Polyurethane thermal insulation 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 being treated with shot blasting to remove rust, the steel pipes can achieve a rust removal level up to Sa2 grade as per GB8923-1988 standard, and the surface roughness can reach R=12.5 micrometers as per GB6060.5-88 standard.

Second Layer: Polyurethane Insulation Layer

The rigid polyurethane foam plastic liquid is injected in one operation into the cavity formed between the steel pipe and the outer sheath using a high-pressure foam machine, commonly known as "foamed-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.