Trunnion Mounted Ball Valve

A trunnion ball valve has additional mechanical anchoring of the ball at the top and the bottom, suitable for larger and higher pressure valves. The trunnion stem absorbs the thrust from the line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure operating torque remains low.

Trunnion ball valves are manufactured with the features of double block and bleed (DBB), cavity relief, fire safe and secondary metal to metal seated etc.

Standard and Specifications:

Trunnion Ball Valve Design Features:

Double block and bleed

API 6D defines a double block and bleed valve as a “single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve with a means of vending/bleeding the cavity between the seating surfaces.”

When the ball is in the closed position, each seat seals off the process medium independently at the same time between the up/down stream and body cavity; it allows bleeding of the trapped cavity pressure (DBB) through drain or vent valve. The double block and bleed function makes it possible to flush the valve under pressure and verify that the seats are sealing properly.

Self Cavity Relief

Trunnion ball valves constrain the ball by bearings. It is only allowed to rotate, but the ball seats can move. It also traps the media in the cavity when the operator closes the valve. It isolates the pipeline and the body cavity in the open and closed position. Thus, the pressure caught in the body cavity might be different from that in the line.  The pressure increases in the cavity when heated. It pushes the ball seat of the downstream side away from the ball by rising pressure against the spring load. When this happens, the pressure gets released.

Secondary Metal to Metal Seat Design

Standard seat design is primary soft seal, and secondary metal to metal seal. Seat insert is designed as pressed-in type which is easy for maintenance. Optional design with primary metal to metal seal and secondary soft seal seat design is also available upon request.

Double Piston Effect Seats-DIB 1 (Optional Upon request)

Medium pressure, both upstream and downstream as well as in the body cavity, creates a resultant thrust that pushes the seat rings against the ball. Valves with double piston effect seat rings require a cavity pressure relief device to reduce the build-up of over pressure in the body cavity.

Trunnion Ball Valve Drawings

Material Specifications

Trunnion Ball Valve Dimensions-API 6D

ANSI Class 150 (Face to face in mm)

ANSI Class 300 (Face to face in mm)