News/Blog
News/Blog
01, 1970
Butterfly valves are a family of quarter-turn rotational motion valves that are used in pipelines to shut-off flow. It is often said that butterfly valves can be used to regulate the flow. However, we do not recommend doing this, as it can damage the valve disk and have a negative effect on the sealing properties. They are widely used across various industries and process media, particularly in water supply, collection, distribution, and pumping stations, with a primary role in flow isolation. Key advantages over other valve types include simple construction and compact design, leading to lighter weight, lower cost, smaller installation footprint, and faster actuation speeds.
The valve body is positioned between the pipe flanges, with common end connection types including flanged, double lug, and wafer configurations.
The disc, attached to the valve body, functions as a gate that controls fluid flow, similar to a gate in a gate valve or a ball in a ball valve. Typically, the disc is bored to accommodate the stem or shaft. Disc design, orientation, and material vary to enhance flow, sealing, and operating torque.
The valve body is lined with a durable elastomer or metal anti-leak seal, securing the disc in place to ensure a complete shutoff when the valve is closed.
The stem, or valve shaft, connects the disc to the actuation mechanism, transmitting torque to operate the valve.
Seals are used at various points within the valve to ensure tight sealing during operation and to isolate process media from internal components. This provides a more flexible and cost-effective design.
Sealing on the seat face is achieved by a continuous T-profile resilient sealing ring, secured on the disc’s periphery by a retaining ring to prevent displacement. In the closed position, the sealing ring presses against the seat face, ensuring a tight seal on both upstream and downstream ends. In the open position, the double eccentric disc design keeps the sealing ring unstressed.
The multiple O-ring shaft sealing system isolates the stem/shaft from process media, providing maintenance-free sealing throughout the valve’s lifespan. Additional common components include bushings, bearings, and fasteners. Actuation-related components such as the handle, lever, gearbox, and handwheel will be covered in the actuation section.
A butterfly valve operates by rotating the valve disc to control fluid flow. In the closed position, the disc blocks the valve bore, while in the open position, it aligns perpendicular to the flow direction, allowing passage. These valves generally support bi-directional flow and shutoff but are not full-bore, making them unsuitable for pigging or swabbing. The body is made of ductile iron with an epoxy powder coating on both internal and external surfaces. Operation methods include handwheels, gears, actuators, or a combination, depending on application requirements and specifications.
Butterfly valves can be operated in several ways, including manual, semi-manual, or fully automatic actuation, depending on the application requirements.
- Electric: These valves use an electric actuator controlled by a 4-20mA signal. Electric actuation is commonly employed in applications requiring high precision and time-sensitive operations.
- Pneumatic: Pneumatic actuation also provides high precision and uses compressed air to control the valve, ideal for various controlled applications.
- Hydraulic: Typically used for applications that demand high torque to open and close the valve, such as in high-pressure and high-viscosity environments.
- Manual: Manual butterfly valves are operated using a handwheel, crank, or lever. Smaller valves are usually fitted with a lever, while larger valves include handwheels and may require a gearbox to transfer torque efficiently. For underground installations without a manhole, actuation is done using an extension spindle, adapter/square cap, and a T-key, allowing operation from ground level.
Overall, butterfly valves generally require less torque for operation, making the sizing and installation of actuators more cost-effective compared to other valve types, such as gate valves.
Butterfly valves provide several key benefits, especially for applications involving sizes larger than DN 200 (200 mm):
- Lightweight and Compact: Thanks to their compact design and smaller face-to-face dimensions, butterfly valves require less installation space. This translates into cost savings, reducing installation costs associated with labor, equipment, and piping support.
- Low Maintenance Requirements: Featuring a simple, cost-effective design with fewer moving parts and wear points, metal butterfly valves have minimal maintenance needs, making them an economical choice over time.
- Fast Acting: A quick 90° rotation of the handle or actuation mechanism achieves full closure or opening of the valve. For larger butterfly valves, a gearbox is typically included to reduce operational torque and simplify valve operation, though this may slightly reduce the speed of actuation.
- Cost-Effective: Due to their streamlined design, butterfly valves require less material and are easier to manufacture, making them a more affordable option compared to other valve types. Cost savings are particularly notable in larger sizes, typically above DN 300.
- Versatility: Butterfly valves are highly versatile, with applications that include installation underground, among other uses.
