Alloy 20 Trunnion Mounted Ball Valve Manufacturer  in Africa

Large corrosive pipelines impose seat loads that can make a conventional floating ball valve difficult to operate. An Alloy 20 trunnion mounted ball valve supports the ball on fixed bearings, allowing the seats to move independently toward its surface. This lowers torque while maintaining shutoff at high pressure. African Valve is a top Alloy 20 Trunnion Mounted Ball Valve Manufacturer  in Africa, supplying Nigeria, Egypt, South Africa, Kenya and Ghana and delivering valves to the Middle East, Europe and other export regions.

Why Is the Ball Fixed?

The ball is held by an upper stem and lower trunnion. Internal pressure does not push the complete ball into the downstream seat. Instead, the pressure load is transferred through the trunnion bearings into the valve body.

Each seat contains springs that maintain initial contact with the ball. Line pressure then acts behind the seat ring and increases the sealing force. This arrangement allows large valves to operate with lower torque than an equivalent floating ball valve.

Single-Piston and Double-Piston Seats

A single-piston-effect seat can relieve excessive cavity pressure back toward the pipeline when cavity pressure rises above line pressure. This is useful where trapped liquid may expand because of temperature.

A double-piston-effect seat can maintain sealing even if pressure in the body cavity rises. This provides additional isolation but may require a separate cavity-relief system.

The two arrangements have different consequences for double block and bleed performance. Seat direction and cavity-pressure philosophy should be confirmed during valve selection.

Stem and Cavity Protection

The stem is generally inserted from inside the body so internal pressure cannot eject it. Anti-static contacts may be fitted between the ball, stem and body to prevent electrical charge accumulation.

Drain and vent connections provide access to the body cavity. They are used for pressure release, seat testing, flushing and maintenance. In chemical service, these connections should be positioned so that trapped corrosive fluid can be handled safely.

Alloy 20 Construction

Forged bodies are commonly ASTM A182 F20, while cast designs may use ASTM A351 CN7M. Alloy 20 contains nickel, chromium, molybdenum and copper and is selected for many sulphuric acid duties.

Soft seats may use reinforced PTFE, modified PTFE or PEEK, depending on the pressure-temperature requirement. Metal seats are chosen for high temperature, abrasive fluids or frequent cycling. Ball coating and seat materials must remain compatible with the process chemistry.

Technical Specifications

Size Range: DN50 to DN1200
Pressure Ratings: Class 150 to Class 1500
Design Standards: API 6D, API 608 and ASME B16.34
Testing Standard: API 6D or API 598
End Connections: Flanged RF, RTJ or butt-weld
Operation: Gearbox, electric, pneumatic or hydraulic actuator

Design Advantages

• Trunnion support reduces seat loading and torque.

• Spring-loaded seats maintain contact at low pressure.

• Full-bore designs may permit pipeline pigging.

• Cavity vents and drains assist testing and maintenance.

• Blow-out-resistant stems improve pressure safety.

• Fire-safe construction can be specified to API 6FA or API 607.

Industrial Service

Typical duties include sulphuric acid transfer, fertilizer terminals, chemical storage, large process headers and high-pressure corrosive pipelines. The design is selected where valve diameter or differential pressure makes floating construction impractical.

Testing and Documentation

Ball finish, trunnion alignment, seat preload and bearing clearance are inspected before assembly. Shell, high-pressure seat and low-pressure closure tests are performed. Torque testing, PMI, NDT and full MTC traceability can be included in the inspection package.