Pre-fabricated polyurethane insulated pipes, full name: High-density polyethylene plastic outer sheath polyurethane foam pre-fabricated buried-insulated pipes, are made up of a working steel pipe for conveying medium, a polyurethane insulation layer, and a polyethylene plastic outer sheath, sequentially combined through equipment. The pre-fabricated buried-insulated pipes with high-density polyethylene plastic outer sheath and polyurethane foam are highly favored for their excellent performance, ease of installation, and long service life. Their structure consists of three parts: the outer protective layer, insulation layer, and anti-seepage layer. The material for the outer protective layer is polyethylene jacketing, glass fiber, or other materials. The installation methods include direct burial, overhead, and trench laying.
On medium and small diameter hot oil pipelines or heating pipelines, an insulating composite layer is added externally to the pipeline to reduce heat dissipation into the soil. Common insulating materials are rigid polyurethane foam plastics, suitable for temperatures ranging from -185 to 120°C. This material is soft in texture, and to enhance its strength, a layer of high-density polyethylene is applied externally to the insulation layer, forming a composite material structure to prevent groundwater from seeping into the insulation layer. The outer surface of steel pipes is treated with shot blasting to remove rust and the inner surface of the protective pipe is subjected to corona treatment using high-pressure polyurethane foam equipment to improve the bonding properties of the insulation pipes. The insulation material is rigid polyurethane foam with a density of 60 to 80 kg/m³, which fills the gap between the steel pipe and the sleeve completely and has certain bonding strength, forming a firm unit among the steel pipe, outer sleeve, and insulation layer. Polyurethane foam has good mechanical and insulating properties, usually capable of withstanding temperatures up to 120°C, and can withstand temperatures up to 180°C through modification or combination with other insulating materials. Polyurethane Foam Insulation Pipe, Polyurethane Foam Insulation Pipe Manufacturer, Polyurethane Foam Insulation Pipe Price, Prefabricated Polyurethane Insulation Pipe, Prefabricated Polyurethane Insulation Pipe Manufacturer, Prefabricated Polyurethane Insulation Pipe Price
Pre-fabricated polyurethane insulated steel pipes are structured in three layers from the inside out:
Layer 1: Working Steel Pipe Layer
According to design and customer requirements, generally seamless steel tubes, spiral steel tubes, and straight seam steel tubes are selected. After advanced shot blasting rust removal treatment, the steel tubes can achieve Sa2 grade of rust removal according to GB/T8923-1988 standard, and the surface roughness can reach R=12.5 micrometers as per GB6060.5-88 standard.
Second Layer: Polyurethane Insulation Layer
Formed by injecting a liquid rigid polyurethane foam into the cavity between the steel pipe and the outer sheath with a high-pressure foaming machine, commonly referred to as "foamed-in-place pipe."
Three Layers: High-Density Polyethylene Protective Layer
Preformed black or yellow polyethylene plastic pipes with specified wall thicknesses. Polyethylene is odorless, non-toxic, feels like wax, and boasts excellent low-temperature resistance, with service temperatures as low as -70 to -100°C. It has good chemical stability, resistant to corrosion by most acids and alkalis (not resistant to oxidizing acids), and is insoluble in general solvents at room temperature. It has low water absorption but can slowly dissolve in certain organic solvents due to its linear molecular structure without swelling, and exhibits excellent electrical insulation properties. Its functions include protecting polyurethane insulation from mechanical damage and providing corrosion and waterproofing. High-density polyethylene polyurethane foam-insulated steel pipes comply with the standards SY/T114-2000 and SY/T115-2001.
