How Does A Double Block and Bleed Trunnion Ball Valve Work？ According to API 6D “Specification for Pipeline Valves” standards, a double block-and-bleed (DBB) valve is a “single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve, with a means of venting/bleeding the cavity between the seating surfaces. […]
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The trunnion ball valve has extra stem at the bottom of the ball, the extra stem called trunnion. The trunnion ball valve seat is spring loaded，the seat is pushed by the spring against the ball to realize the sealing when the valve is under low pressure rating.
Trunnion mounted ball valves are available in many different configurations. They are highly customizable so you can choose the size, type, and actuator that suits your needs. Here are some common types of trunnion ball valves.
Trunnion Mounted Ball Valve has the advantage of low torque, suitable for full size application, self relief seat.
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.