The high-density polyethylene protective layer is pre-made into a black (yellow) plastic pipe with a certain wall thickness, which will be used after the corona process. One of its functions is to protect the polyurethane insulation layer from damage by mechanical hard objects, and the other is to prevent corrosion and waterproof.

One is composed of steel pipe for conveying medium, anti-corrosion outer steel pipe, and ultrafine glass wool filled between the steel pipe and outer steel pipe. It can also be composited by graphite, silicon-calcium tile shell and filled polyurethane foam. Steel casing (steel casing steel) embedding technology is a new waterproof, leak-proof, impermeable, pressure-resistant and fully enclosed embedding technology. It is a major breakthrough in the use of direct burial technology in areas with high groundwater levels.

Internal sliding type: the heat preservation structure consists of working elbow, aluminum silicate, drag reduction layer, microporous calcium silicate, heat insulation layer, stainless steel fastening strip, aluminum foil reflection layer, polyurethane heat preservation layer, outer jacket elbow, and outer Anti-corrosion layer composition.

The high-temperature prefabricated direct-buried heat preservation pipe is composed of steel pipe, glass fiber reinforced plastic inner sheath, and glass fiber reinforced plastic shell. It is characterized by that it also includes a high temperature resistant thermal insulation layer, a lubricating layer, and elastic seals. The utility model effectively solves the problems of heat preservation, sliding lubrication and waterproofing of the exposed pipe ends of the prefabricated direct-buried heat preservation pipe used for high temperature heat transmission at 130°C to 600°C in central heating. The high-temperature prefabricated direct-buried insulation pipe is mainly composed of four parts.

The high-temperature prefabricated direct-buried heat preservation pipe is composed of steel pipe, glass fiber reinforced plastic inner sheath, and glass fiber reinforced plastic shell. It is characterized by that it also includes a high temperature resistant thermal insulation layer, a lubricating layer, and elastic seals. The utility model effectively solves the problems of heat preservation, sliding lubrication and waterproofing of the exposed pipe ends of the prefabricated direct-buried heat preservation pipe used for high temperature heat transmission at 130°C to 600°C in central heating. The high-temperature prefabricated direct-buried insulation pipe is mainly composed of four parts.