In a floating head heat exchanger, only one end of the tube plates at both ends is fixed to the shell, and the other end can move freely relative to the shell, which is called a floating head. The floating head is composed of a floating tube plate, a hook ring and a floating head end cover, and is detachable connection, and the tube bundle can be drawn out from the shell. The thermal deformation of the tube bundle and the shell are not restricted to each other, so no thermal stress is generated. Its advantage is that it is easy to clean between and inside the tube without thermal stress; but its structure is complex, the cost is higher than that of a fixed tube-sheet heat exchanger, the equipment is heavy, the material consumption is large, and the small floating head end cover cannot be checked during operation. The sealing requirements are higher during manufacturing. It is suitable for occasions where the wall temperature difference between the shell and the tube bundle is large or the shell side medium is easy to scale.