What’s The Main Parts of Control Valve

Control valves typically consist of three main parts: the valve body, the actuator, and accessories. The medium flows into the valve body from the inlet and exits from the outlet. The actuator controls the valve’s operation, regulating the flow rate and velocity of the medium. Accessories are used alongside the actuator to meet various control and monitoring requirements.

Valve Body

The valve body of a control valve is designed to withstand fluid pressure and requires materials with adequate strength. Common materials include cast iron, cast steel, stainless steel, and alloy steel. Material selection depends on factors like the medium’s pressure and design temperature. The valve body’s flow passage design follows fluid dynamics principles to minimize flow losses.

Control valves come in different types of valve bodies, such as single-seat, double-seat, angle, and cage configurations. Choosing the appropriate valve type depends on specific process requirements and operating conditions. Besides the shell, internal components of the valve body include the valve seat, valve plug, and stem.

Seat

The seat is a crucial sealing component of the valve body, requiring a high-hardness material to seal tightly against the valve plug. Common materials include hard alloys. Any wear or damage to the seat’s sealing surface can lead to fluid leakage when closed, emphasizing the need for proper protection during use.

Valve Plug

Valve plugs vary in structure depending on the control valve type, including plug-type, disc-type, and spherical variations. The performance of the valve plug directly influences flow regulation and control effectiveness. Valve plugs are typically made of wear-resistant and corrosion-resistant materials, matching or exceeding the valve body’s material properties.

The valve plug and seat form the valve’s sealing pair, with the tight fit determining fluid interception and valve closure. The degree of valve plug and seat opening controls the flow rate.

Stem

The stem connects the actuator to the valve plug, enabling the actuator to control the plug’s opening position. Stems can have linear or rotational movement, with linear stems suited for precise adjustments and rotational stems for wide-range flow rate control.

Actuator

Actuators drive the valve’s opening, closing, and adjustment functions. Common types include pneumatic, electric, and hydraulic actuators, with pneumatic ones being most prevalent due to their simplicity and cost-effectiveness.

Accessories

Accessories complement the actuator, enhancing the valve’s functionality. These include positioners, position maintainers, filter regulators, boosters, and solenoid valves.

• Positioner: Detects and controls the valve’s opening, providing feedback to the control system. Types include pneumatic, electrical, and intelligent variants.
• Position Maintainer: Automatically preserves the valve position when source pressure is interrupted.
• Filter Regulator: Removes impurities from the main gas path and stabilizes air pressure.
• Booster: Amplifies the output voltage of the positioner, accelerating the valve’s action speed.
• Solenoid Valve: Controls valve core direction using electromagnetic attraction for switching positions.