NL8402119A - METHOD FOR MANUFACTURING AN AT LEAST TWO CONCENTRIC METAL TUBES. - Google Patents

Description

32511 1

A method for manufacturing a rigid tubing consisting of at least two concentric metal pipes.

The invention relates to a method for the production of a rigid pipe system consisting of at least two concentric metal pipes with an insulation layer between the metal pipes, preferably a supply pipe for electrically driven submersible pumps *

For the use of electrical energy and cooling resp. lubricants 10 provided with submersible pumps have been proposed a supply line consisting of three concentric metal pipes 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 inner space 15 of the inner tube serves as a transport channel for the cooling or cooling. lubricant. This supply line is fitted within a slightly larger tube, the annular space between the supply line and the larger tube serving as a return transport channel for the cooling or cooling. lubricant.

A series of requirements are imposed on such supply lines, which have hitherto not been satisfactorily met.

Since these supply lines are rigid systems, they must be joined together at the point of use to obtain a long length. This results in the requirement that the location of the pipes is always the same at least at the end of each separate part of the supply line, so that the electrical connection of the individual parts of the supply line can be effected without problems. In order to avoid a longitudinal axial displacement of the individual pipes with respect to each other both during the establishment of the electrical connection and also during the provision of the supply line - this is normally arranged in a vertical position - it is urgent that the metal pipes are connected to the adjacent plastic layers under the influence of forces.

It is the object of the present invention to provide a method of manufacturing a rigid tubing that allows economical fabrication in maintaining dimensional deviations in position and wall thickness of the tubes and ensuring that a connection by existing forces between the individual tubes, whereby the electrically insulating layer is maintained, is possible.

This purpose is achieved in a method of the above-mentioned type by first coating a metal tube with plastic, by sliding the plastic-coated metal tube into a second metal tube with a larger internal diameter and fixing the second metal tube to the plastic layer so that a composite tube is created without longitudinal axial play. It goes without saying that the drawing up of the second metal tube takes place by cold drawing, because otherwise the plastic layer would be damaged by the elevated temperature. It is essential that the plastic layer is slightly deformed, so that a fixed connection is created between the two pipes.

According to a particularly advantageous embodiment of the invention, after the second metal tube has been pulled up, the second metal tube is likewise coated with plastic, and the composite tube so manufactured is placed in a third metal tube, after which the third metal tube firmly on the plastic layer of the second metal pipe. In this way an object is created with three electrically separated metal pipes, which can be used as electric conductors.

The drawing-up is advantageously effected by pulling the tube through a drawing die, wherein during the drawing-up a mandrel held in the region of the drawing die supports the inner tube. Since sensible forces are necessary to realize the connection with forces between the tube to be drawn up and the plastic layer, a deformation of the inner tube is counteracted by the mandrel.

In order to ensure that the plastic layer located between the tubes has an equal wall thickness, it is preferably applied by extrusion.

A particularly economical method of manufacture is obtained if one connects a plurality of metal pipes together at the ends and moves through an extruder, the extruder applying a plastic layer on the pipe surface. After cooling resp. When the plastic hardens, the tubes are separated at the connection points and each individual tube is slid into a metal tube and the metal tube is pulled over the plastic layer, the inner tube being supported with a doom. The composite tubes manufactured in this way are joined together again at the ends and transported through a further 8402119 3 extruder, which applies a further plastic layer to the second tube. After cooling resp. When this plastic layer is cured, the composite tubes are separated at the connection points and each individual composite tube is inserted in a metal tube, which is again drawn onto the plastic layer of the composite tube, the inner tube again being supported by a doom.

The plastic-coated metal tube resp. composite tube is slid into the associated larger metal tube with little clearance, optionally with the aid of lubricants. It is essential that the outside diameter of the plastic layer and the inside diameter of the larger tube do not differ significantly, so that no great difficulties arise when pulling up the outer tube. Therefore, a clearance resp. a difference in diameter of about 1 mm is preferred. To improve sliding, the surface of the plastic layer is effectively coated with the lubricant, preferably a paraffin-based oil. In order not to damage the plastic layer during insertion, the inside of the present outer tube is inserted for sliding in the metal tube or plastic-lined metal tube. composite tube preferably broken.

The invention is further elucidated on the basis of the exemplary embodiments schematically shown in Figs. 1 to 5.

Show:

Fig. 1 shows the supply line in built-in condition, FIG. 2 to 5 the course of the method for manufacturing the supply line.

The supply line 1 is arranged vertically within a tube 2. For supplying a submersible pump (not shown) with lubrication or coolant provides a channel 3, while the annular space 4 between the supply line 1 and the tube 2 for the return transport of the cooling resp. lubricant.

The supply line 1 also serves to supply the underwater pump with electrical energy. For this purpose, three concentric copper pipes 5, 6 and 7 are present, which are electrically insulated from each other by plastic layers 8 and 9, preferably of polyethylene. The copper conductors 5, 6 and 7 transmit the three phases of three-phase current. The copper pipes 5, 6 and 7 as well as the polyethylene layers 8 and 9 are connected to each other under the influence of forces, so that during vertical installation a longitudinal axial displacement of the 40 pipes 5, 6 and 7 relative to each other is avoided. The copper 8402119 4 pipes 5, 6 and 7 are seamless drawn pipes.

The inner tube 5 has, for example, a size of 19 x 1.5, i.e. 19 mm outer diameter and 1.5 mm wall thickness. The adjacent polyethylene layer 8 has a wall thickness of 1.5 mm. The middle copper tube 6 then has the size 25 x 1.5. The adjacent polyethylene layer 9 again has a wall thickness of 1.5 mm. For the external copper tube 7 a size of 31 x 1.5 mm then applies. Deviating from the mentioned dimensions, the wall thickness of the copper pipes 5, 6 and 7 may decrease from the inside to the outside, whereby the aim should be that the pipe cross section of the pipes 5, 6 and 7 is equal.

It may possibly be advantageous to apply a further plastic layer to the copper pipe 7.

To produce a supply line 1, a number of copper pipes 5 are first connected to each other via connecting means 15 known per se and passed through an extruder 11, which applies the polyethylene layer 8 to the copper pipe 5. A separating device 12 separates the polyethylene-coated copper pipes 5 in the region of the connecting means 10 and makes them into separate parts. The polyethylene-coated copper tube 5 is indicated by 5a 20.

In a next working step, the polyethylene-coated copper tube 5a is introduced into a copper tube 6. The outside diameter of the tube 5a and the inside diameter of the tube 6 should not differ too much. To facilitate the joining of the tubes 5a and 6, the outer surface of the tube 5a can be covered with a lubricant, for example a paraffin-based oil. In order not to damage the surface of the polyethylene layer 8 when it is slid in, it is expedient to break the inside of the end face of the tube 6.

After the tubes 5a and 6 have been pushed together, this double tube is placed in a mold 13 and the tube 6 is pulled tight on the tube 5a. The polyethylene layer 8 is thereby slightly deformed. To prevent the inner tube 5 from being deformed by the deformation forces, it is supported by a mandrel 14, which is held in the region of the die 13 by a mandrel rod 15 or in another known manner. The composite tubes manufactured in this way are successively connected again by a tube connector known per se, and passed through a further extruder 16, which produces the polyethylene layer 9 on the composite tube. The composite tube provided with the poly-40 ethylene layer 9 is indicated below with 6a 8402119 *. In the region of the connecting means, the composite tube 6a is again divided into separate lengths with a separator 17. Each individual length 6a is introduced into a further copper tube 7, in which the measures of lubricant, breaking of the 5 sides, respectively. likewise, the proportions of the diameter must be the same as when the tubes 5a and 6 are joined together. The composite tube consisting of the tube 6a and the tube 7 is led into a further mold 18 and the tube 7 becomes rigid on the polyethylene layer 9 of the tube 6a is pulled, a mandrel 19 again supporting the inner tube 5.

In a final working step, the individual lengths of the supply pipe 1 are deburred at the ends, i.e. the pulling tracks are removed and the pulling ends are cut off and the lengths are shortened to e.g. 6 m.

The supply line 1 manufactured according to the method according to the invention is characterized by a connection via forces of the individual copper pipes 5, 6 and 7 to the polyethylene layers 8 and 9, as well as by an exactly concentric arrangement of these layers.

8402119

Claims (7)

1. Method for manufacturing a rigid pipe system consisting of at least two concentric metal housings, with an insulating layer located between the metal pipes, preferably a supply pipe for electrically driven submersible pumps, characterized in that first a metal pipe with plastic, that the plastic-coated metal tube is slid into a second metal tube with a larger internal diameter and the second metal tube is pulled firmly onto the plastic layer, so that a composite tube is created without play in the longitudinal-axial direction. 2. A method according to claim 1, characterized in that after the second metal tube has been pulled up, the second metal tube is also coated with plastic and in that the composite tube thus produced is placed in a third composite tube, after which the third metal tube is firmly on the plastic layer of the second metal pipe. Method according to claim 1 or 2, characterized in that the drawing-up is effected by pulling the tube through a drawing die and that during the drawing-up a mandrel supports the inner tube 20, which is held doom in the area of the drawing die. . Method according to one of the preceding claims, characterized in that the coating with plastic takes place by extrusion. 5. A method according to any one of the preceding claims, characterized in that a number of metal pipes are joined together at the ends and moved through an extruder, the extruder applies a plastic layer on the pipe surface, which, after curing, the plastic tubes are separated at the connection points, each individual tube is slid into a larger diameter metal tube, the metal tube is pulled over the plastic layer, the inner tube supported with a doom, some of such composite pipes are joined together at the ends and transported through a further extruder, which applies a further plastic layer to the second pipe, that after the curing of this plastic layer the composite pipes are separated at the connection points and that each individual composite pipe is a larger metal tube is slid onto the plastic layer of the composite tube sliding, the inner tube being supported by a doom again. Method according to any one of the preceding claims, characterized in that the plastic-coated metal tube resp. composite pipe The associated larger metal pipe can be slid with little lubrication if necessary. 7. A method according to any one of the preceding claims, characterized in that the inner side of the present external tube for sliding in the plastic-coated metal tube resp. composite tube is broken. I I I I H-H 111 n l-t I I I I 8402119