There are 3 main categories of butterfly valves: Rubber-lined, Plastic-lined, and Metal.
Garlock does not offer rubber or metal valves, so our main focus will be on plastic-lined valves; however, a lot of the main concepts apply to all 3 types.
Types of Butterfly Valves
Rubber-Lined Valves
- Less expensive valves for non-demanding, non-abrasive, lower temperature applications
- Normally for 150-300# (PN10-25) flanges
Plastic-Lined Valves
- For use with harsh chemicals, ultrapure applications, sanitary, or abrasive applications
- Normally for 150# (PN10/16) flanges
- The GAR-SEAL® valve is a Plastic-Lined valve
Metal Valves
- For high-pressure or high-temperature applications, or those requiring fire resistance
- Can be used in 150-2500# (PN10-160) flanges
- Can be Single Offset, Double Offset, or Triple Offset
Body Types
There are 4 main body types: Wafer, Lug, Flanged, and Welded.
Wafer
- Features two or more centering holes to help with installation.
- Is lighter and cheaper.
- Cannot be used as a pipe end or as end-of-line service.
- Garlock only offers wafer and lug type valves; the bolt torques are the same for both types.
Lug
- Has bolt holes to connect with pipe flanges.
- Because it has threaded bolts around the entire area, the lug valve is a safer option—most customers can switch from a wafer valve to a lug valve; however, they cannot switch from a lug to a wafer.
- Lugs can be used as a pipe ends or as end-of-line service.
- With some lower-strength body materials, the lug threads are weak; therefore, lug valves may have lower bolt torque ratings than wafer.
- Garlock only offers wafer and lug type valves; the bolt torques are the same for both types.
Flanged
- Has a flange face on both sides of the valve.
- Popular in the very large size valves.
- Some companies use a ‘U’ shaped valve–this is cheaper; but the two flanges are not always parallel, which can cause problems with bolting against the pipe flanges.
- Garlock does not offer this type of valve.
Welded
- Used for very-high-pressure applications.
- Because most plastic lined valves are limited to PN10/16 (150#) flanges, this type is rarely seen with plastic-lined valves.
- Garlock does not offer this type of valve.
Disc Alignment
There are three main ways a disc can be aligned in a valve: zero offset, double offset, or triple offset.
Most plastic lined valves are considered zero offset. Most metal valves and some rubber-lined valves are double or triple offset. Garlock valves are all considered zero offset.
