Control valves in Industrial Control.

Control valves are very important in the control system. they regulate the flow of physical components such as pressure, temperature, and liquid levels. They are widely used with automation systems in industrial processes like mining, cement, power generation, water treatment, oil and gas valve trains, and even in the field of Renewable energy.

Control valves usually exist at the field level of the automation pyramid. They convert the electrical signal from the PLC output to a rotation or linear movement (fully open or closed) or percentage (%) depending on the output hardware of the PLC system.

Control Valve

In previous articles, we discussed in detail the field level and its instrumentations and explained generally its components like control valves and sensors. In this article, we will go deeply into the control valves to learn more about their definitions, advantages, and applications use the electrical control Valve.

What is the meaning of the control valve?

Technically, the control valve is a mechanical device used in industrial processes to do a certain job which is controlling the pressure, temperature, and flow of material or area by regulating the process’s control parameters according to the control signals from the controllers.

What are the components of the control valve?

The control valve components vary based on the type, application, and process using the control valves. It consists of the following:

Housing (Body). Is the valve’s body that contains the internal components such as moving parts, seat, plug, and electronic circuits and components such as sensors and printed circuit Bordss (PCB). This housing is normally fabricated according to the application such as steel, stainless steel, and other alloys.

Actuator. It is the essential part of the control valve. It is responsible for the power to move the control valve’s parties such as the seat, disk, and plug. The result of this force causes the changing of the control action according to the control signal and as a result regulates the flow, pressure, and temperature needed. This actuator could be an Electrical, Pneumatic, or Hydraulic actuator.

Control Valve Components

Positioner. It shows the exact position of the actuator (open, closed, or %) to confirm the reach of the needed position which helps adjust the new action to achieve the requested position. This positioner could be supported by a 4-20 mA transmitter.

Valve trim. They are the internal parts of the valve that act directly with the controlled parameters like flow to determine its capacity and size. These internal parts are Gland Sleeve or bush, Gland packings, Stem, Disk, and Seat.

Some options could be added to the control valve like open and close limit switches to show the indication and status of the control valve and could also be used in other control loops that depend on the position of this control valve such as the DCS and SCADA system.

Control valves also have a bonnet to prevent leakage around the stem. There are also the Gaskets and seals that are used when connecting the valve with other mechanical parts.

What is the operation principle of the control valve?

Based on the feedback signal from the sensors and instrumentation system in the process feed, which represents the process value (Flow, Pressure, or level), the controller or PLC calculates the required control signal and sends it to the control valve.

The control valve’s actuator moves or rotates the internal parts of the control valve to increase or decrease the physical position of the seat to open or close the valve till gets the final position that optimizes the required values.

What are the advantages of the control valves?

Accurate Control of Process Parameters by adjusting, maintaining, regulating, and managing the control parameters for level, temperature, flow, and pressure.
Reliability and Durability where the control valves are designed to work in tough operating conditions such as very high pressure and extremely high or low temperature, and finally a corrosive environment. It has also a long service life when properly maintained.
Easy Automation Compatibility by integrating these items with the main Control systems such as distributed control systems (DCS) or programmable logic controllers (PLC). It also enables remote adjustment and remote monitors using the remote desktop and mobile application.
Energy saving and energy efficiency by optimizing the process condition and minimizing waste through using digital and analog control signals to prevent overpressure and unneeded flow to reduce energy costs.
Maintain safe operating conditions and increase process safety factors by preventing system overpressure or cavitation as well as the ability for system shutoff in emergency cases to protect equipment and personnel in case of any failure or hazardous events.
Improve Process Efficiency and increase Product Quality by Maintaining optimal process conditions which leads to consistent products with maximum quality. It also enhances the process productivity reduces downtime and ensures smooth operation.

What are the applications that use the control valve?

Automotive Industry. Control valves are used to control the flow and pressure of paint in automated systems. To manage fuel and airflow in test benches. And finally, it regulates coolant flow in engine manufacturing and testing.

Cement and steel manufacturing. It is used in all stages of cement manufacturing from crushing to dispatching especially in grinding and pyro processes used in steel furnaces to control the temperature and fuel control.

Oil and Gas Industry. Used to regulate the pressure in oil and gas pipelines, prevent damage, and manage the flow of crude oil and natural gas from production wells. It is also used in distillation and other refining operations to control temperature, pressure, and flow. And finally, it regulates the gas compression and dehydration systems.

Renewable Energy. it is used in Solar Thermal Plants to regulate heat transfer fluids in solar collectors. It is used in Wind Turbines to manage hydraulic systems used for pitch control. It is used in Hydropower where it controls water flow in turbines and spillways.

Power Generation. It manages the flow of steam to turbines in thermal and nuclear power plants and controls the flow of water into boilers to maintain consistent levels and pressure. Finally regulates cooling water flow in heat exchangers and condensers.

Chemical and Petrochemical Industry. It is used to maintain precise flow and pressure of reactants to achieve optimal chemical reactions, manage heating or cooling fluids in reactors, and control reflux and product draw-off to ensure product quality.

Water and Wastewater Treatment. It is used to regulate the flow of water through treatment processes. To ensure safe operation of pumps and pipes by maintaining appropriate pressure levels. And finally, to control the flow of chemicals like chlorine and coagulants for water treatment.

Food and Beverage Industry. To ensure precise flow rates of ingredients in mixing and blending processes, to regulate heating or cooling in pasteurization, sterilization, and fermentation processes. Finally, it manages cleaning-in-place systems by controlling the flow of cleaning agents.

Pharmaceutical Industry. It is used to maintain strict control of fluid flow in sterile manufacturing environments and to regulate small, accurate amounts of ingredients or chemicals

HVAC Systems.it is used to control airflow in heating, ventilation, and air conditioning systems. It regulates water flow for cooling in commercial and industrial buildings. It manages the distribution of steam in heating applications.