GB2152769A - Electrical subsea connector - Google Patents

Abstract

An electrical subsea connector capable of being connected and disconnected underwater comprises at least two connectable/disconnectable insulating bodies (1, 2) each provided with at least one electrical conductor (5, 6, 9, 10), the conductors in the two bodies facing each other in use. A porous non-corroding material (e.g. tissue paper, glassfibre or microporous polymer) is located between the conducing surfaces allowing the passage of electrolyte (sea water) therebetween. The connector is resistant to corrosion. <IMAGE>

Description

SPECIFICATION Subsea electrical connectors A serious problem exists for subsea remotely operated installations such as satellite oil or gas wells.

This relatestothe need for underwater electrical connectors ie a plug and socket which allows electrical power or signals to be connected and disconnected from a cable. It is impracticable to have a cable permanently connected to subsea equipment. This would make both installation and removal of equipmentwith an attached cable impossible.

It is also known that sea water is corrosive and electrically conductive such that any leakage into a conventional plug and socket would cause failure.

Some commercially available devices go to great lengths to exclude sea water from the electrical contacts. Conventional connectors must be mated on the surface in dry air and cannot be disconnected and reconnected subsea satisfactorily. Other known connectors use insulating oil or gel to try to exclude sea water. They are expensive and require special seals, equalising chambers, and very careful installation to be effective. It is importantto be ableto make and break a connector "wet" underwater. It is of even greater advantage if thins operation can be effected remotely without diver or submarine vehicle assistance. Diverless electrical connectors do exist but they are very complicated, expensive and must be operated under stringent conditions.

It is the purpose ofthis invention to overcome the above limitations by adopting a simplified approach.

Instead of resorting to complicated methods to exclude the sea waterthe device makes use ofthe conductive properties of sea water.

According to the present inventions an electrical subsea connector capable of being connected and disconnected underwater comprises (a) at leasttwo insulating bodiescapableofbeing connected and disconnected to one another each containing (b) at least one electrical conductor extending to form a conducting surface on the body, the bodies being so shaped that when connected the said conducting surface on one body faces the said surface on another body and (c) a non-corroding material located between the two conducting surfaces and in contact with them, said non-corroding material having pores capable of allowing the passage of an electrolyte between the two conducting surfaces.

It is believed that by providing pores in the porous material communicating between the conducting surfaces a good electrical path across the connector can be provided by sea water entering the pores.

The electrical conductors extending to form a conducting surfaceonthe insulating body are generally metallic conductors, typically copper. Such metal lic conductors when used to carry pass a current through sea water suffer extensive corrosion. However in the connector according to the present invention the products of electrolysis of sea watertaking place at the conducting surfaces appear two be retained in the porous material thus reducing the rate of corrosion of the conducting surfaces. Deposition of electrolysis products in the pores may increase the conductivity and assist in obtaining good electrical contact. Typically, when using copper conductors, this deposition produces spongy copper retained in the pores.

The porous material may be a non-conductor of electricity, so that conduction takes place solely as a result ofthe passage of ions through electrolyte (sea water) in the pores together with any conduction which may be due to deposition of electrolysis products in the pores. Alternatively, the porous material may be a conductor such as may be obtained by using an organic polymer filled with carbon black.

Any such porous material will have a low conductivity in comparison with copper butthis is in general desirable as leakage currents are reduced.

The porous material whether conducting or nonconductive must not corrode in sea-waterunderthe conditions found in the connector. Forthis reason a porous copper sponge would not be satisfactory as the porous material.

The porous material is preferably compliant.

By "compliant" we mean thatthe material adapts to any irregularities in the surfaces ofthe conducting surfaces brought into contact with itso as to ensure good physical contact between the porous material and the conducting surfaces.

The porosity may resultfrom a fibrous structure as in paper or may be due to the presence of a cellular structure containing substantial proportion of open cells as in some polymerfoams.

The conducting surfaces may be within depressions or cavities in those parts ofthe insulating bodies which are brought into contact when making the connection and the porous material may be in the form of plugs or inserts within said depressions or cavities.

Howeverthe contact resistance across the connector will increase as the thickness of the porous non-conducting material is increased. It is therefore preferred to use a layer of material between the conducting surfaces which layer is as thin as possible.

Preferably the conducting surfaces are so shaped so asto be mating surfaces in the absence ofthe porous material and the porous material is present as a compliant membrane.

The pores communicating across the porous nonconducting material may be pores extending substan tiallyonly in one direction.

Such anisotropic properties may be obtained by the compaction and bonding together lengthwise of non-conducting fibres.

The preferred porous materials are those with a fibrous structure.

However the porous material may be a plastics foam material containing a substantial proportion of open cells.

As indicated above, the porous material is preferably compliant and the connector is preferably The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy.

designed to place the porous material undercom- pression when the connector is in the connected state to ensure good physical contact between the porous material and the conducting surfaces.

Examplesofsuitable porous non-conducting materialsfor use in the present invention are tissue paper, glass fibre sheets microporous polymer membrane.

If more than one electrical contact is to be provided bythe connector it is desirable to design the conductor so thatthe leakage of currentfrom one set of conducting surfaces to the other is kept to a minimum.

Where individual inserts of porous material are provided between pairs of conducting surfaces, the connector may be so designed so that the passage of sea waterfrom one pair of conducting surfaces to another is deterred. In the preferred method of carrying outthe invention connection between a plurality of pairs of conducting surfaces is obtained by means of a porous membrane sandwiched between two flat mating insulating surfaces in which the conducting surfaces are embedded. By using a relatively thin membrane the leakage resistance across the connectorwill be minimised.

The invention will now be illustrated by reference to the accompanying drawings in which Figure lisa cross sectional diagrammaticview of an embodiment ofthe invention, and Figure 2 is a plan view ofthe lower part of the connector with the top part removed.

The connector consists of top and bottom insulating bodies (1,2) having mating flat faces (3,4). Embedded in body lisa copper ring (5) and a copper disc (6).

Wires (7,8) connectthe copper disc to an external source of A.C. current (not shown).

A corresponding ring (9) and disc (10) is provided in body (2). Wires (11,12) connect the disc and ring with an electric load shown diagrammatically at (13). A porous membrane made from fibrous material (tissue paper) is located between surfaces (3) and (4).

The membrane extendstothe outside edge ofthe connectorso that when the connector is immersed in sea waterthe pores will be filled with sea water.

Means may be provided (not shown) to holdthetwo bodies together. These may be made easily releasable so that connection and disconnection underwater, if necessary by remote control, is simple and uncomplicated and effected by conventional guide wire techniques.

In use the connector described above gave a good electrical connection when immersed in sea water.

The leakage currentwas small (less than 2%). The water remained clear.

Corrosion of the copper conducting surfaces was very much smallerthan would be expected. A ring of spongy copperformed is the membrane area adjacent to the conducting surfaces. This greatly assists the formation of a good electrical contact.

Comparative TestA When a connectorwastested as above without the porous membrane, the water became discoloured as a result of the formation of corrosion products and their release into the water surrounding the connector.

Claims (7)

1. An electrical subsea connector capable of being connected and disconnected underwater which com prises: (a) at least two insulating bodies capable of being connected and disconnected to one another, each containing (b) at least one electrical conductor extending to form a conducting surface on the body, the bodies being so shaped that when connected the said conducting surface on one body faces the said surface on another body and (c) a porous non-corroding materiaHocated be- tween the two conducting surfaces and in contact with them, said non-corroding material having pores capable of allowing the passage of an electrolyte between the two conducting surfaces.

2. A connector according to claim 1 wherein the porous material is a non-conductor of electricity.

3. A connector according to either one ofthe preceding claims wherein the porous material is compliant.

4. A connector according to any one of the preceding claims wherein the porous material has a fibrous structure.

5. A connector according to any one of the preceding claims wherein the porous material is in the form of a membrane located between mating conducting surfaces.

6. A connector according to claim 5 wherein the membrane is located between two flat mating insulating surfaces in which the conducting surfaces are embedded.

7. A connector according to any one ofthe preceding claims wherein a first pair of facing conducting surfaces is surrounded by a second pair of facing annular conducting surfaces.