Definition
Control Valves are also known as the final control element in automatic control terminology which is due to the process control valves operating within their system. They can automatically do the job and eliminate the need for you to constantly keep an eye on the system. Depending on its function, the valve must control and regulate flow, temperature, pressure, level, or concentration.
Operation Principles
By manipulating the flowing fluids CV try to keep the variables of a flowing fluids close to desired set point. The variables of a flowing fluids include chemical compounds, steam, gas and water. For accurate control of the flowing fluids, the electronic or pneumatic control signals manipulates the CV and changes its location and thus attains the profitable production requirements CV helps in saving money by reducing unnecessary costs.
Hydraulic, electrical, or pneumatic actuators are responsible for opening or closing automatic control valves and the valve positioners with the help of a modulating valve that can adjust the desired degree of opening of the valve. These modulating valves can be set to different positions from fully open to fully closed based on the desired outcome.
The only thing required for air-actuated valves is a compressed air supply, making it the most commonly used type due to its simplicity, whereas other valves such as electrically operated valves need additional switchgear and cabling. Hydraulically-actuated valves also need a high-pressure supply as well as return lines for the hydraulic fluid.
Air-actuated (pneumatic) control signals are normally operating on a pressure range of 3-15psi (0.2 – 1.0 bar). For industry, an electrical signal of 4-20mA, as well as 0-10V for HVAC system, is required.
State-of-the-art electrical control uses smart communication signal for 4 to 20mA control current. It can signal back the health of the valve and verify its position to the controller.
Main Parts Of Control Valve
Valve Actuator: For moving the valve’s modulating element.
Valve Body: Contains the modulating element such as butterfly or globe.
Valve Positioner: For checking the position of the valve and making sure that its opening degree is the same as the desired number.
Types of Control Valve
Based on the pressure drop profile
High-Recovery valve - Butterfly Valve, Plug Valve, Gate Valve, and Ball Valve.
Low-Recovery valve - Angle Valve and Globe Valve.
Based on functionality
Check Valve -Turbine bypass valve.
Shut-off and On-Off Valve - Gate Valve, Pinch Valve.
Spring-Loaded Safety Valve.
Based on the movement profile of the controlling element
Sliding Stem - Globe Valve, Wedge type gate valve, Angle Valve
Rotary Valve - Ball Valve, and the Butterfly Valve
Based on the actuating medium
Manual Valve,
Pneumatic Valve
Hydraulic Valve
Advantages of using Control Valves
High performance
Easy maintenance
Durability
Adaptability
Economical
Product Variability
Safety
Universal Engineering Services has more than a decades experience in the pressure vessel design for clients in UAE, Oman, Qatar, Kuwait, Bahrain, Saudi Arabia, and many more countries all over the world. UES work to many ASME standards to design and validate pressure vessels, boiler, fittings and piping systems. We are also experts in Stress analysis of piping, structural design, ASME Joint review, Design of Storage tanks, code calculations, FEA/FEM, and spotless service on design management.
**The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations, and write-ups are only for reference and educational purposes.