Pressure vessel

A pressure vessel comprising a rigid container having a deformable partition therein defining two chambers for fluids, each having a fluid port leading thereinto, an elongated central guide member for said partition in one of said chambers, said central guide member comprising a rigid tube extending axially in said container having at least one end secured to one of said ports, said tube having apertures therethrough, a flexible closure member encompassing said tube and the apertures thereof, said closure member having a plurality of closure elements normally extending radially outward from said tube, each closure element comprising a pair of spaced walls joined at their outer ends, one of said walls having apertures therethrough, whereby when said partition is forced inwardly against said flexible closure member to force said flexible closure member against said tube, an apertured portion of one of said walls will be aligned with an uninterrupted portion of an associated wall to prevent extrusion of said partition through the apertures in said tube.