Butterfly Valves Explained: Types, Functions and Industry Applications

The butterfly valve gets its name from the way its central disc moves, similar to a butterfly’s wings as it opens and closes. The disc is positioned in the center of the pipe and rotates to control fluid flow. When the valve is open, the disc turns parallel to the flow, allowing the fluid to pass through. Turning the valve handle moves the disc either parallel or perpendicular to the flow, regulating or shutting off the flow as needed.

Unlike ball valves, the disc remains within the flow even when fully open, which may result in a slight pressure drop. This simple yet effective mechanism makes butterfly valves ideal for quick shutoff and precise flow control across a wide range of applications.

Butterfly valves come in different designs tailored to specific applications based on factors like pressure range, connection type and actuation method. The most common types include wafer-style, lug-style and eccentric butterfly valves.

1. Wafer-Style Butterfly Valves

Wafer-style butterfly valves are designed to fit snugly between two pipe flanges. They are lightweight and cost-effective, often used in low-pressure systems.

One key advantage of wafer-style valves is their ability to seal in both directions, preventing backflow in systems that need bidirectional pressure control. These valves are popular for general-purpose applications due to their compact design, making them ideal where space is limited.

2. Lug-Style Butterfly Valves

Lug-style butterfly valves are installed using threaded inserts, or “lugs,” which enable them to be bolted between flanges. This design allows one side of the piping system to be disconnected without affecting the other side, making lug-style valves particularly useful for systems that require frequent maintenance or isolation.

These valves are more robust than wafer-style valves and can handle moderate to high-pressure environments. Because of their durability, lug-style valves are often preferred for end-of-line service where one side of the valve remains open.

3. Eccentric Butterfly Valves

Eccentric butterfly valves are designed to handle more demanding applications. They come in three variations — single, double and triple eccentric — each providing enhanced sealing and reduced wear on the valve seat.

Single eccentric valves are designed with the disc offset from the valve’s centerline, which reduces friction during operation.

Double eccentric valves feature an additional offset that minimizes contact between the disc and the seat, improving valve lifespan.

Triple eccentric valves are engineered for high-pressure environments and offer a more precise seal, making them suitable for industries like oil and gas, where performance and reliability are critical.

Butterfly valves can be actuated in several ways, depending on the specific needs of a system. Whether the valve is operated manually or through an automated process, the actuation method plays a crucial role in controlling flow and maintaining system efficiency. Below, we outline the key differences between manual and automatic actuation methods to help you determine which option best suits your application.

Thanks to their versatility, butterfly valves are widely used across various industries for managing the flow of gasses, liquids and slurries. Their compact design and fast operation make them suitable for both high-volume and quick-turnaround applications. Here’s a breakdown of the industries and common use cases for butterfly valves.

Butterfly valves offer numerous benefits but also come with certain limitations. Understanding these pros and cons will help you determine if they are the right choice for your system.

Proper maintenance ensures butterfly valves perform reliably over time, reducing the risk of leaks, inefficiencies or damage. Below are some key maintenance practices and troubleshooting tips to keep butterfly valves in optimal condition.

1. Regular inspections: Periodically inspect the valve body, disc and seals for signs of wear, corrosion and leaks. Early detection of issues helps avoid more serious problems later.
2. Lubrication: Ensure the valve’s moving parts are well-lubricated to reduce friction and wear. Use lubricants that are compatible with both the valve’s materials and the fluids in the system.
3. Cleaning: Clean the valve and disc regularly, particularly in applications where slurries or solids are involved. Buildup can affect performance and lead to seal damage.
4. Seal replacement: Over time, the valve’s seals may wear out, leading to potential leaks. Replacing seals periodically helps maintain the valve’s effectiveness.
5. Troubleshooting common issues: If the valve becomes difficult to operate or begins to leak, check for buildup or damage to the disc, seals or actuators. Regular maintenance will often resolve these issues, but if they persist, professional servicing may be required.

Selecting the right butterfly valve for your specific system is key to achieving efficient and reliable flow control. Whether you’re managing high-pressure pipelines or regulating flow in water treatment, understanding the different valve types will help you optimize performance.

What is a butterfly valve?

A butterfly valve is a quarter-turn valve used to regulate or isolate fluid flow in a piping system. The valve uses a rotating disc to control the flow, offering fast operation and a compact design that makes it suitable for a wide range of industrial applications.

How does a butterfly valve work?

A butterfly valve operates by rotating a central disc either parallel or perpendicular to the flow of fluid. When the valve is open, the disc rotates to allow fluid to pass. When closed, the disc blocks the flow by positioning itself across the pipe.

Are butterfly valves directional?

Most butterfly valves are designed to be bidirectional, meaning they can control flow in both directions. However, some systems may prefer a specific flow direction to reduce torque, improve efficiency and prolong the valve’s lifespan.

Can a butterfly valve be used for flow control?

The most common application for butterfly valves is on/off control, however butterfly valves can be used for light throttling or controlling fluid flow. They are not a good choice for applications requiring precise flow control, and extended time in the partially open position can increase wear on the disc and seat, impacting the longevity of the valve.

How do you install a butterfly valve?

Butterfly valves are installed between two pipe flanges. It’s important to align the valve properly to avoid obstruction to the disc’s rotation. Make sure to allow enough space for the disc to move freely when the valve opens and closes and follow specific installation guidelines for the valve type being used (wafer-style, lug-style, etc.).