The regulating valve belongs to the series of control valves. Its main function is to adjust the pressure, flow, temperature and other parameters of the medium, and it is the final control element in the process loop. According to the characteristics of the stroke, the regulating valve can be divided into: straight stroke and angular stroke. Straight stroke includes: single seat valve, double seat valve, sleeve valve, angle valve, three-way valve, diaphragm valve; angular stroke includes: butterfly valve, ball valve, eccentric rotary valve, full-function ultra-light regulating valve. According to the driving mode, the regulating valve can be divided into: pneumatic regulating valve, electric regulating valve and hydraulic regulating valve; according to the regulating form can be divided into: regulating type, cut-off type, regulating cut-off type; according to flow characteristics can be divided into: linear, equal percentage , Parabola, quick opening. The regulating valve is suitable for air, water, steam, various corrosive media, mud, oil and other media.
The regulating valve is used to regulate the flow, pressure and liquid level of the medium. According to the signal of the adjustment part, the opening of the valve is automatically controlled to achieve the adjustment of the medium flow, pressure and liquid level.
Control valves are divided into electric control valves, pneumatic control valves and hydraulic control valves. This manual mainly introduces two kinds of electric control valve and pneumatic control valve. The regulating valve is composed of two parts: electric actuator or pneumatic actuator and regulating valve. The adjustment is usually divided into two types, straight-through single-seat type and straight-through double-seat type. The latter has the characteristics of large flow capacity, small imbalance and stable operation, so it is usually especially suitable for occasions with large flow, high pressure drop and less leakage. The flow capacity Cv is one of the main parameters for selecting a regulating valve.
The flow capacity of the regulating valve is defined as: when the regulating valve is fully open, the pressure difference between the two ends of the valve is 0.1MPa, and the fluid density is 1g/cm3, the flow rate of the regulating valve per hour is called the flow capacity, also called The flow coefficient is expressed in Cv, and the unit is t/h. The Cv value of the liquid is calculated by the following formula. According to the flow capacity Cv value, check the table, you can determine the nominal diameter DN of the regulating valve. The flow characteristic of the regulating valve is the relationship between the relative flow of the medium flowing through the regulating valve and its opening under the condition that the pressure difference between the two ends of the valve remains constant. The flow characteristics of the regulating valve include linear characteristics, equal percentage characteristics and parabolic characteristics.
