Polyurethane thermal insulation pipes are structured in three layers from inside to outside:

One Layer: Working Steel Pipe Layer

Generally, seamless steel pipes, spiral steel pipes, and straight seam steel pipes are selected based on design and customer requirements. After being treated with shot blasting to remove rust, the steel pipes can achieve a rust removal grade up to Sa2 as per GB8923-1988, with a surface roughness of R=12.5 micrometers as per GB6060.5-88.

Second Layer: Polyurethane Insulation Layer

Formed by injecting the liquid raw material of rigid polyurethane foam plastic into the cavity between the steel pipe and the outer sheath with a high-pressure foaming machine, commonly known as "foamed pipe-in-pipe."

Three Layers: High-Density Polyethylene Protective Layer

Preformed black or yellow polyethylene plastic pipes with specified wall thickness. Their functions include: 1) protecting the polyurethane insulation from mechanical damage, and 2) providing corrosion and water resistance.