How Does A Trunnion Ball Valve Work?

Trunnion ball valves are quarter-turn valves used to stop the flow of medium in pipelines. These valves feature a round or spherical disk in the center that rotates to start or stop the flow. Trunnion Ball valves are extremely versatile and are commonly used in industrial applications where tight shut-off is required.

The trunnion ball valve has upper stem and down stem or trunnion plate  to support the ball so that the ball will not move during the pressure from the pipeline. This support is in the shape of a shaft and is called a trunnion.

The trunnion absorbs any added pressure from the flow, reducing stress on the ball and seats of the valve. The trunnion mounted 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 mounted ball valves are used in high-pressure, large scale applications where low operating torque is required.

How is a Trunnion Mounted Ball Valve Constructed?

Here is a look at the different parts of a trunnion-mounted ball valve.

Body
The body of the valve is the casing that holds and protects the internal parts of a trunnion mounted ball valve. It can be made of carbon steel, stainless steel, low-temperature carbon steel, duplex, super duplex, Inconel, and more depending on the application.

Stem
The stem of a trunnion mounted ball valve connects the ball to the actuator. It is connected to the ball and it controls the movement of the ball.

Seats
The seats of a trunnion-mounted ball valve surround the ball. When the actuator is turned, the seats hold the ball snugly in place, sealing off any access. Trunnion ball valves have spring-loaded seats that move towards the ball as it is held firmly in place.

Trunnion
In the trunnion mounted ball valves,the bottom stem is called “trunnion” and it keeps the ball firmly in place.

Spring
The trunnion ball valves are with the spring pushing the seat to enable the sealing between the ball and seat.

How Does A Trunnion Ball Valve Work?

When the trunnion ball valve is in closed position and there is high line pressure from up stream,the pressure pushes the seat from the upstream to reach and contact the ball to enable the seal between the upstream seat and ball.

When the trunnion ball valve is in closed position and there is low line pressure from up stream,the seat is pushed by the spring to enable sealing between the up stream seat and ball.

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