HDPE Jacketed Galvanized Steel Insulated Pipe

• ​Introduction

HDPE Jacketed Galvanized Steel Insulated Pipe, a composite pipeline system integrating multiple functional layers, is mainly composed of an inner galvanized steel pipe, a middle thermal insulation layer, and an outer HDPE (High-Density Polyethylene) jacket. It combines the excellent mechanical strength and corrosion resistance of galvanized steel pipes, the efficient thermal insulation performance of the insulation layer, and the outstanding weather resistance, impact resistance, and chemical stability of HDPE jackets.

• ​Main Functions

Thermal Insulation: The rigid polyurethane foam layer with low thermal conductivity minimizes heat loss during medium transportation, ensuring energy efficiency.

Corrosion Resistance: The HDPE outer jacket is resistant to chemical corrosion, moisture, and aging, protecting the inner pipe and insulation layer from external environmental damage.The inner galvanized steel pipe forms a zinc coating on the surface through galvanization, which acts as a barrier to prevent the steel pipe from being corroded by the transported medium.

Mechanical Protection: The HDPE jacket has high impact strength and toughness, preventing the pipeline from being damaged by external forces during transportation, installation, or operation.

Sealing Performance: The integrated structure of the pipe ensures good airtightness, avoiding water vapor infiltration into the insulation layer and maintaining long-term insulation effectiveness.

• ​Tubing Standards

ASTM A53，ASTM A106，ASTM F2165-19 ； EN 10255，EN 10240，EN 253； GB/T 3091，GB/T 13793，GB/T 9711，GB/T 8163，GB/T 29047，CJ/T 114.

• ​Material & Performance

Working Steel Pipe: ASTM A53: Grade A、B，ASTM A106: Grade A、B、C； EN 10255: S195T、S235JRH、S275JRH、S355JRH； GB/T 3091: Q215A/B、Q235A/B、Q355B, GB/T 8163：10#，20#，Q355，Q420， GB/T 13793: Q195、Q215A/B、Q235A/B、Q355B、Q390B；

Insulation Layer: Polyurethane foam (PUR) （Nominal Density：60(+15/-5) kg/m³，Thickness ：32-60mm，Thermal Conductivity: ≤ 0.029 W/m·K@50℃，Closed Cell Content: ≥90%，Water Absorption: <5%，Temperature Resistance：-40℃ ~ 120℃）;

Outer Jacket: High-density polyethylene（HDPE）.

Key Performance :

Thermal Insulation Performance – The insulation layer effectively blocks heat or cold transfer, significantly reducing energy loss during transportation and maintaining stable medium temperature.

Structural Integrity and Mechanical Properties – The HDPE jacket has good mechanical strength, able to withstand external forces such as impact and extrusion during installation or burial without easy damage.The insulation layer, HDPE jacket, and inner working pipe are tightly bonded, without delamination or detachment, ensuring a stable overall structure.The inner working pipe can withstand the pressure of the transported medium, with no leakage or deformation under normal working conditions.

Environmental and Corrosion Resistance – The HDPE jacket has strong chemical corrosion resistance, able to resist erosion from acids, alkalis, microorganisms, and other chemical factors in the soil, while being resistant to UV aging for a long service life.The HDPE jacket has excellent sealing performance, effectively preventing groundwater or moisture from seeping into the insulation layer and avoiding impact on insulation efficiency.The zinc coating provides excellent corrosion resistance, extending the service life of the steel pipe.

Long-term Stability and Durability – In long-term high or low temperature environments, the insulation layer will not show obvious aging phenomena such as shrinkage or hardening, and the HDPE jacket will not become brittle, maintaining stable performance.

• ​Manufacturing Process

Steel Pipe Preparation : Select galvanized steel pipes that meet the standard requirements, and conduct strict inspection on their outer diameter, wall thickness, zinc coating thickness, and surface quality . Then, use a pipe cleaning machine to remove oil, dust, and other impurities on the inner and outer surfaces of the steel pipe to ensure good bonding between the steel pipe and the insulation layer.

Foam Injection : The steel pipe is placed inside the HDPE jacket, and liquid polyurethane is injected and foamed under controlled conditions.

Curing & Cooling : The foam is cured to achieve optimal density (typically 60-80 kg/m³) and mechanical strength.

Quality Inspection: Tests include thermal conductivity, foam density, adhesion strength, and HDPE jacket integrity.

Final Assembly :Fittings (elbows, tees, etc.) are pre-insulated and ready for on-site installation.