Globe Vs Butterfly Valve: How To Pick The Right Control Valve

The selection of control valves is a critical step in industrial and engineering applications. Especially when managing the flow of different fluids, choosing the right valve can significantly impact costs, efficiency, and system stability. 

This article takes butterfly valves and globe valves as examples to explore in detail how to choose the appropriate valve type based on different operating conditions, highlighting their respective advantages, disadvantages, and application scenarios.

Types of Control Valves and the Importance of Selection

There are many types of control valves, with globe valves and butterfly valves being the most common. While butterfly valves offer higher flow capacity, lower cost, and minimal pressure drop, globe valves are often favored in industrial projects. This is mainly because globe valves provide better flow control and stability under high-pressure differential conditions. 

However, selecting the right valve type is no simple task, as it involves numerous considerations such as flow capacity, response time, cost, size, and environmental temperature.

The Complexity of Control Valve Selection

Choosing the appropriate control valve requires evaluating over 45 factors, including but not limited to:

• Flow capacity

• Response time

• Cost

• Size

• Failure mode

• Environmental temperature and service conditions

Given the many variables and application requirements, it is challenging to provide a universal selection guide applicable to all situations. However, establishing basic "rules of thumb" can simplify the selection process, aiding in the choice of suitable valves for different application scenarios.

Core Steps for Selecting Control Valves

1. Determine the Service Type: Modulating or On-Off

Modulating Service: Used for regulating flow based on specific flow requirements.

On-Off Service: Designed for applications where the valve is either fully open or fully closed.

Different valve types perform differently in these services. Due to their structure, some valves are inherently better suited for flow control, while others excel in on-off operations. For example, globe valves are typically better for regulating flow, while gate valves are more appropriate for large on-off applications.

2. Determine Valve Size

Small Valves (2-6 inches): For smaller sizes, globe valves are often preferred due to their superior flow control and relatively lower cost in this range.

Large Valves (Above 6 inches): For larger valves, costs increase significantly with material requirements. Thus, selecting a cost-effective valve with stable performance becomes crucial.

3. Evaluate Pressure Drop (DP)

Pressure drop (DP) refers to the difference in pressure between the upstream and downstream sides of the valve and has a significant impact on valve performance. High-pressure drops can lead to issues like cavitation, flashing, and clogging. Under such conditions, globe valves are often prioritized as they handle high-pressure drops better and provide precise flow control.
This explains why globe valves are frequently chosen over butterfly valves in many industrial projects.

4. Assess the Need for Flow Control Precision

High-Precision Control: Globe valves excel in precise flow regulation, making them ideal for applications requiring exact flow adjustments.

General Control: If flow precision is not critical, butterfly valves are a more cost-effective choice, especially for large sizes and low-pressure-drop applications, where they can help save significant costs.

Types and Applications of Butterfly Valve Designs

Butterfly valves can be categorized into concentric and eccentric designs:

Concentric Design:

The valve stem is located at the center of the valve. This design is suitable for general-purpose applications.

Eccentric Design:

Includes double-offset and triple-offset designs, typically used for high-performance applications. These are ideal for scenarios requiring metal-to-metal sealing, offering high sealing performance during closure.

Eccentric designs are particularly well-suited for applications where the valve needs to maintain stable control at an opening angle of around 60 degrees. Although these designs are generally more expensive, they provide superior performance.

Summary of the Selection Process

1.Determine the Service Type:

For modulating service, choose valves suited for precise flow regulation.

For on-off service, select valves designed for fully open or closed operation.

2.Determine Valve Size:

Small Sizes: Globe valves are recommended for better flow control and cost efficiency.

Large Sizes: Consider cost and precision requirements, with butterfly valves often being more economical for large sizes.

3.Evaluate Pressure Drop:

For high-pressure drop, globe valves are preferred to ensure better flow control and prevent issues like cavitation and flashing.

For low-pressure drop, butterfly valves can help reduce costs.

4.Flow Control Precision:

For high-precision applications, globe valves are ideal.

For general control, butterfly valves, particularly high-performance designs, are sufficient and cost-effective.

5.Cavitation and Flashing:

In cases where cavitation and flashing are likely, globe valves are recommended. If the application involves no solid particles or high-viscosity fluids, consider using a globe valve with anti-cavitation trim for optimal performance.

6.Handling Solid Particles:

For applications involving fluids with solid particles, select wear-resistant valve designs such as Y-pattern globe valves or angle valves, which are better suited for such scenarios.

Conclusion

Selecting control valves is a complex decision-making process that requires a thorough evaluation of fluid characteristics, application requirements, cost, and service life. By understanding the core needs of modulating and on-off services and choosing valves based on factors such as pressure drop and control precision, system efficiency and reliability can be ensured.

Additionally, it is recommended to have detailed discussions with valve suppliers before making a final decision to ensure the valve design meets the specific operating conditions and application requirements.

TFW is a professional valve manufacturer, offering a wide range of standard valves as well as custom designs to meet exact customer specifications. If you have any questions, please contact us.