Vihung - Model API 6D - Trunnion Mounted Ball Valves - Brochure

Trunnion valves have mechanical anchoring of the ball at the top and the bottom to avoid axial displacements in the flow direction. During normal operation pressure compresses the seat onto the ball to achieve valve sealing, such construction also ensures automatic cavity relief in case of overpressure in body cavity. As isolation valves, they intercept the flow by opening and closing the port and are mainly recommended on tight shut-off gas and liquid services; trunnion control valves with cage trim are engineered for those services where continuous pressure and flow rate regulation are required.