter, relay, booster valve, retaining valve, pressure reducing valve, filter, oil mist device, stroke switch, position transmitter, solenoid valve, hand wheel mechanism.
(2) the supplementary function of the attachment and the function of the valve. Necessary increases, unnecessary does not increase. If necessary, adding accessories will increase the price and reduce the reliability.
(3) the main function of the positioner is to improve the output force and movement speed, without these functions, can not take, not with the locator is good.
(4) fast response system, no valve action fast, optional converter.
(5) strict explosion-proof occasions, optional: electrical converter + pneumatic positioner.
(6) solenoid valve should choose reliable products, to prevent it from action without action.
(7) no hand wheel mechanism is recommended for important occasions to prevent human misoperation.
(8) it is better to be supplied by the manufacturer and the assembly is supplied on the valve to ensure the reliability of the connection between the system and the assembly.
(9) when ordering, the name, type, specification, input signal and output signal of the accessories should be provided.
(10) again: please pay attention to the importance of these small things, especially the reliability, if necessary, supporting pneumatic components in Japan, such as solenoid valve.