Regulating valve selection steps
1, the type ofcontrolvalve selection
There are many types ofregulating valve, commonly used through single seat, straight through doubleseat,Angle, diaphragm,small flow, three, V ball, butterfly, sleeve type, ball type, etc.in the specific selection, the following considerations can be made: (1)SpoolshapestructureMainly according to the selected flow characteristics and unbalanced force and other factors considered
(2) wearresistance
When the fluid medium is asuspension containing high concentration of abrasive particles, the internal
material ofthe valve should be hard.
(3)corrosion resistanceAs the media is corrosive, choose simple valves as far as possible.(4) temperature and pressure ofthe mediumWhen the temperature and pressure ofthe medium are high and vary greatly, the material ofthe valvecore and valve seat should be selected bythe temperature and pressure change ofthe valve.(5)to preventflash and cavitationFlashand cavitation occuronlvin liquid media.in the actual production process. flash and cavitation will form vibration and nose. shorten the serviceife ofthe valve, so the valve should be prevented from flash and cavitation when selecting the valve.

2. the choice ofregulating valve actuator
in order to make the regulating valve work properly, the equipped actuator should be able to generateenough outputforce to ensure the height ofthe sealand valve opening.For double-acting pneumatic, hydraulic and electric actuators, there is generally no return spring.The magnitude ofthe force is independent of its direction ofoperation, so the key to selecting theactuator is to know the maximum outputforce and the rotation toraue ofthe motor.Forsingle action of the pneumatic actuator, the outputforce and the opening ofthe valve, the force onthe valve will also affectthe movement characteristics, so the requirements in the entire opening rangeofthe valve toestablish a force balanc

3. Determine the type of actuator, After the output force of the actuatoris determined, thecorresponding actuatoris selected according to the reguirements of the process environment.

For on-site explosion-proof requirements, pneumatic actuatorshould be selected.From the aspect ofenergy saving, electric actuator should be selected as far as possible.fthe adiustment precision is high, you can choose hydraulic actuator.For example, the speed regulation of the transparent machine in power plant, the temperature regulationcontrol ofthe catalytic unit reactor in oil refinery, etc.

4.the mode ofaction selection ofthe regulatingvalve

The mode ofaction ofthe regulating valve is onlyavailable when the pneumatic actuator is selectedThe mode of action is formed by the combination of positive and negative effects ofthe actuator and the
valve
There are 4 combination foms that are positive (gas type), positive and negative (gas type), anywaygas type), anti (gas type), through the formation ofthe four combination ofregulating valve mode ofactionhas two kinds ofgas open and gas offThe choice ofthe mode of action ofthe regulating valve is mainly considered from three aspects:
A)Process production safety;
B) dielectric characteristics;
C)Ensure product quality and minimize economicloss

selectthe specific parameters ofthe regulating valve
1Type offluid to be controlled
2. Fluid Temperature
3.Fluid Viscositv
4 Specific gravity offluid
5.Required circulation capacity(maximum and minimum)
6.Valve inlet pressure(maximum and minimum)
7.Valve outlet pressure(maximum and minimum)
8.Pressure drop under normal flow condition
9Pressure dropatshutdown
10.Maximum permissible noise level
11.Inletandoutletpipe diameterand wallthickness
12.Body material 13.instrumentsignal(4-20MA0-10V,etc)"
14. Valve diameter m
15.Body construction
16.Required actuator size (the best configuration is 1.2-1.5 times of the driving torque calculatedaccording to the data aftervalve selection)
17.Drive energy (electric, pneumatic, electro-hydraulic) 18.Other required process conditions (such as: time explosion proof, etc.