How to Select the Right Control Valve for Process Industries

Control Valve for Process Industries

The choice of a proper control valve is one of the critical aspects in the development and operation of efficient process systems. A good control valve will help in achieving stable flow, pressure, temperature, or liquid level, while the improper control valve will lead to inefficient process control.

The control valve selection is not only about matching the right valve size with the pipe size. The process parameters, flow behaviour, the drop in pressure, media properties, valve design, and actuator requirements are some of the aspects that need to be taken into account when choosing the valve. Knowledge on how to select a control valve for process industries can assist engineers and operators in making the right choice.

What Is a Control Valve?

A control valve is a device which is installed in an automated process system as a means of controlling the flow of fluid, gas or steam. A control signal from the controller acts upon the valve to regulate the flow passage.

In terms of applications, a control valve can be used in industry to:

•       Control flow rate
•       Control pressure
•       Control temperature
•       Control liquid level

A flow control valve controls the amount of fluid flowing through a process system, whereas a pressure control valve assists in maintaining the needed pressure in downstream or upstream processes. Likewise, a temperature control valve helps adjust the flow of the heating or cooling media so that the process can be maintained at a certain temperature.

Why Choosing the Right Control Valve Matters?

The correct selection of an industrial control valve can have a significant impact on process stability, efficiency, and equipment performance. A wrongly selected valve can work either close to the fully open position or close to the fully closed position.

Oversizing is one of the most prevalent problems in control valve selection. A valve that is oversized for the necessary flow may be poor in terms of controllability, because small displacements may lead to substantial changes in flow. Meanwhile, the undersized valve may limit process capability and fail to provide necessary flow.

Valve selection will help you get:

• Smooth process control
• Smooth flow regulation
• Sustainable pressure and temperature control
• Energy conservation
• Minimum valve wear
• Better automation efficiency
• Higher process reliability

Thus, a selected valve will be appropriate not only for current working conditions but also for possible changes in flow, pressure and process demands.

Key Factors to Consider When Selecting a Control Valve

Some important factors have to be considered when selecting a control valve.

Process Media

First, it is important to consider media parameters for your process. The valve can operate with different media: liquids, gases, steam, air, chemicals or other process fluids. Such media parameters as viscosity, density, temperature and the presence of suspended matter can influence material selection and valve design.

Materials of construction of the body, trim, seat and seal shall be compatible with the process media and conditions of service.

Flow Requirements

The minimum, normal and maximum flow rates required should be taken into consideration. It is very important for the control valve sizing process as well as for establishing whether the chosen valve is capable of providing stable control at all ranges of operating points.

Valve should be able to withstand process variations without losing its controllability.

Pressure and Pressure Drop

Operating pressure and available pressure drop are among the key control valve selection factors. The pressure drop through the valve directly influences the valve flow capacity.

Inadequate pressure drop may affect the valve capability to control the process; on the other hand, too high pressure drop may cause such problems as energy loss, noise, vibration, cavitation and others, depending on the particular application.

Valve Type and Flow Characteristics

The type of control valve determines the flow characteristics and advantages.

Globe control valve is typically chosen for applications where good throttling and control is required. This type of valve can give proper control in different process conditions.

Angle seat control valve can be used for applications where compact design, quick opening and handling of compatible fluids, steam or gas is required.

There are other types of automatic control valves which could be chosen based on different criteria such as flow capacity, pressure rating, and shut off requirement and installation space.

The appropriate control characteristic should be also considered. Linear or equal-percentage flow characteristics could be more appropriate for certain applications.

Operating Temperature

Extreme high or low process temperatures may impact valve body, seat, seal and packing materials. Therefore, process temperature considerations must be taken into account in the selection process.

It is important that the chosen industrial control valve is made from materials capable of operating in the desired temperature range.

Requirements for Installation and Maintenance

Installation space, pipeline arrangement and accessibility for maintenance can be a factor in selecting a valve. The valve must be easy to install and maintain in an existing process system.

The factors like maintenance, spares and operational costs need to be taken into consideration while selecting a control valve manufacturer in India or a control valve supplier in India.

How to Choose the Right Type of Control Valve

Selecting the right control valve depends on the process requirements, flow conditions, and type of media being handled. Common options include:

Globe Control Valves

Globe Control Valves are designed for precise throttling and effective flow, pressure, and temperature control. They are suitable for demanding process applications where accurate regulation is required.

Butterfly Control Valves

Butterfly Control Valves are well suited for large pipeline applications. Their compact and lightweight design makes them practical where high flow capacity and efficient installation are required.

Angle Seat Control Valves

Angle Seat Control Valves provide fast response for applications involving steam, water, air, and process fluids. They are suitable for reliable flow control in various industrial processes.

3/2 Mixing and Diverting Control Valves

3/2 Mixing and Diverting Control Valves are used for combining or redirecting process flows. They are suitable for mixing and diverting applications in process plants and utility systems.

How to Size a Control Valve

Proper control valve sizing helps achieve stable flow regulation and reliable process performance. Consider the following factors when selecting the right valve size:

Determine the Required Flow Rate

Identify the minimum, normal, and maximum flow rates required by the process. This provides a suitable basis for selecting the valve size and capacity.

Calculate Pressure Drop

Determine the pressure difference across the valve under operating conditions. The available pressure drop is important for selecting a valve that can provide effective flow control.

Understand Cv and Kv Values

Cv and Kv indicate the flow capacity of a control valve. Comparing these values with the required process flow conditions helps determine the appropriate valve size and configuration.

Avoid Oversizing and Undersizing

An oversized valve may make precise control difficult, while an undersized valve may restrict the required flow. Selecting the correct size helps maintain efficient and stable process control.

How to Select the Right Control Valve Actuator

Selecting the right actuator depends on the valve type, operating conditions, response requirements, and desired safety function. Common actuator options include:

Pneumatic Actuators

Pneumatic actuators use compressed air to operate the control valve and are widely used for fast and reliable operation in process industries.

Electric Actuators

Electric actuators use an electric motor to operate the valve. They are suitable for applications requiring automated, remote, or controlled valve operation.

Spring Return and Double-Acting Actuators

Spring return actuators use a spring to move the valve to a defined position when the actuator loses its operating supply. Double-acting actuators use air pressure for both opening and closing, offering controlled operation in both directions.

Fail-Open and Fail-Closed Requirements

The required failure position should be considered during actuator selection. Fail-open actuators move the valve toward the open position during a loss of power or air supply, while fail-closed actuators move it toward the closed position, depending on the actuator and valve configuration.

Control Valve Selection for Different Process Industries

Control valve selection varies by industry based on process conditions, media, flow requirements, pressure, temperature, and safety considerations. The right valve configuration helps support reliable and efficient process control.

Oil and Gas

Control valves are used for flow, pressure, and temperature regulation across oil and gas processing and pipeline systems. Valve selection should consider demanding operating conditions and process media.

Chemical and Petrochemical

Chemical and petrochemical plants require control valves suitable for process fluids, varying temperatures, pressures, and flow conditions. Material and configuration should match the specific application.

Power Generation

Control valves are commonly used for steam, water, fuel, and other utility systems in power plants. Reliable flow and pressure control are important for efficient plant operation.

Pharmaceutical

Pharmaceutical processes require valves selected for hygienic service and precise process control. The valve design and materials should suit the process and cleaning requirements.

Food and Beverage

Control valves help regulate fluids and process media in food and beverage production. Hygienic design, suitable materials, and reliable operation are key selection factors.

Water and Wastewater Treatment

Control valves are used for regulating water flow, pressure, and treatment processes. Selection depends on flow requirements, media, and the operating conditions of the treatment system.

Steel and Other Heavy Industries

Heavy industries require robust control valve solutions for demanding process and utility applications. Valve selection should consider high temperatures, pressures, process media, and operating conditions.

Control Valve Selection Checklist

Use this practical checklist to review the key factors before selecting a control valve for your process application:

•   Process fluid – Identify the type and properties of the fluid being handled.
•   Flow rate – Determine minimum, normal, and maximum required flow.
•   Pressure – Check inlet and outlet pressure conditions.
•   Temperature – Consider minimum and maximum operating temperatures.
•   Pressure drop – Determine the available pressure drop across the valve.
•   Valve size – Select a size suitable for the required flow and piping system.
•   Material – Choose body and internal materials compatible with the process.
•   Cv/Kv – Verify the required flow capacity of the valve.
•   Control accuracy – Define the required level of flow or process control.
•   Leakage requirements – Select the appropriate shut-off or leakage class.
•   Actuator type – Choose pneumatic, electric, or another suitable actuator.
•   Fail-safe action – Determine whether fail-open, fail-closed, or another position is required.
•   Connection type – Verify flange, threaded, or other piping connection requirements.
•   Maintenance requirements – Consider accessibility, servicing, and replacement needs.

Why Choose Asten Controls for Control Valve Solutions?

Asten Controls is a company providing industrial valve solutions for processes requiring control of flow, pressure and automation processes. It helps the customers to choose the right valve solutions according to the process requirement and the operating conditions.

• Range of control valves: Asten Controls provides control valves which suit different industrial flow and automation requirements.
• Selection of valve for an application: Valve solutions can be selected considering the process media, pressure, temperature, and flow and control requirements.
• Modifications in configuration: Modifications and configurations can be made for special requirements of an application.
• Engineering and manufacturing: Engineering skills and manufacturing help in providing reliable industrial valve solutions.
• Process industries assistance: Technical support can help in choosing appropriate process control valves and automated valve solutions.

In short, as a control valve manufacturer in India, Asten Controls provides solutions customized according to the requirements of the applications.

Frequently Asked Questions about Control Valve Selection

How do I choose the proper control valve?

To select the proper control valve, you have to first evaluate the media of process, the desired flow, pressure, temperature, pressure drop and control needs. Thereafter you have to choose the proper valve type, size, and material and actuator arrangement.

What needs to be considered for choosing the proper control valve?

Some important considerations are the properties of media, minimum and maximum flow, pressure, temperature, pressure drop, requirement of shut-off, valve materials, flow properties, actuator type and installation requirements.

How can I determine the size of the control valve?

Sizing of the control valve is usually done based on flow and process conditions. Sizing calculation may involve flow coefficient requirements, pressure drop, fluid density or specific gravity, temperature and other process parameters. But sizing cannot be determined using only the nominal pipeline size.

Which control valve is better suited to my application?

It really depends on your particular application. Globe control valve would be appropriate for precise throttling, while an angle seat control valve is chosen for some compact and high cycle applications.

How do I choose a control valve actuator?

Take into account the necessary force/torque, power source, response time, control signal and safety. The pneumatic actuators are widely used in the field of automation processes, electric actuators are used in cases when electrical drive is required.

How pressure drop influences control valve selection?

Pressure drop influences the flow capacity of the valve and its controllability. Insufficient pressure drop reduces controllability, too large pressure drop leads to energy losses and vibrations/noise in some cases.

Conclusion: Selecting the Right Control Valve for Your Process

Choosing the right control valve requires taking into account different aspects of process conditions and needs. Properties of media, flow range, pressure, temperature, pressure drop, valve type, and sizing and actuator selection are important factors.

Asten Controls will help you get control valve solutions suitable for different applications, which include pneumatic control valves, globe control valves, angle seat control valves, and many others.