RU2251186C2 - Method for terminating multiconductor heating cable (alternatives) - Google Patents

Abstract

FIELD: cable engineering; terminating multiconductor heating cables of any shape.

SUBSTANCE: proposed method designed to terminate multiconductor heating cables of any shape, including flat, convexo-concave, and round ones, during their manufacture or repairs and to eliminate displacement of conductors relative to one another and to mold in the coarse of covering junction points of conductors with insulation due to additionally strengthening (stiffening) conducting cores at this section, as well as to eliminate pores and clearances between insulating material and conductors at points of their interconnection involves following procedures. According to first alternative for flat and convexo-concave cables, these procedures are as follows: prior to inserting cable section to be terminated in mold chamber insulated conductors on end section are bent in curve toward outer surface of end section, side conductors being preferably bent in horizontal plane and intermediate ones, preferably in vertical plane; conductors are bent in definite manner to definite size. According to second alternative for round cable, procedures are as follows: prior to placing end section into mold insulated conductors on end section disposed directly at outer surface are bent in curve toward outer surface of end section, mentioned conductors being bent in definite manner and to definite size.

EFFECT: enhanced quality of termination; facilitated procedure.

16 cl, 6 dwg

Description

The invention relates to cable technology, in particular to the technology of termination of a multicore heating cable of any shape: flat, convex-concave, round, during its manufacture or restoration. The heating cable is used in the oil industry as an equipment for traveling electric heating of a highly viscous oil and gas mixture of wells equipped with sucker rod pumps, submersible pumps, in order to reduce the viscosity of the produced fluid, to prevent and eliminate asphalt, tar and paraffin deposits, as well as to prevent freezing of water pipes in water injection systems, oil transportation systems and gas.

Operation of the heating cable in borehole conditions (aggressive environment, gas factor, increased pressure along the wellbore) leads to increased requirements for insulation and sealing of the conductive conductors of the heating cable, especially to the termination of the heating cable, where the conductive conductors are interconnected to form a closed electrical circuit after connecting the other ends of the cable on the surface to the power source. The end section with the junction of the cores between each other is the least protected in the design of the heating cable, since the insulation must be applied to this section autonomously from the general insulation of the conductive wires, namely: after connecting the conductive wires to each other according to the scheme required for the heating conditions.

In the cable industry, various methods of applying polymer insulation to the cable end section are used, for example, during cable repair (see N.I. Belorussov. Production of cables and wires with plastic insulation. M-L., “Energy”, 1966, p. 81 -83).

Known, for example, is a method consisting in winding the junction of the cable cores with tape with an adhesive layer with an overlap of about 50%.

Another method is known, including winding the prepared portion of the cable with tape, but from the same material as the general insulating sheath of the cable, followed by placing the wrapped portion in a mold with electric heating. The winding is carried out to a diameter slightly larger than the diameter of the insulation or sheath.

However, termination of the end section by such methods does not provide high-quality insulation and sealing of the end section for reliable operation of the heating cable in an aggressive environment. Conductors in the place of their connection at the end are not protected from the penetration of well fluid, gas between the insulation and the conductors. As a result, mechanical destruction of the insulation, violation of its dielectric properties and electrical breakdown of the cable.

There is a method of terminating a heating cable designed to operate in an aggressive environment, including preparing a multicore cable to connect conductive wires to each other at the end (free) section of the cable to form a closed electrical circuit and connect the stripped ends of the wires to each other using a metal sleeve. At the same time, the conductors are led into the sleeve from two sides, that is, at least one conductive core of the multicore cable is bent 180 ° and led towards the other wires, thereby covering the free end of the sleeve with the insulating sheath of the curved conductive core, which eliminates the open, weakly protected end at the end cable section. After that, insulating heat-resistant shells of at least two layers with overlap on both sides are laid sequentially on a metal sleeve (the junction of the cores), on which a heat-shrinkable tube and a protective casing are laid (see RF certificates for utility model No. 14474, class N 01 B 7 / 18, dated March 23, 2000).

Although this method of terminating the heating cable allows improving the quality of insulation from the end of the cable end portion, such termination does not exclude the ingress of aggressive medium into the junction of the conductive conductors and through it into existing cavities inside the cable, for example, between the side surfaces of the insulating shells of each core . As a result - electrical breakdown and cable failure. The insufficient quality of termination of the cable end section is explained by the following reasons. Firstly, the protective casing does not prevent the well fluid from entering the junction, since under high pressure the fluid penetrates through the cable armor (the armor is not hydraulic protection) in the cable cavity. Secondly, bending the cable core to a large angle (180 °) with an extremely small bend radius of curvature unacceptably deforms and weakens the insulation coating of the conductive core, which can lead to insulation failure in this place in the first place. In addition, heat shrink tubes do not cover the entire range of materials used for cable insulation.

To eliminate the ingress of borehole fluid into the cavity of the end section, it is known to use the technology of cable termination by applying an insulating coating to the junction of the cores in the mold by extruding the insulating mass into the cavity of the mold and then cooling (see French patent No. 2086837, class H 02 G 1/00, from 1971).

A significant disadvantage of this method is that during the application of the insulating material there is an arbitrary displacement of the interconnected cores relative to each other and the mold, as a result, the uniformity of the insulating layer at the end section is not ensured, which significantly reduces the quality of the insulation of the heating cable and makes use of such cable in an aggressive environment is impossible.

The closest in technical essence to the claimed method is a method of terminating a multicore heating cable, including preparing a multicore cable, consisting of insulated conductive conductors, to connect conductive conductors to each other on the free end of the cable to form a closed electrical circuit, to connect the stripped ends of conductive conductors , placement of the end section with interconnected cores in the forming mold, installation in the inter-core spaces at the indicated end section of the liner cable, spacers (round or shaped) made of insulating material to exclude the displacement of conductive conductors in the mold chamber and subsequent supply of molten insulating material under pressure to the mold chamber and cooling (see USSR Autosvid No. 694926 , CL H 02 G 1/14, 1978).

A disadvantage of the known method is the displacement of the end portion relative to the side walls of the chamber of the mold in the case when the spacer insert between the cores is used from a polymeric material identical in properties to the extruded insulating material. The displacement is caused by the ductility of the liner under the action of the high temperature of the insulating material. In the case of using more durable materials for the liner, the lack of adhesion to the surface of these materials leads to a sharp deterioration in the quality of insulation of the end portion of the heating cable.

The technical problem to which the proposed technical solution is directed is to improve the quality of the termination of the heating cable by eliminating the displacement of the conductive conductors relative to each other and relative to the mold in the process of applying insulation to the joint of the conductors by giving additional conductivity to the conductive conductors in this section (stiffness), as well as the exclusion of pores and voids between the insulating material and conductive veins at the point of their connection with each other at one simplification of the method.

This technical problem is solved due to the fact that in the known method of terminating a multicore heating cable, including preparing a multicore cable consisting of insulated conductive conductors, to connect conductive conductors to each other on the free end of the cable to form a closed electrical circuit, to connect the stripped ends of conductive veins, placement of the end section with interconnected cores in the chamber of the mold-forming mold, followed by feeding into the chamber ess-forms of molten insulating material under pressure and cooling, new in the first embodiment - for a flat or convex-concave cable - is that before placing the end section of a flat or convex-concave cable in the mold chamber, insulated conductive conductors at the specified end section bend in a curve towards the outer surface of the end portion, and the side cores are preferably bent in a horizontal plane, and the middle cores are preferably in a vertical plane, side veins are bent to obtain a transverse dimension of the end section of a flat or convex-concave cable between the outer surfaces of curved side veins, which differs from the transverse dimension of the mold chamber by 0 ÷ + 10%, and at least one middle core is bent to obtain a height dimension end of the cable from the longitudinal axis of a flat or convex-concave cable to the outer surface of the curved middle core, which differs from half the height of the mold chamber by 0 ÷ + 10%, after which the stripped ends of the conductive the sludge is interconnected and the cable end portion is placed in the chamber of the mold so that the curved side cores abut against the opposite side walls of the mold chamber, and the bent middle cores abut the upper and / or lower walls of the mold and fix the cable end portion with the common insulating forming sheath in the mold chamber and the insulating material are applied to the cable end portion overlapping the common insulating forming sheath.

At least one middle conductive core is bent twice in opposite directions.

The direction of the bend in adjacent middle veins alternate. Each side core is bent at least once in the horizontal plane and at least two times in the vertical plane in opposite directions relative to each other.

In the method of terminating a multicore heating cable according to the second embodiment, for a round cable, it is new that before the end section of the round cable is placed into the mold, the insulated conductive wires located on the said end section located directly at the outer surface are bent in a curve towards the outer surface of the end section, the bending of these cores is preferably in planes passing through the longitudinal axis of the cable and the longitudinal axis of the conductive core until overall dimension between the outer surfaces of curved cores, which differs from the overall dimension of the mold chamber by 0 ÷ + 10%, after which the stripped ends of the conductive conductors are connected to each other, the cable end section is placed in the forming mold so that the curved cores abut external surfaces into the walls of the inner cavity of the mold chamber and rigidly fix the end portion of the cable with a superimposed common insulating formative sheath in the mold chamber, and the insulating material blown to the end portion of the cable with an overlap on a common insulating formative sheath.

The angle between the points of contact of the curved cores with the cavity of the mold chamber is preferably 360 ° / n, where n is the number of curved cores.

According to the first and second options:

The bending of the conductors along the curve is carried out on a limited length with a large radius of curvature.

Touching the curved cores and the walls of the chamber of the mold is carried out according to the minimum area.

Insulating material is applied to the cable end portion overlapping the common insulating forming shell and the armor.

Insulating material is applied to the end portion in the form of a solid tip.

And on top of the solid tip impose an additional insulating layer.

Due to the fact that before applying insulation to the junction of the conductive conductors at the end section of the heating cable, it is proposed to bend the conductive wires with the proposed method, and bending the conductors smoothly, without bending and at a limited length, it became possible to give additional rigidity to the conductors at the end section, which allows the subsequent placement of this section in the chamber of the forming mold with some interference tightly secure this section in it and thereby avoid the displacement of the cores completely each other, as well as the displacement of the cores relative to the side walls of the chamber of the mold without the use of additional tools, in particular inserts. As a result, the insulating layer is applied uniformly to the junction of the cores, the insulation has a uniform structure, defects in the form of bubbles and voids are eliminated.

It is preferable to bend the side conductors (for a flat and convex-concave cable) towards the outer surface in a horizontal plane, and bend the middle conductors preferably in a vertical plane, which gives additional rigidity to the design of the cable end section of this shape, thereby eliminating the core displacement in the process of applying insulation in the mold. The proposed bending of the cores in this section allows you to form the overall dimensions of the end section before placing it in the mold chamber, corresponding to the overall dimensions of the chamber and thereby ensure that the curved surfaces touch the chamber walls, which also ensures a fixed position of the cores in the end section during insulation application under mold pressure. In this case, the bending of the cores allows you to do without the use of special inserts-spacers to eliminate the displacement of the cores, which significantly improves the quality of the termination of the heating cable, simplifies the process of applying insulation.

For a round cable, it is enough to bend at the end section only the cores located directly on the outer surface of the end section, while bending the cores according to the proposed scheme allows the overall dimensions of the end section of the round cable to exceed the overall dimensions of the mold chamber, which allows, firstly, to give additional rigidity to the cores at the end section, and secondly, to ensure the installation of the end section in the chamber with some interference, which eliminates the displacement of the cores when applying insulation in place connection of cores in the chamber under pressure, to exclude the displacement of cores relative to each other when applying insulating material under pressure to the cable end section.

Performing a bend on a limited length with a large radius of curvature eliminates violations of the insulating sheath on each core at the bend.

And the insulation at the end portion in the form of a solid tip with an overlap on the general forming insulating sheath or additionally on the armor makes the end portion of the cable monolithic, uniformly protecting the cable from penetration of well fluid both from the end of the cable and from the side of the tip overlapping to the armor of the cable, This ensures high quality overlay insulation coating, uniform in thickness for all conductive wires. To increase reliability, an additional insulating layer is applied over the solid tip.

The proposed method for terminating a multicore heating cable is illustrated by drawings, where Fig. 1 shows an end section of a three-core heating cable with curved cores with a number of cores n = 3, top view; figure 2 is a flat (convex-concave) cable, side view, (n = 3); figure 3 - the same, with n = 4; figure 4 is the same for n = 3 or n = 4; figure 5 - placement of the end section in the chamber of the mold; figure 6 - end section of the finished heating cable.

The proposed method is as follows.

A multicore heating cable (flat, convex-concave or round), consisting of insulated conductive conductors 1 with heat-resistant insulation 2, on which a common shape-forming insulating sheath 3, a cushion under armor 4 and armor 5 are laid, are prepared for connecting conductive conductors 1 to each other on the free end of the cable. To do this, on a limited length at the end of the cable, remove the armor 5, the pillow 4 (in the form of a tape or a hose) and the general forming shell 3. Remove the insulation 2 from each conductive core 1 to a length that connects the core 1 to each other, for example, by means of metal sockets 6.

Conductors 1 at the prepared end are bent over a limited length, for example, along a second-order curve (or transcendental function) with a large radius of curvature towards the outer surface of the cable end section.

In the case of a flat or convex-concave cable, the side cores 1 are preferably bent in a horizontal plane (FIG. 1).

The side core 1 can be bent according to another law, for example, at least once in the horizontal plane and at least two times in the vertical plane in opposite directions relative to each other. The middle cores 1 are preferably bent in a vertical plane. When the number of cores 1 in the cable is three (n = 3), the middle core 1 is bent in a vertical plane at least once relative to the longitudinal axis of the cable (figure 2). At least one middle core 1 can be bent twice, but in opposite directions from the cable axis (FIG. 4), the bending direction alternating on adjacent middle conductors (FIGS. 3 and 4). For a round cable, conductive conductors 1 are bent, located directly at the outer surface of the cable. They can be all cores 1, for example, at a three-core cable, and maybe some of the cores can be medium, which do not bend in a round cable. The bending of the cores of a round cable is preferably carried out in planes passing through the longitudinal axis of the cable and the longitudinal axis of the conductive core 1. The angle between the planes in which the cores are bent is of the order of 360 ° / n, where n is the number of bent cores.

Thus, the cores in a limited length section, before they are connected to each other and the insulation material is applied to this section, are bent in a curve towards the outer surface of the cable end section. As a result, all the cores are spaced apart in relation to each other in such a way that the gap between the cores increases, which in the subsequent process will ensure high-quality insulation. And the curved shape of the cores in a limited section gives additional rigidity to the structure at the end section and subsequently - high-quality continuous pressure application of continuous insulation at the junction of cores 1 in the form of a tip.

In a flat or convex-concave cable, the side cores 1 are bent to obtain a transverse dimension of the end portion of the cable between the outer surfaces of the curved side cores, different from the transverse dimension of the mold chamber 0 ÷ + 10%, and at least one middle core is bent to obtain a size in height of the end section from the longitudinal axis to the outer surface of the curved middle core, which differs from half the height of the mold chamber by 0 ÷ + 10%. In a round cable, the bending of the conductors 1 is carried out until the overall dimension between the outer surfaces of the curved conductors is formed, which differs from the overall dimension of the mold chamber by 0 ÷ + 10%.

After that, the stripped ends of the cores 1 are connected to each other, for example, in a “star”, for example, by means of a metal outlet 6. Then, the end section of the cable with curved and interconnected cores 1 is placed in the chamber 7 of the mold 8. In this case, the section the cable with the common forming shell 3 attached to it (or with the armor 5 placed on it) is rigidly fixed in the center of the chamber 7, for which this section of the cable is laid in the bore 9 of the chamber 7 of the mold 8, and the curved cores 1 are abutted against the walls of the chamber 7. For flat (issue of the bent-concave cable, the lateral veins abut against the side walls of the chamber 7, and the middle veins abut against the upper and / or lower walls of the chamber 7. In this case, various options for touching the curved veins 1 of the chamber walls are possible.

Examples of touching the walls of the camera in the case of a flat (convex-concave) cable:

- curved side conductors with a number of conductive wires n = 3 abut in two angles located in the lower half of the mold. The middle core, bent, for example, twice in a vertical plane in different directions, abuts against the upper and lower walls of the mold chamber;

- curved side cores of the cable with the number of cores n = 4 abut in two angles located in the lower half of the mold, and the middle two curved cores abut in two corners in the upper half of the mold;

- the curved side cores of the cable with the number of cores n = 5 abut in two angles in the upper half of the mold, and one of the middle cores - the central one, bent twice in opposite directions, abut against the upper and lower walls of the chamber of the mold.

For a round cable, curved cores abut against the walls of the chamber 7 of the mold 8 with external surfaces, while the angle between the points of contact of the curved cores 1 of the chamber walls is preferably 360 ° / n, where n is the number of curved cores. With this arrangement of curved cores, the most uniform rigidity of the end section before applying insulation is ensured, and the area of additional insulation between the surfaces of the conductive wires at the end of the cable increases.

Touching the curved cores and the walls of the mold chamber is carried out according to the minimum touch area.

The halves of the mold 8 are tightly interconnected, an insulating material, for example thermoplastic elastomer or copolymers and block copolymers of propylene, is supplied under pressure. As soon as the insulating material begins to protrude through the control holes of the mold, the supply process of the insulating material is terminated. Next, the mold is cooled and disassembled. The isolation of the end portion is obtained in the form of a solid tip 10, for example, in the form of a parallelepiped. The tip 10 can be installed overlapping both on the common insulating sheath 3 of the cable and on the armor 5. The tip is removed from the tip and produced

electrical breakdown tests. To increase reliability, an additional layer 11 of insulating material, for example, made of thermoplastic elastomer, is applied over the tip.

Tests confirm the high quality of insulation and tightness of the termination of the heating cable.

Thus, the proposed method for terminating a multicore cable designed for traveling electric heating allows to ensure high reliability of insulation of the cable end section - the junction of the conductive conductors with each other. The insulation imposed in this way on the cable end section excludes the penetration of well fluid and gas into the junction of the conductors both from the cable end and from the armor side. Electrical breakdown in this section is excluded due to involuntary closure of the cores, since they are spaced apart in space and additional rigidity is given to them.

Claims (16)

1. The method of terminating a multicore heating cable, including preparing a multicore cable consisting of insulated conductive cores, to connect the cores to each other at the free end of the cable to form a closed electrical circuit, to connect the stripped ends of the conductive cores to each other, to place an end section with interconnected cores in the chamber of the mold, followed by feeding molten insulating material under pressure and cooling into the chamber of the mold, I distinguish characterized in that before placing the end portion of the flat or convex-concave cable into the mold chamber, the insulated conductive wires at the indicated end portion are bent in a curve towards the outer surface of the end portion, the side conductors being preferably bent horizontally and the middle conductors preferably in a vertical plane, while the side cores are bent to obtain a transverse dimension of the end portion of a flat or convex-concave cable between the outer surfaces lateral veins, which differs from the transverse size of the mold chamber by 0 ÷ + 10%, and at least one middle core is bent to obtain a size along the height of the cable end section from the longitudinal axis of the flat or convex-concave cable to the outer surface of the curved middle core , which differs from half the height of the mold chamber by 0 ÷ + 10%, after which the stripped ends of the conductive wires are connected to each other and the cable end section is placed in the chamber of the mold so that the curved side conductors abut against The side walls of the mold chamber are bent, and the curved middle conductors abut against the upper and / or lower walls of the mold, while the cable end portion with the common insulating form-forming sheath overlaid is placed in the mold chamber and rigidly fixed and the insulating material is laid on cable end section with overlapping common insulating forming sheath. 2. The method according to claim 1, characterized in that at least one middle conductive core is bent twice in opposite directions. 3. The method according to any one of claims 1 and 2, characterized in that the direction of the bend in adjacent middle conductors alternate. 4. The method according to claim 1, characterized in that each side strand is bent at least once in the horizontal plane and at least two times in the vertical plane in opposite directions relative to each other. 5. The method according to any one of claims 1 to 4, characterized in that the cores are bent along a curve over a limited length with a large radius of curvature. 6. The method according to any one of claims 1 to 5, characterized in that the curved wires and the walls of the mold chamber are touched according to the minimum area. 7. The method according to any one of claims 1 to 6, characterized in that the insulating material is applied to the end portion of the cable overlapping the common insulating forming shell and armor. 8. The method according to any one of claims 1 to 7, characterized in that the insulating material is applied to the end portion in the form of a solid tip. 9. The method according to any one of claims 1 to 8, characterized in that an additional insulating layer is applied over the solid tip. 10. The method of terminating a multicore heating cable, including preparing a multicore cable consisting of insulated conductive cores, to connect the cores to each other at the free end of the cable to form a closed electrical circuit, to connect the stripped ends of the conductive cores to each other, to place an end section with interconnected cores in the chamber of the mold, followed by feeding molten insulating material under pressure and cooling into the chamber of the mold, excellent characterized in that before placing the end portion of the round cable into the mold, the insulated conductive conductors on the specified end portion located directly at the outer surface are bent in a curve towards the outer surface of the end portion, the bending of these conductors is preferably carried out in planes passing through the longitudinal the axis of the cable and the longitudinal axis of the conductive core to the formation of a dimension between the outer surfaces of curved wires lying in the same plane, different from the overall the actual size of the internal cavity of the mold by 0 ÷ + 10%, after which the protected ends of the conductive conductors are interconnected, the cable end portion is placed in the mold so that the curved wires abut the outer surfaces against the walls of the internal cavity of the mold chamber wherein, the cable end portion with the common insulating forming sheath applied is placed in the mold chamber and rigidly fixed and the insulating material is applied to the cable end portion with overlapping on the general insulating form-forming shell. 11. The method according to claim 10, characterized in that the core is bent along a curve along a limited length with a large radius of curvature. 12. The method according to any one of claims 10 and 11, characterized in that the angle between the points of contact of the curved cores with the cavity of the mold chamber is preferably 360 ° / n, where n is the number of curved cores. 13. The method according to any one of paragraphs.10-12, characterized in that the touch of the curved cores and the walls of the chamber of the mold is carried out according to the minimum area. 14. The method according to any one of claims 10 to 13, characterized in that the insulating material is applied to the end portion of the cable overlapping the common insulating forming shell and armor. 15. The method according to any one of paragraphs.10-14, characterized in that the insulating material is applied to the end portion in the form of a solid tip. 16. The method according to any one of paragraphs.10-15, characterized in that on top of the solid tip impose an additional insulating layer.

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