Polyurethane insulated pipes consist of a three-layer structure from the inside out:

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 the surface treatment with shot blasting to remove rust, the steel pipes can achieve a rust removal level up to Sa2 grade according to GB8923-1988 standards, and the surface roughness can reach R=12.5 micrometers as per GB6060.5-88 standards.

Second Layer: Polyurethane Insulation Layer

Formed by injecting a liquid rigid polyurethane foam into the cavity between the steel pipe and the outer sheath with a high-pressure foam machine, commonly referred to as "foam-in-place 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 layer from mechanical damage by hard objects, and 2) corrosion and water resistance.