2. At present, small heating enterprises mostly use artificial polyurethane foaming technology to wrap two cloths and three oils. This method is better than rock wool, but the insulation quality is uneven, especially the insulation treatment at elbows and joints, and the quality is difficult to guarantee. Practice has proved that the leakage accidents of this kind of pipeline mostly occur at the joint;
3. Large heating companies generally use finished insulation pipes with shells, also known as prefabricated polyurethane insulation pipes;
This insulation pipe is divided into three layers from the inside out:
The first layer is the working steel pipe layer, seamless steel pipe (GB8 163-87) spiral welded pipe (GB9711-88; SY/T5038-92) and straight welded pipe (GB3092-93). The surface of steel pipe is treated with advanced derusting technology, and the derusting grade of steel pipe can reach the level specified in national standard GB8923- 1988, and the surface roughness can reach the corresponding standard GB6060.5-88.
The second layer is polyurethane insulation layer, which is made by injecting rigid polyurethane foam plastic stock solution into the cavity formed between the steel pipe and the outer protective layer with a high-pressure foaming machine. Commonly known as "pipe-in-pipe foaming process". Its function is waterproof, heat preservation and supporting the self-weight of heating network. Rigid polyurethane foam is usually selected as insulation layer.
The third layer is a black (yellow) plastic pipe prefabricated with a high-density polyethylene protective layer with a certain wall thickness, which is used to protect the polyurethane insulation layer from mechanical hard objects and prevent corrosion and water ingress.
The third insulation pipe has high initial investment, but its service life is longer than the first two insulation pipes. It can be preliminarily estimated that if the pipeline can be extended for ten years, the benefits to the enterprise are self-evident.