Steel-insulated steel pipe structure using a single insulating material layer or a variety of insulation materials composite layer (the composite layer containing air layer, adiabatic radiation layer, etc.), the external protective pipe using steel external pipe or glass fiber reinforced plastic outer pipe. The internal sliding external fixation of steel heat-insulated steel pipe is the working steel tube when heated expansion, the steel tube movement, the displacement, and the insulation structure layer and outer casing into a whole structure, do not produce movement. The external fixation is the working steel pipe and the outer protection tube fixed at the same time, in each section of the pipeline and the Compensator's two ends, must set two very big reinforced concrete buttress, can guarantee the pipeline the fixed. No guide bracket is provided.
External fixation because of the need to set up reinforced concrete pier, so the construction of large, investment, long duration, and the pier is a direct buried steel pipe weak parts, the site is easy to produce "Hot bridge", also prone to water seepage phenomenon, the pipeline operation is not normal, the site also prone to accidents. The internal sliding internal fixation of steel insulated steel pipe is to fix the steel pipe through a certain structure form, make full use of the strength and rigidity of the outer protective pipe and the friction between the outer protective pipe and the soil, so that the inner tube is fixed without the reinforced concrete structure, and the reinforced concrete buttress can be saved. Only the steel pipe is used as the outer protective tube to adopt the internal fixation form. Fixed end has insulation facilities to reduce the thermal bridge effect, while the external protection tube should be sufficient strength to meet the requirements of horizontal thrust pipe. For the "Steel set steel" insulation structure, the use of internal fixation structure has a great advantage. According to the different protective pipe, but also can be divided into steel-sleeve steel structure and steel-clad steel composite structures.