A heat exchanger comprising an elongated tubular cylindrical member having fluid ingress and egress openings adjacent to its opposite ends and external flanges at opposite ends one of which flanges has a counterbore facing in the direction away from the cylindrical member. A plurality of graphite tubes within the cylindrical member having their opposite ends connected to graphite headers one of which is connected through a graphite end member to one end of the cylindrical member and the other of which has an outside diameter slightly less than the inside diameter of the cylindrical member and within which it is slidable or floats. The floating header has an external circumferential groove with outwardly inclined ends. A seal is provided at the end of the cylindrical member at which the floating header is located which seal includes packing in the counterbore in the adjacent flange and a gland member slidable on the floating header and adjustable towards the flange. A part of the gland member overlies one end of the external groove in the floating header member. A second graphite end member abuts the end of the floating header facing in the direction away from the cylindrical member and is clamped thereto by a clamp plate engaging the other side of the end member. A sleeve formed of a plurality of arcuately shaped parts is located in the circumferential groove in the floating header with an end underlying the gland member and has an external groove spaced from the gland member in which a split ring is located extending radially of the sleeve and having its radial outer or circumferential surface inclined radially outwardly in the direction away from the cylindrical member. A retainer ring surrounds the split ring and is connected to the clamp plate at the end of the second end member facing in the direction away from the cylindrical member by a plurality of bolts.
