Steel-in-steel insulated steel pipe consists of an inner carrier pipe, an outer protective steel pipe, and an intermediate insulation layer. Two coats of anti-rust paint are sprayed on the carrier pipe. The insulation layer consists of high-temperature fiber felt, ultra-light porous calcium silicate insulation tiles, and PU foam. The coated steel pipe surface is blast-cleaned and wrapped with six layers of glass fiber and resin coating.
Performance characteristics of steel-in-steel insulation: waterproof, high-temperature resistant, and high-pressure resistant; suitable for a medium temperature of 350°C and a pressure of 2.5 MPa; low heat loss; insulation effect better than any traditional insulation; strong anti-corrosion capability; high strength of the anti-corrosion layer, not easily damaged; long service life of 30–50 years.
Steel-in-steel insulated steel pipe consists of a steel carrier pipe and a steel outer jacket, with the annulus filled with ultra-fine glass wool and an anti-corrosion coating; graphite, calcium silicate clay pipe shells, and filled PU foam composites may also be used. Steel-in-steel buried technology is a waterproof, leak-proof, seepage-resistant, pressure-resistant, and fully enclosed embedding technology. Direct-buried laying represents a major technical breakthrough for high groundwater-table conditions.
The primary issue for the protective pipe of a direct-buried pipeline is strict waterproof reliability. In addition to good mechanical strength, the casing is connected by welding high-strength steel plate, so waterproof sealing reliability is very high, and high-temperature resistance cannot be matched by other outer jackets. Anti-corrosion coating: protects the outer steel pipe, prevents corrosion of the steel pipe, and extends the service life of the steel pipe.
Outer protective steel pipe: protects the insulation from groundwater erosion, supports the carrier pipe, and can bear certain external loads to ensure normal operation of the carrier pipe. PU foam layer: maintains the medium temperature and keeps the outer pipe surface at a normal temperature.
Barrier layer and reflective layer: ensure that organic foam materials do not enter the inorganic fire-resistant high-temperature layer, and reflect heat from the high-temperature layer. Inorganic rigid insulation layer: high-temperature resistant, ensures the interface temperature with the organic insulation layer, and ensures that the foam does not carbonize. Drag-reduction layer: ensures thermal expansion and contraction of the carrier pipe.
