DESIGN PRINCIPLE

 

Concentric Valve: Ex. Rubber Lined Valve

  • No offsets / completely concentric
  • Shaft located in centerline of seating plane
  • Shaft located in centerline of pipe
  • 100% rubbing
  • Both temperature and pressure limited
  • Only with Soft Seats
  • Position Seated

 

Single Offset: Ex. Wafer Disc Butterfly / Ball Valve

  • Shaft located to one side of seating plane
  • Shaft located in centerline of pipe
  • Concentric seating cone
  • 100% rubbing
  • Allows for uninterrupted seating surface
  • Position Seated

 

Two Offset: Ex. High Performance Butterfly Valve (HPBV)

  • Shaft located to one side of seating plane
  • Shaft located one side of centerline of pipe
  • Concentric seating cone
  • About 30% rubbing
  • Allows for camming action into the seat
  • Position seated
  • Metal-seated versions are Class IV or Class V leakage

 

Three Offset: Ex. Triple Offset Valve (TOSV)

  • Shaft located to one side of seating plane
  • Shaft located one side of centerline of pipe
  • Canted or inclined seating cone
  • ELLIPTICAL seating shape causes substantial rubbing at 6 and 12 o’clock locations
  • About 10% rubbing
  • Torque seated

 

Quad Offset: Ex. Four Offset Valve (4OSV)

  • Shaft located to one side of seating plane
  • Shaft located one side of centerline of pipe
  • Canted or inclined seating cone
  • Seating cone is elongated resulting in circular seating shape
  • ~0% rubbing
  • Torque seated

 

Penta Offset: Five Offset Valve (5OSV)

  • Shaft located to one side of seating plane
  • Shaft located in the middle or slightly to one side of centerline of pipe
  • 3D figure not named yet in geometry
  • Circular seating shape in one plane only
  • Seal moving faster from seat
  • Higher Cv value
  • ~0% rubbing
  • Torque seated