BALL VALVE HAVING IMPROVED INHERENT RANGEABILITY

摘要

In accordance with the present invention, a ball valve, provided with a floating ball that is rotatable through substantially 90.degree., includes a pair of seats adjacent the upstream and downstream sides of the valve at least one of which seats is a one-piece lubricant-impregnated metal seat that makes full face direct sealing contact with the ball at all times during movement of the ball between its fully open and fully closed positions. The seat includes a concave central surface portion which defines a pattern of spaced holes extending through the seat in the direction of the axial flow passage through the valve housing, said holes providing the only paths for fluid flow through the seat, whereby the seat effects a significant reduction in the pressure of fluid flowing through the ball valve due to the fluid to metal contact of fluid passing through the holes in the seat. The full face direct sealing contact between the ball and central surface portion of the seat is operative to prevent leakage of fluid from the bore of the ball through any of the holes in the seat that are covered by a surface portion of the ball, and permits fluid to flow through only those holes in the seat that directly communicate with the bore of the ball as the ball is rotated from one position to another about its axis of rotation. Since the ball in the present invention is a floating ball, and makes full-face contact with a seat that is constructed of good bearing material, the valve need not employ a thin flexible metal seat to provide a seal between the ball and the housing as in the Baumann arrangement, and allows the ball to seal directly to the seat throughout the stroke of the ball. The holes that are shrouded are truly "off", not just flowing less. In addition, due to the floating nature of the ball, and its full-face contact with the multi-hole seat, the valve design is self-compensating for wear, and continues to seal well even after wear has occurred.