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API 6D ball valve selection guide

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Home News Full Bore Trunnion Ball Valve Vs Reduced Bore Trunnion Ball Valve: How To Select The Optimal Design?
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In industrial valves, trunnion ball valves are widely used in petroleum, natural gas, chemical engineering and other sectors due to their stability and high-pressure resistance. There are two primary design types of trunnion ball valves: full bore trunnion ball valves and reduced bore trunnion ball valves. Each design has its own merits and drawbacks, making them suitable for different application requirements. This article analyzes the differences between these two trunnion ball valve designs to help users select the optimal option based on their specific needs.


Full Bore Trunnion Ball Valve

The full bore trunnion ball valve is designed with a ball bore diameter identical to the inner diameter of the pipeline. This design ensures almost zero resistance to fluid flow. Its key advantages include:

  • Minimal fluid resistance: Since the ball bore matches the pipeline inner diameter, the full bore design ensures nearly unobstructed fluid flow, maintaining high flow rates.

  • Ideal for high-flow systems: In applications requiring large flow volumes, full bore trunnion ball valves maximize fluid passage without restricting flow velocity.

  • Easy maintenance and cleaning: The full bore design eliminates narrow internal sections, facilitating cleaning and maintenance. It is particularly effective in preventing clogging and wear in fluids containing solid particles or those requiring regular cleaning.

  • Lower pressure drop: Without flow restrictions, full bore trunnion ball valves exhibit lower pressure drop in most applications, thereby reducing energy loss and improving system efficiency.

The disadvantage of full bore trunnion ball valves is their relatively large size and weight, which makes them suitable for large-diameter pipelines and high-flow environments.


Reduced Bore Trunnion Ball Valve

In a reduced bore trunnion ball valve, the diameter of the ball bore is smaller than the inner diameter of the pipeline. This design is suitable for applications where flow and pressure need to be regulated to a certain extent. The advantages of reduced bore trunnion ball valves include:

  • Compact size, space-saving: The reduced bore design results in a relatively smaller valve footprint, making it ideal for installation environments with limited space. It is commonly used in small-to-medium diameter pipeline systems or scenarios where space conservation is a priority.

  • Precise flow control: For applications that do not require high-flow rates, reduced bore trunnion ball valves can effectively restrict flow to meet process requirements while minimizing unnecessary energy consumption.

  • Suitable for low-flow systems: In low-flow or small-scale applications, reduced bore trunnion ball valves deliver sufficient control precision without causing pressure surges due to excessive flow.

However, the disadvantage of reduced bore trunnion ball valves is that they may cause higher fluid resistance, which reduces flow efficiency—especially in applications requiring large flow volumes.


How to Select the Optimal Design?

The selection between a full bore trunnion ball valve and a reduced bore trunnion ball valve depends on the following factors:

  • Flow requirements: If the system demands high flow rates and minimal fluid resistance, the full bore trunnion ball valve is the optimal choice. For low-flow requirements, the reduced bore trunnion ball valve offers a more cost-effective solution.

  • Space constraints: In applications with limited installation space, the reduced bore trunnion ball valve is more suitable. Its compact design provides an advantage in tightly arranged pipeline layouts or confined installation areas.

  • System efficiency and pressure drop: Full bore trunnion ball valves deliver lower pressure drop and superior flow control performance, making them suitable for systems with high efficiency requirements. If the system has low flow demands, reduced bore trunnion ball valves can still provide reliable control.

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Top entry trunnion mounted ball valve with a one piece body that removes the bolted body joint from the pressure boundary. Seats and seals are serviced through the top cover without cutting the valve out of the pipeline. Nominal Size: 1 inch to 36 inch Pressure Class: ASME Class 150 to 2500 Body Material: WCB, LCC, CF8M, CF3M, A105 forged Body Style: One piece top entry Ball & Stem: CF8M or F316 with ENP coating Seat Material: PTFE, RPTFE, PEEK or metal End Connection: Flanged RF / RTJ, butt weld Operation: Gear, pneumatic or electric actuator Maintenance: In line, through the top cover Design Standard: API 6D / ISO 14313 Test Standard: API 598, API 607 fire safe Options: Sealant injection, cavity relief, extended stem
A high pressure trunnion mounted ball valve for Class 900 to 2500 service, built to API 6D PSL3 with a forged or cast body, spring loaded seats, double block and bleed and sealant injection ports. Suited to wellheads, gas gathering and high pressure process isolation.   Nominal Size: 2 inch to 24 inch (DN50 to DN600) Pressure Class: ASME Class 900 / 1500 / 2500 Body Material: A105 forged, WCB cast, A182 F316, F51 duplex Ball & Stem: A182 F316 with ENP or hard chrome Seat Material: PTFE, RPTFE, PEEK or metal to metal End Connection: Flanged RF / RTJ, butt weld, hub Operation: Gear, pneumatic or electric actuator Design Standard: API 6D / ISO 14313, ASME B16.34 Test Standard: API 598, shell 1.5x and seat 1.1x Fire Safe: API 607 / API 6FA Material Certificate: EN 10204 3.1 with heat number traceability Temperature Range: -29 C to +200 C, trim dependent
Nominal Size :3/4"~60" (DN20~DN1500) Pressure Class :150LB~2500LB (PN10~PN420) Temperature Range: -20℃ ~ +200℃ Body Material :C95800 Nickel Aluminum Bronze Ball Material :C95800 Nickel Aluminum Bronze Stem Material :C95800 Nickel Aluminum Bronze Seat Material :PTFE, RPTFE, PEEK End Connection :Flanged RF Operation: Manual (Lever / Gear), Pneumatic, Electric Design Standard: ASME B16.34, API 608 Test Standard: API 598, ISO 5208 Face to Face: ASME B16.10 Fire Safe Standard: API 607
Nominal Diameter: 0.5" (DN15) Pressure Class: Class 300 (PN50) Temperature Range: -29℃ to +425℃ Body / Bonnet: ASTM A216 WCB cast carbon steel Ball: A105N / WCB with hard chrome plating, or 304 / 316 stainless steel (optional) Stem: 410 / 420 stainless steel or 17-4PH precipitation hardening stainless steel Seat: PTFE, RPTFE, PPL (reinforced PTFE) Sealing Materials: PTFE / RPTFE / PPL (seat), flexible graphite or PTFE (stem packing) End Connection: Flanged (RF Raised Face, conforming to ASME B16.5) Operation: Lever (90° open/close, with optional locking hole) Design Standards: ASME B16.34, API 608 Inspection & Test Standard: API 598 Face-to-Face Dimension: In accordance with ASME B16.10