Ball valve having improved inherent rangeability

摘要

A ball valve (10) having improved inherent rangeability comprises a floating ball (14) of conventional design that is rotatable through substantially 90 DEG between a pair of seats (17,18) respectively located adjacent the upstream and downstream sides of the valve within a valve housing. At least one of the seats is a one-piece lubricant-impregnated metal seat (18) configured to provide a concave central surface portion (18a) that makes full-face direct sealing contact with the ball (14), and which defines multiple spaced holes (19) that extend through the seat to increase the fluid-to-metal contact of fluid passing through the seat thereby to reduce the pressure between the upstream and downstream sides of the valve. The pattern of holes may be such as to cause the valve to exhibit an equal percentage of flow characteristic for at least a portion of the ball rotation and/or a linear flow characteristic for at least a portion of the ball rotation. When only one such multiple hole seat is used in the valve, the other seat can be a standard round hole seat, or a slotted seat, or a V-seat. In each case, the direct sealing contact between the ball and the multiple hole seat prevents fluid leakage from the ball bore through any holes in the seat that are covered by a surface portion of the ball whereby the valve exhibits improved inherent rangeability.