US Patent 10228065 Flexible seat ball valve

A system includes a ball valve. The ball valve includes a housing, a ball, and a first valve seat assembly. The housing includes a chamber, a first fluid passage intersecting the chamber, and a second fluid passage intersecting the chamber. The ball is disposed in the chamber and is configured to control fluid flow between the first and second fluid passages. The first valve seat assembly is disposed between the ball and the housing. The first valve seat assembly includes a first seat configured to seat against the ball both above and below a pressure threshold, and a second seat configured to seat against the ball only above the pressure threshold, wherein the second seat has a coefficient of friction that is lower than the first seat.