Spiral steel pipe for insulation treatment of technical requirements
 
 Spiral steel pipe insulation treatment after people used to be called insulation steel pipe, insulation steel pipe insulation layer is made of rigid polyurethane foam filling, for spiral steel pipe insulation quality requirements are as follows.
 
1. Polyurethane foam should be free of stains, no shrinkage delamination cracking phenomenon. The bubble hole should be uniform and fine, the average size of the bubble hole should not be greater than 0.5 mm.
 
2. The insulation layer of spiral steel pipe should be uniformly filled with the annular space between the working steel pipe and the outer sheath. Any cross-section of the insulation layer on the sum of the area of the cavity and bubble area of the entire cross-sectional area should not be greater than 5%, and the size of a single hole in any direction should not exceed one-third of the actual insulation layer after the same location.
 
3. The density of polyurethane foam in any position of the insulation layer should not be less than 60kg/m3.

4. Spiral steel pipe insulation layer radial compression strength or radial relative deformation of 10% when the compression force should not be less than 0.3Mpa.
 
5. The water absorption rate of polyurethane insulation layer should not be greater than 10%.
 
6. The closed porosity of polyurethane foam should not be less than 88%.
 
7. The thickness of the insulation layer should be in accordance with the design, and should ensure that the surface temperature of the outer sheath is not greater than 50℃ when it is in operation.
 
8. The thermal conductivity λ50 of polyurethane foam without aging should not be greater than 0.033 [W/(m-K)] in the state of 50℃.
 
The insulation layer of spiral steel pipe is an important part of the insulation steel pipe, it is the key link to ensure the temperature of the transported medium, polyurethane foam has good mechanical properties and adiabatic properties, usually can withstand 120℃, through modification or combination with other insulation materials can withstand 180℃. High quality polyurethane raw materials and strict production process can produce perfect spiral steel pipe.