What is a Butterfly Valve?
These valves are often used in industrial, commercial, residential, oil and gas, water treatment, and chemical processing. The Butterfly Valve gets its name from the disc that rotates in the body to control the flow offering throttling capability with a moderately low pressure drop. The majority of butterfly valves are directional.
Concentric is the most affordable design and gets its name from the centered placement of the disc pivot point between the pipe center line and the valve seat centerline. This design relies on the elastic deformation of the seating material when closed for the seal, as a result, only materials like EPDM, Buna-N, and Viton are available. The advantages are relatively inexpensive and leak-tight shutoff. The disadvantages are high seating/unseating torque, limited to low pressure/temperature application, and limited lifespan of the elastomeric seat.
The double offset design (aka high performance) is more expensive, and the name comes from the design where the disc pivot point is offset both in the pipe center line and the valve seat centerline. The cam action of double offset configuration allows the disc to form a seal with minimal elastic deformation. This design allows for the use of additional seating materials like PTFE. While there are some metal seat designs available, they require special design since they rely on elastic deformation to seal. The advantages are easier to open/close, longer lifespan, and can be used at higher pressures/temperatures as compared to concentric Butterfly Valves. The disadvantages are limited pressure/temperature range and limited sealing options.
The triple offset design has an additional offset on the seat configuration. This additional offset enhances the cam action when closing and the valve no longer relies solely on elastic deformation to seal. This enhanced cam action permits the use of a wide variety of metal on the seating surfaces. The advantages are easier to open/close, longer lifespan, and can be used at higher pressures/temperatures as compared to other butterfly designs.