Vacuum calibrating method pre-insulated pipe outside casing extrusion line is the most advanced and popular machinery in the world. HSD brand absorbs the advanced technology from German and improve to meet development. Especially compared with internal pressure method, Vacuum calibrating method is much better than it for stiffness, pressure resistance and surface smooth.

Rigid polyurethane spraying polyethylene winding prefabricated directly buried insulation pipe consists of steel working pipe, spraying polyurethane rigid foam insulation layer and winding polyethylene outer protective pipe.

1. Remove rust from steel pipe surface
2. Preheat the steel pipe to get it ready for polyurethane spraying
3. Spray polyurethane evenly on steel pipe outer surface
4. Wrap melted HDPE strap around the PU foam
5. Trim the pipe ends

• Density, thermal conductivity, compressive strength and other indices of the polyurethane insulation layer are uniform and consistent. Therefore overall performance of the pipe is superior.
• The polyurethane insulation layer is formed by free foaming. Since polyurethane is foamed perpendicular to the axial direction of the pipe, compressive strength of the insulation layer is improved.
• The polyurethane insulation layer is formed after spraying. The raw materials are sprayed onto the outer surface of the steel pipe in a liquid form, and then begins to foam. Due to the high reaction activity of the spraying polyurethane raw materials, adhesion between steel pipe surface and polyurethane foam layer is stronger.
• Roughness of the surface of polyurethane foam layer is more conducive to increase bonding effect between insulation layer and outer HDPE protective layer.
• Polyurethane insulation layer can be sprayed according to the thickness required by customers with a thickness of 15-20mm. Costs can be significantly saved.
• Prefabricated directly buried insulation pipes produced using the "spray winding" process, with polyurethane insulation layer and polyethylene outer protective layer thickness adjustable according to users needs. The production process does not require additional molds and tooling, making it simple and easy to operate. Due to the absence of expansion stress on the polyethylene outer protective layer during foaming in the "spray winding" process, thickness of the polyethylene outer protective layer can be relatively thinner, reducing costs for customers.
• The polyethylene outer protective layer is formed by circumferential winding, therefore circumferential elongation and tensile strength are significantly improved. Circumferential strength of polyethylene protective layer is stronger.
• As this is a completely automatic production line, Production speed is improved and production quality is consistent and superior.