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Regulating valve selection method
Time：2019/5/7 16:23:03
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With the acceleration of modern engineering, the regulating valve plays an important role in the modern industrial system and has become an indispensable actuator for its powerful functions. For example, electric control valves and pneumatic control valves have been widely used in automatic control systems. When we are using it, it is a very important step to be familiar with the selection method of the regulating valve. So, what are the control valve selection methods?
The selection method of the regulating valve is as follows:
When selecting the regulating valve, firstly collect the physical parameters of the complete process fluid and the working conditions of the regulating valve, including: fluid composition, temperature, density, viscosity, normal flow, maximum flow, minimum flow, maximum flow and minimum flow. Import and export pressure, maximum pressure difference, etc. In the technical aspect, it mainly grasps and determines the structure, flow characteristics, rated flow coefficient Kv value, caliber size, process allowable pressure difference calculation, actuator selection, material and installation of the regulating valve itself. The general principles to be followed when selecting and installing a regulating valve are as follows:
The structural form of the regulating valve should meet the requirements of temperature, pressure, fluidity, flow direction, adjustment range and tightness of the medium.
The flow characteristics of the regulating valve should be able to meet the system characteristics for reasonable compensation. The flow characteristic of the regulating valve realizes the relationship between the relative flow rate of the medium flowing through the valve and the relative displacement of the valve stem. Commonly used are equal percentage, linear, quick opening and parabolic characteristics. The general principle of selection is that the flow characteristic of the regulating valve should be The characteristics of the adjustment object and the characteristics of the regulator are reversed, which makes the overall characteristics of the adjustment system close to linear. The selected flow characteristics are usually carried out under the requirements of the process system. The linear flow characteristics are applicable to: 1) the differential pressure change is small and almost constant; 2) the main parameters of the process flow are linear; 3) the system pressure loss is mostly distributed in the adjustment On the valve; 4) the external interference is small, the set value changes little, and the adjustable range is small. Applicable range of equal percentage characteristics: 1) The actual adjustable range is large; 2) The change of opening degree and the pressure difference on the valve are relatively large; 3) The pressure loss of the pipeline system is large; 4) The process system load fluctuates greatly; 5) The regulating valve Often run at a small opening.
The diameter of the regulating valve should be able to meet the flow requirements of the process. Based on the known fluid conditions, the necessary Kv values are calculated and the appropriate regulator valve diameter is selected.
The material of the regulating valve should meet the requirements of temperature, pressure, pressure difference and corrosivity of the medium.
Regulating valve actuator output force: should meet the requirements of pressure difference in the field, its stiffness should meet the requirements of system stability, and the switch type should meet the requirements of safe operation of the system.
When selecting the regulating valve, it is necessary to consider that in special cases, the valve should meet the requirements of operation time and split control through auxiliary devices such as valve positioner, solenoid valve and limit switch.
The selection method of the regulating valve is very important, and the correct selection of the regulating valve is very beneficial to the stability and high efficiency of the system.
The selection method of the regulating valve is as follows:
When selecting the regulating valve, firstly collect the physical parameters of the complete process fluid and the working conditions of the regulating valve, including: fluid composition, temperature, density, viscosity, normal flow, maximum flow, minimum flow, maximum flow and minimum flow. Import and export pressure, maximum pressure difference, etc. In the technical aspect, it mainly grasps and determines the structure, flow characteristics, rated flow coefficient Kv value, caliber size, process allowable pressure difference calculation, actuator selection, material and installation of the regulating valve itself. The general principles to be followed when selecting and installing a regulating valve are as follows:
The structural form of the regulating valve should meet the requirements of temperature, pressure, fluidity, flow direction, adjustment range and tightness of the medium.
The flow characteristics of the regulating valve should be able to meet the system characteristics for reasonable compensation. The flow characteristic of the regulating valve realizes the relationship between the relative flow rate of the medium flowing through the valve and the relative displacement of the valve stem. Commonly used are equal percentage, linear, quick opening and parabolic characteristics. The general principle of selection is that the flow characteristic of the regulating valve should be The characteristics of the adjustment object and the characteristics of the regulator are reversed, which makes the overall characteristics of the adjustment system close to linear. The selected flow characteristics are usually carried out under the requirements of the process system. The linear flow characteristics are applicable to: 1) the differential pressure change is small and almost constant; 2) the main parameters of the process flow are linear; 3) the system pressure loss is mostly distributed in the adjustment On the valve; 4) the external interference is small, the set value changes little, and the adjustable range is small. Applicable range of equal percentage characteristics: 1) The actual adjustable range is large; 2) The change of opening degree and the pressure difference on the valve are relatively large; 3) The pressure loss of the pipeline system is large; 4) The process system load fluctuates greatly; 5) The regulating valve Often run at a small opening.
The diameter of the regulating valve should be able to meet the flow requirements of the process. Based on the known fluid conditions, the necessary Kv values are calculated and the appropriate regulator valve diameter is selected.
The material of the regulating valve should meet the requirements of temperature, pressure, pressure difference and corrosivity of the medium.
Regulating valve actuator output force: should meet the requirements of pressure difference in the field, its stiffness should meet the requirements of system stability, and the switch type should meet the requirements of safe operation of the system.
When selecting the regulating valve, it is necessary to consider that in special cases, the valve should meet the requirements of operation time and split control through auxiliary devices such as valve positioner, solenoid valve and limit switch.
The selection method of the regulating valve is very important, and the correct selection of the regulating valve is very beneficial to the stability and high efficiency of the system.