How to Choose the Right Butterfly Valve

Introduction

Butterfly valves are a type of quarter-turn valve that is commonly used in a wide range of industrial applications. They are named after the butterfly-like shape of their disc, which rotates around a central axis to control the flow of fluid through the valve. Butterfly valves are known for their simplicity, reliability, and cost-effectiveness compared to other types of valves.

However, not all butterfly valves are created equal, and choosing the right one for your specific application is crucial. The wrong butterfly valve can lead to leaks, flow control issues, and even safety hazards. On the other hand, the right butterfly valve can ensure optimal performance, efficiency, and safety in your operation.

This article will discuss the basics of butterfly valves, the factors to consider when choosing a butterfly valve for your application, and specific considerations for several industries including food processing, refineries, shut-off valves, ship building, and other applications. By the end of this article, you will better understand how to choose the right butterfly valve for your needs.

Butterfly Valve Basics

A butterfly valve is a quarter-turn valve that controls the flow of fluid through a pipe by rotating a disc-shaped component in the valve body. The disc is attached to a stem that passes through the center of the disc and is connected to an actuator, which can be manually operated or automated. When the valve is fully open, the disc is perpendicular to the flow of fluid, allowing for maximum flow. When the valve is fully closed, the disc is parallel to the flow of fluid, blocking the flow completely.

A butterfly valve typically consists of the following components:

Body
The main housing of the valve contains the disc, stem, and actuator.

Disc
The disc is the component that rotates within the valve body to control the flow of fluid.

Stem
The stem connects the disc to the actuator and passes through the center of the disc.

Actuator
The actuator is the component that opens and closes the valve. It can be manually operated or automated, depending on the application.

Seat
The seat is the component that provides a tight seal around the disc when the valve is closed.

Bolts
The bolts hold the valve components together and secure the valve to the piping system.

There are three main types of butterfly valves:

Wafer Butterfly Valves
Wafer butterfly valves are designed to fit between two flanges and are held in place by bolts that pass through the valve body and the flanges. They are the most common type of butterfly valve and are suitable for various applications, such as HVAC systems, pharmaceutical processing, food processing, water treatment plants, or chemical processing. 

Lug Butterfly Valves
Lug butterfly valves have threaded inserts on either side of the valve body that allow them to be bolted to the pipe. They are often used in applications where the valve needs to be easily removed from the piping system for maintenance or replacement.

Flanged Butterfly Valves
Flanged butterfly valves have flanges on either side of the valve body that allow them to be bolted directly to the pipe. They are suitable for applications where high-pressure or high-temperature fluids are being transported.

Factors to Consider When Choosing a Butterfly Valve

When choosing a butterfly valve for your application, it is important to consider several factors to ensure optimal performance, efficiency, and safety. The following are some of the key factors to consider:

Fluid Characteristics

The fluid transported through the valve will have a significant impact on the type of butterfly valve that is suitable for the application. Factors to consider include:

Temperature
The fluid’s temperature can affect the construction material, as some materials may not be suitable for high-temperature applications.

Pressure
The pressure of the fluid can impact the design of the valve, as higher pressure applications may require a stronger valve construction.

Viscosity
The fluid’s viscosity can affect the flow rate and the valve size required.

Corrosiveness
If the fluid is corrosive, the valve material must resist corrosion.

Application

The specific application will also influence the type of butterfly valve required. Factors to consider include:

Industry
Different industries have different requirements for butterfly valves. For example, food processing applications may require valves that are easy to clean and have sanitary designs.

Function
The function of the valve (e.g., shut off, throttling) will determine the type of valve required.

Location
The valve’s location (e.g., above or below ground) will impact the design and construction.

Size of the Valve

The required valve size will depend on the flow rate and pressure of the transported fluid. Therefore, choosing the right valve size is important to ensure optimal performance and prevent issues such as flow restriction or leakage.

Material of Construction

The material of construction impacts one’s choice in that different materials are better suited for different fluid characteristics and applications. Common materials for butterfly valves include stainless steel, PVC, and cast iron. 

Stainless Steel
Stainless steel is highly durable and corrosion-resistant, making it ideal for use in applications with harsh chemicals, high temperatures, and corrosive environments, such as in the chemical processing, food and beverage, and pharmaceutical industries. Stainless steel also has a smooth surface finish, making it easy to clean and maintain, which is important in industries where cleanliness and hygiene are critical.

PVC
 PVC (polyvinyl chloride) is a lightweight and cost-effective material commonly used in applications with low-pressure and low-temperature requirements, such as in water treatment plants and swimming pool systems. PVC is resistant to chemical corrosion and easy to install and maintain.

Cast Iron
Cast iron is a durable and long-lasting material commonly used in applications with high pressures and temperatures, such as in the oil and gas industry. Cast iron is also relatively inexpensive compared to other materials, making it a cost-effective choice for applications where cost is a significant factor.

Cost and Budget Considerations

The cost of the valve will depend on the type of valve required, the construction material, and the valve’s size. Therefore, balancing cost considerations with the required performance and safety features is important.

Environmental and Safety Requirements

Environmental and safety regulations may dictate the type of valve required. For example, valves used in the food industry may need to meet FDA and USDA requirements for food safety. In contrast, valves used in high-pressure applications may need to comply with specific safety standards.

Butterfly Valves in Various Applications

Butterfly Valves in Food Processing Applications

Butterfly valves are widely used in the food processing industry due to their sanitary design and ease of cleaning. However, when choosing butterfly valves for food processing applications, there are some specific considerations to keep in mind.

Special Considerations

Sanitary Design
Butterfly valves used in food processing applications must be designed to prevent bacterial growth and contamination. Valves with smooth, crevice-free surfaces are easier to clean and less likely to harbor bacteria.

Clean-in-Place (CIP) and Sterilize-in-Place (SIP) Compatibility
CIP and SIP systems are commonly used in food processing plants to clean and sanitize equipment without disassembly. Butterfly valves used in these applications must be compatible with these systems and withstand the chemicals used in the cleaning process.

Traceability
Traceability is important for identifying the source of food contamination in the event of a recall. To ensure food safety and quality control, butterfly valves used in food processing applications should be traceable.

Materials

Stainless Steel
Stainless steel is the most common material used for food-grade butterfly valves due to its corrosion resistance, durability, and ease of cleaning.

PVC
PVC is also commonly used for food-grade butterfly valves due to its low cost and ease of installation. However, it is not suitable for high-temperature applications.

Other Materials
Other materials used for food-grade butterfly valves include brass, bronze, and aluminum. However, these materials may not be suitable for all food processing applications.

Regulations & Requirements

FDA
Butterfly valves used in food processing applications in the United States must meet FDA requirements for food contact materials.

USDA
Butterfly valves used in meat and poultry processing applications must meet USDA requirements for food contact materials.

3A Sanitary Standards
The 3A Sanitary Standards organization provides guidelines for designing, constructing, and installing equipment used in the food processing industry.

European Hygienic Engineering and Design Group (EHEDG)
The EHEDG provides guidelines for hygienic engineering and the design of equipment used in the food processing industry in Europe.

Butterfly Valves in Refinery Applications

Butterfly valves are commonly used in the refining industry due to their ability to handle a wide range of pressures and temperatures. However, when choosing butterfly valves for refinery applications, there are some specific considerations to consider.

Special Considerations

High Temperatures and Pressures
Refinery applications often involve high temperatures and pressures, so butterfly valves used in these applications must be able to withstand these conditions.

Corrosive Environments
Refinery environments can be highly corrosive, so butterfly valves used in these applications must resist corrosion.

Fire-Safe Design
In refinery applications, butterfly valves may require fire-safe design features to prevent the spread of fire.

Materials

Carbon Steel
Carbon steel is a common material used for butterfly valves in refinery applications due to its high strength and resistance to corrosion.

Stainless Steel
Stainless steel is also commonly used for butterfly valves in refinery applications due to its high resistance to corrosion and high temperatures.

Alloy Steel
Alloy steel is used for butterfly valves in applications that require even higher strength and resistance to corrosion than carbon or stainless steel.

Regulations and Requirements

API Standards
The American Petroleum Institute (API) provides standards for butterfly valves used in the refining industry, including API 609 and API 598.

API 609: Butterfly Valves: Double Flanged, Lug- and Wafer-Type

Specifies the requirements for design, materials, manufacturing, testing, inspection, and marking of double-flanged, lug- and wafer-type butterfly valves. This standard applies to butterfly valves used in petroleum, petrochemical, and gas industry applications.

API 598: Valve Inspection and Testing

Provides guidelines for inspecting and testing industrial valves, including butterfly valves, to ensure their proper operation and performance. This standard outlines the testing requirements, including hydrostatic shell testing, seat leakage testing, and other applicable testing methods.

NACE Standards
The National Association of Corrosion Engineers (NACE) provides standards for materials used in corrosive environments, including butterfly valves used in refineries.

ASME Standards
The American Society of Mechanical Engineers (ASME) provides standards for the design and construction of pressure vessels and piping used in refineries. Butterfly valves used in these applications must comply with these standards.

Safety Regulations
Besides industry standards, butterfly valves used in refinery applications must comply with safety regulations, including those set by the Occupational Safety and Health Administration (OSHA).

One example of the Occupational Safety and Health Administration (OSHA) regulating butterfly valves is the requirement for properly guarding the valve handles to prevent accidental operation. According to OSHA’s Standard for Control of Hazardous Energy (Lockout/Tagout), control valves, including butterfly valves, must be properly guarded or de-energized before maintenance or servicing activities are performed.

Butterfly Valves in Ship Building Applications

Butterfly valves are commonly used in ship building applications due to their compact design, easy operation, and ability to handle a wide range of fluids. However, when choosing butterfly valves for ship building applications, there are some specific considerations to keep in mind.

Special Considerations

Saltwater Environment
Ship building applications involve exposure to saltwater, so butterfly valves used in these applications must resist corrosion.

Vibration and Shock
Ship building applications involve high levels of vibration and shock, so butterfly valves used in these applications must be able to withstand these conditions.

Space Constraints
Ship building applications involve limited space, so butterfly valves used in these applications must be compact in design.

Materials

Bronze
Bronze is a common material used for butterfly valves in ship building applications due to its high resistance to corrosion in saltwater environments.

Stainless Steel
Stainless steel is also commonly used for butterfly valves in ship building applications due to its high resistance to corrosion and strength.

Other Materials
Other materials used for butterfly valves in ship building applications include aluminum bronze, nickel, aluminum bronze, and titanium.

Regulations and Requirements

International Standards
Butterfly valves used in ship building applications must comply with international standards, such as those set by the International Maritime Organization (IMO).

The International Maritime Organization (IMO) provides regulations and guidelines for the safe operation of ships and the prevention of marine pollution. One example of the IMO regulating butterfly valves is the requirement for marine-grade butterfly valves in certain applications on board ships.

Classification Societies
Classification societies, such as Lloyd’s Register and the American Bureau of Shipping, provide regulations and requirements for butterfly valves used in ship building applications.

The American Bureau of Shipping (ABS) provides classification and certification services for ships and offshore structures, including inspecting and testing various equipment and components used in these applications. While ABS does not specifically regulate butterfly valves, it does guide the design, construction, and installation of these valves for use in marine applications.

Safety Regulations
Besides industry standards, butterfly valves used in ship building applications must comply with safety regulations, including those set by the International Convention for the Safety of Life at Sea (SOLAS).

The Safety of Life at Sea (SOLAS) is an international convention that sets minimum safety standards for ships, including safety equipment and procedures. While SOLAS does not specifically regulate butterfly valves, it does provide requirements and guidelines for the safety and reliability of shipboard equipment, including valves.

Butterfly valves can be a good choice for ship building applications due to their compact design, easy operation, and ability to handle a wide range of fluids. However, the specific operating conditions of the application and the relevant regulations and requirements must be considered when choosing butterfly valves for ship building applications.

Butterfly Valves as Shut Off Valves

Butterfly valves can be used as shut-off valves in many applications due to their ability to quickly and easily control flow. However, when choosing butterfly valves as shut-off valves, there are some specific considerations to keep in mind.

Special Considerations

Tight Shut-Off
When used as shut-off valves, butterfly valves must provide tight shut-off to prevent leakage.

Pressure and Temperature
The butterfly valves used as shut-off valves must be able to withstand the pressure and temperature of the application.

Operating Conditions
The application’s operating conditions, such as the frequency of operation, must also be considered when choosing butterfly valves as shut-off valves.

Benefits and Drawbacks

Benefits
Butterfly valves used as shut-off valves offer several benefits, including low cost, low torque operation, and the ability to handle a wide range of flow rates.

Drawbacks
However, butterfly valves used as shut-off valves may have some drawbacks, including the potential for cavitation and erosion and a limited range of operating pressures and temperatures.

Applications

Water and Wastewater Treatment
Butterfly valves are commonly used as shut-off valves in water and wastewater treatment applications due to their low cost and ease of maintenance.

HVAC Systems
Butterfly valves are also commonly used as shut-off valves in heating, ventilation, and air conditioning (HVAC) systems due to their low torque operation and ability to handle a wide range of flow rates.

Process Control
Butterfly valves can be used as shut-off valves in many process control applications, such as those in the chemical and pharmaceutical industries.

Overall, butterfly valves can be a good choice for shut-off valve applications that require low cost, low torque operation, and the ability to handle a wide range of flow rates. However, the specific operating conditions of the application must be considered when choosing butterfly valves as shut-off valves.

Other Applications for Butterfly Valves

Butterfly valves are used in a wide range of industries and applications beyond food processing, refineries, shut-off valves, and ship building. Some examples of other industries and applications where butterfly valves are commonly used include HVAC systems, water treatment plants, chemical processing, and power generation. When choosing butterfly valves for these applications, there are some specific considerations to keep in mind.

HVAC Systems
Butterfly valves are commonly used in HVAC systems to regulate air and water flow. When choosing butterfly valves for HVAC applications, it is important to consider factors such as size, temperature range, and sealing requirements

Water Treatment Plants
Butterfly valves are commonly used in water treatment plants to regulate water flow and chemicals. When choosing butterfly valves for water treatment applications, it is important to consider factors such as corrosion resistance, material compatibility, and pressure ratings. 

Chemical Processing
Butterfly valves are commonly used in chemical processing applications to regulate the flow of chemicals. When choosing butterfly valves for chemical processing applications, it is important to consider factors such as material compatibility, corrosion resistance, and temperature range. 

Power Generation
Butterfly valves are commonly used in power generation applications to regulate the flow of steam and other fluids. When choosing butterfly valves for power generation applications, it is important to consider factors such as corrosion resistance, temperature range, and pressure ratings. 

In addition to these few examples, butterfly valves are versatile and can be used in various industries and applications. However, when choosing butterfly valves for specific applications, it is important to consider the application’s operating conditions and requirements to ensure that the selected valve is appropriate for the task.