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Butterfly Valve vs Ball Valve

Views: 55     Author: Site Editor     Publish Time: 2023-01-31      Origin: Site

Choosing the correct valve for your application is an important task when designing a process system. A valve's properties and characteristics determine its suitability for a particular application. However, for some applications, multiple different valve types may work.

Both butterfly valves and ball valves offer unique benefits, so choosing between them in certain processes is not a hard choice. It can be problematic when a process requires valve characteristics that both valves have. We need a deeper understanding of the butterfly valve vs ball valve in order to pick the correct valve.

When designing a system that controls the fluid flow, you’ll probably need to choose between a ball valve and a butterfly valve. Both these valves find applications in various industries, and each has its set of benefits. To choose the right product for your system, you must understand the butterfly vs ball valve features, working principles, advantages, and disadvantages.

What makes butterfly valves and ball valves comparable?

In terms of operation mechanisms, both valves are arguably the simplest of the valve types available. They are extensively used in domestic, commercial, and industrial applications for flow control of fluids across a wide range of temperatures and pressures. They are quarter-turn rotary valves (90° turn from fully closed to fully open). Both valve types can be controlled manually, with an electric actuator or with a pneumatic actuator. Butterfly and ball valves are relatively cheap, easy to maintain, reliable, and have a longer life expectancy than other valve types.


These similarities do not mean the valves are interchangeable in all process functions. Instead, it suggests and corroborates why we need to take a closer look at the valves' characteristics and for which applications to use each valve.


Understanding the butterfly valve

A butterfly valve has a disc (E) driven by a lever or handwheel (A). When closed, the disc is perpendicular to the pipe flow direction. A seal (F) which seats within the valve body (D) ensures a tight closure with the valve disc. There is a near linear relationship between a butterfly valve's stem (C) position and flow rate. The butterfly valve can be controlled manually, electrically, or pneumatically.


At larger diameters, butterfly valves are generally regarded as cheaper than ball valves. They have the least amount of parts and are relatively lightweight, requiring less support. The weight advantage of butterfly valves to ball valves can be significant at larger pipe diameters. There is a higher probability of leakage at high-pressure differences between the sides of a butterfly valve disc and the seal compared to a ball valve. Also, in applications with large pipe diameters, this high-pressure difference makes it difficult to open the valve, thereby requiring a bypass valve to balance both side’s pressure before the valve can be opened.


There is a pressure drop across the butterfly valve as the disc remains inside the flow even when fully open. This hinders using butterfly valves in process streams that need to be pigged, such as in the oil and gas industry. Butterfly valves are typically ON/OFF valves and are not suitable for precise fluid flow control.


Understanding the ball valve

A ball valve has a hollow spherical ball (F) that is pivoted at one or both ends. The top end of the ball is attached to a shaft (C), which is rotated by a handle (A) to change the valve position to open or close. When fully open, the hole in the ball lies parallel with the pipe flow direction. The ball rests on a seat (E) inside the valve body (G). The ball valve can be controlled manually, electrically, and pneumatically.


Ball valves can also have three-way or four-way flow directions in a T or L shaped bore. A ball valve’s flow characteristics can be read in our technical article on controlling fluid flow with ball valves.


The bore in a ball valve can vary from a size smaller than the pipe diameter (reduced port or reduced bore), a size equal to the pipe diameter (full port), or a V-port design. The design of the ball does affect flow characteristics. A ball valve can have a pressure drop across the valve in a reduced port ball valve or almost zero pressure drop in a full port ball valve, while a V-port design is ideal for stable flow control.


Unlike butterfly valves, ball valves have zero leakage when fully closed. The fluid pressure upstream of the valve pushes the ball against the seal, ensuring a positive shutoff position. Ball valves will easily open at a high-pressure difference on both sides of the valve and therefore do not require a pressure-balancing bypass.


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