In addition to the quality of the product itself, whether the user has correctly installed, used, and maintained, the correct calculation and selection of the control valve is very important. Due to the error of calculation and selection, the whole system will be affected, and it will not even be put into use or cause huge economic losses.
Choice of Actuator
1.Select the type of execution mechanical drive according to the site conditions: when the site can only provide air source and control signal, select the pneumatic actuator. When the site can only provide power and control signals, choose an electric actuator. If there is no air source, power supply and control signal, only the force-type regulating valve can be selected.
2. Characteristics of electric actuators: the advantage is that the driving source (power supply) is convenient, and the control circuit is simpler than that of the pneumatic actuator. , it is recommended to prefer pneumatic type.
3.Characteristics of pneumatic actuators: The advantages are stable performance, good protection, obvious cost savings when used in batches, light weight and long life. The disadvantage is that the control circuit is relatively complex, the optional accessories are cumbersome, and the cost of a single unit is high if there is no air source.
Selection of Pneumatic Actuator Accessories
According to the conditions available on site and the different requirements of the control system, the following accessories can be selected to achieve these requirements:
1.Solenoid Valve: Realize the switching of the pneumatic actuator to control the air source, so as to realize the opening or closing function of the pneumatic valve.
2.Valve Monitor: Also called limit switch box, used for valve position switch display or remote feedback of working position signal when the valve is running.
3.Air source triplet: filter the control air source, adjust the decompression, and lubricate the cylinder.
4.Manual Gearbox Operator:When the controller of the control system fails, the valve can be operated manually.
5.Electro Pneumatic Positioner: Receive 4-20mA control signal to turn the on-off valve into a pneumatic regulating valve with regulating performance.
Selection of body material and sealing material
1.The valve body pressure rating, operating temperature and corrosion resistance should not be lower than the requirements of the process connection pipeline.
2.Cast iron valve should not be used for water vapor or wet gas with more water and flammable and explosive medium.
3.When the ambient temperature is lower than -20℃, cast iron valve should not be used.
4.For strong corrosive medium, the selection of corrosion-resistant alloy must be based on the type, concentration, temperature and pressure of the medium, and the appropriate corrosion-resistant material must be selected.
5.When selecting the material of the seal (fluororubber, plastic, PTFE), the temperature, pressure and concentration of the working medium must meet the use range of the material, and consider the physical and mechanical damage to it when the valve acts.
6.Typical special media should choose typical corrosion-resistant alloy materials.