【2026 Basic Knowledge】System understanding of control valve structure
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A control valve consists of two main parts: the actuator and the valve body components. Based on the type of energy used, they can be classified into pneumatic, electric, and hydraulic types; based on the stroke, they can be divided into straight-stroke and rotary-stroke types. The following outlines the definition, components, and classification methods of control valves.
I. Definition of control valves The International Electrotechnical Commission (IEC) defines a control valve (referred to as a Control Valve abroad) as an end element in industrial process control systems that is operated by power; it consists of a valve body containing a component that adjusts the flow rate of the process fluid, and this valve body is connected to one or more actuators. The actuator is used to respond to the signals sent by the control element. In short, a control valve is the end-effector in a process control system that receives control signals and adjusts the fluid flow to achieve control of process parameters.
II. Composition of the control valve The control valve consists of two main parts: the actuator and the valve body components. Actuator: A driving device that generates a corresponding thrust based on the signal pressure, causing the push rod to move and thereby driving the valve core to operate. Valve body components: the regulating section, which is in direct contact with the medium; it changes the throttling area under the action of the actuator to achieve flow regulation.
III. Classification of control valves by energy source: Control valves can be primarily divided into three categories based on their energy source. The structural differences among these three types of valves lie mainly in the type of actuator used; the valve body itself can be common to all of them.
IV. Classification of control valves according to stroke characteristics: Straight-stroke type: The valve stem moves in a straight line, such as straight-through single-seat valves, straight-through double-seat valves, sleeve valves, angle valves, three-way valves, diaphragm valves, etc. Angle-type: The valve stem performs rotational motion (0~90°), such as butterfly valves, ball valves, eccentric rotary valves, and all-functional ultra-lightweight control valves.
V. Classification of valves by purpose and function: Shut-off valves: Primarily used to stop or allow the flow of media, such as gate valves, globe valves, ball valves, butterfly valves, etc. Control valves: Primarily used to regulate parameters such as the flow rate and pressure of a medium, including control valves, throttle valves, pressure reducing valves, etc. Check valves: Used to prevent the backflow of fluid, including check valves of various designs. Shunt valves: Used to distribute, separate, or mix fluids, such as three-way valves and distribution valves. Safety valves: Used for overpressure safety protection, including various types of safety valves.
VII. Classification of valves according to the operating temperature of the medium
VIII. Classification of valves by valve body material: Non-metallic material valves: such as plastic valves, ceramic valves, etc. Metal material valves: such as cast iron valves, cast steel valves, stainless steel valves, alloy steel valves, etc. Valves with metal bodies lined: such as plastic-lined valves, enamel-lined valves, rubber-lined valves, etc.
IX. Valve internals The valve internals refer to the components within a control valve that are in direct contact with the fluid being controlled and that play a role in regulating flow. These mainly include: the valve disc (valve leaf): which, together with the valve seat, forms the throttling orifice and is the key component for regulating flow. Valve seat: Forms a sealing pair with the valve core and withstands erosion by the medium. Valve stem: Connects the actuator to the valve core and transmits thrust. Guide sleeve: Ensures the straightness of movement or rotational precision of the valve spool. Sealing gasket: Ensures sealing between the valve body and the upper valve cover. The structural features of the valve internals are also one of the important criteria for classifying various types of valves.
A control valve, also known as a regulating valve, is an ultimate control element used in the field of industrial automation process control. It receives control signals from a control unit and uses power to adjust process parameters such as flow rate, pressure, temperature, and liquid level; it generally consists of an actuator and a valve.