Abstract: A valve system includes a conduit having a flow of fluid therethrough, and a butterfly valve assembly. The butterfly valve assembly includes a shaft extending obliquely within the conduit, a butterfly disk, and a first bearing assembly positioned on an external surface of the conduit. The butterfly disk includes a passage sized to receive the shaft therethrough, wherein the butterfly disk is operable to restrict the fluid flow through the conduit when the butterfly valve assembly is in the closed position. The first bearing assembly is configured to receive a first end of the shaft therethough, wherein the first bearing assembly includes a plurality of tapered roller bearings circumferentially-spaced within a bearing race and configured to maintain the butterfly disk at a substantially constant axial position when the butterfly valve assembly is in the closed position.