Control valves are control devices that are used to manage and control fluid flow, pressure, temperature, or liquid level by varying the flow passage size. In process systems of production wells, oil and gas plants, Chemical and Petrochemical industries, refineries, and power plants, Control valves are frequently used to control or manage any of the process parameters.

The piping systems of industrial, commercial, residential, and other civic facilities carry the lifeblood of modern civilization, like arteries and veins. And the valves in those piping systems serve the functions of allowing, stopping, regulating, and controlling the flow, to fulfill the intended objectives of the system.

Valves are an essential part of any piping system that conveys liquids, gases, vapors, slurries and mixtures of liquid and gaseous phases of various flow media.

Some valves are self-actuated while others are manually operated or have actuators that are powered with electric motors, are pneumatic or hydraulic, or a combination to operate the valve. Valves are manufactured with metals and non-metals.

What is a Control Valve?

The control valve is an automated valve that can make precise adjustments to regulate and monitor any commodity flowing through a piping system. The function of a control valve is to provide throttling control in response to signals from a control system, using an actuator and a positioner. They are considered the ‘‘final control element’’ in an automated and usually very sophisticated ‘‘control loop.’’

A control valve receives the information from various sensors and transmitters in a control loop and processes that data to manage the control of the fluid parameter. The following figure shows a typical control loop for a control valve

Components of Control Valve

Control valves have basically three interactive components:

  1. a valve body subassembly (either with a reciprocating or rotating stem),
  2. an actuating device (usually a spring diaphragm type),
  3. a valve positioner (an instrument that converts an electronic control signal from a controller, or computer, into an air signal to control the position of the control valve stem), and
  4. an air set or regulator to supply air pressure to the positioner.

Control Valve Features

The most common valve body style used as a control valve is the globe valve. Although many other body styles such as angle valves, Three-way valves, Eccentric rotary plug valves, semispherical ball valves, Ball Valves, Butterfly valves, etc are used, the globe valve provides the most effective means to regulate and control flow.

Control valves use signals received from instruments positioned throughout the piping system to automatically make adjustments that regulate the commodity within the pipe. Though control valves can perform many functions, they are typically used to control the flow of a commodity within a pipe or to limit its pressure.

Control valves must be arranged within a run of the pipe so that they can be easily operated. To achieve this, control valve manifolds are configured. Control valve manifolds make control valves readily accessible to plant workers.

Applications of Control Valves

  1. Used for on – off applications.
  2. It can be used for throttling purposes.
  3. It can be used for pressure and flow control.
  4. Low pressure applications and large flow control.
  5. Can be used for corrosive liquids at low pressure and temperature.

Advantages of Control Valves

  1. It provides control over flow rate.
  2. It has effective and rapid functioning.
  3. It has durable service life.
  4. It has compact design which facilitates minimal consumption of space.
  5. It have minimum pressure drop.

Disadvantages of Control Valves

The only disadvantage of control valves is that they require control signal throughout its working period.

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