Jinan insulated pipe is composed of a steel pipe conveying the medium, an anti-corrosion outer steel jacket, and ultra-fine glass wool filled between the steel pipe and the outer steel jacket; graphite, calcium-silicate tile shells, and filled PU foam composites may also be used. Steel-casing (steel-in-steel) burial technology is a new waterproof, leak-proof, seepage-resistant, pressure-resistant, and fully enclosed burial technology, representing a major breakthrough in applying direct-buried laying in areas with high groundwater tables. The primary issue for the protective jacket of direct-buried pipelines is the reliability of tight waterproofing; in addition, good mechanical strength is required. Because of high strength, steel casings use welded connections, and waterproof sealing reliability is very high; moreover, their high-temperature resistance cannot be matched by other outer protective jackets. In areas with high groundwater tables, to ensure that groundwater does not affect normal operation of steam direct-buried pipelines, a strong, sealed steel-pipe outer shell is the preferred outer protective layer.

　　The structure of Jinan insulated pipe is classified by sliding mode into two types: internally sliding and externally sliding.

　　1. Internally sliding type: the insulation structure consists of the carrier pipe, aluminum silicate, a friction-reducing layer, microporous calcium silicate, a thermal barrier, stainless-steel fastening bands, an aluminum-foil reflective layer, a PU insulation layer, an outer steel jacket, and an external anti-corrosion coating.

　　2. Externally sliding type: the insulation structure consists of the carrier pipe, a glass-wool insulation layer, an aluminum-foil reflective layer, stainless-steel fastening bands, sliding guide supports, an air insulation layer, an outer protective steel pipe, and an external anti-corrosion coating.

　　Structural Mechanism of Jinan Insulated Pipe:

　　1. Anti-corrosion coating: protects the outer steel pipe from corrosive substances, extending the service life of the steel pipe.

　　2. Outer protective steel pipe: protects the insulation from groundwater corrosion, supports the carrier pipe, and can bear certain external loads to ensure normal operation of the carrier pipe.

　　3. PU foam layer: maintains the medium temperature and keeps the outer jacket surface at ambient temperature.

　　4. Isolation/reflective layer: ensures that organic foam does not enter the inorganic rigid high-temperature layer; reflects some heat from the high-temperature layer.

　　5. Inorganic rigid insulation layer: withstands high temperature, ensures the interface temperature with the organic insulation layer, and prevents the foam from being carbonized.

　　6. Friction-reducing layer: ensures free thermal expansion and contraction of the carrier pipe.

　　7. Carrier pipe: ensures normal flow of the conveyed medium.