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.