1). The control valve type shall be comprehensively selected according to the process variables (temperature, pressure, pressure drop, and flow rate), fluid characteristics (viscosity, corrosivity, toxicity, suspended solids or fiber, etc.), requirements of the control system (adjustable ratio, leakage, and noise, etc.) and the pipe connection form of the control valve. 2). Generally, the through single and double seat regulating valves and ordinary sleeve valves with small volume, large carrying capacity, and advanced technology are preferred. Low S value energy-saving valve and fine and small regulating valve can also be selected. 3). The following valve list can be selected according to different occasions, such as: Straight through single seat control valve It is generally suitable for occasions with a small leakage, small flow, and small pressure difference before and after the valve. However, valves with a diameter less than 20mm are also widely used in occasions with large differential pressure; It is not suitable for high viscosity or fluid containing suspended particles. Straight through two seat control valve It is generally applicable to occasions with lax requirements for leakage, large flow and large pressure difference before and after the valve; However, it is not suitable for high viscosity or fluid containing suspended particles. Sleeve control valve It is generally suitable for occasions where the fluid is clean and does not contain solid particles. Where the pressure difference between the front and back of the valve is large and the liquid may flash or cavitate. Control ball valve The industrial ball valve is suitable for occasions with high viscosity, fiber, granular and dirty fluids. The regulation system requires a wide adjustable range (r up to 200 ∶ 1; 300 ∶ 1). When the valve seat gasket is made of soft material, it is suitable for occasions requiring tight sealing. "O" type ball valve is generally applicable to the occasion of two-position cut-off. "V" type ball valve is generally suitable for the continuous regulation system, and its flow characteristics are approximately equal percentage. Angle control valve It is generally applicable to the following occasions: Fluids with high viscosity or suspended solids (flushing liquid pipe can be connected if necessary); Gas-liquid miscible phase or fluid easy to flash; Where right angle piping is required. High-pressure angle control valve In addition to various occasions in 5), it is also suitable for occasions with high static pressure and large differential pressure. However, the material and structural form of valve internals must be reasonably selected to prolong the service life. Eccentric rotary valve It is suitable for occasions with large flow capacity, adjustable specific width (r up to 50 ∶ 1 or 100 ∶ 1), large differential pressure, and tight sealing. Control butterfly valve It is suitable for occasions with large diameter, large flow, and low-pressure difference; Our butterfly valve wholesale is generally applicable to thick and turbid liquid and fluid containing suspended particles; For occasions requiring tight sealing, rubber or PTFE soft sealing structure shall be adopted; For corrosive fluids, corresponding corrosion-resistant lining shall be used. Three-way control valve It is suitable for shunting and merging occasions where the fluid temperature is below 300 ℃ and is used for simple proportioning adjustment. The temperature difference between the two fluids shall not be greater than 150 ℃. Bellows seal control valve It is suitable for vacuum systems and occasions where the fluid is highly toxic, volatile, rare, and valuable. Low-temperature control valve It is suitable for low-temperature conditions and deep freezing. When the medium temperature is - 100 ~ 40 ℃, it can be equipped with a heat sink (heat absorption here) and a flexible graphite packing valve. When the medium temperature is - 200 ~ - 100 ℃, the long neck low-temperature valve should be selected. Low noise control valve It is applicable to the occasions where liquid flash, cavitation, and gas flow rate at the valve contraction surface are greater than the sound speed and the estimated noise exceeds 95dB (a). Self-operated control valve It is suitable for occasions with small flow change, low regulation accuracy requirements, or difficult instrument air supply. In the production process of a special process, the special regulating valve shall be selected according to the user experience.