The role and principle of the regulating valve

The regulating valve is used to regulate the flow, pressure and liquid level of the medium. According to the signal of the adjustment position, 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 used by the electric actuator or pneumatic actuator and the regulating valve 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-seater and straight-through two-seater. 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 the control valve. The flow capacity of the control valve is defined as: when the control valve is fully opened, the pressure difference between the two ends of the valve is 0.1MPa, and the fluid density is 1g/cm3, the flow diameter per hour The flow rate of the regulating valve is called the flow capacity, also called the flow coefficient, expressed in Cv, the unit is t/h, and 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. The meanings of the three fluence characteristics are as follows: (1) Equal percentage characteristics (logarithm) The relative stroke and relative flow of equal percentage characteristics are not linear, and the change in flow caused by the unit stroke change at each point of the stroke is related to this point The flow rate is proportional to the flow rate, and the percentage of the flow rate change is equal. Therefore, its advantage is that when the flow rate is small, the flow rate changes small, and when the flow rate is large, the flow rate changes greatly, that is, at different opening degrees, it has the same adjustment accuracy. (2) Linear characteristic (linear) The relative stroke and relative flow of the linear characteristic have a linear relationship. The flow change caused by the change of unit stroke is constant. When the flow is large, the relative value of the flow changes little, and when the flow is small, the relative value of the flow changes greatly. (3) Parabolic characteristics The flow rate changes in proportion to the two sides of the stroke, and generally has an intermediate characteristic between linear and equal percentage characteristics. From the analysis of the above three characteristics, it can be seen that in terms of its adjustment performance, the equal percentage characteristic is the best, its adjustment is stable and the adjustment performance is good. The parabolic characteristic is better than the linear characteristic. Any one of the flow characteristics can be selected according to the requirements of the use occasion. The regulating valve is used to regulate the flow, pressure and liquid level of the medium. According to the signal of the adjustment position, 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-seater and straight-through two-seater. 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 the control valve. The flow capacity of the control valve is defined as: when the control valve is fully opened, the pressure difference between the two ends of the valve is 0.1MPa, and the fluid density is 1g/cm3, the flow diameter per hour The flow rate of the regulating valve is called the flow capacity, also called the flow coefficient, expressed in Cv, and the unit is t/h. The Cv value of the liquid is calculated by the following formula. Look up the table according to the Cv value of circulation capacity