China control valve manufacture-Datian Valve, the specialist of China valve manufacture, main product range: control valve, ball valve, automatic recirculation valve, gate valve, globe valve, check valve, choke valve, safety valve, plug valve, diaphragm valve, strainer, pressure reducing valve and valve products(china heat pump).

Valve type selection:

(1) determine the nominal pressure, not to go with Pmax sets the PN, but by the temperature, pressure, material three conditions from the table to find the corresponding PN and meet the selected valve PN value.

(2) to determine the type of valve, the leakage to meet process requirements.

(3) to determine the type of valve, the working pressure should be less than the valve to allow pressure, such as not to be considered from the particular perspective or select it valve.

(4) the temperature of the medium in the valve operating temperature range, ambient temperature to meet the requirements.

(5) consider the valve attempts to prevent the media not clean.

(6) based on the chemical properties of the media to consider valve corrosion problems.

(7) media based on differential pressure and with a hard object, consider the erosion of the valve and resistance to wear and tear issues.

(8) consider the performance of comprehensive economic effect, the price ratio. Need to consider three questions:

a.simple structure (as simple as higher reliability), easy maintenance, spare parts source;

b.life;

c.price.

(9) the preferred order.

Butterfly valve- a single seat valve – seat valve – sleeve valve – angle valve – three-way valve – ball valve – eccentric
rotary valve – diaphragm valve.

Choice of implementing agencies:
(1) The easiest is a pneumatic membrane type, followed by the piston, and finally the electric type.

(2) The main advantage of electric actuators is the driving source (power), but the price is high, reliability, water proof than the pneumatic actuator pneumatic, it should be preferred.

(3) old electric actuator bulky, we have electronic precision small high reliability electric actuator (corresponding high price).

(4) the old ZMA, Model ZMB diaphragm actuators can be eliminated to improve the multi-spring light the executive body on behalf of the (performance, weight, height decreased by about 30%).

Piston executing agency varieties specification in (5) more old, big and stupid proposal is no longer selected, the choice of a light structure.

The choice of materials:

(1) body pressure rating, the use of temperature and corrosion resistance such should not be less than the requirements of the process pipe connection, and preference should be given to the factory styling products.

(2) water vapor or moisture content of more wet gas and inflammable and explosive media, should not use cast iron valves.

(3) the ambient temperature is below -20 ℃ (especially the north), should not use the cast iron valve.

(4) cavitation erosion of the more serious media temperature and pressure differential Cartesian coordinates of a temperature of 300 ℃, the pressure difference of the region other than 1.5MPa two o’clock connection throttling sealing surface should be used wear-resistant materials such as cobalt-based alloy or surfacing Division Terai alloy and so on.

(5) strong corrosive medium, the choice of corrosion resistant alloy according to the different types of media concentration, temperature, pressure, choose a suitable corrosion-resistant materials.

(6) valve body with the throttle and treat them separately, the body wall throttle speed is small and allows a certain degree of corrosion, the corrosion rate of about 1mm /; cutting pieces are high-speed erosion, corrosion will bow [from the leak to increase , the corrosion rate should be less than 0.1mm /.

(7) the choice of lining material (rubber, plastic), the medium temperature, pressure, concentration must meet the use of the material, and considering the valve moves to its physical and mechanical damage (such as shear failure) .

(8) vacuum valve should not use the body lined with rubber, plastic structure.

(9) water treatment system, two shut-off valve should not use rubber lining materials.

(10) the typical corrosion resistant alloy material of the typical media options:

a.sulfuric acid: 316L, Hastelloy, Alloy 20.

b.nitrate: aluminum, C4, steel, C6 steel.

c hydrochloric acid: Hastelloy B.

d.HF: Monel.

e. acetic acid, formic acid: 316L, Hastelloy.

f.phosphate: can nickel Seoul, Hastelloy.

g.urea: 316L.

h.caustic soda: Monel.

i.chlorine: Hastelloy C.

j.sea: can nickel Seoul, 316L.

Reproduced in:http://www.famens.com/html/2012/5-10/F1011983260.htm

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