RU2679825C1 - High-temperature coupling of cable input for submersible motor - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to the field of electrical engineering, in particular to end connectors for cables in a liquid medium. Cable entry coupling for a submersible electric motor contains interconnected housing and shank, filled with compound, conductive cable wire with a plug tip, built into the block. Wire is passed through a through hole and is released on a part of its length from a lead protective sheath, worn on a tapered element. Coupling is made up of individual couplings (4) located at the end of each wire of a conductive cable. Each coupling includes housing (5), shank (6) and nipple (7) connected by means of a threaded connection. Housing is made with a through hole for passing wire (2) and has external conical element (10) to cover the lead protective sheath. On the end side of the nipple, facing the outer cone body element, a reciprocal internal conical element is provided, which provides sealing of the lead protective sheath placed between them.EFFECT: invention provides high maintainability of the coupling, increased reliability and increased service life.1 cl, 3 dwg

Description

The invention relates to the field of electrical engineering, in particular to end connectors for cables located in a liquid medium, and can be used in cable entries for hermetically connecting a cable line to submersible motors of a pumping unit designed for oil production from wells.

A fairly large number of cable entry couplings are known for a submersible electric motor, described in the technical literature [see, for example, International Translator “Installations of Submersible Centrifugal Pumps for Oil Production” - M .: Oil and Gas, 1999. P. 410-412], and also in patents for invention: RU 2588608 (C1), publ. 07/10/2016; US 6397945 (B1) dated 06/04/2002, US 6910870 (B2) dated 06/28/2005, US 2009/0317997 (A1) dated 12/24/2009.

All of these couplings contain a housing (or a housing with a shank of variable cross section, interconnected by screws), which is fixed to the end of the cable using sealing elements or filling with a sealing compound. Inside the housing are the ends of the insulated cable wires, freed from the lead sheath, connected to the plug lugs brought out through the holes on the block of the plug lugs. The tightness of the connection of the ends of the cable wires exempted from the lead sheath with the plug lugs is ensured by sealing joints around each wire in the form of spring blocks and elastomeric conical elements or by soldering the lead sheath of the cable with a steel sleeve or by mechanical compression of the lead sheath. To mechanically hold the cable from axial movement and additional protection against the effects of liquid, the inner tail of the sleeve is filled with a sealing compound or soldering is applied at the junction of the metal body, the shank and the cable armor. For a special cable having a steel sheath, use welding of a metal case with a metal sheath of the cable.

However, during operation, when high temperatures are reached, followed by cooling to the reservoir temperature, the tightness of couplings using elastomeric seals can be compromised due to the high difference in the thermal expansion coefficients of steel, rubber and polymeric materials, which will lead to the penetration of the borehole fluid to the outer surface the insulating layer of the cable core, freed from the lead sheath.

The disadvantages of couplings using seals by soldering are the complexity of the design, because the soldering process of two heterogeneous materials, for example, lead and stainless steel, requires qualified specialists, while the control at the place of the soldered seam is difficult and the material structure of the insulating layer cannot be controlled, and due to local heating of the cable insulation layer under the lead sheath during soldering, it is possible violation of the integrity of the insulation (latent defect), which during operation can lead to electrical breakdown.

The disadvantages of couplings, sealed by welding, is the design complexity due to the use of a specialized cable having a steel sheath instead of lead.

The closest technical solution for the totality of features to the claimed is a high-temperature cable entry coupling for a submersible electric motor company Novomet-Perm [patent RU 2588608, H02G 15/04, publ. 07/10/2016], which contains a metal casing and a metal shank of variable cross section, fixed to the end of the cable and interconnected by screws. The cable is disconnected into its three wires, covered with a lead sheath and an insulating sheath. On the end side of the housing around the through holes for transmitting cable wires, there are protrusions in the form of bushings with a tapering conical section at the open end on the shank side. The ends of the wires, freed from the lead sheath and partially freed from the insulating shells, through the openings in the protrusions are led out into the internal cavity of the housing and connected by a threaded connection to the plug lugs inserted into the block of the plug lugs made of ceramic. A ceramic insulator is mounted on each conductive wire, fixed with a sealing ring and fixed in the recesses of the housing with a sealing ring. The insulators are buried in the terminal block, fixed inside the housing with a retainer ring. Separated from the conductive wire, the lead sheath is pulled on top of the protrusion and forms a sealing ring with an external conical wall around its base on the end surface of the housing. The lead sheath is mounted on top of the protrusion with the help of a crimped sleeve worn on it, repeating the configuration of the protrusion and having an inner chamfer on the end that is in contact with the o-ring. The crimp bushings of all wires are integrated into the clamping stop, made in the form of an annular part mounted on the inner wall of the shank. To seal the places of mechanical fastening of lead shells, the space between the end surface of the housing and the pressure stop and around the crimp sleeve is filled with a high-temperature compound. A ring is put on the end of the housing on the side of the plug lugs, which serves as a seal when the coupling is connected to an electric motor.

The disadvantages of this coupling are: design complexity due to the manufacture of a housing with three conical elements, and unregulated compression of the lead sheath of the cable, which entails the introduction of increased requirements for the thickness of the lead sheath of the cable, which are not always feasible. In this connection, during the assembly of the structure, an uncontrolled displacement of the insulation can occur, which leads either to inability to assemble or to the formation of a gap between the insulator and the cable’s own insulation. In addition, the assembly technology involves flaring, followed by the introduction of a metal cone guide under the lead sheath, which can lead to damage to the insulation (latent defect).

The noted disadvantages reduce the reliability and service life of the cable entry coupling of the submersible motor.

The objective of the present invention is to provide a simple design of a high-temperature coupling with high maintainability, having increased reliability due to guaranteed compression of the lead sheath and increased service life due to improved assembly technology and the ability to visually monitor the state of insulation during milling.

The specified technical result is achieved by the fact that a high-temperature cable entry coupling for a submersible electric motor, including a shank connected to each other and a compound filled with a compound, a conductive cable wire with a plug end mounted in the block, which is passed through the through hole and is released from the lead protective part of its length the sheath stretched over the conical element according to the invention is made of separate couplings located at the end of each conductive wire the abel, the housing, the shank and the nipple of which are connected by means of a threaded connection, the housing being made with an external conical element for accommodating a lead protective sheath and a nipple, and a response inner conical element is made on the end side of the nipple facing the external conical element of the housing, providing sealing of the lead protective shell placed between them, and the nipple and the housing are interconnected by means of a nut fixed on the housing.

The invention is illustrated by drawings, where in FIG. 1 - presents a General view of the proposed cable entry sleeve; in FIG. 2 is a longitudinal section of one of the coupling bodies; in FIG. 3 is a longitudinal section through a sealing position of a lead sheath.

Cable 1 is disconnected to its constituent wires 2. The place of disconnection of cable 1 to wires 2 is protected by armor 3. The proposed high-temperature cable entry coupling for a submersible motor is made of separate independent couplings 4 (Fig. 1). The wires 2 are covered with a lead sheath 8 and an insulating sheath 9 (Fig. 2).

Each independent coupling 4 (Fig. 2) contains a metal casing 5, a shank 6 of constant or variable cross-section wound thereon, and a nipple 7.

The housing 5 and the nipple 7 have a through hole designed to pass the cable wire 2. On the end side of the housing 5 from the side of the cable 1, an external conical element 10 is formed (Fig. 3), expanding in the direction of the through hole. On the end side of the nipple 7, facing the side of the cone element 10, a counter inner cone element 11 is made. The housing 5 and the nipple 7 are interconnected by means of a metal nut 12, which is fixed to the housing 5 by means of a threaded connection.

The end of the wire 2, freed from the lead sheath 8 and partially freed from the insulating sheath 9, through the through holes in the housing 5 and the nipple 7 is brought out into the internal cavity of the housing 5 and passes through the block 13. To the copper core 14 freed from the sheaths is screwed to the end of the wire 2 the plug tip 15 mounted in the block 13 and sealed relative to its sealing ring 16. The block of the plug tip 13 is sealed relative to the housing 5 by the sealing ring 17. Separated from the conductive wire 2 and lead sheath 8 is hermetically clamped between the oppositely arranged inner and outer tapered elements 10 and 11, having equivalent or different cones, and forms a sealing ring 18 with conical walls.

For mechanical fixation of wire 2, the inner cavity of the shank 6 is filled with a high-temperature compound 19. In front of the shank 6, a protective armor 20 made of steel tape or pipe is put on the wire 2.

At the end of the housing 5 from the side of the plug tip 15 put on the ring 21, which serve as a seal when attaching the coupling to the motor. O-rings 16, 17, 21 are made of a gas-oil-resistant rubber compound that can withstand temperatures up to 315 ° C (600 degrees Fahrenheit).

The Assembly of the high-temperature sleeve cable entry separate view is as follows.

Cable 1 is disconnected into its component wires 2 (Fig. 1) and freed from lead sheath 8 and insulating sheath 9 (Fig. 2) to the required length. On each wire 2, a protective armor 20 is installed, slightly missing it to the end of cable 2. The transition of the cable of native cross section to single wires is also protected by armor 3 (Fig. 1).

On each individual wire 2 install an independent clutch 4 as follows. On the wire 2 (Fig. 2) with armor 20, a shank 6 and a nut 12 are successively installed, which are retracted to the required length for ease of assembly. Then, a preliminary process of cutting the ends of the conductive wire 2 is carried out - the lead sheath 8 is removed from the end of the wire 2 to the required length. The end of the prepared conductive wire 2 is passed through the through hole of the nipple 7 and take it to the installed armor 20 on the wire 2.

After that, wire 2 is formed for assembly, for this, using a special device, the lead sheath 8 is expanded, separating it from the insulating sheath 9 by the required angle.

The end of the wire 2 thus prepared is passed through the opening of the housing 5 so that the expanded portion of the lead sheath 8 touches the cone element 10 (Fig. 3).

The nipple 7 (Fig. 2) is brought to the expanded portion of the lead sheath 8 until it touches the conical element 11 (Fig. 3), then the nut 12 is brought in until it contacts the body 5.

Then connect the nipple 7 and the housing 5 by means of a threaded connection through the nut 12 with the required torque, while controlling the absence of rotation of the nipple 7 and the housing 5 around its own axis.

While tightening the nut 12, the nipple 7 and the housing 5 are moved, and the expanded portion of the lead shell 8 is clamped between the conical elements 10 and 11, forming a sealed lead-shaped sealing ring 18, blocking the fluid access inside the housing 5, regardless of the thickness of the lead shell 8 After the formation of the mechanical connection of the lead sheath 8 between the nipple 7 and the housing 5, it is checked for leaks.

Next, pre-install the sealing ring 17 (Fig. 2) on the block 13, the nut 22 on the shank 6 and produce the final process of cutting the end of the wire 2.

From the end of the wire 2, measure the required length from the housing 5, cut off the excess and remove the insulating sheath 9 to the required length, then cut the thread on the freed end of the copper core 14.

Thus prepared the end of the wire 2 with a threaded thread on a copper core 14 is passed through the block 13, which is inserted into the housing 5 until it stops.

The housing 5 is connected to the shank 6 using a threaded connection with the required torque.

On the threaded end of the copper core 14, which appeared in the hole of the block 13, screw the plug tip 15 with a ring 16 pre-installed on it.

Then fill the free internal cavity in the shank 6 and the housing 5 with a high-temperature compound 19.

The installation of the coupling 4 (Fig. 1) on the next separate wire 2 is carried out similarly.

In addition, synthetic dielectric high-temperature grease with high hydrophobicity can be applied to the contact surfaces of the coupling parts to provide additional protection against liquid penetration.

The formation of a sealed lead seal at the transition from lead to steel, independent of the thickness of the lead sheath, increases the manufacturability of the coupling, and the elimination of cylindrical elements and removal of cable insulation at the last stage increases the reliability of the coupling by reducing latent defects.

Due to the greater difference in the KTP value of lead in relation to the KTP of steel during heating, the lead volume increases in a confined space and, as a result, additional compaction in the annular space of the transition from lead to steel. When cooled, the annular space of the transition of lead to steel remains constantly tight.

The conical shape of the lead seal allows you to maintain the tightness of this compound during prolonged use under conditions of reaching a maximum temperature of 315 ° C, followed by cooling to a minimum temperature of the reservoir fluid (thermal cycling mode).

High maintainability of the coupling is achieved due to the possibility of reuse of its constituent parts.

The proposed high-temperature cable entry coupling of a separate type can be used when operating in high-temperature environments, such as environments associated with the use of steam (SAGD) for gravity drainage of wells to increase hydrocarbon production, as well as when operating electric centrifugal installations in periodic mode (work with subsequent inflow stop), in high-temperature wells with a significant temperature difference.

Claims (1)

A high-temperature cable entry coupling for a submersible electric motor, including a housing connected to each other and a shank filled with a compound, a conductive cable wire with a plug end mounted in a block, which is passed through a through hole and released to its length from a lead protective sheath worn on a conical element characterized in that it is made of separate couplings located on the end of each wire of the conductive cable, the housing, the shank and the nipple of which are connected to with the help of a threaded connection, the housing being made with a through hole for passing the wire and with an external conical element for accommodating a lead protective sheath and a nipple, and a response inner conical element is made on the end side of the nipple facing the external conical element of the housing, which provides sealing between them a lead protective sheath, and the nipple and the housing are interconnected by means of a nut fixed on the housing.

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