Wafer Style or Lug Style – typical
- Designed to maintain a seal against bi-directional pressure differential to prevent backflow in systems designed for unidirectional flow
- Accomplishes this with a tightly fitting seal, i.e., gasket, o-ring, precision machined, and a flat valve face on the upstream and downstream sides of the valve
- A lug-style butterfly valve used in dead end service generally has a reduced pressure rating
- For example, a lug-style butterfly valve mounted between two flanges has a 150 psi pressure rating.
- The same valve mounted with one flange, in dead end service, has a 75 psi rating
Flanged – it is not uncommon to see a flanged butterfly valve in high performance applications
- Have threaded inserts at both sides of the valve body
- Allows Flange Butterfly Valve to be installed in a system using two sets of bolts and no nuts
- Installed between two flanges using a separate set of bolts for each flange
- This setup permits either side of the piping system to be disconnected without disturbing the other side
Concentric Butterfly Valve
- Has a resilient rubber seat with a metal disc.
Double Eccentric Butterfly Valve – also known as a High Performance Butterfly Valves or Double Offset Butterfly Valve
- Different type of materials are used for the seat and disc.
Triple Eccentric Butterfly Valve – also known as Triple Offset Butterfly Valve
- Seats are either laminated or a solid metal seat design
- Design prevents gulling and scratches between the metal seat and the metal disc due to its unique construction
- Only time the seal comes into contact with the seat is at the point of complete closure
- Generally used in applications which require bi-directional tight shut-off in Oil & Gas, LNG/NPG terminal and tanks and Chemical Factories
- Widely use for dirty/ heavy oil to prevent extrusion.
