Heating pipeline insulation cannot be a one-size-fits-all solution for the entire country. Consider Harbin and Guangzhou: one endures temperatures plummeting to minus 20 or 30 degrees Celsius, while the other is hot and humid; consequently, the challenges facing their respective pipelines are entirely different. The appropriate thickness of the insulation layer-and the extent to which moisture protection is required-depends entirely on where the pipeline is buried.
In the North, the primary concern is freezing. If a pipeline loses too much heat during its journey from the heating station, the terminal users' homes will fail to warm up adequately. Furthermore, if the insulation layer is insufficiently thick, the surface of the pipe may actually freeze in areas where soil temperatures are low. Therefore, in places like Harbin, the insulation layer for direct-buried hot water pipes of the same diameter is often 30 to 50 percent thicker than that found in southern cities. This additional investment in thicker insulation is not for aesthetic purposes; rather, it is to ensure that the water temperature remains within standard limits even after traveling hundreds of meters.
The situation in the South is quite different. Winters are not as severe, so the pressure to prevent freezing is significantly lower. In the South, the thickness of the insulation layer is determined primarily by considerations of energy conservation and burn prevention; there is no need to blindly adopt the standard thicknesses used in the North, as doing so would unnecessarily drive up costs and encroach upon valuable space within pipe corridors. However, the South faces a specific challenge that rarely troubles the North: moisture. Due to high groundwater levels-and the fact that soil becomes saturated during the plum rain season and typhoon weather-pipelines are constantly exposed to dampness. If the outer protective casing is even slightly compromised, moisture will seep in; once the polyurethane foam insulation becomes damp, its thermal performance plummets drastically. The combination of a hot, humid environment and high-temperature steam causes the foam to age at a much faster rate than it does in the North.
Consequently, the moisture-resistance design for pipelines in the South must be significantly reinforced. The wall thickness of the outer protective casing is typically selected at its maximum limit; pipe joints require double-layer heat-shrinkable sleeves or even electrofusion welding; and some coastal projects mandate that the closed-cell ratio of the foam insulation exceed 95%, followed by rigorous water penetration testing. Furthermore, for critical points prone to water ingress-such as valve wells and expansion joints-drainage systems and sealed inspection ports are absolutely indispensable. While moisture protection is certainly a requirement in the North as well, the drier climate ensures that-provided the pipe joints are sealed according to specifications and the outer casing remains undamaged-major moisture-related issues rarely arise.