It is composed of a steel pipe for conveying the medium, an anti-corrosion outer jacket steel pipe, and ultra-fine glass wool filled between the steel pipe and the outer jacket steel pipe. It can also be made of graphite, silicon calcium tile pipe shell and filled with polyurethane foam. The steel casing (steel in steel) burial technology is a new burial technology that is waterproof, leak-proof, anti-slip, pressure-resistant and fully enclosed. It is a major breakthrough in the use of direct burial technology in areas with high groundwater levels. The primary problem of the protection pipe of the direct buried pipeline is the reliability of tight waterproofing. In addition, it must have good mechanical strength. The steel casing is welded due to its high strength, and the reliability of waterproof sealing performance is very high. In addition, its high temperature resistance is also unmatched by other external protective pipes. In areas with high groundwater levels, in order to ensure that groundwater does not affect the normal operation of the steam direct buried pipeline, the outer protective layer is preferably a solid and sealed steel pipe shell.