The characteristics of the three flow characteristics of control valves
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Control valves are used to regulate the flow rate, pressure, and level of a medium. They consist of an electric actuator (or a pneumatic actuator) and the control valve itself. Control valves include electric control valves, pneumatic control valves, and hydraulic control valves, among others. The product types include electric three-way valves, three-way control valves, pneumatic control valves, electric three-way flow-dividing control valves, and self-acting pressure control valves, among others. The flow coefficient is one of the main parameters for selecting control valves. The flow characteristic of a control valve refers to the relationship between the relative flow rate of the fluid passing through the valve and its opening degree, under the condition that the pressure difference across the valve remains constant. The flow characteristics of control valves include linear, equal percentage, and parabolic characteristics. The meanings of the three dosing characteristics are as follows: 1. Logarithmic: For this characteristic, the relative stroke and relative flow rate do not follow a linear relationship; at each point along the stroke, the change in flow rate resulting from a unit change in stroke is proportional to the flow rate at that point, with the percentage change in flow rate remaining constant. Therefore, its advantage is that the flow rate changes little when it is low, but changes significantly when it is high; in other words, it maintains the same adjustment accuracy at different opening degrees. 2. Linearity: The relative stroke of the linear characteristic is in a straight-line relationship with the relative flow rate. The change in flow rate caused by a change in unit stroke remains constant. When the flow rate is high, the change in the relative value of the flow rate is small; when the flow rate is low, the change in the relative value of the flow rate is large. 3. Parabolic characteristic: The flow rate varies proportionally to the square of the stroke, exhibiting an intermediate characteristic that is roughly between linear and equal percentage characteristics.
The flow characteristics of control valves can be divided into three types: equal percentage characteristic, linear characteristic, and parabolic characteristic. 1. Equal percentage characteristic: For every unit change in the valve opening, the change in flow rate is proportional to the current flow rate; this type is suitable for maintaining relatively uniform control performance when the load varies significantly. 2. Linear characteristic: There is a linear relationship between the valve opening and the flow rate; for each increase in valve opening, the flow rate increases by a fixed proportion, making it suitable for applications where the load does not change much. 3. Parabolic characteristic: It lies between linear and equal percentage behavior; the effect of changes in opening degree on flow rate is small at first, but it increases as the opening degree grows, making it suitable for applications that require fine adjustments in the initial stage. .