Butterfly Valve vs. Ball Valve

Classification of butterfly valves can be according to its configuration or mounting type. For configuration, it pertains to how the valve disc closes and engages with the valve seal. This ranges from the simplest concentric design to the most complex triple-offset design that provides optimal sealing at high pressures. Mounting of butterfly valves on pipes could be of the wafer type, semi-lug, lug, or double-flanged style. The lug styles offer easy access during maintenance, while the wafer type offers the best resistance at high pressure. Further details on the types of butterfly valves can be found in this article. 

Features of a Ball Valve

Unlike a butterfly valve, a ball valve uses a hollow, spherical disc to control flow. When the valve opens, the disc’s hole aligns with the flow, allowing fluids to pass through. Whereas, in the closed position, the ball’s hole rotates to a perpendicular position with the flow, stopping it entirely. Similar to the butterfly valve, a ball valve is a quarter-turn valve, which makes for fast and efficient valve operation as well as automation.

Types of Ball Valves

Ball valves have several types of designs as it pertains to port design.

• • Full-Port Ball Valve: This valve disc design has a hole that is the same size as the pipeline. As a result, it provides uninterrupted flow with no friction loss.

• • Reduced-Port Ball Valve: The hole in the ball is slightly smaller than the pipe, which creates some restriction of flow. Also, this valve design increases the velocity of flow and allows for a smaller and lighter ball at a lesser cost.

• • V-Port Ball Valve: The ball and seat in this design are v-shaped. During operation, the small end of the V opens first, providing a more stable flow. This design is ideal where better flow control is needed or flow velocities are higher as the construction is relatively more sturdy.

• • Trunnion Ball Valve: Unlike other designs with support only from the top, this design also has support from the bottom. Trunnion ball valves are ideal for high-pressure and large-diameter applications due to the extra support against high loads.

• • Cavity-Filler Ball Valve: This design is ideal for applications that want to avoid residue staying inside the valve. Cavity-filler ball valves have extended seats that eliminate the presence of any crevices where residue could accumulate. Because, over time or if the fluid running through the valve changes, the presence of such residue could result in contamination. The use of this design is common in applications such as food production and healthcare.

Comparing Butterfly Valves vs Ball Valves

Feature	Butterfly Valves	Ball Valves
Weight	Have lighter weight even at larger pipe diameters.	Becomes significantly heavy at larger pipe diameters and may require support.
Size	Suitable for large pipe diameters, even above DN 150.	Weight limits its use to sizes of DN 50 and below.
Installation Space	Require smaller installation space.	Installation space is larger than a butterfly valve for the same valve size.
Pressure	Associated with significantly more pressure drop. Also prone to leakage in high-pressure applications.	Full port design offers no flow restriction, so pressure drop is insignificant. Excellent seal in high-pressure applications.
Maintenance	Have a simpler design with fewer internal parts, so maintenance is typically easier and less expensive.	In contrast, ball valves have more complex internals with multiple components. Hence, maintenance is usually more rigorous and expensive.

Making the Right Choice Between a Butterfly Valve and a Ball Valve

When deciding between a butterfly valve vs a ball valve for your project, consider the following factors:

• • Sealing Requirements: If tight shut-off is critical, especially in high-pressure applications, a ball valve is preferable. This is because butterfly valves are prone to leakage and are more difficult to open as pressure increases. When using butterfly valves in high-pressure applications, consider using a bypass valve.

• • Space Constraints: In applications with limited space, the compact design of butterfly valves could prove more advantageous.

• • Pressure Drop: If pressure drop across the valve is a big issue, then a full-port ball valve is the go-to option.

• • Application Specifics: Take into account specific requirements or regulations that govern the application. For example, in food processing and pharmaceuticals where hygiene is important, the smooth crevice-free design of butterfly valves is preferable.

Other Selection Tips

Although there are exceptions to every rule, it is advisable to select a ball valve if:

• • There is a need for a valve that can effectively handle both liquid and gas media.

• • The system requires pigging.

• • The system generates high pressure.

• • The application requires fast cycle times.

• • There is a requirement for multi-port flow patterns.

• • Pipe diameters are small (less than DN 50 or 6 inches).

Whereas, a butterfly valve is preferable if:

• • The system is handling less pressure.

• • Pressure drop and leakage do not bear significant risk to the application.

• • Flow media is water.

• • The system does not require pigging.

• • Low setup cost is desirable