When designing a system to control fluid flow, one must choose between a ball valve and a butterfly valve. Both valves are used in various industries and have their benefits. To select the appropriate product for the system, it is necessary to understand the features, working principles, advantages, and disadvantages of butterfly and ball valves.
Understanding the Differences Between Butterfly Valves and Ball Valves
Ball valves and butterfly valves are popular types of control valves in the market due to their simplicity. They can handle various fluid mediums and work efficiently across a wide range of temperatures and pressure. These valves are designed to operate with a 90-degree rotation to go from fully open to fully closed and vice versa. They are also available in both manual and automatic versions that can be operated using electric, pneumatic, or hydraulic actuators. These valves are widely accepted due to their affordability, easy maintenance, reliability, and durability. Let’s examine each valve in more detail.
A hand wheel or lever drives the disc of butterfly valves. When the valve is closed, the disc sits perpendicular to the fluid flow direction, and a seal on the valve body ensures a tight and secure closure. The stem position corresponds to the flow rate while opening or closing the valve.
Fig 2: Butterfly Valve (A) Handwheel, (B) Gearbox, (C) Stem, (D) Body, (E) Disc, (F) Seal, (G) Packing
Butterfly valves offer a lightweight, low-maintenance option with minimal parts required. They are also more cost-effective than ball valves, especially in larger diameter sizes. However, they may not be suitable for high-pressure applications due to the high-pressure differences between the valve’s seal and the sides, which can make it challenging to open. To address this issue, a bypass valve can be used to balance the pressure difference and ensure smooth operation.
The butterfly valve’s ability to interrupt fluid flow even when fully open causes a pressure drop across the valve, making it unsuitable for certain applications such as pigging. Furthermore, their usage is limited to ON/OFF operation, and they cannot be utilized for high-precision fluid control.
Fig. 3: Ball Valve (A) Handle, (B) Handle screw/Bolt, (C) Shaft, (D) Packing, (E) Seat, (F) Ball, (G) Body.
A hollow spherical ball held in position at one or both ends is the main feature of ball valves. The valve has a shaft that is attached to the top end of the ball, allowing it to rotate and either open or close the valve. When fully open, the hole lies parallel to the fluid flow direction. The valve body contains a seat that holds the ball, and it can have a flow direction of two-way, three-way, or four-way.
Ball valves offer different hole designs, such as V-port and full-port, depending on the application requirements. The V-port design provides stable flow control, while the full-port design minimizes or eliminates pressure drop. If the bore size is smaller than the pipe diameter, some pressure drop may occur.
In contrast to butterfly valves, ball valves do not experience leakages when fully closed. They also easily open even when exposed to high differential pressure between the valve’s sides, eliminating the need for a bypass valve.
Butterfly Valve vs Ball Valve – Advantages and Disadvantages
Butterfly valves and ball valves each have their set of advantages and disadvantages. Here are some of the pros and cons of each type of valve :
Advantages of Butterfly Valves:
- Lightweight and require little support
- Easy to install and maintain
- Relatively low cost, especially for larger sizes
- Quick quarter-turn operation
- Can be used for throttling flow
Disadvantages of Butterfly Valves:
- Not suitable for high-pressure applications
- Pressure drop across the valve, limiting its use in certain applications
- Limited precision control
- Limited ability for pigging
Advantages of Ball Valves:
- Suitable for high-pressure applications
- No pressure drop when fully open
- Available in different designs such as V-port and full-port
- Reliable sealing, no leakage when fully closed
- Easy to operate even with high differential pressure on the valve’s sides
Disadvantages of Ball Valves:
- More expensive compared to butterfly valves, especially for larger sizes
- Requires more support due to its weight
- Can experience ball seat wear over time, causing leakage
- Slower operation compared to butterfly valves
Choosing between a butterfly valve and a ball valve will depend on the specific application and the required features.
Butterfly Valve vs Ball Valve
|Parameter||Butterfly Valve||Ball Valve|
|Weight||Lightweight Valves. Hence, transfers less load to pipe supports.||Heavy Weight is the characteristic of Ball Valves|
|Structure||The butterfly valve consists of a thin disk in a thin body. Simpler design.||Ball valves have a sphere-like disc inside a bulky body. Complex design.|
|Space Requirement||The installation Space requirement of the butterfly valve is less.||Ball valves need more installation space than butterfly valves.|
|Leakage||At high differential pressure, butterfly valves are prone to leakage.||Ball valves provide a tight seal.|
|Flow Restriction||The butterfly valve disc restricts the flow by creating a large pressure drop.||Ball valves have less pressure drop as compared to butterfly valves.|
|Application||Suitable for ON/OFF control and proportional control||Suitable for modulating and ON/OFF Control. However, they are more used for isolation purposes.|
|Cost||Butterfly valves are cheaper||Ball valves are expensive|
|Connection||Butterfly valves have a flange style with a lug or wafer design||A range of connections is available for ball valves.|
|Uses||Used for Liquid service applications||Ball valves are capable of handling both liquid and gas.|
|Operating Condition||Mainly used for low-temperature and pressure services||Suitable for high temperature and pressure services|
|No of Ports||Butterfly valves can have only two ports||Ball valves can have more than two ports.|
Both butterfly valves and ball valves have their own set of advantages and disadvantages. Butterfly valves are lightweight, easy to install, and cheaper than ball valves, making them ideal for low-pressure and low-temperature applications. On the other hand, ball valves provide a tight seal, have less flow restriction, and can handle both liquid and gas, making them suitable for high-pressure and high-temperature applications. The choice between these two valves ultimately depends on the specific needs of the system and the application requirements. Therefore, it is important to carefully consider the parameters discussed in the table and make an informed decision.