OA17780A - Method for forming an electrical connection. - Google Patents

Abstract

A method of forming an electrical connection in a conduit for transporting a fluid. The pipe (I) comprises an internal hollow tube (2) and a heating layer (4) comprising first carbon fibers. A groove forming step (101) is carried out in which a groove (6) is formed in the heating layer, an interface preparation step (102) in which a junction layer (7) is deposited on the heating layer of the groove, and an installation step (103) in which a connecting strip (8) comprising second fibers formed of a second electrically conductive material is wound on the junction layer

Description

Method for forming an electrical connection

TECHNICAL AREA

The present invention relates to a method for forming an electrical connection on a device, for example a pipe for transporting a fluid requiring at least occasionally heating, said fluid comprising for example a hydrocarbon.

STATE OF THE PRIOR ART

More particularly, the invention relates to a method implemented on a device comprising a heating layer, said heating layer comprising first carbon fibers, the first electrically conductive material.

The device is for example a heating pipe for the transport of a fluid comprising for example a hydrocarbon.

The object of the invention is therefore to form an electrical connection on such a pipe (pipeline) to supply an electrically conductive composite layer with electricity. This type of pipe is used in very cold environments, both on land and at sea, and sometimes at sea at very great depths. Under these conditions, the fluid can either freeze, or coagulate, or freeze, thicken or form deposits of paraffin or hydrate. These transformations of the fluid can generate plugs and hinder the transport of the fluid in the pipe. This is why these pipes can be heated to avoid these drawbacks.

One technique is the electric heating of these pipes by conductive copper lines placed around the pipes. The heating is first concentrated around these lines, and then distributed by conduction. This technique is thus inefficient.

Another technique is the electric heating of these pipes by a layer of carbon fiber. Document CN2800021-Y describes a pipe for transporting a hydrocarbon, having a plastic tube reinforced with glass fibers, and a first layer of carbon fiber electrically supplied to heat the tube. These pipes produce a better distributed heating.

Document FR-2958991 describes an improved pipe for the transport of a hydrocarbon, which further comprises a reinforcing layer suitable for improving the mechanical strength. This document further describes means for assembling between conduits and electrical supply means. However, these feeding means are inefficient and complex to implement.

Document FR-2958994 describes a heating blanket that can be used to heat an element for transporting a hydrocarbon, such as a pipeline, a pipe, a valve or a wellhead.

Document FR-2958995 describes another system for heating these elements, which comprises such a membrane or flexible heating blanket.

The device is thus, for example, a heating device that is substantially flat, or curved, rigid or flexible.

DISCLOSURE OF THE INVENTION

The object of the present invention is to improve the electrical supply means for these devices comprising a heating layer having electrically conductive carbon fibers.

To this end, the method for forming the electrical connection comprises the following steps of forming an electrical connection:

an interface preparation step in which a junction layer formed of an electrically conductive junction material is deposited on at least one zone of “i.

the heating layer, and

- An installation step in which is deposited on the junction layer a connection strip comprising second fibers formed of a second electrically conductive material, and said connection strip having at least a portion projecting from said device and which forms a terminal for the power supply of the device.

Thanks to these arrangements, an electrical connection is directly formed. This electrical connection has low electrical resistance, and does not cause local heating during operation. This avoids a risk of damaging the heated device. The device is thus more reliable.

In various embodiments of the method according to the invention, it is optionally possible to have recourse in addition to one and / or other of the following arrangements.

According to one aspect of the invention, the device is a pipe for transporting a fluid, and in which the pipe comprises:

- an internal hollow tube extending in a longitudinal direction and intended to transport a fluid in the tube, and

- Said heating layer located in the thickness of the pipe, and before said steps of forming an electrical connection, the following steps are carried out:

- A groove forming step in which a groove is formed in the heating layer, said groove being intended to accommodate the electrical connection, and in which:

- in the interface preparation step, the junction layer is deposited on an area of the heating layer released in the groove produced during the groove formation step, and

- In the installation step, the connection strip is wound around the pipe, in the groove and on the junction layer, and said portion protrudes from the groove.

According to one aspect of the invention, the groove comprises a first surface in the longitudinal direction and a second surface in a direction opposite to the longitudinal direction, and in which the junction layer is deposited on a single surface among the first and second surfaces. .

According to one aspect of the invention, the groove has a triangle or trapezoidal shape, said groove extending throughout the thickness of the heating layer.

According to one aspect of the invention, the groove is formed by machining the heating layer.

According to one aspect of the invention, a protection step is further carried out in which a protective layer is formed by depositing on the connection strip, a composite strip comprising third fibers embedded in a matrix, said third fibers being formed from a third material which is not electrically conductive.

According to one aspect of the invention, after said steps of forming an electrical connection, a heating step is carried out in which the electrical connection is heated to crosslink at least the junction layer.

According to one aspect of the invention, the junction material is a polymer charged with electrically conductive particles.

According to one aspect of the invention, the particles are made of silver, copper, graphene, carbon black, carbon nanotubes.

According to one aspect of the invention, the second fibers are braided.

According to one aspect of the invention, the second material is copper.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will become apparent from the following description of at least one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings.

On the drawings:

- Figure la is a longitudinal sectional view of a composite heating pipe;

- Figure lb is a side cross view of the pipe of Figure la;

- Figure 2 is a longitudinal sectional view of the pipe of Figure 1 modified according to a first step of the method to form an electrical connection;

- Figure 3 is a longitudinal sectional view of the pipe of Figure 1 modified according to a second step of the method to form an electrical connection;

- Figure 4 is a longitudinal sectional view of the pipe of Figure 1 modified according to a third step of the method to form an electrical connection;

- Figure 5 is a longitudinal sectional view of the pipe of Figure 1 modified according to a fourth step of the method to form an electrical connection;

FIG. 6 is a diagram showing the succession of steps of an embodiment of the method for forming an electrical connection on the pipe of FIG. 1;

FIG. 7 is a view in longitudinal section of a pipe to which the method is applied several times to make several electrical connections;

- Figures 8 to 10 are cross sections of pipes produced with three variants of winding the connection strip in the groove.

In the various figures, the same numerical references designate identical or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

In the present description, the terms “front” and “rear” are used with respect to the longitudinal direction X. The terms “upper” or “upwards” and “lower” or “downwards” are used with respect to the vertical direction Z, upwards, perpendicular to the longitudinal direction X and to the transverse direction Y.

The term "pipe" of the present invention should be understood as being a device comprising a tube for transporting a fluid at least between an inlet and an outlet, the device being able to comprise other elements, such as a valve, or by-passes. multiple.

Figures la and lb show a pipe 1 for applying the method according to the invention, said pipe 1 being in longitudinal section along a plane XZ and in cross section along a plane YZ. In these figures, only an upper half above the X axis is shown, the other lower half being substantially identical by symmetry with respect to the X axis.

The pipe 1 comprises a hollow tube 2, extending in the longitudinal direction of axis X between a first and second end la, lb of the pipe. This tube 2 comprises an internal surface 2a close to the X axis, and an external surface 2b more distant from the X axis. Inside the internal surface 2a extends a cavity 2c between an inlet and an outlet. of the cavity located at each end. The cavity 2c is adapted to transport the fluid between said inlet and outlet.

The driving 1 a a section of form noticeably cylindrical in the plan YZ, but other shapes could be carried out. Tube 2 can be realized with a material

electrically conductive, such as steel, as shown in the figures for the present embodiment of the pipe.

The tube 2 can be made with an electrically insulating material, for example a polymer. This material can advantageously be a polyamide (PA), or a polyvinylidene fluoride (PVDF).

On this tube 2, there are for example at least the following layers, from the inside (close to the X axis) to the outside (away from the X axis):

- a first insulation layer 3,

- a heating layer 4, and

- a second layer of insulation 5.

Line 1 can include other layers. For example, the tube can be covered with a protective layer to limit corrosion of said tube, generally made of steel. For example, the tube can also be covered with an adhesion layer to facilitate the adhesion of the next layer (insulation layer 3) on said tube. For example, the pipe can also include an external thermal insulation layer, for example above or integrated into the second insulation layer 5.

The first and second electrically insulating layers 3, 5 are electrically insulating. They consist, for example, of a polymer or of a composite comprising glass fibers embedded in the polymer (matrix) or of a composite comprising kevlar fibers embedded in the polymer. The polymer is advantageously suited to adhere well to the other layers: the tube 2 and the heating layer 4. This polymer is optionally identical to that used in the heating layer 4 and / or in the tube 2 as mentioned above.

The heating layer 4 is a composite comprising at least carbon fibers embedded in a polymer. This polymer can advantageously be a polyamide (PA), or a polyvinylidene fluoride (PVDF).

The carbon fibers are able to conduct an electric current to heat the tube by the Joule effect. The electrical resistance R of such a heating layer 3 between the first and second ends (la, lb) of the pipe can be approximated by the following formula:

R P fiber

L ⁿ - ^D _t ^{nucleus E} p- ^{COs2 α} in which:

- Pfibre is a resistivity of carbon fibers, for example having for p-value _flbre = _1.9.10 ~ ⁵ Ω.ηι at a temperature of 20 ° C, which is substantially 1,100 times more resistive than copper at 20 ° C,

- L is a length of the heating layer 4 between the first and second ends (la, lb) in the longitudinal direction X,

- D _moy is an average diameter of the heating layer 4,

- E _p is a thickness of the heating layer in a transverse direction, and

- a is an angle of inclination formed by the carbon fibers with respect to the direction of the X axis.

By virtue of the angle of inclination of the carbon fibers in the heating layer 4, a desired electrical resistance R for the heating can be obtained.

By virtue of this heating layer 4 comprising carbon fibers well distributed in the polymer material of this layer, the heating tube 2. In addition, if one or more electrically broken fibers can deteriorate other characteristic fibers.

at a place all the same carbon, electrical is more homogeneous around the several carbon fibers of the pipe, the current continue to pass through the unbroken ones. Thus, the (resistance) are few

The different layers of the pipe 1 can be manufactured by known means using preformed strips of composite, each preformed strip extending in one direction and comprising fibers (carbon, glass or kevlar) embedded in a polymer matrix. The fibers are optionally oriented in said direction of the preformed strip.

The object of the present invention is to provide the electrical connection enabling the heating layer 4 of the pipe 1 to be supplied with electricity.

In particular, it is proposed to use a method 100 to form an electrical connection 10 in which the following steps are carried out (FIG. 6):

- a groove formation step 101 in which

a groove 6 is formed in the heating layer 4, 102 in - a step of interface preparation which we deposit a junction layer 7 formed of a material of j anointing conductor of electricity: sure at less a zone of layer of throat heating 4 θζ and

a step of placing 103 in which is wound on the junction layer 7 (and optionally on the heating layer) a connection strip 8 comprising second fibers formed of a second electrically conductive material, and said strip connection 8 having at least one portion 8a projecting from said groove 6 to form a terminal suitable for supplying electricity to the pipe.

The area of the heating layer is a part of said layer, on which the junction layer is added to improve electrical conduction.

The electrical connection 10 is therefore the set of the following elements: groove 6 filled with at least one junction layer 7 and a connection strip 8.

Additionally, the preceding steps may be followed by a protection step 104 in which a protective layer 9 is formed by winding on the connection strip 8, a composite strip comprising third fibers embedded in a matrix, said third fibers being formed from a third material which is not electrically conductive, for example glass or Kevlar.

Finally, a heating step 105 is optionally carried out in which the electrical connection 10 is heated in order to crosslink at least the junction layer 7, and possibly the other layers of the electrical connection: the connection strip 8, the protective layer 9.

FIGS. 2 to 5 represent the pipe 1 in longitudinal section X in the state of the successive steps 101 to 104, respectively.

In Figure 2, the groove 6 is formed in a continuous pipe 1, that is to say having over its entire profile the three layers stacked on the tube 2: the first insulation layer 3, the heating layer 4 and the second layer of insulation 5.

The groove 6 is for example formed by machining on this pipe in the rough state, for example by removing material, and for example by a method of turning the pipe.

This groove 6 is a notch having a radial section in a triangle or trapezoid with at least two lateral internal surfaces 6a, 6b which face each other in the longitudinal direction X. These first and second surfaces 6a, 6b are advantageously inclined with respect to the direction longitudinal X, for example at an angle of between 30 degrees and 60 degrees.

The groove 6 extends from the outside inwards (towards the X axis) and passes through at least the second outermost insulation layer 5. It then passes through the heating layer 4 partially or entirely. It also advantageously extends in a small proportion in the first insulation layer 3, for example only 10 percent of its thickness. This ensures that the entire thickness of the heating layer 4 is notched by the groove 6.

In the case of a notch with a radial trapezoidal section, this further comprises a bottom surface 6c which extends horizontally parallel to the longitudinal direction X. The groove 6 thus has a sufficient width to install the electrical connection 10.

In Figure 3, a junction layer 7 is deposited in the groove 6 formed in the previous step. This junction layer 7 is for example deposited on only one of the two surfaces among the first surface 6a and the second surface 6b. If the groove 6 (electrical connection 10) is made near a second end lb of the pipe 1 in the longitudinal direction X, and the current to be generated in the heating layer 4 will have to propagate in said layer towards the first end 1a, it is above all necessary to cover the first surface 6a opposite the second end 1b, as shown in the figures.

This junction layer 7 is formed from an electrically conductive junction material. For example, the junction material is a polymer which is intrinsically electrically conductive or non-electrically conductive, and / or possibly charged with electrically conductive particles. The particles are chosen from a list comprising a metal such as silver, copper, or graphene, carbon black, and carbon nanotubes.

Particles are small elements of spherical, elliptical or any other shape. They have a size (greater distance), for example less than 0.1 mm, and preferably less than 0.01 mm. These particles can thus be mixed or loaded into a polymer without too much affecting its viscosity. These particles are in powder form.

This junction material provides the electrical connection 10 with very good electrical conduction properties, that is to say a very low electrical resistance, which makes it possible to avoid localized heating in said electrical connection 10.

In FIG. 4, a connection strip 8 is wound in the groove 6 from the bottom surface 6c to a thickness substantially equivalent to the heating layer 4. This connection strip 8 is superimposed on the junction layer 7. It is applied also leaves free a portion 8a of length of the connection strip 8 outside the groove 6 (not wound in the groove). This portion 8a forms an electrical connection terminal which can be used as an element for supplying the pipe 1 with electricity.

Several variants can be envisaged for winding the connection strip 8 in the groove 6. These variants are presented at the end of the description and in Figures 8 to 10.

The pipe or a set of pipes electrically connected to each other must include at least two electrical connections (two electrical connection terminals), the first being connected to a first phase of the power supply and the second being connected to a second phase of the supply. the power supply, to generate a current in the heating layer 4 of the pipe 1 via the connections 10. The power supply can be in current or in voltage, of direct or alternating type. This power supply therefore has at least two phases, and is possibly three-phase.

The connection strip 8 comprises second fibers formed from a second electrically conductive material.

The second fibers are braided or not braided.

The second material of these second fibers is for example copper.

The assembly formed in FIG. 4, junction layer 7 and connection strip 8 is optionally heated to crosslink the polymers of the matrices of its components.

In FIG. 5, a protective layer 9 is formed on the connection strip 8 by winding on this connection strip 8 a composite strip comprising third fibers embedded in a matrix, said third fibers being formed of a third non-conductive material d 'electricity.

The third material is, for example, glass or kevlar.

The portion 8a remaining free of the connection strip 8 is not covered. The composite strip of the protective layer 9 is wound on a first side and on a second side of this portion to keep this portion 8a free and protruding from the protective layer 9.

The assembly formed in FIG. 5, junction layer 7, connection strip 8 and protective layer 9 is optionally heated or optionally heated again to crosslink the polymers of the matrices of its components.

The polymer used in the matrices of the various composite materials is, for example, a polyamide (PA), or a polyvinylidene fluoride (PVDF).

Thanks to the method used, electrical connections can be formed at any point along the length of the pipe 1.

It is also possible to form more or less deep electrical connections in the layers of a pipe, as shown in FIG. 7. In this figure, the

pipe 1 has five layers above the tube 2: - a first layer insulation 3χ, - a first layer heating 4χ, - a second layer insulation 3 ₂ , - a second layer heating 4 ₂ , and

- a third layer of insulation 5.

The materials of these layers are of the same type as those described above. For example, the insulation layers 3i, 3 ₂ , 5 are made of glass fibers embedded in a polymer matrix, and the heating layers 4i, 4 ₂ are made of carbon fibers embedded in a polymer matrix, advantageously identical to the previous one. .

In the example of figure 7, one forms as before:

- a first electrical connection 10a at the level of the first heating layer 4χ,

- a second electrical connection 10b at the level of the second heating layer 4 ₂ , and

- a third electrical connection 10c between the first and second heating layers 4i, 4 ₂ .

The third electrical connection 10c differs from the previous ones in that it does not include a free portion exiting outside the pipe 1, and passing through the protective layer 9c, and in that the junction layer 7 extends into the groove 6 from the first heating layer 4i to the second heating layer 4 ₂ .

The other two electrical connections 10a, 10b have this free portion which comes out of each of the respective protective layers 9a, 9b.

By virtue of this pipe 1 with two heating layers and these three electrical connections, the first and second electrical connections can be located on the same side of the pipe 1 in the longitudinal direction X, for example near the second end of the pipe. as shown in the figure. The third electrical connection 10c is located opposite the pipe near the second end lb. The first heating layer makes electricity pass from a first end to the second end of the pipe 1, while the second heating layer returns; it transmits electricity from the second end to the first end of the pipe 1. The power supply of the pipe 1 being carried out on one side only, it is easier to achieve.

The two heating layers 4i, 4 ₂ contribute to the heating of the pipe 1 by the Joule effect. Such a pipe 1 is more thermally efficient.

We now detail in Figures 8 to 10 alternative methods for winding the connection strip 8 in the groove 6.

In the first variant of FIG. 8, the connection strip 8 comprises a first end 8b placed at the bottom of the groove 6. The strip is then wound for example in a clockwise direction around the axis X, until it covers said first end 8a in one or more successive layers, then extend radially towards the second end 8a which thus forms the so-called “free” portion 8b.

Only the second end 8a of the connection strip 8 is left free radially to form the electrical connection terminal.

In the second variant of FIG. 9, the connection strip 8 comprises a first end 8b held radially at a distance from the groove 6. It is then wound in the groove 6 for example in a clockwise direction around the axis X, according to one or more turns. Then, it extends radially towards the second end 8a which thus forms the so-called “free” portion 8b.

The two ends 8a, 8b of the connection strip 8 are left free radially, each or both being able to form the electrical connection terminal.

In the third variant of FIG. 10, the connection strip 8 comprises a first end 8b placed at the bottom of the groove 6. The strip is then wound in a first direction, for example clockwise around the axis X, until it is covered. said first end 8a in one or more successive layers. Then, it extends radially, forming a loop 8c which returns radially towards its starting point. Then, the connection strip 8 is in a second direction, for example anti-clockwise around the axis X (opposite to the first direction), covering the previous layers in one or more successive layers, up to the second end 8a which can stay in the throat 6.

The two ends 8a, 8b of the connection strip 8 are in the groove 6, and an intermediate loop 8c between the first and second end 8a, 8b, extends radially freely, to form the electrical connection terminal.

The method according to the invention can also be applied to other heating devices (other than a pipe), such as devices as described in documents FR-2958994 (heating blanket) and FR-2958995 (inflatable system having a heating membrane). We refer to the descriptions of these published documents for the implementation of these.

Thus, these heating devices comprise, as for a heating pipe, a heating layer in their thickness which is composed of an electrically conductive material. This material comprises, for example, carbon fibers embedded in an elastomer.

In the case of such heating devices, the method according to the invention also comprises the following steps:

an interface preparation step 102 in which a junction layer formed of an electrically conductive junction material is deposited on at least one zone of the heating layer, and

a step of placing 103 in which is deposited on the junction layer (and optionally on the heating layer) a connection strip comprising second fibers formed of a second electrically conductive material, and said connection strip having at least a portion projecting from said device and which forms a terminal for the supply of electricity to this device.

Claims (10)

A method of forming an electrical connection on a device comprising a heating layer (4), said heating layer comprising first carbon fibers, the first electrically conductive material, and in which the steps of forming a following electrical connections: - an interface preparation step (102) in which a junction layer (7) formed of an electrically conductive junction material is deposited on the heating layer, and - an installation step (103) in which is deposited on the junction layer (7) a connection strip (8) comprising second fibers formed of a second electrically conductive material, and said connection strip having at least one portion (8a; 8b; 8c) projecting from said device and which forms a terminal for the power supply of the device. 2. The method of claim 1, wherein the device is a pipe for transporting a fluid, and wherein the pipe (1) comprises: - an internal hollow tube (2) extending in a longitudinal direction (X) and intended to transport a fluid in the tube, and - Said heating layer (4) located in the thickness of the pipe, and in which the said steps of forming an electrical connection are carried out before: - a groove forming step (101) in which a groove (6) is formed in the heating layer, said groove being intended to accommodate the electrical connection, and in which: - in the interface preparation step (102), the junction layer (7) is deposited on an area of the heating layer released in the groove produced during the groove formation step (101), and - In the installation step (103), the connection strip (8) is wound around the pipe (1), in the groove and on the junction layer, and said portion protrudes from the groove. The method of claim 2, wherein the groove (6) comprises a first surface (6a) in the longitudinal direction and a second surface (6b) in a direction opposite to the longitudinal direction, and in which layer junction (7) is filed sure only one surface among first and second surfaces • 4. Process according to claim 2 or the claim 3, in which the throat (6) a a form in triangle or trapezoid, said groove extending throughout the thickness of the heating layer. 5. Method according to one of claims 2 to 4, wherein the groove (6) is formed by machining the heating layer (4). 6. Method according to one of claims 1 to 5, wherein a protective step is further carried out (104) in which a protective layer (9) is formed by depositing on the connection strip (8), a strip. composite (9) comprising third fibers embedded in a matrix, said third fibers being formed of a third electrically non-conductive material. 7. Method according to one of claims 1 to 6, wherein, after said steps of forming an electrical connection, a heating step is carried out (105) in which the electrical connection is heated to crosslink at least the layer of junction (7). 8. Method according to one of claims 1 to 7, wherein the junction material is a polymer charged with 5 electrically conductive particles. 9. The method of claim 8, wherein the particles are silver, copper, graphene, carbon black, carbon nanotubes. 10. Method according to one of claims 1 to 9, wherein the second fibers are braided. 11. A method according to one of claims 1 to 10, wherein the second material is copper.