External Trunnion Ball Valve VS Internal Trunnion Ball Valve

External trunnion ball valves have the trunnion （the shaft supporting the ball）located the external of the valve body, while internal trunnion ball valves have the trunnion (trunnion block/supporting plate supporting the ball) located inside the valve body, while

In external trunnion ball valve design, the stem takes almost all of the force caused by the line pressure, and then friction that is generated by this also causes the high operating torque.

With internal trunnion ball valve design, the trunnion rotates on PTFE bearings, thus minimizing the friction caused by the side thrust which comes from the line pressure on the ball.

Internal Trunnion Ball Valves VS External Trunnion Ball Valve

Feature	Internal Trunnion	External Trunnion
Trunnion Location	Inside Valve Body	Outside Valve Body
Torque	Lower	Higher
Friction	Less	More
Application	Larger, High pressure	Smaller, High Pressure
Cost	Higher	Lower
Reliability	Better	Good
Durability	Better	Good