Insulation pipe, also known as prefabricated insulation pipe fittings, is a kind of directly buried prefabricated insulation pipe with good insulation performance, safety and reliability, and low cost. The problems of insulation, sliding lubrication and waterproofing of prefabricated insulation pipes for medium-high temperature heat transfer in urban central heating are effectively dealt with. Thermal insulation pipe fittings not only have advanced technology and applicability that traditional trench and overhead pipeline laying can not match, but also have remarkable social and economic benefits, and are also powerful measures for energy saving of heating. The application of directly buried heating pipe technology in insulation pipe fittings indicates that the development of heating pipe technology in China has entered a new starting point.
First layer: working steel pipe layer, according to the design and customer's request, seamless pipe (GB8163), spiral welded pipe (GB9711; SY / T5038) and straight welded pipe (GB3092) are generally selected. After the surface of steel tube is treated by advanced shot peening rust removal technology, the grade of steel tube rust removal can reach Sa2 grade in GB8923-standard, and the surface roughness can reach R=12.5 micron in GB6060.5 standard. The surface of steel pipe is decontaminated and rusted, then coated with a layer of anticorrosive material. Its function is waterproof, and the other is to improve the bonding surface between the insulation layer and the steel pipe, so as to make it a whole.
The second layer is polyurethane insulation layer, which is made by one-time injection of rigid polyurethane foam plastics into the cavity formed between the steel pipe and the special steel mould by high-pressure foaming machine. That is commonly known as "mold foaming process". PU foam can be full, any quality problems for direct inspection. Its function is waterproof, but heat preservation, and the third is to support the self-weight of the heating network. When the temperature of delivery medium is -50 ~120 ~C, rigid plastics are chosen as insulation layer; when the temperature of delivery medium is -50 ~150 ~C, rigid plastics are selected as insulation layer.
The third layer: FRP maintenance layer is made by mechanical wet winding. Its function is to protect the polyurethane insulation layer from mechanical hard damage, and the second is anti-corrosion and waterproof. It has good weather resistance, acid resistance and seawater resistance. However, rigid and semi-rigid unsaturated resins such as 306, 191, 189, 196, etc., must be used for the resin. Glass fibers and cloth must be made of medium and low alkali fibre yarn drawn by platinum clamp pot or tank kiln. The high alkali content fibre yarn drawn by earthen pot must be restrained to ensure the quality of production.
The heat preservation material commonly used in yellow jacket heat preservation pipe is rigid polyurethane foam plastic, and the applicable temperature is - 185 - 120 C. In order to improve its strength, a layer of high density polyethylene (HDPE) is added outside the insulation layer to form a composite structure to prevent the open water from penetrating into the insulation layer. Therefore, it is particularly important to introduce the function, characteristics and application scope of yellow jacket insulation pipe.
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