What is a Control Valve?

Control Valves are designed to control and regulate pressure, flow, temperature, etc. They can do the job automatically and eliminate the need to constantly monitor the system. You can select the right control valve for the specific pressure required. It is interesting to know that Control Valves are also known as the final control element in automatic control terminology because of the process control valves operating in their systems.

What is a pressure control valve?

The valve basically controls the flow of fluid. Control valves work by changing the size of the flow passage. Control valves can directly control flow rate and quantities such as temperature, pressure and liquid level. The pressure control valve is responsible for keeping system pressures in the right range towards the desired limit. They can help to safely maintain the set pressure in the system in which they operate. You can find them in almost all hydraulic systems today.

Pressure control valves are available in different types such as relief, relief, sequence, reducing and balancing. In order to achieve the required pressure control with the help of these pressure control valves, a restriction is needed. And almost all of these types are usually closed valves and only the reducing type is usually open.

Working Principles of Control Valves

By manipulating the flowing fluid, control valves attempt to keep the variables of a flowing fluid such as chemical compounds, steam, gas and water close to the desired set point. The control signal here, which can be electronic or pneumatic, controls the CV and changes its position, ensuring accurate control of the flowing fluid and achieving profitable production requirements. It also helps save money by reducing unnecessary costs.

Hydraulic, electric or pneumatic actuators are responsible for opening and closing automatic control valves and valve positioners with the help of a modulating valve that can set the desired degree of opening of the valve. These modulating valves can be set to different positions, from fully open to fully closed, according to the desired result.

For air-actuated valves (pneumatic control valve) all that is required is a compressed air supply, making it the most widely used type due to its simplicity, while other valves, such as electrically operated valves, need additional switchgear and wiring. Hydraulically operated valves need a high-pressure supply as well as return lines for hydraulic fluid.

Air-operated (pneumatic) control signals normally operate in the pressure range 3-15psi (0.2 – 1.0 bar). For industry, an electrical signal of 4-20mA and 0-10V is required for the HVAC system.

State-of-the-art electrical control these days uses intelligent communication signal for control current from 4 to 20mA. It can feedback the status of the valve and verify its position to the controller.

Main sections of the CV

Automatic control valves have three main control valve parts: Actuator, Positioner and Valve Body.

• Actuator This part is responsible for moving the modulating element of the valve.
• Valve Body: Contains the modulating element such as Sphere or Disk.
• Valve Positioner: This unit is responsible for controlling the position of the valve and making sure that the degree of opening is the same as the desired number.

There are different types of control valves, but some are more popular than others. We will briefly discuss the most popular ones.

How CVs are classified is based on different characteristics such as pressure drop profile, movement profile of the control element, operating environment and functionality.

Different classifications, advantages and disadvantages

When classifying control valves based on pressure drop profile, there will be two common types, High Recovery valve and Low Recovery valve. Butterfly Valve, Plug Valve, Gate Valve and Ball Valve are considered as high recovery valve type. The Low Recovery valve type is the Mole Valve and Globe Valve.

The classification of control valves based on functionality includes: Check Valve (e.g.: Turbine bypass valve), Close and Open Valve (e.g.: Gate Valve, Pinch Valve) and Spring Loaded Safety Valve.

Last but not least is to differentiate control valves according to the medium that sets them in motion. This feature includes different types such as Manual Valve, Electric Valve, Pneumatic Valve and Hydraulic Valve.

Advantages of Using Control Valves

High performance and easy maintenance are just some of the great features that a high-quality control valve offers. Durability and the ability to withstand various conditions are among the other advantages you can expect from such units. You can use control valves in different industries such as gas, power, steel, petrochemical, etc.

Control valves not only save you money by eliminating unnecessary costs, but also help to minimize product variation as well as process. At the same time, they bring security through defined standards to each process of the units involved.

Now that you know all the necessary information about control valves, you can learn more about their parts and different types by studying other related articles on the Orbital Valve site. And if you have any questions, feel free to write to us and one of our experts will solve all your problems.