Industrial process control valves are available in a very wide array of materials, types, and configurations. The first step of the selection procedure for a valve application should be choosing the valve type, thus narrowing the selection field to a more manageable level. Valve types, ball, butterfly, globe, and plug for example, are generally defined by the closing mechanism of the valve.
A
butterfly valve uses a flat disc that is positioned, paddle-like, in the fluid flow path. It rotates around a central axis (the stem) over a 90 degree rotational arc from open (position parallel to the flow direction) to closed (perpendicular to flow). Butterfly valves referred to as
resilient seated are generally used in lower pressure, lower temperature applications and create a seal through compressing the disc into some type of elastomer seat. Another type of butterfly valve, used in higher pressure and higher temperature applications, are known as
high performance butterfly valves (HPBF). They have highly machined discs and seats which are precisely seated together. Butterfly valve body materials include cast iron, bronze, and stainless steels. It is common to line the butterfly valve with another material to provide special protection from the process media.
Butterfly Valve Advantages:
- Lower cost
- Minimal lay length
- Easy to automate
- Generally lower torque
Butterfly Valve Disadvantages:
- High wear rate - seals are in flow paths
- Not a good choice as a control valve. Has a very nonlinear flow coefficient.
- Not great for erosive flowing media.
Butterfly valves, like other valve types, have applications where they outperform.
Careful consideration and consultation with a valve expert is a first step toward making a good selection.
