GB2606006A

GB2606006A - Subsea penetrator

Info

Publication number: GB2606006A
Application number: GB2105730.2A
Authority: GB
Inventors: Crichton Alan
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2022-10-26
Also published as: GB202105730D0

Abstract

An electrical penetrator (1) suitable for a subsea environment is disclosed. The penetrator (1) comprises an electrically conducting conductor core (3), a pair of electrically insulating insulator bodies (5) axially spaced apart from one another and mounted radially outwardly of the conductor core (3), and a seal body (4) mounted to the conductor core between the two insulator bodies (5) and axially spaced therefrom. The penetrator (1) further comprises a penetrator housing (2) and first and second chambers (8) formed by the penetrator housing (2) between the seal body (4) and the insulator bodies (5). The seal body (4) comprises an inorganic pressure seal and at least one of the chambers (8) contains a set, compressed, filler (figure 3, 16). The filler (figure 3, 16) may be a silicone filler. The insulator bodies (5) may comprise a polymer or a polymeric material, in particular polyether ether ketone. A method of assembling an electrical penetrator (1) is also disclosed. The filling method may comprise vacuum filling or a displacement filling process.

Description

SUBSEA PENETRATOR

This invention relates to a subsea, or underwater, penetrator and a method of assembling the penetrator.

Subsea, or underwater, penetrators are designed to operate beneath the surface of the water. Subsea penetrators have various applications including power, control and instrumentation. Penetrators typically comprise a number of different materials, each of which may have different properties and responses when subjected to subsea pressure or in response to temperature changes when deployed. The effect of these differences may reduce lifetime, or reliability, of the penetrator. Thus, an improved subsea penetrator is desirable In accordance with a first aspect of the present invention, a method of assembling an electrical penetrator comprises mounting a seal body to a conductor core; and mounting the combination of seal body and conductor core in a cavity in a penetrator housing; sealing the conductor core to the housing with the seal body; mounting a first electrically insulating insulator body to one side of the electrically conducting conductor core; and mounting a second electrically insulating insulator body to another side of the conductor core; such that the seal body is mounted between the first and second insulator bodies and axially spaced therefrom on the conductor core; wherein first and second chambers are formed by the penetrator housing, between the seal body and each of the first and second insulator bodies; filling each of the first and second chambers with a filler through an aperture formed between the first or the second insulator body and the conductor core, allowing the filler to set, and applying pressure to compress the filler.

Applying compression to pre-load the filler compensates for potential delamination or air gaps formed due to the filler material relaxing over time Preloading the filler may also improve its electrical performance The pressure may be applied by a retaining plate which stays in place, with a pre-load pressure acting on the silicone and in turn on the mating surfaces, or components.

The filler may comprise a compliant material, in particular one of a silicone rubber, a gel, oil, elastomeric or polymeric material.

The compliant filler fills the chamber free of voids or entrapped air and is compliant enough to at least partially deform under loading or pressure The filling may comprise one of a vacuum filling, or a displacement filling process.

The seal body may comprise an inorganic material The seal body may be sealed to the penetrator housing by heating the seal body to at temperature at which the seal melts and allowing the seal to cool.

The method may further comprise, prior to assembling the insulator bodies to the conducting core, etching, moulding, or machining sections of the body to have a reduced circumference, then applying an electrically conducting conductor layer in those sections to return the circumference to its original thickness.

The insulating bodies may be kept free of conductor layer at their ends nearest to the seal body, when assembled The method of applying pressure may comprise fitting a retaining plate over a shoulder formed in insulating body and applying a predetermined force to the plate.

The mechanical force may be applied by tightening screws holding the retaining plate to the housing.

In accordance with a second aspect of the present invention, an electrical penetrator comprises an electrically conducting conductor core; a pair of electrically insulating insulator bodies axially spaced apart from one another and mounted radially outwardly of the conductor core; and a seal body mounted to the conductor core between the two insulator bodies and axially spaced therefrom; the penetrator further comprising a penetrator housing and first and second chambers formed by the penetrator housing between the seal body and the insulator bodies; wherein the seal body comprises an inorganic pressure seal and at least one of the chambers contains a set, compressed, filler.

The filler may be a silicone filler.

The insulator bodies may be at least partially encased in an electrically conducting conductor layer.

This provides earth continuity from the housing and electrical stress control by eliminating non-uniformity of the insulation surface caused by air pockets in the insulator.

The conductor layer may comprise a metal, in particular nickel.

The conductor layer may be applied by plating, spraying, or vapour deposition.

The insulator may comprise a polymer or polymeric material, in particular polyether ether ketone.

The penetrator may further comprise one or more seals between an outer surface of the conductor layer on the insulator body and an inner surface of the penetrator housing.

This prevents the filler from escaping from the chamber during the fill process, before the filler sets, or when pressure is applied An example of a subsea penetrator and associated method of assembly in accordance with the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a section through an example of a subsea penetrator according to the present invention; Figure 2 shows an end view of the penetrator of Fig. 1 Figure 3 shows more detail of the penetrator of Fig.1; and, Figure 4 is a flow diagram illustrating a method of assembling a subsea penetrator according to the invention.

The drive to reduce overall lifecycle costs, both capital expenditure (CAPEX) and operational expenditure (OPEX), associated with new deep-water oil and gas developments means that improvements to existing designs, manufacturing processes and operation are desirable. Subsea penetrators that have reduced maintenance requirements, or need for intervention, are desirable.

One aspect of penetrator design which may affect reliability is the extent to which electrical breakdown is successfully mitigated. Electrical penetrators for use in medium or high voltage power applications, or for deployment subsea in deep water and subject to high pressure use insulating materials to separate or isolate an electrical conductor from the body in which it is mounted. Power is transmitted through a wall or bulkhead in which the penetrator is fitted via the conductor, but the insulating material may be subject to electrical breakdown due to electrical stresses caused by electric fields generated by the power flow through the conductor. Thus, the insulating materials are chosen to have a relatively high breakdown strengths, for such applications. The breakdown strength of air is low, so trapped air or air gaps need to be avoided. A commonly used method is to fill these gaps by using filling materials such as silicone rubbers. However, delamination may occur at joining surfaces, due to factors such as material relaxation, or expansion or contraction due to differences in material coefficient of thermal expansion (CTE). Even if formed without air gaps, this relaxation, or differential expansion or contraction may result in an air gap being formed after deployment. If the air gap is subjected to a sufficiently high stress, this may result in electrical breakdown or partial discharge (PD). Conventionally, the insulation has been provided by overmoulding or casting epoxy or other materials directly onto the conductor core pin.

The present invention aims to reduce or eliminate the partial discharge effects of this delamination or air gap formation by compressing a filler material in its ambient state on critical surfaces. Another benefit of compressing the seals is that electrical performance, or breakdown strength, of elastomeric materials is improved by the application of pressure.

Figs.I to 3 illustrate an example of a penetrator according to the invention The penetrator 1 comprises a housing 2, a conductor core 3, or conductor rod and an inorganic seal body 4. The penetrator provides a primary barrier between seawater and other fluids. The conductor core 3 comprises an electrically conducting material, such as a metal, for example nickel, copper or copper alloys. These may be plated with silver or gold for increased electrical conductivity and/or to provide enhanced corrosion resistance. The inorganic seal body 4 may comprise a glass or ceramic material. The seal body 4 advantageously comprises a hot formed seal which seals the housing 2 to the conducting core 3. An insulator body 5, in the form of a sleeve, typically a cylindrical sleeve, is mounted towards each end of the conductor, axially spaced from the ends of the conductor and axially spaced from the seal body 4. The insulator comprises a solid material, such as a polymer, for example polyether ether ketone (PEEK). The spacing of one end of the insulator body 5 from the seal body 4 allows a void or chamber 8 to be formed, between the seal body and the end of insulator body, by the housing 2 in combination with the insulators 5 and the seal body 4. The housing may have a section 11 of increased thickness immediately surrounding the insulators 5 and seal 4, as well as a section 12 of reduced thickness further from the penetrator 1.

Fig.2 shows an end view, with the conductor core 3 in the centre, insulator 5 radially outward of the conductor core and an end plate, or retaining plate, 9. The housing sections 11, 12 of increased and reduced thickness are radially outward of the other parts. Each insulator body 5 is provided with electrical stress control in the form of a conductive layer 6 (which can be seen in more detail in Fig.3) around a substantial part of the insulation body. The conductor layer 6 may comprise a metal layer, such as nickel, applied by plating, vapour deposition, or other suitable method. The conductive layer is applied as illustrated in Fig.3, leaving an end 13 closest to the seal body 4 exposed (without any conducting layer) as well as a short mid-section 7. In order to achieve a substantially uniform surface of the cylindrical sleeve, with the insulator outer surface and conductor layer flush, the insulator may be machined, or moulded to have a reduced circumference in the sections that are to receive the conductor layer.

When assembled in the housing 2, the void or air gap 8 formed between the seal body 4 and the insulator body 5 is filled with an insulative compliant filler 16, such as silicone rubber. One or more seals may be provided between a circumferential section of the conductive layer 6 on the insulator body 5, closest to the seal body 4 and the housing 2. For example, the, or each, seal may comprise 0 seals. These seals 14 retain the compliant filler 16 in situ whilst it sets. The retaining plate 9 engages with a shoulder 15 of the plated insulator body. Screws from the retaining plate fit into the housing body and can be tensioned to apply a predetermined amount of force to the insulator and thence onto the set compliant filler. The compression of the compliant filler 16 on the spherical surface of the seal body 4, the conductor rod 3 and the un-plated radiused face of the insulation body by use of the retaining plate 9, pre-loaded to a defined force by use of screws and washers, improves the performance and reliability of the penetrator. The compression or pre-load compensates for potential delamination, air gap formation, as a result of material relaxation, or expansion or contraction as an effect of temperature, due to differences in material CTEs etc. Preloading the compliant filler also increases its electrical performance. The penetrator 1 when assembled may comprise a self-contained subassembly for insertion into a wall or flange or bulkhead of subsea equipment, such as a pump or drive.

The example illustrated in Figs. 1 to 3 is for a single conductor core penetrator.

However, a similar arrangement for a multiple core penetrator may be used. The multiple conductor cores may have individual inorganic seals for each conductor core, arranged as a pattern of holes in the bulkhead, or multiple conductor cores may be housed in a common housing with multiple through-holes, the housing itself having an inorganic seal to the bulkhead into which the penetrator is inserted. Fig.4 illustrates an example of a method of assembling a penetrator according to the invention. Suitable insulator bodies 5 are prepared 30, for example by machining to shape and then providing a conducting layer over selected sections of the insulator body, for example by plating, spraying, or vapour deposition. The penetrator housing, conductor cores and inorganic seal are prepared 31. The seal body 4 is pre-formed and loosely assembled in the housing 2, along with the conductor core 3, in most cases, substantially at a mid-point axially along the conductor core. The housing, conductor core pin 3 and pre-formed seal body 4 are positionally aligned and retained in position as the whole sub-assembly is heated 32 to a temperature at which the inorganic material of the seal melts and then is allowed to cool to ambient temperature, forming an inorganic seal between the housing 2 and conductor core upon cooling. The insulation sleeves are fitted 33 and held in situ to form an internal chamber or void 8. Suitable elastomeric seals, such as 0-ring seals are fitted between the housing 2 and the outer conductive surface of the insulation sleeve 6.

The internal chamber or void is then filled 34 with the compliant filler, for example an elastomeric or rubber compliant filler, such as silicone rubber. This filler both evacuates the air from the void and maintains the position of the insulation sleeve 5, as the compliant filler sets. Retaining plates are fitted 35. After the filler has set, which may be several hours, the retaining plate 9 which holds the insulation sleeve in place, is used to compress 35 the insulation body 5 onto the compliant filler and the seal body, using screws 10. By filling the internal void 8 with compliant filler, free of entrapped air, partial discharge effects can be reduced or prevented. Compressing, or pre-loading, the filler allows the filler to go through thermal and/or pressure cycling, whilst maintaining intimate surface contact with the components around it. Simply allowing the filler to set in its natural state, without any preloading, would allow the surfaces to move apart when subjected to temperature changes, due to the different thermal expansion coefficients of the materials from which each component is made.

The example described is applicable to various products, for example, a subsea pump. For a subsea pump, the relatively low pressure side at seawater or depth pressure, is typically about 400 Bar and the relatively high pressure side is the pump interface at about 1034 Bar. However, the penetrator has many other uses, such as for passing communication or power through a hull or bulkhead of a diving bells, subsea transformer, variable speed drive, or other subsea equipment. The penetrator may need to operate at pressures over a wide range, from low to high pressures, for example from 1 bar up to 1861 bar, or at any value in between.

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

CLAIMS1 A method of assembling an electrical penetrator, the method comprising mounting a seal body to a conductor core; and mounting the combination of seal body and conductor core in a cavity in a penetrator housing; sealing the conductor core to the housing with the seal body; mounting a first electrically insulating insulator body to one side of the electrically conducting conductor core, and mounting a second electrically insulating insulator body to another side of the conductor core; such that the seal body is mounted between the first and second insulator bodies and axially spaced therefrom on the conductor core; wherein first and second chambers are formed by the penetrator housing, between the seal body and each of the first and second insulator bodies, filling each of the first and second chambers with a filler through an aperture formed between the first or the second insulator body and the conductor core; allowing the filler to set; and applying pressure to compress the filler.
2. A method according to claim 1, wherein the filler comprises a compliant material, in particular one of a silicone rubber, a gel, oil, elastomeric or polymeric material.
3. A method according to claim 1 or claim 2, wherein the filling comprises one of a vacuum filling, or a displacement filling process.
4. A method according to any preceding claim, wherein the seal body comprises an inorganic material.
5. A method according to any preceding claim, wherein the seal body is sealed to the penetrator housing by heating the seal body to at temperature at which the seal melts and allowing the seal to cool.
6. A method according to any preceding claim, wherein the method further comprises, prior to assembling the insulator bodies to the conducting core, etching, moulding, or machining sections of the body to have a reduced circumference, then applying an electrically conducting conductor layer in those sections to return the circumference to its original thickness
7. A method according to any preceding claim, wherein the insulating bodies are kept free of conductor layer at their ends nearest to the seal body, when assembled.
8. A method according to any preceding claim, wherein the method of applying pressure comprises fitting a retaining plate over a shoulder formed in insulating body and applying a predetermined force to the plate.
9. A method according to claim 8, wherein mechanical force is applied by tightening screws holding the retaining plate to the housing.
10. An electrical penetrator comprising an electrically conducting conductor core; a pair of electrically insulating insulator bodies axially spaced apart from one another and mounted radially outwardly of the conductor core; and a seal body mounted to the conductor core between the two insulator bodies and axially spaced therefrom; the penetrator further comprising a penetrator housing and first and second chambers formed by the penetrator housing between the seal body and the insulator bodies; wherein the seal body comprises an inorganic pressure seal and at least one of the chambers contains a set, compressed, filler.
11. A penetrator according to claim 10, wherein the filler is a silicone filler.
12. A penetrator according to claim 10 or claim H, wherein the insulator bodies are at least partially encased in an electrically conducting conductor layer.
13. A penetrator according to claim 12, wherein the conductor layer comprises a metal, in particular nickel.
14. A penetrator according to claim 12 or claim 13, wherein the conductor layer is applied by plating, spraying, or vapour deposition.
I0A penetrator according to any of claims 10 to 14, wherein the insulator of the insulating bodies comprises a polymer or polymeric material, in particular polyether ether ketone
16. A penetrator according to any of claims 10 to 15, wherein the penetrator further comprises one or more seals between an outer surface of the conductor layer on the insulator body and an inner surface of the penetrator housing.