You must have heard about control valves at well sites, gas plants, refineries, and petrochemical plants. However, what exactly is a valve? Basically, a valve is used for controlling, managing and directing the flow of fluids, temperature, pressure, or liquid levels by varying the size of the flow passage. Thus, read on to learn more about components, uses and working of these valves that are so commonly used in industries.

What Is The Use Of A Control Valve?

In process plants, there are usually thousands of control loops which are networked together to produce a final product. Each of the control loops so designed has a basic function to keep some important process variable such as pressure, flow, variable, or temperature within a required operating range to ensure the best quality of the final product. Furthermore, the loops receive and internally create disturbances that keep the process variable.

However, the effect of such load disturbances often goes beyond a desired set point. In such a situation a controller such as a mini valve processes the information, decides what needs to be done and gets the process variable back to where it was before the load disturbance occurred.

What Does A Valve Consist Of?

Valves such as a mini valve consist of the following parts:

1) Body- The body is basically a pressure vessel that contains an orifice otherwise called an opening. The controlled liquid flows through the body of the valve and monitors the flow regulation behavior.

2) Trim- A trim is a central part of the valve which often comes in contact directly with the fluid. The trim can consist of a seat, disc, plug, or stem.

3) Actuator- An actuator essentially consists of an electric or pneumatic medium that provides the force required by a valve to function.

4) Bonnet- The bonnet prevents any leakage by mounting for the guide and actuator and providing a medium wherein the stem can pass through.

What Is The Working Principle Behind A Control Valve?

Pneumatic Actuated- Pneumatic actuators modulate the control action by using an air or gas signal from an extended source. An actuator starts working when it receives a signal through the top port, thereafter it distributes this signal across the actuator’s diaphragm, which in turn, exerts pressure on the diaphragm plate. The plate then moves downward in such a way that it strokes the valve.

Electric Actuated- Electric actuators are motor-driven devices that use electric signals to create motor shaft rotations. The movement so created through the rotation helps to drive the stem in the valve for flow modulation.

A valve in simple words is an end device that is used to control the process based on the information collected from transmitters and sensors. Through the information collected the valve decides the course of action to get the process variable to the desired set point.

James Brown is the author of this article. For further detail about Control Valves. Please visit the website: airmite.com