WO2004069520A1

WO2004069520A1 - Method of producing flat pipes for high-pressure transport of fluids and pipes thus obtained

Info

Publication number: WO2004069520A1
Application number: PCT/ES2003/000071
Authority: WO
Inventors: Juan Francisco Hidalgo Rico
Original assignee: Uralita Sistemas De Tuberias S.A.
Priority date: 2003-02-10
Filing date: 2003-02-10
Publication date: 2004-08-19
Also published as: AU2003216923A1; AU2003216923A8; WO2004069520A8

Abstract

The invention relates to a method of producing flat pipes which are intended for the high-pressure transport of fluids. The inventive method takes account of factors which reduce pipe resistance in order to minimise the effects thereof by adequately controlling cooling and the hot work performed on the pipe. The method is based on several steps comprising: an initial plastic extrusion step which is performed with a circular tube nozzle; subsequently, a series of mechanical steps which are carried out at a constant temperature; and, finally, two steps involving cooling with staggered, decreasing temperatures which freeze the final structure, maintaining the memory effect. The invention also relates to the pipe thus obtained.

Description

MANUFACTURING PROCEDURE DΞ FLAT PIPE FOR HIGH PRESSURE FLUID TRANSPORTATION

AND PIPE SO GOT

DESCRIPTION

OBJECT OF THE INVENTION

The present invention relates to a manufacturing process of flat pipe for the transport of high pressure fluid as well as the pipe thus obtained, where the process takes into account the factors that decrease the resistance of the pipe minimizing its effect by means of a proper control of cooling and hot work carried out on the pipe.

The procedure is based on an initial stage of plastic extrusion with a tube nozzle with a circular section after which a set of mechanical work stages are arranged at staggered and decreasing temperatures.

These stages consist of immersions in various sections of a bathtub with temperature staggering where in the first section a hot and flat temperature crushing of the pipe is carried out.

In the next two stages the structure is cooled progressively by staggering the cooling temperature.

The freezing of the internal plastic structure allows to establish a memory effect on the pipe for the recovery of the flattened configuration at the time of storage when the internal pressure ceases and a volume reduction is required again for efficient storage.

Also the object of the invention is the pipe obtained by this procedure.

BACKGROUND OF THE INVENTION

The use of flattened section pipes is a known solution since the storage of circular section pipes not only stores the pipe but the entire internal volume.

By adopting the pipe a flattened shape the section corresponding to the internal cavity of the pipe is reduced so that in a same winding volume it is possible to incorporate a greater number of turns resulting in more efficient storage.

This type of solution is especially valid when the pipeline has to transport fluids at low pressure.

In circular section pipes the pressure gives rise to a uniform tension state where the surface of the pipe has only tangent stresses that give rise to tensile stresses.

On the contrary, if the section is elliptical (or close to this configuration) with a certain degree of crushing, the internal pressure tends to deform the pipe towards a final configuration closer to the circular section. This deformation results in an increase in the tension in the internal faces where the degree of concavity is greater since they suffer a degree of flexion that results in a tensile stress greater than that of any other place.

The elaboration of specially reinforced pipes in these walls prevents adequate deformation either to allow the circular section to recover (at the time of work or circulation of fluids under high pressure), or to recover the flattened configuration once the internal pressure ceases since they can permanent deformations have appeared.

Flat pipe manufacturing processes are known for various applications. Japanese patent JP11218268 describes a process that makes use of a plastic belt for the manufacture of a double flat tube of high resistance and with small deformations. This plastic belt works in melting conditions and is properly positioned around a spiral body on which it performs work on the pipe.

Japanese patent JP02127919 refers to a method of manufacturing a flat tube without the need for bending means. The flattened configuration is carried out using males and molds where the passage of the tube is forced in certain crushing ratios.

Finally, the Japanese Patent is cited

JP61001417 describing a method of manufacturing flat tubes specially designed for avoid breaking the walls during manufacturing by using a flexible inner last.

The present invention consists of a manufacturing process that results in a pipe resistant to high pressures and with memory effect for the recovery of the original flattened form after use.

DESCRIPTION OF THE INVENTION

The present invention relates to a method of manufacturing flat pipe for high pressure fluid transport and the pipe thus obtained.

This procedure consists in the application of hot work in a controlled way on the plastic pipe of the newly extruded circular section.

Once the pipe is hot out of the nozzle, a three-stage sequence is applied. The first stage is at a temperature between 40 and 60 degrees depending on the material and the section of the pipe, at a constant temperature where a train of pairs of facing rollers apply pressure to crush them.

The immersion in fluid allows to dissipate the heat generated by the work on the pipe and in turn prevents rapid and irregular cooling due to the dissipation of heat with the environment. The fluid increases the degree of convection and therefore ensures the working temperature in a narrower range. In this hot stage, the ductility of the walls admits large deformations although it is necessary to prevent these deformations from becoming excessive and a union between the internal walls of the pipe.

Once this first stage is finished, the pipe goes to a second section of the bathtub that is between 20 ° and 30 ° and therefore colder; temperature also chosen depending on the material and the thickness of the pipe.

In this second section there is a first controlled cooling in which the internal structure of the material begins to freeze, obtaining on the one hand the memory effect and on the other hand the controlled contraction without the appearance of cracks.

Finally, the pipe is subjected to a second cooling between G ° and 8 ° for the total cooling after which it is wound for handling.

In pipes where the thickness is greater it is necessary that the mechanical work is carried out at higher temperatures to avoid a greater degree of creep of the material due to the "creep" effect avoiding pinches or joints located between the internal walls of the pipe.

Likewise the object of this invention is the flat pipe thus obtained.

DESCRIPTION OF THE DRAWINGS

This descriptive report is complemented, with a set of drawings, illustrative of the example preferred and never limiting the invention.

Figure 1 shows a diagram of the preferred embodiment of this invention on the manufacturing process of the flat pipe.

PREFERRED EMBODIMENT OF THE INVENTION

In this preferred embodiment of the invention for the manufacture of flat pipe for high pressure fluid transport an extrusion (1) of the plastic in a circular section tube is carried out to be worked mainly hot and subsequently freeze its structure.

Once the tube (4) leaves the extrusion head (1.1) it is submerged in a bathtub (2) differentiated into three sections:

• A first section (2.1) of hot work has a train (2.1.1) of pairs of facing rollers working on the pipe (4) compressing it until it reaches the proper crushing degree. In this preferred embodiment, a 50 ° bath is used with a margin of 2 °.

• After this first section, the tube (4) is conformed to the final flat configuration after which it enters a second section (2.2) of the bathtub a

25 ° to subject the pipe to a not excessively sharp cooling and thus avoid strong contractions that give rise to permanent cracks or tensions that decrease the subsequent resistant capacity of the pipe (4). • Finally, a third section (2.3) is passed at 8 ° for the final cooling of the internal structure of the plastic - of the walls of the tube so that it keeps the flattened configuration by memory even after being subjected to high pressure .

Once cooled the pipe (4) is wound (3) for handling.

Variations in materials, shape, size and arrangement of the component elements, described in a non-limiting manner, do not alter the essentiality of this invention, being sufficient to proceed to its reproduction by an expert.

Claims

I ^a .- Manufacturing process of flat pipe for high pressure fluid transport and pipe thus obtained, characterized in that it consists of a first stage of plastic extrusion in a tubular configuration of circular section after which three stages are carried out in bathtub immersion (2):

• A first in a first section (2.1) of the bathtub (2), with the fluid between 40 ° and 60 °, which includes mechanical compression work by means of a train (2.1.1) of pairs of facing rollers until the configuration is obtained final flattened,

• A second in a second section (2.2) of the bathtub (2), with the fluid between 20 ° and 30 °, where the pipe (4) is subjected to non-abrupt cooling;

And>

• A third in a third section (2.3) of the bathtub (2), with the fluid between 6 ° and 10 ° for total cooling and freezing of the internal structure of the plastic of the tube walls (4), operations after that the pipe is wound (3).

2 .- ^or flat pipe according to claim characterized in that shows a flattened section resistant to high pressure, carried out by the method of the first claim and with memory effect for the recovery of the flattened shape after leaving the internal pressure of work.