Selection of actuator for electric control valve

Selection of actuator for electric control valve

Selection of electric control valve actuator:

(1) The simplest is the pneumatic diaphragm type, followed by the piston type, and finally the electric type.

(2) The main advantage of 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 pneumatic actuator, so pneumatic actuator should be preferred.

(3) The old electric actuator is bulky. We already have electronic fine and small electric actuators with high reliability (the price is correspondingly high).

(4) The old ZMA and ZMB thin film actuators can be eliminated and replaced by multi spring light actuators (performance is improved, weight and height are reduced by about 30%).

(5) There are many kinds and specifications of piston actuator. It is recommended to choose a new light structure instead of the old, big and stupid one.

Selection of materials for electric control valve:

(1) The pressure resistance grade, service temperature and corrosion resistance of the valve body shall not be lower than the requirements of the process connecting pipeline, and the manufacturer's finalized products shall be preferred.

(2) Cast iron valves should not be used for steam or wet gas with more water and flammable and explosive media.

(3) When the ambient temperature is lower than - 20 ℃ (especially in the North), cast iron valve should not be selected.

(4) For the rectangular coordinates composed of medium temperature and differential pressure with serious cavitation and erosion, when the temperature is 300 ℃ and the differential pressure is 1.5MPa, wear-resistant materials shall be selected for the throttling sealing surface, such as cobalt based alloy or surface surfacing stellite alloy, etc.

(5) For highly corrosive medium, the selection of corrosion-resistant alloy must be based on the type, concentration, temperature and pressure of the medium.

(6) The valve body and throttling parts shall be treated separately. The throttling speed of the inner wall of the valve body is small and certain corrosion is allowed, and the corrosion rate can be about LMM / year; the throttling parts will bow [up and leak more when subjected to high-speed scouring and corrosion, and the corrosion rate shall be less than 0.1mm/year.

(7) When selecting lining materials (rubber and plastic), the temperature, pressure and concentration of the working medium must meet the application range of the material, and the physical and mechanical damage (such as shear damage) caused by valve action shall be considered.

(8) The vacuum valve should not be lined with rubber and plastic structure.

(9) Rubber lining material should not be selected for the 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: Hastelloy B.

d. Hydrofluoric acid: Monel.

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

f. Phosphoric acid: Inconel and 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 tetrafluoro, which is called the "king of corrosion resistance". Therefore, all tetrafluoro corrosion-resistant valves (main products of Wozhong) should be selected first, and alloys should be selected only when necessary (such as temperature > 180 ℃, PN > 1.6).