GB2613797A

GB2613797A - Electrical coupling

Info

Publication number: GB2613797A
Application number: GB2118075.7A
Authority: GB
Inventors: Inge Folgerorø-Holm Jan
Original assignee: Siemens Energy AS
Current assignee: Siemens Energy AS
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-06-21
Also published as: GB202118075D0; WO2023113997A1

Abstract

An electrical coupling 20 comprises a pair of hollow cylindrical tubes 19. Each tube 19 comprises an electrical feedthrough piston 22 mounted in the tube 19, and piston rings (figure 3, 23) to moveably seal the piston 22 to the tube 19. Each tube 19 of the coupling 20 is adapted to be fitted to a first housing 13 common to the pair of hollow cylindrical tubes 19. At least one of the pair of hollow tubes 19 of the coupling is adapted to be coupled to a second housing (figure 3, 25), a cable, or an umbilical 17. The other of the pair of hollow cylindrical tubes 19 is adapted to be coupled to a cable or umbilical 18. The first housing 13 comprises a fluid filled, non-pressure compensated housing, and the second housing (figure 3, 25) comprises a gas filled housing. The cable or umbilical 17, 18 is fluid filled and pressure compensating.

Description

ELECTRICAL COUPLING

This invention relates to an electrical coupling, in particular for a subsea, or underwater sensor.

In subsea or underwater applications, as well as in topside applications in harsh environments, in particular offshore, electrical systems that are used to monitor and operate plant and equipment for oil and gas installations, or offshore wind or tidal power generation need to be protected from the possibility of seawater getting into the sensitive electrical equipment. However, it also needs to be possible to operate equipment, e.g. electrical actuators, and to extract the data from the monitoring and send the data to be processed. Thus, improved electrical feedthroughs are desirable.

In accordance with a first aspect of the present invention, an electrical coupling comprises a pair of hollow cylindrical tubes, each tube comprising an electrical feedthrough piston mounted in the tube and piston rings to moveably seal the piston to the tube; wherein each tube of the coupling is adapted to be fitted to a first housing common to the pair of hollow cylindrical tubes; wherein at least one of the pair of hollow tubes of the coupling is adapted to be coupled to a second housing, a cable, or an umbilical; and wherein the other of the pair of hollow cylindrical tubes is adapted to be coupled to a cable or umbilical; wherein the first housing comprises a fluid filled, non-pressure compensated housing; wherein the second housing comprises a gas filled housing; and wherein the cable or umbilical is fluid filled and pressure compensating. In accordance with a second aspect of the present invention, an electrical sensor system comprises an electronics chamber, a first housing connected to the electronics chamber; at least one of a second housing, cable or umbilical coupled by a coupling according to the first aspect to the first housing; and at least one of a cable or umbilical coupled by the coupling to the first housing.

The coupling may be coupled to two cables or umbilicals.

The cable or umbilical may comprise an electrical flying lead.

The cable or umbilical may comprise a communication or data carrying medium, or wire.

The gas in the second housing may comprise nitrogen or air.

The fluid may comprise any media suitable for providing pressure compensation in the otherwise non-pressure compensated first housing, cable or umbilical, but preferably, the fluid in the first housing, cable or umbilical comprises high dielectric strength oil, in particular silicon oil.

An example of an electrical coupling and associated system will now be described, with reference to the accompanying drawings in which: Figure 1 illustrates an example of a typical subsea pipeline system in which subsea sensors may by monitored in a system having an electrical coupling according to the present invention; Figure 2 illustrates a first example of an electrical coupling according to the present invention; and, Figure 3 illustrates a second example of an electrical coupling according to the present invention The drive to reduce overall lifecycle costs, both capital expenditure (CAPEX) and operational expenditure (OPEX), associated with deep-water oil and gas developments means that improvements to existing designs, manufacturing processes and operation are desirable. Reducing operational costs of maintenance of subsea equipment relies on remote operation and monitoring of the status of the equipment and adapting the operation to reduce the rate of wear, or scheduling equipment replacement to coincide with other works that also require vessel or diver services, to reduce the overheads. The electrical equipment, such as sensors systems, that carries out the operation and monitoring needs to be reliable and protected from damage, even if associated parts of the electrical system are damaged.

The present invention has been designed to address the problems faced by subsea electrical systems, such as subsea pressure and temperature sensors, where avoiding ingress of seawater is particularly important. However, the design may also be used in any electrically operated subsea application and for electrically operated topside applications, in harsh environments, or where there is high temperature variation causes thermal expansion in a pressure compensated system. Subsea or offshore operational conditions mean that sensors for use in those conditions must meet regulatory standards. Sensors typically provide data to a topside or other location via a hose or umbilical. Conventionally, the communications cable in the umbilical or hose enters a housing, of a subsea unit in which the sensor is operating, through a penetrator into the housing. Redundancy may be provided by having two independent electrical flying leads to the sensor, with two penetrators into the housing, which may be independent, or a hammerhead design. The independent hoses have one hose onto one penetrator through the housing at a first location and another hose onto another penetrator, alongside, at a second location in the housing. The hammerhead arrangement is one whereby the first and second locations are diametrically opposite, rather than alongside each other. In both cases, the penetrators are fully rated for a test pressure, which means that they are expensive to produce. If one communications cable, or hose, fails, the other will continue to allow data flow. The pressure compensation on the seawater side is provided by the hose. Typically, a penetrator in the form of a 4-pin electrical feedthrough with a hose adaptor is required for each of the two cables. However, using two penetrators, one for each independent flying lead, makes setting this up quite complex, as well as there needing to be independent harness interfaces for each cable.

Fig.1 illustrates a typical installation in which a sensor, such as a pressure or temperature sensor, may be installed. One or more sensors in a sensor unit 1 may be installed subsea 2, for example, in a pipeline, or other media carrying body and be exposed to process media, which may for example, comprise a process fluid such as gas, or oil, together with water, as well as sand and/or chemicals. Alternatively, there may be electrically operated actuators in an all-electric system, for example sensors may provide position feedback, in order to adapt the control signals to move the actuator to a required position. For a monitored pipeline, having multiple sensors in the pipeline allows particular issues to be located more easily, although an alternative would be to have a single sensor where the process media enters a pipeline section. For other types of condition monitoring, for example, where there is depth monitoring, or valve position monitoring, a subsea electronics module (SEM) is provided to receive arid process the data. Monitoring of actuator control arid feedback on a bus link may be via one hose, and power through another, separate hose. Similarly, ethernet applications may be provided, with power coming through one hose, or cable, and the ethernet link through the other hose, or cable.

Data from the, or each, sensor in the sensor unit I may be collected in a control centre 4, the data being received at the control centre via communications lines in electrical flying leads in a hose or umbilical 5. The communications lines may range from a few metres in length to several hundred metres. The control centre may be either subsea 2 or topside 3, or at a remote location, for example when used as a part of an automated condition monitoring system. The received data may be monitored by operators or to automated to some extent. When detected data indicates operator intervention is required, the operator may send a control signal to the control centre and through communications lines to cause a change in operation, such as reducing the flow rate of the process media in a section of the pipeline. In an automated system, this may be done in response to a trigger value being reached. Accurate measurement of parameters allows changes to be made as needed.

Regulatory requirements are being altered to require any oil volume behind a penetrator to be pressure compensated. The subsea hose or umbilical is oil filled under pressure topside before deployment, so that it will tend to flow out of the hose or umbilical in the event of damage, preventing seawater ingress for a minimum period of time. A housing to hose adapter is filled with oil from the hose oil volume. The present invention addresses the requirement for pressure compensation, whilst also simplifying the design and making it possible to use a sensor comprising one penetrator that is fully rated for the test pressure, along with two electrical feedthroughs which have a lesser specification, rather than the more expensive hammerhead sensor, comprising two frilly rated penetrators.

The present invention, examples of which are further illustrated in Figs.2 and 3, provides the same level of electrical redundancy for dual subsea instruments, with the use of only one frilly rated penetrator 14, together with a non-pressure compensating housing, coupled by the penetrator to a 1 atmosphere chamber 11 in which the electronics are housed. The chamber formed by the non-pressure compensating housing 13 comprises two electrical feedthroughs 22 with lower specifications than the penetrator, which couple the non-pressure compensated housing 13 to the hoses 16, 17, as well as providing pressure compensation for that housing 13 in conjunction with each hose, or in another example, with a second housing 25 in place of the hose. The penetrator is fitted between an electronics chamber II, which may, for example, contain one or more sensors and a non-pressure compensated housing 13, as shown in Fig.2. A dual hose adaptor or coupling, featuring a pressure equalizing electrical feedthrough in connection with each hose connection or leg, enables redundancy to be introduced, whilst also providing pressure compensation as required in the standard. The pressure equalising electrical feedthroughs of each hose are able to slide inside

S

respective tubes and are located in a pressure equalised surrounding at all times. This contrasts with the conventional hammerhead design which comprises fixed fully rated penetrators which take full pressure on one side and are defined to be a part of the pressure integrity barrier, so are more costly to provide. These penetrators have no moving parts, so cannot provide pressure compensation for the housing that they couple into, in the way that the present invention does. With the sliding electrical feedthroughs, if a hose leg is compromised, the piston acts as a seal to prevent water intrusion to the non-pressure compensated housing 13. Fig.2 illustrates a first example of a system comprising an electrical coupling according to the present invention.

An enclosure 10 comprises a 1 atmosphere chamber 11 for the electronics 12, such as a subsea sensor, subsea electronics module or signal converter, coupled to a first non-pressure compensated housing 13 by a penetrator 14. The housing 13 typically comprises a metallic housing, for example sea water resistant, or corrosion resistant metal, such as alloy 625, super-duplex or 316L. In a system comprising a dual redundant communications link 15, 16 in a hose or umbilical 17, 18, typically the communication link has four wires, two signal and two power, and the penetrator is an eight pin penetrator, to be able to receive the eight wires 15, 16 from the hose legs 17, 18. Other combinations may be used according to the specific requirement, for example a six wire link. A coupling 20 comprising a pair of hollow, cylindrical tubes 19, typically made of a corrosion resistant metal, such as alloy 625, super-duplex or 316L, to match the hose material, is mounted in an opening of the housing 13 at the end remote from the penetrator 14. Each tube further comprises an electrical feedthrough, also functioning as a piston 22, sealed to the inner surface of the tube 19 towards the tube by piston rings 23. The piston rings may comprise an elastomeric material, such as rubber, nitrile, or other elastomers suitable for subsea use. The wire or wires from one hose are connected to an outlet of the penetrator 14 and to a termination on the piston 22. The feedthroughs in the piston 22 connect with wires terminated at the hose end of the piston. The wires of the cable on each side of the moveable piston are sufficiently slack at the termination on each end of the piston, to be able to move with the piston movement without damage. The communication link wires 15, 16 are fed through the pistons, with suitable seals and connected through the penetrator 14 to the sensor electronics. Electrical power and signals to and from the electronics inside the latm chamber 11 is then able to be transmitted to the topside, or other destination and C) appropriately processed for control and monitoring purposes. The cable mounting is loose enough to move with the piston without pulling out, but terminated at each end of the moveable part. There may be multiple wires through one feedthrough, or just a single wire. Typically, there are four wires per feedthrough., but there may be six or even more.

The hose is typically a form of rubber, or elastomer, with metal ends for the hose to join to the tubes 19. When the hose 17, 18 has been deployed subsea, the section of the hose that is beyond the end of the adaptor tubes 19 is exposed to seawater 24, at a higher pressure than atmospheric pressure. Before deployment, the hose is filled with fluid at a pressure above atmospheric pressure, so that even in the event of damage to the hose when deployed subsea, the internal pressure still tends to cause the filling fluid to force its way out, to prevent seawater from entering the hose and damaging the sensitive parts within it. The filling fluid is typically a medium able to provide pressure compensation, in particular, a high dielectric strength fluid, for example, an oil, such as silicone oil. The coupling 20 and electrical feedthrough piston 19 therein provide another barrier to seawater entering the housing 13 and damaging the penetrator 14. Contact of seawater with the material of the penetrator may result in electrical breakdown of the insulation surrounding the pins of the penetrator and consequently, a short circuit across the pins.

As required by the standard, pressure compensation of the fluid volume behind the penetrator, i.e. in the housing 13 on the other side of the penetrator to the sensor electronics 12, is provided by the movement of the piston 22 in the coupling 20 into the fluid filled hose 17, 18 in response to an increase in pressure in the non-pressure compensated housing 13. A reduction in pressure within the housing 13 will result in the piston 14 moving back towards the housing 13, under the effect of the pressure of the fluid within the hose 17, 18. The movement is small, typically less than 25mm, more typically, movement of the electrical feedthrough piston 14 is up to lOmm, depending on the differential pressure between the housing 13 and hose 17, 18.

Fig.3 illustrates an alternative design in which the second hose is replace by a 30 pressure compensation medium in the form of a second housing 25, typically made from the same material as the hose and containing a gas. As the gas is more compressible than the fluid within the first housing 13, an increase in pressure in the first housing 13 causes the piston to compress the gas and move towards the second housing 25. That housing is still subject to pressure from the external seawater, so a reduction in pressure within housing 13 will result in the piston electrical feedthrough moving back towards the housing 13. This design may be used where there is a retrofit in a system with only a single data cable and hose. The coupling 20 may be standardised to fit an opening 21 in the sensor unit housing, but if only one cable exists, the pressure compensation is provided by the second housing 25 for that piston 22, which may be a flexible housing, susceptible to the external water pressure. With a single cable, there is only one oil filled hose as the pressure compensating housing. In another example, the housing 25 may comprise a more rigid material than that of the hose 18, but as the filling is gas, the gas is more compressible than the oil in the housing 13, so the piston is still able to move back and forth in response to pressure changes in the housing 13. A typical gas in this case would be nitrogen. An alternative is to use air.

Without the coupling 20, the direct connection of the hoses 17, 18 to the sensor unit 10 means that a break in one hose would cause all the fluid filling to come out of both hoses 17, 18 eventually. Although pressure compensation, for example by means of bellows, is known for subsea equipment, the present invention provides a simple and effective solution which is easily retrofitted, as well as suitable for building into new products. With a single penetrator 14 in the sensor unit housing 11 and a coupling 20 with two harness outlets 19, pressure compensation of the fluid volume 13 behind the penetrator can be achieved, connecting electrical power and signal to and from the electronics inside the latm chamber 11, without affecting reliability. Any oil filled electrical flying leads used in subsea applications with a redundancy requirement may be connected using both parts of the coupling. In existing installations with only a single electrical flying lead, the coupling may still be used, with an additional housing providing pressure compensation through the second part of the coupling.

In subsea instrument applications which have a dead volume inside a non-compensating housing, the coupling of the present invention may be retrofitted, either where no such compensation was previously available, or in cases where other means of pressure equalizing features cannot be used. The electrical feedthrough piston 22, 23 acts as a diaphragm, separating the dead volume 13 in the sensor unit 10 from the electrical flying lead 15, 16, as well as maintaining equalized pressure conditions for all the sections of the system. In the event of a rupture to one section of the hose 17, 18 of the lead, the pressure equalizing electrical feedthrough coupling functions as a seal between the surrounding environment, typically seawater and the undamaged sections of the system. This avoids the need to have two fixed 4-pin high pressure electrical feedthrough penetrators connected to two individual electrical flying lead adaptors to achieve full electrical redundancy for dual subsea instruments. The pressure compensation works to keep the pressure inside the oil filled void 13 formed by the non-compensating housing at the same pressure as the two flying leads in their hose or umbilical. As the oilfield hoses 17, 18 are flexible the internal pressure is equalized to the surrounding pressure. The equalizing of the hose pressure into the opposing oil filled void 13 is achieved by the piston movement of the two electrical feedthroughs 22.

If there is a rupture in one of the hoses, then the electrical feedthrough 22 functions as a seal towards the external environment and maintains full functionality for the redundant sensor channel, in the example of Fig.2.

The examples have been described for subsea operation, but there may also be some situations where such an adaptor or coupling is useful topside, for example where there is a lot of spray or rainfall and high temperature variations, so that the sensor units need some sort of pressure compensation, but they must also prevent water ingress in so doing.

While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.

The foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention disclosed herein. While the invention has been described with reference to various embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular means, materials, and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may affect numerous modifications thereto and changes may be made without departing from the scope of the invention in its aspects.

It should be noted that the term "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. Elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

CLAMS1 An electrical coupling comprising a pair of hollow cylindrical tubes, each tube comprising an electrical feedthrough piston mounted in the tube and piston rings to moveably seal the piston to the tube; wherein each tube of the coupling is adapted to be fitted to a first housing common to the pair of hollow cylindrical tubes; wherein at least one of the pair of hollow tubes of the coupling is adapted to be coupled to a second housing, a cable or umbilical; and wherein the other of the pair of hollow cylindrical tubes is adapted to be coupled to a cable or umbilical; wherein the first housing comprises a fluid filled, non-pressure compensated housing; wherein the second housing comprises a gas filled housing; and wherein the cable or umbilical is fluid filled and pressure compensating.
2. An electrical system comprising an electronics chamber, a first housing connected to the electronics chamber; at least one of a second housing, cable or umbilical coupled by a coupling according to claim 1 to the first housing; and at least one of a cable or umbilical coupled by the coupling to the first housing.
3. A system according to claim 2, wherein the coupling is coupled to two cables or 20 umbilicals.
4. A system according to claim 2 or claim 3, wherein the cable or umbilical comprises an electrical flying lead.
5. A system according to any of claims 2 to 4, wherein the cable or umbilical comprises a communication or data carrying medium, or wire.
6. A system according to any of claims 2 to 5, wherein the gas in the second housing comprises nitrogen or air.
7. A system according to any of claims 2 to 6, wherein the fluid in the first housing, cable or umbilical comprises high dielectric strength oil, in particular silicon oil.
8. A system according to any of claims 2 to 7, wherein a penetrator is mounted between the first housing and the electronics chamber.
9. A system according to any of claims 2 to 8, the system comprising a sensor system and the electronics chamber comprising a sensor electronics chamber.