CJT 114-2000 Pre-fabricated directly-buried insulation pipe made of polyurethane foam for high-density polyethylene outer protective pipes

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The standard CJT 114-2000 \"Prefabricated Direct-Burial Insulated Pipes Made of Polyurethane Foam for High-Density Polyethylene Outer Sheaths\" addresses the manufacturing and acceptance of such pipes, which are suitable for use in applications where the temperature of the medium being transported (continuous operating temperature) does not exceed 120 degrees, the occasional peak temperature does not exceed 140 degrees, and the operating pressure does not exceed 2.5 MPa. I would like to ask whether the operating pressure of the medium is greater than 2.5 MPa; it only acts on the inner steel pipe – what does it have to do with the polyurethane layer and the HDPE outer protective tube? And why is it necessary to limit the operating pressure to no more than 2.5 MPa? What should be done if the working pressure is greater than 2.5 MPa? Does this mean that this specification is no longer applicable, or that this method of insulation and corrosion protection using polyurethane foam plastic prefabricated pipes with high-density polyethylene outer coatings is no longer suitable? Seeking help from experts