Valve Types, Applications, Components, and Accessories

The role of control valves in the industrial process loop is becoming increasingly important. As a reliable control valve manufacturer, we would like to introduce the different types of control valves, components, functions, application scenarios, and valve accessories, in a systematic and professional way in this article.

If you are looking for more details, kindly visit Xingyu.

In this section, we are going to offer a brief introduction regarding control valves to help you understand what a control valve is and the role it plays.

What is a Control Valve?

As industrial automation processes evolve, the usage of control valves in process loops continues to grow. Almost every plant integrates hundreds of control loops, which are interconnected to maintain numerous significant process variables within specific limits to ensure the quality of the final product. Critical parameters include pressure, flow, temperature, level, and more. Sensors and transmitters gather these variables and relay them to the controller. The controller compares the actual values against targeted setpoints and sends corrective signals to control valves, modulating the valve opening to achieve desired conditions.

In essence, a control valve is a vital component of a control loop and serves as a critical control element within industrial processes. It comprises a pneumatic, electric, or hydraulic actuator paired with a valve that regulates the flow capacity, temperature of fluids, and pressure levels both upstream and downstream. Its applications are extensive, spanning industries such as petroleum, chemicals, pharmaceuticals, textiles, paper production, oil refining, iron, steel metallurgy, and numerous others.

Principles of Operation For Control Loop

As we know, control valves are the most common final control elements used in the process control industry. The core function of a control valve is to manage the temperature, pressure, level, or flow of a medium while compensating for load disturbances, ensuring that the regulated variable approaches its set point. The medium may be water, steam, oil, gas, or other types of compounds.
Containing a sensor, transmitter, control valve, and controller, a control loop operates in a structured manner.

The sensor and transmitter monitor process variables within the loop, acting as observatory instruments for detecting changes in specific parameters such as temperature, pressure, or level of the medium. The collected data is sent to the controller, which functions analogously to the brain; the process variable received from the transmitter is juxtaposed against the set point, prompting a corrective signal to the control valve. The control valve, as the final control element, acts as the hand in this control loop, making it the most vital part of an automated control system.

Numerous types of control valves exist, each engineered for specific applications—read this post for more details on the different types of control valves.

Common Types of Control Valves

The globe type control valve stands out as the most frequently used final control element in process loops, hence its spherical name. Based on the ports of the globe valve body, there are variations including 2-way control valves, 3-way mixing control valves, and 3-way diverting types.

When we discuss butterfly control valves, we often refer to high-performance models, including double eccentric and triple eccentric configurations. Butterfly valves can frequently replace other valve types in applications, as they offer the same core functions but generally provide enhanced safety features and improved performance. Utilizing butterfly control valves can lead to reduced maintenance needs, better flow control accuracy, and lower risks of failures such as leaks. They are particularly effective in water treatment processes because of their superior sealing capabilities and the ability to withstand high water pressure. Furthermore, they represent a cost-effective solution in large-diameter pipelines.

The segmented ball type control valve, which is characterized by its v-port or segmented ball design, is extensively employed in fluid systems across various industries due to its affordability, durability, and outstanding closing capabilities. However, like butterfly valves, they do not perform optimally in applications that require high-flow precision and sensitivity; their need for substantial torque for opening and closing limits fine adjustments. Additionally, there is often a gap between the stem and the ball, complicating precise flow rate settings for fluid control applications.

A highlight in innovative valve technology is the eccentric plug rotary control valves. This design merges the robust nature, compactness, and extended stem seal life characteristic of globe valves with operational simplicity and reliability. This type of valve showcases an offset construction, with one shaft positioned behind the valve seat and the other off-center for functional purposes.

The reduced trim full ball valve, featuring a triangular window design, comes into play in instances where control valve oversizing is diagnosed post-plant startup. Without the option to adjust piping to accommodate smaller valves, the reduced trim full ball valve serves as an optimal solution, allowing for enhanced flow rates while closely matching the inherent flow characteristics desired.

Components for Control Valves

Control valves commonly fall into two significant categories: linear and rotary motion. The linear type control valve operates through sliding motion, while the rotary control valve relies on quarter-turn motion. Therefore, we will outline each component associated with these two classes of control valves.

Linear Motion Control Valve (Globe Type)

Above is a cross-sectional view of a globe type control valve, displaying its main components.

• Valve body: The primary section of the control valve, responsible for carrying fluid pressure and regulating variable parameters.
• Bonnet: This component holds pressure and seals the valve body and stem through stem seal packing, allowing for easy assembly and maintenance.
• Trim: Typically comprises a stem, plug, and seat, where the stem connects to the actuator and the plug modulates fluid flow through the valve.

Rotary Motion Control Valve (Butterfly Type and Ball Type)

Rotary control valves, often classified as quarter-turn valves, share similar component definitions with linear control valves. The bonnet on most rotary valves is integrally cast with the valve body.

Accessories

Actuator

The actuator serves as the mechanical device that leverages external power to modulate the valves.

Control valve actuators can be categorized into several types: pneumatic actuators, electric actuators, hydraulic actuators, and self-operated actuators. Among these, pneumatic and electric actuators feature predominantly in industrial process control loops.

Pneumatic Actuator

The pneumatic actuator encompasses multiple designs, including multi-spring diaphragm actuators, single-spring diaphragm actuators, and rotary piston actuators.

How to Select the Right Actuator for Your Application

An automated control valve requires an actuator for operation, and distinguishing between pneumatic and electric actuators is crucial for selecting the most appropriate actuator for your setup.

Conclusion

As the complexity of industrial processes grows, the role of control valves remains critical. Proper selection and integration of control valves, their components, and accessories contribute to the effectiveness and efficiency of industrial applications. If you want to learn more, kindly visit Valve Accessories and explore our offerings.

To enhance your automation systems, discover more about Automation Components. For any specific inquiries or to discuss your requirements, feel free to reach out to us for tailored solutions in valve integration.