How to Choose the Right Butterfly Valve: A Comprehensive Guide

In modern industrial piping systems, butterfly valves have become one of the most widely used types of valves due to their compact structure, rapid opening and closing, and superior flow control performance. From water treatment and chemical processing to urban heating systems, butterfly valves play a critical role under various operating conditions. However, faced with the wide variety of butterfly valve types, materials, and sealing methods on the market, determining how to select the most suitable butterfly valve based on specific medium characteristics, operating conditions, and control requirements has become a significant challenge in engineering design, operation, and maintenance. This article aims to provide a comprehensive guide to butterfly valve selection, covering the basic characteristics of butterfly valves, sealing forms, common types and their applications, key selection considerations, and practical case studies. This guide will help engineers, technicians, and operators make accurate and informed choices in different industrial applications.

A butterfly valve is a relatively simple type of valve. Its disc is installed along the diameter of the pipeline and rotates around an axis within the cylindrical passage of the valve body. The rotation angle typically ranges from 0° to 90°, with 90° representing the fully open position. This simple yet effective design offers several advantages. The valve is compact and lightweight, typically consisting of only a few components, making it easy to operate. A simple 90° rotation is sufficient to fully open or close the valve.

When fully open, the only obstruction to the flow of the medium is the thickness of the valve disc itself. As a result, the pressure drop caused by the valve is minimal, while the flow control performance is excellent. This makes butterfly valves particularly suitable for pipelines where precise flow regulation is required. Moreover, due to their simple structure, these valves are generally more cost-effective to manufacture and maintain compared to more complex valve types such as globe or gate valves. Their compact size also makes them suitable for installations in pipelines with space constraints, which is an increasingly common requirement in modern industrial facilities.

Butterfly valves mainly employ two types of sealing: elastic (soft) sealing and metal sealing.

Elastic Sealing: Elastic-sealed butterfly valves feature sealing rings that can either be embedded in the valve body or attached around the periphery of the disc. The primary advantage of elastic seals is their excellent sealing performance, which ensures effective shutoff. However, these valves are generally limited by temperature constraints, making them suitable for ambient or relatively low-temperature environments. Soft seals are commonly used in water, wastewater, and low-pressure fluid applications, providing a reliable seal while allowing smooth operation with minimal torque.

Metal Sealing: Metal-sealed butterfly valves are capable of withstanding higher working temperatures and typically have a longer service life compared to elastic-sealed valves. While achieving perfect sealing is more challenging, metal-sealed valves are better suited for high-temperature or harsh environments where durability and longevity are critical. They are commonly used in steam, gas, and corrosive media pipelines where elevated temperatures or pressures would degrade soft sealing materials. Metal sealing can take various forms, such as line contact or face contact, and is often paired with eccentric disc designs to enhance sealing performance and minimize wear over extended service life.

Understanding the difference between these sealing methods is crucial when selecting a butterfly valve, as the choice directly impacts both operational efficiency and maintenance requirements. The specific application, medium characteristics, and temperature range will determine which sealing type is most appropriate.

After understanding the basic characteristics and sealing forms of butterfly valves, it is essential to consider the common types and the scenarios in which they are most suitable. Butterfly valves are available in a variety of designs, each with unique structural and performance features that make them suitable for different industrial conditions.

Wafer-Type Butterfly Valves: These valves are installed between two pipe flanges using tie bolts. Their compact structure makes installation and removal convenient, and they are ideal for applications with limited space. Wafer-type valves are widely used in HVAC systems, water distribution pipelines, and chemical processing plants where space constraints are common.

Flanged Butterfly Valves: Flanged valves have integral flanges on the valve body, which are bolted directly to the pipeline flanges. This design provides superior sealing performance and allows the valve to withstand higher pressures. Flanged butterfly valves are commonly used in industrial pipelines that require higher pressure ratings and reliable sealing, such as chemical processing, power plants, and oil and gas distribution networks.

Concentric (Liner-Sealed) Butterfly Valves: These valves are suitable for pipelines that require complete sealing, zero leakage during gas testing, high durability, and operating temperatures between -10°C and 150°C. They are used in various media, including freshwater, wastewater, seawater, brine, steam, natural gas, food, pharmaceuticals, oils, and various acids and bases. Concentric butterfly valves are typically soft-sealed and provide reliable performance in standard industrial applications.

Soft-Seal Eccentric Butterfly Valves: These valves are designed for bidirectional opening and closing as well as flow regulation. They are commonly used in ventilation and dust removal pipelines, as well as in coal gas pipelines and water systems in metallurgy, light industry, electric power, and petrochemical systems. The eccentric design reduces friction between the disc and seat, extending valve life and ensuring smooth operation.

Double-Eccentric Metal-Seal Butterfly Valves (Metal-to-Metal Line Contact): These valves are ideal for urban heating, gas, and water supply pipelines that transport coal gas, oil, acids, and alkalis. They serve as regulating and throttling devices, providing stable operation under higher temperatures and pressures.

Triple-Eccentric Metal-Seal Butterfly Valves (Metal-to-Metal Face Contact): Used not only in large-scale Pressure Swing Adsorption (PSA) gas separation control systems but also widely across petroleum, petrochemical, chemical, metallurgical, and power industries. These valves are excellent substitutes for gate and globe valves, particularly under demanding conditions such as strict throttling regulation, high sealing requirements, severe wear, or low-temperature (cryogenic) operations. Triple-eccentric valves allow precise control while minimizing wear and extending operational life.

Given the wide variety of butterfly valves and complex operating conditions, how can engineers accurately select the most suitable valve in practice? Multiple key factors must be considered, as they directly affect the valve's performance, service life, and the overall efficiency and safety of the pipeline system.

The properties of the medium, such as temperature, pressure, and corrosiveness, are primary considerations. For conventional water, a soft-seal butterfly valve is sufficient. For steam or high-temperature fluids, a hard-seal butterfly valve is required. For corrosive media, such as acid or alkali solutions or seawater, selecting a butterfly valve made from appropriate stainless steel materials is essential, based on the degree of corrosiveness. Temperature is also critical: soft-seal valves are suitable for ambient conditions; hard-seal valves should be used above 120°C; and for temperatures above 400°C, special valve body materials are required to meet the operational temperature range.

Different operating conditions place varying demands on butterfly valves. For pipelines requiring throttling, flow regulation, and handling of slurry media, valves with a short structural length, fast opening and closing (¼ turn), and low-pressure cutoff are highly suitable. In applications involving dual-position regulation, reduced ports, low noise, cavitation, vaporization, minor atmospheric leakage, or abrasive media, butterfly valves can also perform effectively, though specialized designs may be necessary. Large-diameter pipelines (e.g., DN1000+) particularly benefit from butterfly valves due to their short structural length and suitability for large flows, meeting both space and flow control requirements.

The choice of actuation method should be based on automation and control requirements. Pneumatic or electric actuators are appropriate for automated or intelligent control systems. Where no air supply is available, electric drives are preferable. For large-diameter valves, manual operation can be challenging, and powered actuation ensures easier and safer opening and closing. Selecting the appropriate actuation method can improve operational efficiency and reduce the likelihood of mechanical failure during valve operation.

Butterfly valves can be connected via flange, wafer, grooved, or butt-welded connections. Different connection types are suited for different pipeline systems and installation environments. Flanged connections provide better sealing for high-pressure pipelines, while wafer connections are convenient in installations with limited space. Proper selection of connection type ensures system integrity, reduces leakage risk, and facilitates maintenance.

Practical case studies help illustrate how to select the appropriate butterfly valve in real-world scenarios, applying theoretical knowledge to solve operational challenges.

A chemical plant required the transportation of a corrosive acidic solution, with flow regulation needed at approximately 80°C. After thorough evaluation, a stainless steel soft-seal eccentric butterfly valve was selected. This valve resisted corrosion from the acidic solution, provided reliable sealing performance, offered smooth operation due to its eccentric structure, and met the flow control requirements of the plant.

In an urban heating system, the pipeline transported high-temperature hot water or steam, and the valve needed to function as a regulating and throttling device. A double-eccentric metal-to-metal line-seal butterfly valve was chosen. It could withstand high temperatures, and although the metal seal could not achieve perfect sealing, it met the operational requirements. The double-eccentric design ensured stable opening and closing and allowed effective flow regulation and throttling.

Selecting the right butterfly valve not only affects the safety and reliability of a pipeline system but also directly impacts operational efficiency and service life. By fully understanding the basic characteristics, sealing types, common models, and applicable operating conditions of butterfly valves, combined with practical case analyses, engineers can make more scientific and informed valve selection decisions. Whether for industrial chemical pipelines, urban heating systems, or other complex operational scenarios, proper butterfly valve selection ensures precise, efficient, and safe fluid control, providing a solid foundation for the stable operation of the entire system.