Threaded channel closure for tubular heat exchanger comprising channel header wherein the gasket is provided at the shoulder of the channel, tongue of the diaphragm is provided to apply pressure on the gasket to achieve the sealed joint, outer compression ring provided at back side of the diaphragm and being loaded by push bolts, provided at the periphery of threaded lock ring, outer compression ring being supported by channel cover, which is kept in position by threaded lock ring, characterized in that, the channel header being provided with plurality of radial holes on its periphery, approximately at the centerline of the width of the outer compression ring in its assembled condition; the outer compression ring being provided with plurality of radial through holes matching the set of holes in number as well as angular position.