CH664809A5 - METHOD FOR PRODUCING A PIPELINE, WHICH HAS AT LEAST TWO COAXIAL METAL PIPES. - Google Patents

Description

DESCRIPTION The present invention relates to a method for producing a pipeline, in particular a supply line for electrically driven underwater pumps, which pipeline has at least two metal tubes arranged coaxially to one another with an insulating layer located between the metal tubes.

For the supply of submersible pumps with electrical energy and coolants or lubricants, a supply line is known which consists of three coaxially arranged metal tubes which are electrically insulated from one another by a plastic layer. The three concentric tubes form the three phase conductors for supplying the submersible pump with electrical energy, while the interior of the inner tube serves as a transport channel for the coolant or lubricant. This supply line is laid within a somewhat larger pipe, the annular space between the supply line and the larger pipe serving as a return channel for the coolant or lubricant.

Such supply lines are subject to a number of requirements that have not yet been met to full satisfaction.

Since these supply lines are rigid systems, they have to be joined together to achieve a great length at the place of use.

This results in the requirement that the position of the pipes, at least at the end of each individual supply line section, is always the same, so that the electrical connection of the individual supply line sections can be accomplished without problems. In order to avoid a longitudinal axial displacement of the individual pipes against each other both during the establishment of the electrical connection and after the laying of the supply line - this is usually laid in a vertical position - it is imperative that the metal pipes are non-positively connected to the adjacent plastic layers.

The present invention aims to provide a method for producing a pipeline, which enables economical production while maintaining the dimensions with regard to the position and wall thickness of the pipes and which ensures a non-positive connection between the individual pipes while maintaining the electrically insulating layer.

The method according to the invention corresponds to the characterizing features of claim 1. It goes without saying that the second metal tube is pulled on by cold drawing, since otherwise the plastic layer would be affected by the elevated temperature. It is essential that the plastic layer is slightly deformed, so that there is a firm bond between the two metal tubes.

According to claim 2, after the second metal tube has been pulled on, the second metal tube is also advantageously coated with plastic and then introduced into a third metal tube, whereupon the third metal tube is firmly attached to the plastic layer of the second metal tube. In this way, an object is obtained with three metal tubes which are electrically separated from one another and which can be used as electrical conductors.

According to claim 3, the drawing of the metal pipe onto the plastic layer is expediently accomplished by pulling the pipe through a drawing die, a mandrel held in the area of the drawing die supporting the inside of the first metal pipe during the drawing. Since considerable forces are required to achieve the non-positive connection between the metal pipe to be drawn up and the plastic layer, deformation of the first metal pipe is counteracted by the mandrel.

So that the art between the metal pipes5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

664809

material layer is the same wall, this is advantageously applied according to claim 4 by extrusion. Particularly economical production is achieved if, according to claim 5, a large number of metal pipe pieces are connected to one another at the ends and conveyed through an extruder, the extruder applying a plastic layer to the pipe surface. After the plastic layer has hardened, the metal tube pieces are separated again at the connection points and each individual tube piece is pushed into a second metal tube and the metal tube is pulled down onto the plastic layer of the first metal tube, the inside of the first metal tube being supported with a mandrel groove. The coated pieces of the second metal tube are in turn connected to one another at the ends and conveyed through a further extruder, which produces a further plastic layer on the second metal tube. After this plastic layer has hardened, the metal pipe pieces are separated again at their connection points and each individual pipe piece is pushed into a third metal pipe, which in turn is drawn onto the plastic layer of the second metal pipe, the inner side of the first metal pipe in turn being supported by a mandrel.

According to claim 6, the plastic-coated metal tube is inserted into the respective larger metal tube with a slight play, for example with the aid of lubricants. It is essential that the outside diameter of the plastic layer and the inside diameter of the larger pipe do not differ significantly, so that no major difficulties arise when the outer pipe is subsequently pulled on. A clearance or a diameter difference of approximately 1 mm is therefore preferred. To improve the sliding, the surface of the plastic layer is expediently coated with a lubricant, preferably with a paraffinic oil. So that the plastic layer is not damaged during insertion, the inner edge of the respective outer tube is expediently broken before inserting the plastic-coated metal tube.

An exemplary embodiment of the method according to the invention is described below using the schematic drawing.

Fig. 1 shows a supply line in the installed state, and

2 to 5 show the process sequence for producing this supply line.

The supply line 1 is housed within an outer tube 2. A channel 3 ensures the supply of a submersible pump, not shown, with lubricants or coolants, whereas the annular space 4 between the supply line 1 and the outer pipe 2 serves for the return transport of the coolant or lubricant.

The supply line 1 also serves to supply the submersible pump with electrical energy.

For this purpose, three coaxial copper tubes 5, 6 and 7 are provided which are electrically insulated from one another by plastic layers 8 and 9, preferably made of polyethylene. The copper tubes 5, 6 and 7 transmit the three phases of three-phase current. The copper tubes 5, 6 and 7 as well as the plastic layers 8 and 9 are non-positively connected to one another, so that in a vertical arrangement the copper tubes 5, 6 and 7 are displaced axially

against each other is avoided. The copper pipes 5,6 and 7 are provided as seamless drawn pipes.

For example, the inner copper tube 5 has a dimension of 19x1.5, i.e. 19 mm outer diameter and 1.5 mm wall thickness. The adjoining second plastic layer 9 in turn has a wall thickness of 1.5 mm. The outer copper tube 7 then has a dimension of 31 × 1.5 mm. In a change to the stated masses, the wall thickness of the copper pipes 5, 6 and 7 can decrease from the inside to the outside, it being desirable that the line cross section of the copper pipes 5, 6 and 7 is the same.

It may be advantageous to apply a further plastic layer to the outer copper tube 7. To produce a supply line 1, a large number of pieces of copper pipe 5 are first connected to one another by means of connectors 10 known per se and passed through an extruder 11, which produces the plastic layer 8 on the copper pipe 5. The coated copper tubes 5 are severed in the area of the connectors 10 by means of a separating device 12, again resulting in several tube pieces.

In a next step, the plastic-coated copper tube 5 is inserted into a second copper tube 6. The outside diameter of the first copper tube 5 and the inside diameter of the second copper tube 6 should not be too different. In order to facilitate the joining of the copper tubes 5 and 6, the outer surface of the first copper tube 5 can be coated with a lubricant, for example a paraffinic oil. So that the surface of the plastic layer 8 is not damaged during insertion, it is expedient to break the inner edge of the end face of the second copper tube 6. After the copper pipes 5 and

6 are pushed into one another, this double tube is inserted into a drawing die 13 and the second copper tube 6 is pulled tight onto the first copper tube 5. The plastic layer 8 made of polyethylene is slightly deformed. In order to prevent the first copper tube 5 from being deformed by the deformation forces, it is supported by a mandrel groove 14, which is held in the region of the drawing die 13 by a mandrel rod 15 or in another known manner. The composite pipes thus produced are in turn connected one after the other by known pipe connectors, passed through a second extruder 16, which produces the plastic layer 9 on the second copper pipe 6. In the area of the connectors, the coated second copper tube 6 is also divided into individual lengths by means of a separating device 17. Each individual length of the copper pipe 6 is inserted into a third copper pipe 7, the measures of lubricant, edge breakage and also the diameter ratios as when joining the copper pipes 5 and 6 should prevail. The composite pipe consisting of the coated copper pipe 6 and the third copper pipe 7 is inserted into a further drawing die 18 and the third copper pipe

7 tightened onto the plastic layer 9 of the second copper tube 6, a mandrel groove 14 again providing support for the first copper tube 5.

In a final work step, the individual lengths of the supply line 1 are straightened at the end, i.e. the drawbars are removed and the drawing ends are cut off and cut to a length of e.g. 6 m cut to length.

The supply line 1 produced according to the described method is characterized by a non-positive connection of the individual copper pipes 5, 6 and 7 with the plastic layers 8 and 9 and by an exactly concentric arrangement of these layers.

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

B

1 sheet of drawings

Claims (7)

664809 1. A method for producing a pipeline, in particular a supply line for electrically driven underwater pumps, which pipeline has at least two coaxially arranged metal pipes (5, 6) with an insulating layer (8) located between the metal pipes, characterized in that first a first metal pipe ( 5) is coated with a plastic layer (8), that the plastic-coated metal tube is pushed further into a second metal tube (6) with a larger inside diameter and that finally the second metal tube (6) is firmly attached to the plastic layer (8), so that results in a composite pipe without axial play. 2. The method according to claim 1, characterized in that after the second metal tube (6) has been drawn on, the second metal tube is also coated with a plastic layer (9) and then introduced into a third metal tube (7), whereupon the third metal tube (7 ) is firmly attached to the plastic layer (9) of the second metal tube (6). 2nd PATENT CLAIMS 3. The method according to claim 1 or 2, characterized in that the pulling of the metal tube (6; 7) on the plastic layer (8; 9) is accomplished by pulling the tube through a drawing die (13) and that during the pulling one in the area the mandrel (14) held by the drawing die (13) supports the inside of the first metal tube (5). 4. The method according to claim 1 or 2, characterized in that the coating of the metal tubes (5, 6) with plastic is carried out by extrusion. 5. The method according to claim 1, characterized in that a plurality of metal pipe pieces (5) are connected to one another at the ends and are conveyed by an extruder (11), that the extruder (11) on the pipe surface applies a plastic layer (8) that after Hardening of the plastic layer (8), the metal pipe pieces (5) are separated again at their connection points (10), so that each individual pipe piece (5) is inserted into a second metal pipe (6) with a larger diameter, so that the second metal pipe (6) is placed on the Plastic layer (8) of the first metal tube (5) is pulled down, the inside of the first metal tube (5) being supported with a mandrel (14) such that a large number of such coated pieces of the second metal tube (6) are connected to one another at the ends and by one Another extruder (16) are conveyed, which produces a further plastic layer (9) on the second metal tube (6) that after curing this plastic ffschicht (9) the metal pipe pieces (6) are separated again at their connection points and that each individual pipe piece (6) is inserted into a third metal pipe (7) which is pulled onto the plastic layer (9) of the second metal pipe (6), whereby in turn, the inside of the first metal tube (5) is supported by a mandrel (14). 6. The method according to claim 1 or 2, characterized in that the plastic-coated metal tube (5; 6) in the respective larger metal tube (6; 7) with slight play, for example with the aid of lubricants, is inserted. 7. The method according to claim 1 or 2, characterized in that the inner edge of the respective outer metal tube (6; 7) is broken before inserting the plastic-coated metal tube (5; 6).