Abstract: A heating furnace tube, a method of using the same and a method of manufacturing the same which have been developed with a view to eliminating inconveniences occurring when a carbon-containing fluid is made to flow in the heating furnace tube. The heating furnace tube which comprises a rare earth oxide particle distributed iron alloy containing 17-26 wt. % of Cr and 2-6 wt. % of Al. The method of manufacturing this heating furnace tube which comprises the steps of forming or inserting an insert metal on or into at least one of a joint end portion of one heating furnace tube element and that of the other heating furnace tube element, bringing these two joint end portions into pressure contact with each other directly or via an intermediate member, and diffusion welding the two heating furnace tube elements to each other by heating the insert metal.

Abstract: A clamp-type isolating pipe joint is disclosed, which can connect pipes by providing insulation between them, is easy to assemble and disassemble, has high reliability and allows easy replacement of parts and is inexpensive to manufacture and install. The joint comprises hubs weldable to connectable pipes, a seal ring interposed between butted surfaces of the hubs and a clamp disposed around the circumferences of the hubs for clamping itself with bolts in the radial direction of the hubs to be fixed as insulated from each other. The clamp and hubs are insulated by interposing between them a metal plate with an insulating resin coat formed thereon. Insulation layers are also provided between the seal ring and the hubs.