Polyurethane Insulated Pipeline, full name: High-Density Polyethylene Plastic Outer Sheath Pre-fabricated Direct Burial Insulated Pipe with Polyurethane Foam Insulation, consisting of a working steel pipe for conveying medium, a polyurethane insulation layer, and a polyethylene plastic outer sheath, which are sequentially combined outward by equipment.
National standard polyurethane insulated steel pipes are structured in three layers from inside to outside.
Layer 1: Working Steel Pipe Layer - Generally, seamless pipes (GB8163-87), spiral-welded pipes (GB9711-88; SY/T5038-92), and straight seam welded pipes (GB3092-93) are selected according to design and customer requirements. After being treated with advanced shot blasting rust removal technology, the steel pipes can achieve rust removal grade Sa2 as per GB8923-1988 standard, with a surface roughness of R=12.5 micrometers as per GB6060.5-88 standard.
Second Layer: Insulating polyurethane layer, formed by injecting the liquid raw material of rigid polyurethane foam plastic into the cavity between the steel pipe and the outer sheath with a high-pressure foaming machine in one go. This is commonly referred to as the "pipe-in-pipe foaming process." Its functions include: 1) waterproofing, 2) thermal insulation, and 3) supporting the weight of the heating network. When the temperature of the conveying medium is between -50℃ and 120℃, rigid polyurethane foam plastic is used as the insulation layer.
Layer 3: High-density polyethylene protective layer, pre-made black (yellow) plastic tubes with specified wall thickness. Its functions include: 1) protecting the polyurethane insulation layer from mechanical damage by hard objects, and 2) anti-corrosion and waterproof properties.
Product Structure: The pre-fabricated buried steam insulation pipe consists of a core tube (working steel pipe), a reducing layer, an insulating layer, a reflective layer, a fastening steel strip, a sliding bracket, an air layer, an outer protective steel pipe, spray-painted polyurethane, and wrapped glass fiber reinforced plastic.
Features:
The outer protective layer is made of steel pipes, offering high strength and resistance to damage, capable of bearing significant upper loads. To achieve a long service life, anti-corrosion treatment is required for the steel sheath.
The rolling support structure design is rational, featuring low rolling friction, which reduces the load on the fixed supports. The mechanical analysis principle is simple, significantly enhancing the pipeline stability and safety.
The vacuum layer completely eliminates the heat conduction and convection through the air layer, reducing heat loss. Compared to an air layer structure, it can lower the outer wall temperature by 8-13°C under the same insulation thickness.
The vacuum pump system completely resolves the issue of external steel casing inner wall being corroded by hot and humid air, significantly extending the service life of directly buried steam pipelines. The product lifespan is now up to 30 years.
