The heat medium conveyed by PU insulated pipes is characterized by high temperature, high pressure, and high flow velocity, which impose greater expansion forces and impact forces on the PU insulated pipe. Therefore, during installation of PU insulated pipes, technical issues such as material selection, connections, supports and hangers, thermal compensation, venting, and drainage of the PU insulated pipe must be resolved. Below PU Insulated Steel Pipe Manufacturer Let us introduce the issues involved.
Joints of outdoor heating PU insulated pipe are welded. When PU insulated pipe is connected to valves and equipment, flanges are used.
(3) Slope of PU insulated pipe
PU insulated pipe should be laid to a slope to facilitate removal of air and condensate and to ensure normal system operation.
1) For steam PU insulated pipe in which steam and condensate flow in the same direction, the slope is generally 0.003, not less than 0.002, and the slope is toward the drain point;
2) For steam–condensate PU insulated pipe, the slope shall be not less than 0.005, with the slope toward the drain point;
3) The slope of hot-water PU insulated pipe shall be 0.003, and not less than 0.002, and the slope direction shall facilitate deaeration.
Classification of PU Insulated Pipe:
Classified by Protective Jacket Material
(1) HDPE plastic (commonly known as the outer jacket) protective jacket.
(2) Glass-fiber-reinforced unsaturated polyester resin plastic (commonly known as FRP) protective jacket.
(3) Protective jackets made of other materials, such as spiral-welded steel pipe, longitudinally welded steel pipe, corrugated pipe, etc.
2. By insulation-layer structure
(1) Single type: suitable for heating media below 150°C, of which the ordinary type is suitable for heating media below 120°C, and the high-temperature type is suitable for heating media of 120–150°C (recommended operating temperature below 140°C). The insulation layer of this insulated pipe consists of a single insulation material—rigid PU foam—with a protective jacket on the outside of the insulation layer.
(2) Composite type: suitable for high-temperature heating media. The insulation layer of this insulated pipe consists of two insulation materials. The insulation layer, the protective jacket of the insulation layer, and the carrier pipe conveying the heat medium are not firmly bonded together. The inner layer is a new high-temperature-resistant insulation material, such as centrifugal glass wool felt, composite silicate, or foam glass; the outer layer is made of rigid PU foam.
3. By structural form of the insulation layer and the heat-medium steel pipe
(1) Sliding (unbonded) insulated pipe: A layer of low-melting-point coating, such as low-grade asphalt and heavy oil, is applied between the insulation layer and the steel pipe. It melts upon heating, the pipe can expand freely within the insulation layer, and the insulation layer and the backfill sand layer remain stationary. This separation type is mainly used for high-temperature composite insulated pipes, such as steam pipes.
(2) Bonded insulated pipe: The steel pipe, insulation material, and protective jacket are firmly bonded together to form an integral structure. When the steel pipe thermally expands due to the temperature rise caused by the conveyed medium, the insulation layer expands and moves together. Bonded insulated pipes are mainly used when the heat-medium temperature is below 150°C.
4. By insulated-pipe processing location
(1) Factory-prefabricated insulated pipe: the insulated pipe is processed in the factory.
(2) Field-prefabricated insulated pipe: This product is a simple direct-buried heating pipe that emerged in the 1990s, with the aim of saving construction costs of heating pipes. Steel pipes are transported to the construction site for foam insulation, and after insulation an FRP protective jacket is wound on.
That concludes the requirements and classification of PU insulated pipe. We hope it is helpful. For more information, please follow us. PU Insulated Steel Pipe Manufacturer
