The flow characteristics of the regulating valve are mainly four kinds of flow characteristics such as linear percentage fast opening and parabola. When installed in the actual control process, the differential pressure of the valve will change with the change of flow, that is, the pressure loss of the piping part will be small when the flow is small, the differential pressure of the valve will become larger, and the differential pressure of the valve will become smaller when the flow is large This is different from the inherent characteristics of the valve characteristic called the effective flow characteristic of the fast start characteristic of the inner valve is disk-shaped, mainly used for opening and closing action. 
Regulating valve spool surface shape
The flow control characteristics of the valve are determined by the combination of the flow characteristics of the valve and the process piping pump, etc. According to the ratio of valve pressure loss in each control object and system, the proportion of valve pressure loss in the control object system is selected in the following table Flow characteristics of the valve Flow control or liquid level control less than 40% Flow control or liquid level control more than 40% pressure control or temperature control less than 50% pressure control or temperature control more than 50% Linear because the pressure loss of the pipe is proportional to the square of the flow rate increases, if the characteristics of the valve body are simple linear changes, the differential pressure of the valve increases when the flow is small, the valve flow will be very large, the valve pressure difference decreases when the flow is large, and the flow can not be proportional to the opening of the valve To this end, adding the characteristics of the pipe and pump to achieve a flow control that is independent of the flow size and only proportional to the valve opening is the purpose of the design of equal percentage characteristics.
Piping system and pressure loss
The action of regulating valve can be selected according to the combination of the drive device and the valve body.
Drive and valve body combination and valve action (example of a single seat valve)
Valve action includes positive action reverse action holding type action 3 ways diaphragm type and cylinder type pneumatic drive positive action is through the increase of pressure signal TO CLOSE the valve method, also known as AIR TO CLOSE reverse action is through the increase of pressure signal to OPEN the valve method, also known as AIR to open or The electrical operation signal can be converted into a pneumatic signal through the locator. When the operation signal is suspended or the air source is interrupted and the power is cut off, please select the valve TO CLOSE or open considering the safety rationality of the procedure.
For example, when controlling the amount of acid through the valve in the procedure of mixing water and acid, it is safe and reasonable to close the acid control valve when the electric signal line is broken or the air signal piping is leaked and the air source is interrupted and the power is cut off. The reverse action valve should be used.
Post time: Aug-05-2023
