| 摘要 |
The pipeline consists -viewed cross-sectionally- innermost of a media pipe (1) of a plastic material, e.g. PVC. The media pipe (1) is surrounded by a protection pipe (2), which has an inner diameter larger than the outer diameter of the media pipe (1). The protection pipe (2) is supplied with one or more channels going lengthwise (6), which may be placed on the outside of the pipe (1) and in heat conducting connection with the pipe (2). Pipe (2) is made of a water vapour impermeable material with a good heat conductivity, e.g. aluminium, and the channels (6) are made of the same material as the pipe (2). Around the protection pipe (2) there is an insulation (4), for instance of polyurethane foam, which on the outer side is covered by a vapour impermeable steel cap (5). In one or more of the channels (6) electric heating cables (3) are inserted. In other channels (6), electric conductors may be inserted, e.g. pilot wires. The heat supply is controlled by e.g. a thermostat, and is e.g. adjusted such that the temperature on the outside of the media pipe (1) is approximately the same as on the inside of the pipe (1). A pipeline according to the invention will prevent water vapour transmission from the inner side of the media pipe (1) into the insulation (4), hereby avoiding frost burst of the media pipe (1). |
