There are two main methods for laying insulation pipelines: direct burial and trenches. The difference in design between the two is not just about whether there is a trench; there are differences in insulation layer design and project cost.
Direct burial installation involves burying insulation pipes directly into the soil. The advantage of this method is that the pipe is in direct contact with the soil, and the friction of the soil can constrain the axial displacement of the pipeline, thereby achieving compensation-free direct burial installation. The integrity of the insulation layer is good, and heat loss is less than that of trench installation. Using polyurethane-insulated direct-buried pipes can reduce project costs, have lower network heat loss, have a service life several times longer than trench-installed pipes, and shorten the construction period.
Trench installation requires constructing specialized underground trenches to accommodate insulation pipes. Pipe heat dissipation conditions differ-direct-buried pipes transfer heat to the soil through insulation layers, while trench pipes use insulation layers to transfer heat to the air inside the trenches. Different heat transfer media result in different insulation layer thickness designs. If water accumulates in the trench, the pipes may be submerged, so trench installation requires higher waterproofing and drainage.
There are also differences in material selection. Direct-buried pipes usually use polyurethane foam insulation combined with polyethylene outer protective pipes, which have good integrity and strong waterproofing. In the past, materials like rock wool and perlite were commonly used for trench installation, which have strong water absorption but quickly lose insulation performance once moisture occurs.
Overall, direct burial laying is currently the mainstream practice, and trench laying is gradually being replaced. However, in special situations such as complex geological conditions and dense underground pipelines, trench laying still has room for improvement. Design should be chosen based on site conditions and project budget, which is more reasonable than blindly applying one approach.