District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory made fitting assemblies of steel service pipes, polyurethane thermal insulation and a casing of polyethylene

This document specifies technical requirements for steel-based thermal pre-insulated components designed for underground single-pipe hot water distribution networks within central heating systems. The components are manufactured with a core of steel pipe, surrounded by a layer of polyurethane foam for thermal insulation, and an outer protective casing made of polyethylene material. These factory-prepared fittings are intended to ensure mechanical integrity, thermal efficiency, and long-term durability when installed in subterranean environments. The specification addresses dimensional tolerances, material properties, and performance criteria for the insulation and jacketing layers to prevent heat loss and protect against moisture ingress. It outlines testing methodologies to verify the structural stability and thermal resistance of the assembled units under operational conditions. The standard applies to the production, quality control, and acceptance of these pre-insulated steel pipeline components used in regional heating infrastructure. By defining consistent manufacturing parameters, it supports the safe and reliable operation of underground heating networks where corrosion resistance and thermal continuity are critical for system performance.