CA2161017A1

CA2161017A1 - Heat insulated pipeline

Info

Publication number: CA2161017A1
Application number: CA 2161017
Authority: CA
Inventors: Erik Winther Christensen
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-21
Filing date: 1994-04-19
Publication date: 1994-10-27
Also published as: DK45593A; DK170312B1; SE9503707D0; FI955021A; SE503982C2; DK45593D0; WO1994024473A1; SE9503707L; FI955021A0

Abstract

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).

Description

Heat insulated pipeli.ne The present invention deals with a heat insulated pipeline of the type mentioned in the introdction to Claim 1.

Such a pipeline is known from DE publication no. 3728820.

Such pipelines are used among other things for transportation of cold or hot water, e.g. as district heating pipes.

It has gradually become common to use media pipes made of synthetic materials e.g. PE. However, one disadvantage of these pipes is the diffusion of water vapour through the pipe wall. This water vapour diffusion is proportional to the difference in temperature between the inner and the outer side of the pipe wall of the media pipe.

In the pipeline known from DE publication no. 3728820 the protection pipe is made of plastics, which has a poor thermal conductivity. The parts of the protection pipe which are close to the heating cable will thus be heated, while parts further away will have a lower temperature. Therefore a diffusion of vapour will occur through the pipe wall in the media pipe to the space between the media pipe and the protection pipe and from that pipe through the pipe wall of the protection pipe into the insulation, which then becomes humid and loses its insulation ability. As a result the vapour diffusion increases further and there will be risk of frost burst of the pipes. Furthermore this well-known pipeline is difficult to pro-duce.

The purpose of the invention in question is to present a heat insulated pipeline which does not have the disadvantages of the already known pipelines. This aim is reached by constructing a pipeline of the type mentioned in the introduction to Claim 1 as indicated in the characterizing part of Claim 1.

Firstly, it is hereby obtained that no diffusion of water vapor occurs through the protection pipe into the insulation. Secondly, the added heat will be evenly distributed over the entire protection pipe and at the same time an evenly distributed supply of heat to the space between the media pipe and the protection pipe will take place. Thirdly, the pipeline is easy to assemble and therefore inexpensive to produce, as electrical heating cables can be inserted in the channels after the pipe has been produced.

By following the directions of Claim 2 it is attained that the channels yield the least possible resistance against the intoduction of a heating cable.

By following the directions of Claim 3 it is attained that the protection pipe complete with channels becomes simpler and therefore less expensive to produce.

By following the directions of Claim 4 it is attained that there is no vapour diffusion through the wall of the media pipe.

By following the directions of Claim 5 it is attained that vapour, which, under extreme conditions when the heat supply fails, has diffused through the wall of the media pipe into the space between the media pipe and the protection pipe, can be ventilated into the atmosphere.

By following the directions of Claim 6 it is attained that no humidity can penetrate the insulation from the outside, and the pipe will have the necessary rigidity.

The invention will be explained in detail in the following, referring to the drawing showing a cross section of a pipeline produced according to the invention.

As shown in the drawing a heat insulated pipe consists, according to the invention, of an inner media pipe 1, made of a synthetic material e.g. PE. The media pipe 1 is surrounded by a protection 2l6lni7 WO 94!24473 PCT/DK94/00155 pipe 2, the inner diameter of which is larger that the outer diameter of the media pipe 1 such that there is a space 9 between the media pipe 1 and the protection pipe 2.

The protection pipe 2 is made out of a vapour tight materal with a good heat conveyance ability, e.g. aluminium. The protection pipe 2 is supplied with a number of channels 6 going lengthwise the pipe and may be placed on the outside of the pipe 2 and in heat conducting connection with the protection pipe. The channels 6 are primarily made of the same material as the protection pipe 2. Some of the channels 6 or all channels are connected to a source of heat, e.g. hot water or steam. As shown, electric heating cables 3 may also be placed in some of the channels. In other channels electric conductors for other purposes, e.g. pilot wires, may be placed.

The channels 6 may advantageously be oriented in a way such that their central axis 7 is parallel with the central axis 8 of the protection pipe 2. The channels 6 may have the same thickness as pipe 2 and may, as shown, have a circular cross section.

The channels 6 and the protection pipe 2 may advantageously be procuced in one piece by extrusion.

Around pipe 2 there is a heat insulating material 4, e.g.
polyurethane foam, and on the very outside the pipe is provided with an outer pipe 5 which is impermeable to water and vapour.

The heat supply may be adjusted such that the temperature on the outside of the media pipe 1 is at least as high as on the inside of the pipe. By this a diffusion of vapour from within and out through the wall of the media pipe is prevented.

The space 9 between the media pipe 1 and the protection pipe 2 is aired into the atmosphere. Thus aqueous vapour which under extreme conditions of failing heat supply has penetrated into the space 9 may vanish into the atmosphere.

2lslnl7 WO 94/24473 -~ - - PCT/DK94/00155 The pipes 2, 6, 4 and 5 may be prefabricated and the media pipe 1 may be inserted into the prefabricated pipe as the mounting proceeds.

The invention is not restricted to the described and illustrated design. The channels 6 and the pipe 2 may e.g. have a different sectional form. The channels 6 may also be constructed as hollows in the protection pipe 2.

Claims

Claim

1. Heat insulated pipeline which, by cross section, on the inner side consists of a media pipe (1) of synthetic material, e.g. PE, a protection pipe (2) surrounding the media pipe (1), the inner diameter of which is larger than the outer diameter of the media pipe (1), and one or more cables (3) bearing against the outside of the protection pipe (2) and, around the protection pipe (2) a cap (4) of insulating material, e.g. polyurethane foam, characterized by the fact that the protection pipe (2) is made of a vapour impermeable, primarily good heat conducting material, e.g.
aluminium, and the protection pipe (2) is equipped with one or more channels (6) going lengthweise the pipe and placed on the outside of the pipe (1), the walls of which are primarily made of the same material as the protection pipe (2) and in heat conducting connection with the pipe (2), and by the fact that some of the channels (6) or all channels are connected to a heat source, for example by the passing of electric heating cables (3) through the channels (6).

2. Insulated pipeline according to claim 1, characterized by the fact that the channels (6) have a circular cross section and are placed on the protection pipe (2) such that their central axis (7) is parallel with the central axis (8) of the pipe (2).

3. Insulated pipeline according to claims 1 and 2 characterized by the facts that the channels (6) are made as an integrated part of the pipe (2).

4. Insulated pipeline according to claim 1 characterized by the fact that the heat supply to the channels (6) is controlled by e.g.
a thermostat, and is preferentially so high that the temperature on the outer side of the media pipe (1) is at least as high as inside the media pipe.

5. Insulated pipeline according to claim 1 characterized by the fact that the space (9) between the media pipe (1) and the protection pipe (2) is aired into the atmosphere.

6. Insulated pipeline according to claim 1 characterized by the fact that the cap (4) is surrounded by a water and vapour impermeable outer pipe (5).