A Trunnion-Mounted Ball Valve uses a Trunnion, or lower stem to support the ball within the valve body. Characteristics of a Trunnion-Mounted Ball Valve are:
- The ball is fixed, it does not float
- The ball is centered by the stem at the top and trunnion at the bottom
- The seal is formed by the seats moving toward the ball
- More complex than floating ball valves
The Trunnion-Mounted Ball Valve is made up of the following basic components. Body, Ball, Seat/Seat Assemblies, Upper Stem, Trunnion and End Connections. These valves are often supplied with flanged or butt-weld ends.
The advantages of Trunnion-Mount Ball Valves are:
- No size limit to the use of trunnion-mounted ball valves
- Trunnion supports the weight of larger balls
- May be used in higher pressure applications
- Seat Moves to the Ball
- Lower Torque and Actuation Costs
- Ease of Operation
- Double Block and Bleed Capabilities
The Trunnion seat design is manufactured in one operation that machines the metal seat holder / retainer to which the seat insert is added. In some configurations the seat insert is then locked into place by rolling the seat lip into the insert groove, resulting in an extremely reliable seal.
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