Improved the mechanical properties of the outer sheath.

2.Reduced the wall thickness of the outer casing.

3.Reduced the water absorption rate of the thermal insulation layer.

4.Enhanced the closed cell rate of the insulation layer.

5. Reduced the axis eccentricity of the insulation pipe.

6.Enhanced the uniformity of the overall pipeline insulation density.

7. Increased the compressive strength of the insulation layer.

8. Decrease the thermal conductivity of the insulation layer to reduce energy loss.