Polyurethane thermal insulation pipes are composed of three layers from inside to outside:

Layer 1: 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 processed by the shot blasting rust removal technique, the steel pipes can achieve a rust removal level up to Sa2 grade as per GB8923-1988, with a surface roughness of up to R=12.5 micrometers as per GB6060.5-88.

Second Layer: Polyurethane Insulation Layer

Formed by injecting a liquid polyurethane foam into the cavity between the steel pipe and the outer sheath with a high-pressure foam generator, commonly known as "pipe-in-pipe foaming."

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 damage by mechanical hard objects, and 2) anti-corrosion and waterproofing.