TRUNNION-MOUNTED BALL VALVE WITH A FLEXIBLE VALVE SEAT

摘要

A trunnion-mounted ball valve, comprising, a valve body including a central body and two opposite tubular sections, the central body having a body cavity and the tubular sections having respective ducts with a common longitudinal axis and respective inner ends facing said body cavity, a trunnion mounted ball rotatably connected to the valve body and rotatable about an axis of rotation orthogonal to said longitudinal axis between an open position and a closed position, the ball having a through hole which is aligned to said ducts in the open position and transversal to said ducts in the closed position, a first and a second seat ring each of which has a guide portion slidably engaging a respective tubular section in the direction of said longitudinal axis and a head portion having a valve seat, the valve seats of the first and second seat rings abutting on opposite sides of said ball, wherein the head portion of at least one of said seat rings has at least one annular groove directed radially with respect to said longitudinal axis, wherein a backup ring is housed in said annular groove and is associated to an elastic preloading device arranged to apply between the seat ring and said backup ring elastic forces parallel to said longitudinal axis, said elastic preloading device acting in correspondence with two opposite angular sectors (α) of said backup ring, each of said angular sectors (α) being symmetric with respect to a diametric axis of said backup ring orthogonal to said axis of rotation