Duplex Trunnion Mounted Ball Valve Manufacturer in Africa

Large-bore pipelines and higher-pressure process systems can create operating torque and seat loads beyond the practical range of a floating ball design. A trunnion-supported ball limits ball movement and allows the seats to move toward the sealing surface. African Valve is a prominent Duplex Trunnion Mounted Ball Valve Manufacturer  in Africa, supplying South Africa, Nigeria, Egypt, Angola, other African countries and export projects.

Trunnion Support Mechanism

The ball is supported by upper and lower trunnions or bearings. It rotates through 90 degrees but does not move significantly downstream under line pressure. Spring-energised seats move toward the ball and maintain sealing contact.

This arrangement reduces operating torque compared with a similarly sized floating ball valve and suits large diameters, high pressure classes and automated operation.

Body and Seat Arrangements

The body may use two-piece, three-piece, side-entry or top-entry construction. The selected pattern depends on pipeline layout, maintenance access, pressure class and end connections.

Soft-seat designs may use PTFE, RPTFE or PEEK. Metal seats are considered for abrasive particles, elevated temperature or severe cycling. Depending on the project, the valve may include cavity-pressure relief, double-block-and-bleed arrangements, emergency sealant injection and anti-static protection.

Duplex Material Selection

Cast pressure parts may use ASTM A995 Grade 4A, while forged or wrought parts may use ASTM A182 F51. The body, ball, stem, trunnions, seat retainers, springs and bearings should use compatible materials selected for both corrosion and mechanical loading. ASTM A995 covers duplex castings for pressure-containing parts, while ASTM A182 covers forged valves and components.

Duplex steel provides higher strength and improved chloride resistance compared with common austenitic stainless steel, but heat treatment, ferrite balance and welding remain important.

Technical Specifications

Size Range: DN50 to DN1200

Pressure Ratings: ASME Class 150 to Class 1500

Design Standards: API 6D, API 608 and ASME B16.34 as applicable

Testing Standard: API 6D or API 598

End Connections: Flanged RF, RTJ or butt weld

Operation: Gearbox, pneumatic actuator, hydraulic actuator or electric actuator

Body Materials: ASTM A995 Grade 4A or ASTM A182 F51

Ball Design: Trunnion mounted

Body Construction: Side entry, top entry, two-piece or three-piece

Seat Options: Soft seated or metal seated

Bore Type: Full bore or reduced bore

Pressure-Assisted Sealing

Seat springs provide initial contact at low pressure, while line pressure increases the sealing force during operation. The arrangement should be reviewed for the required isolation direction and cavity-relief method.

Actuator sizing must consider maximum differential pressure, seat friction, temperature and breakaway torque. The actuator should not be selected from nominal valve size alone.

Installation and Maintenance Access

The pipeline should provide enough support to prevent body loads from affecting seat alignment. Side-entry designs normally require removal from the line for major internal work, while top-entry versions can provide access through the cover. Drain, vent and sealant connections should remain reachable after insulation and actuator installation.

A full-bore configuration may be specified for piggable or low-restriction pipelines, but bore continuity and pig passage must be confirmed from the complete valve design.