A METHOD FOR ISOLATING A SPIRALLY WOUND PIPE

Abstract: The present invention relates to a method for isolating a spirally wound pipe of a thermoplastic hole profile. The invention is characterized in that through each of the mainly radially directed side walls (2) of a hole profile (1) in the pipe at least one axially directed hole (3, 3a) is made so that a row of holes (3, 3a) located in line with each other is formed through the entire pipe, while the pipe is in a horizontal position and a row of holes (3a) is located uppermost in the pipe, a foaming lancet (4) is introduced into said or another row of holes (3, 3a) through the pipe, a foaming insulating mass (5) is dosed by turns into each segment of the spirally wound pipe after the lancet (4) is stepwise drawn back out of the holes (3, 3a), after which all boring holes (3) on the end surface of the pipe are plugged up, when the foaming is completed.

Description: A method for isolating a spirally wound pipe The present invention relates to a method for isolating a spirally wound pipe of a thermoplast hole profile, which is joined together by extruder welding or gluing. An advantage of a spirally wound pipe with a hole profile is that a desired ring stiffness is achieved with a con¬ siderably lower material thickness than for a single- walled pipe. When installing in arctic areas or in areas with a periodically cold climate, isolation of the pipe¬ lines is required. According to a previously known practise, also pipelines of such spirally wound pipes are furnished with an outer isolation layer, which may be encased by an outer protective sheath. Such an arrange¬ ment is relatively curbersome and significantly increases the material consumption. The purpose of the present invention is to eliminate this problem, which is achieved by means of an arrangement characterized in that - through each of the mainly radially directed side walls of a hole profile on one end of the pipe except for the side wall on the other end of the pipe, at least one axially directed hole is made so that a row of holes located in line with each other is formed through the entire pipe up to said end, - the spirally wound pipe is maintained in a horizontal position and rotated around its longitudinal axis, until such a row of holes is located uppermost in the pipe, - a foaming lance is led into said or another row of holes up to the closed side wall, after which a foaming isolating mass is dosed by turns into each segment of the spirally wound pipe as the lance is stepwise drawn back out of the hole, - when the lance has been removed, all boring holes on the end surface, provided with holes, of the spirally wound pipe are plugged up except for the the uppermost one, which is plugged up after the foamed isolating mass penetrates out through this boring hole. By means of this arrangement, an extremely good isolation is achieved at the same time as the ring stiffness of the pipe further improves so that the wall thickness of the hole profile may be further decreased, which decreases the manufactu¬ ring costs. The remaining characteristics of the inven¬ tion are presented in the accompanying claims 1 to 9. The invention is next described in more detail with reference to the accompanying drawing, in which Fig. 1 shows an end of a spirally wound pipe, in which holes are arranged for feeding the isolating mass according to the invention, and Fig. 2 shows a section along line A-A of Fig. 1, in which a foaming lance is introduced into a row of boring holes lowermost in the spirally wound pipe. According to the invention, the isolation of the spirally wound pipe of a thermoplastic hole profile 1 of a mainly rectangular cross-section is performed as follows: - Through each of the mainly radially directed side walls 2 of the hole profile 1 in the spirally wound pipe, except for the side wall 2a at one end of the pipe, at least one radially directed hole 3, 3a is made so that a row of holes 3, 3a located in line with each other is formed through the entire pipe up to said end surface. Both end surfaces of the hole profile are chamfered and closed in a suitable manner in this or other previous step. - The spirally wound pipe is maintained in a horizontal position and rotated around its longitudinal axis, until such a row of holes 3a is located uppermost in the pipe, - A foaming lance 4 is introduced either into said row of holes 3a or another row of holes 3, which is located on a lower level, to a hollow space, which is limited by the closed side wall 2a. The foaming isolating mass 5 is dosed through the foaming lance 4 by turns into each segment of the spirally wound pipe as the foaming lance 4 is stepwise drawn back out of the holes 3, 3a, until all segments of the spirally wound pipe are fed with a dosed amount of the isolating mass. - When the foaming lance 4 has been removed from the row of holes 3, 3a, all possible boring holes 3 in the spirally wound pipe's end surface provided with holes are plugged up, except for the uppermost boring hole 3a, which acts as an evacuation opening for the air, which is displaced by the foaming isolating mass 5. Not until isolating mass 5 penetrates out of the hole 3a, indica- ting that the entire spiral cavity in the pipe is filled with the isolating mass, the uppermost boring hole 3a is plugged up. The boring holes 3, 3a may either be made subsequently as a new turn of the hole profile has coincided with the spirally wound pipe or after the entire pipe is joined together. In the first case, the equipment must be arranged to sense when the pipe, which during the joining-together process is continuosly in a slow rotation, reaches a position, in which a hole 3, 3a should be made. This may be arranged in such a way that the spindle, around which the hole profile is wound up in connection with the manufacturing of the spirally wound pipe, has stop or sensing means, which give a starting impulse to a boring or milling device each time the pipe comes in the correct working position. In the case that the boring holes 3, 3a are made first in a later step, when the spirally wound pipe has a final length, a boring or milling tool of a mainly the same length as the pipe has to be used. This places relatively great demands on both the correct adjustment of the tools and the pipe such that the desired result is obtained. Depending on the properties of the foaming isolating mass, one or two rows of holes 3, 3a may be received. For an isolating mass of a low viscosity and a relatively long foaming time as well as good dosing properties, only one row of boring holes 3a is needed, since then the liquid isolating mass has time to run down into the bottom section of the pipe before the foaming starts. When using a more slowly flowing and/or rapidly foaming isolating mass, two rows of boring holes 3, 3a are preferable, which are totally diagonally positioned in relation to each other, whereby the isolating mass does not have to be transferred before the foaming begins, which possibilitates the utilization of an isolatating mass with a very rapid foaming. In certain cases, a bowing distance of ca. 90° between the two rows of boring holes 3, 3a may be preferable, especially if the isolating mass is lightly flowing, before a time after the foaming has started, whereby the leakage of the isolating mass through the below boring hole 3 on the end surface of the pipe is avoided. For avoiding air pockets, e.g an asymmetric foam increase in the profiles, small evacuation holes 6 for air may be received in the radially directed side walls 2 of the profile. These evacuation holes 6 are preferably made uniformly distributed along the centre line of the radially directed side walls 2. A suitable isolating mass is a polyurethane foam, which has reached a very wide use as an isolating material around the world. The foaming may be either performed directly on the product after the manufacturing of the spirally wound pipe itself or on site in connection with the installation of the pipelines.

Claims: Claims : 1. A method for isolating a spirally wound pipe of a thermoplastic hole profile (1), which is joined together by extruder welding or gluing, characterized in that - through each of the mainly radially directed side walls (2) of a hole profile (1) in the spirally wound pipe except for a side wall (2a) on one end of the pipe, at least one axially directed hole (3, 3a) is made so that a row of holes (3, 3a) located in line with each other is formed through the entire pipe up to said end, - the spirally wound pipe is maintained in a horizontal position and rotated around its longitudinal axis, until a similar row of holes (3, 3a) is located uppermost in the pipe, - a foaming lance (4) is led into said or another row of holes (3, 3a) to the closed side wall (2a), after which a foaming isolating mass (5) is dosed by turns into each segment of the spirally wound pipe as the lance is stepwise drawn back out of the hole (3, 3a), - when the lance (4) has been removed, all boring holes (3) in the end surface, provided with holes, of the spirally wound pipe are plugged up except for the uppermost boring hole (3a), which is plugged up after the foamed isolating mass (5) penetrates out through this boring hole (3a). 2. A method according to Claim 1, characterized in that the boring holes (3, 3a) are made after a new turn of the hole profile has been joined together to the spirally wound pipe. 3. A method according to Claim 1, characterized in that the boring holes (3, 3a) are made with a long bore or milled after the pipe has reached its full length. 4. A method according to any of the Claims 1-3, characterized in that two rows of holes (3, 3a) diagonally in relation to the each other are made. 5. A method according to any of the Claims 1-3, characterized in that two rows of holes (3, 3a) at a circular distance of 90° are made. 6. A method according to any of the preceding Claims, characterized in that preferably uniformly divided evacuation holes (6) are made along the centre line in the radially directed side walls (2) . 7. A method according to any of the preceding Claims, characterized in that the isolating mass (5) is a polyethylene foam. 8. A method according to Claim 4, charactetized in that the foaming lancet (4) is introduced into that row of holes (3), which is located lowermost, and that the upper row of holes (3a) is a deaeration and balancing channel. 9. A method according to any of the preceding Claims, characterized in that the foaming is performed at the factory directly after the manufacturing of the spirally wound pipe. 10. A method according to any of the Claims 1-8, characterized in that the foaming is performed in site in connection with the installation of a pipeline.

Inventors: BLOMQVIST GUNNAR, HEDE HANS, LINDVALL STEFAN, BLOMQVIST, GUNNAR, HEDE, HANS, LINDVALL, STEFAN
Applicants: KWH PIPE AB OY, OY KWH PIPE AB
Application year: 1992
Main classification: F16L59
IPC codes: F16L59