Internal sliding, external fixed

Polyurethane insulated pipes may undergo movement as they expand when heated. Displacement can also occur. Both the insulation structure layer and the outer casing form an integral structure. It is preferable to fix the working pipe and the outer protective pipe together for external fixation. At both ends of each section of pipe and the compensator, two large reinforced concrete support piers should be installed. This is beneficial for maintaining the stability of the pipe's fixation. External fixation requires the installation of reinforced concrete support piers, which increases the construction area, investment, and sometimes extends the construction period.

2. Internal sliding and fixed interior

By fixing the working form to the outer steel pipe, the strength of the outer protective pipe is fully utilized, as well as the friction between the outer protective pipe and the soil, to further secure the inner pipe. Without the need for reinforced concrete, this saves the use of reinforced concrete piers. Only by using steel pipes as the outer protective pipe can the inner fixing method be employed. The fixed end features thermal insulation to reduce thermal bridge effects. Moreover, the strength of the outer protective pipe meets the requirements for horizontal pipe thrust. For steel-clad steel thermal insulation structures, using an inner fixing structure offers significant advantages.

3. Cleverly utilizes an outer sliding and inner fixed design

The thermal insulation material of the polyurethane-insulated pipe and the working steel pipe are combined through a series of processes to form an integrated unit. The thermal insulation structure and the working steel pipe must move together during pipeline thermal expansion. There is a gap of 10-20 cm between the outer casing and the thermal insulation structure layer. This design not only provides excellent insulation but also serves as an excellent channel for moisture expulsion.