National standards for pipeline thermal insulation do not consist of a single document but rather a comprehensive system based on pipeline types, application scenarios, and engineering stages.
To date, the core national standards can be categorized into four main types: First is GB/T 4272-2024, *General Technical Specifications for Thermal Insulation of Equipment and Pipelines*, which serves as the "fundamental law" for all thermal insulation projects. It outlines general requirements for material selection, design, construction, and acceptance, applying to insulation projects operating between -196°C and 850°C; it is a mandatory foundational standard. Regarding specific products, the primary standard for prefabricated insulation pipes intended for direct burial (commonly known as "black jacket pipes") is GB/T 29047-2021, *Prefabricated Directly Buried Insulation Pipes and Fittings-Rigid Polyurethane Foam with High-Density Polyethylene Outer Casing*. This standard regulates the three-layer structure-comprising a steel pipe, a polyurethane foam insulation layer, and an outer casing-and applies to scenarios with long-term operating temperatures not exceeding 120°C and peak temperatures not exceeding 130°C. For the design and construction phases, the anti-corrosion and thermal insulation of buried steel pipelines must comply with GB/T 50538-2020, *Technical Standard for Anti-corrosion and Thermal Insulation Layers of Buried Steel Pipelines*, which applies to buried pipelines transporting media at temperatures up to 350°C. Finally, regarding quality inspection, GB/T 29046-2023, *Test Methods for Technical Indicators of Prefabricated Insulation Pipelines for Urban Heating*, is used in conjunction with the others; it provides standardized methods for testing the appearance, structure, and performance of the aforementioned insulation pipes. It is crucial to note that the latest published versions of these standards apply; for instance, the 2012 version of GB/T 29047 has been superseded by the 2021 version, and the testing standard has been updated to the 2023 version. Therefore, one must verify the standard number and year during engineering practice.