GB2124038A - Improvements in sealed connections and cable terminations for underwater insulated conductors - Google Patents

Abstract

A connection for connecting cables 3, 4 under water includes a steel housing 1. A seal includes a gland seal 10 with an integral flexible impervious cylindrical boot 11. The boot is supported by a sleeve 6 and retained in a groove 7 therein. After assembly the cavity 22 is filled with a substantially incompressible compound via filler hole 20. A drilling 9 through the housing and sleeve allows external pressure to be communicated to the flexible wall of the boot and thence to the incompressible compound thereby reducing the pressure gradient across the seal and reducing the risk of leakage <IMAGE>

Description

SPECIFICATION Improvements in sealed connections and cable terminations for underwater insulated conductors This invention relates to connections for underwater insulated conductors particularly where a housing of the connection may experience large variations in external pressure and where it is necessary to prevent the external environment from penetrating the connection.

When dealing with electric cables under water it is desirable to be able to make in-line cable-to-cable connections, to make connections between sheathed cables and oil filled conduits, and to make connections through the walls of vessels. These walls may be the hulls of ships or oil rigs, or the walls of diving bells, or the walls of instrument cases, for example.

In this specification the term "splice" will be used to refer to in-line cable connections and the term "penetrator" will be used to describe vessel wall or bulkhead or similar connections. Splices and penetrators are usually intended to be permanent. Other connections, referred to as "connectors", may be intended to be easily disconnectable and reconnectable.

The connections must be resistant to water, especially sea water, and must prevent the water from reaching the conductors, which might then be subject to short circuits or at least corrosion.

It is known in this respect to cover the cables in the immediate region of the connection housing with a heat shrunk or moulded sheath or similar cover in order to increase the conduction path length and so reduce the possibility of a short circuit should the connection leak.

A watertight seal in a connection must not only prevent the ingress of water but must also be able to withstand substantial variations in pressure across its sealing surfaces. A cable splice will for example be assembled above the surface of the water and subsequently be allowed to sink to depths where it will be subject to large external pressures. The seal must remain good at all times. Further, a penetrator may experience reversal of the pressure gradient across the connection. For example across the wall of a diving bell there are, while diving, large external pressures due to the depth, but after the bell is recovered and for the duration of the decompression of the divers in the bell the helium based atmosphere within is at a greater pressure than the atmosphere outside.The problem is particularly acute as helium will penetrate and escape through any surface not thoroughly sealed.

It is known to effect a seal around a splice or in a penetrator by encapsulating all connections in a solid resin which preferably includes a length of the sheathed conductor in order to increase the conduction path length should any leak occur and any water penetrate the connection. It is also known to mould a resilient external sheath around the connection and the cable where it joins the connection to prevent the ingress of water.

However, such an arrangement has to be prepared in a strictly controlled environment, since the materials most suited to form the external sheath of a subsea cable, e.g. polythene, are difficult to bond to. The repair of such connections is therefore difficult to effect as the encapsulation makes the conductors inaccessible and the moulded sheaths make the reforming of a sealed connection a task for specialists with bulky equipment. The problem is particularly acute on, for example, an offshore oil rig, where a doubtful or damaged connection must be replaced, and may hold up production while the personnel and equipment needed to make repairs are flown in. This is time consuming and expensive.

Further, safety regulations require that the conductors of a connection may not be subject to excessive heat, which may damage the components of the connection which effect the seal. This means that joints may not readily be soldered by unskilled personnel in known connections.

An object of this invention is to provide a connection with a seal which provides good isolation of a conductor from the external environment and is effective through a broad range of external pressures.

A further object of the invention is to provide a connection which may be easily disassembled and reassembled on site by unskilled personnel but will still maintain a good seal in use.

A further object of this invention is to provide a connection which is flexible in application and can for example be used with sealing inserts which allow different environments to exist each side of the connection with no through leakage, which maintain the seal when from time to time the pressure gradient across the connection may be reversed, and which may allow the connections to be disconnected and reconnected.

According to the invention there is provided a connection for one or more insulated conductors comprising a housing having a passage therein for receiving a prepared end of the conductor(s) to be connected, seal means arranged to be positioned around said conductor(s) and within said passage, means for filling said connection with a substantially incompres-sible compound so that the compound is in pressure-transmitting relation to the seal means, and means for communicating the pressure external of the connection, to which pressure one side of the seal means may be exposed, to the compound within the connection and thence to the other side of the seal means.

The pressures on each side of the seal means may thus be made substantially equal so that there is no pressure gradient across the seal means to encourage leaking; alternatively a pressure amplifying arrangement may be used to ensure that the pressure in the incompressible compound is maintained at a higher pressure than the external pressure thereby providing a pressure gradient which opposes leakage through the seal means.

In a preferred embodiment, the seal means comprises a gland seal with an integral impervious cylindrical boot. The end of the boot is sealed to the housing and the cavity within the boot is filled with the incompressible compound. The external pressure is transmitted to the compound through a passage or drilling in the wall of the housing and thence through the flexible wall of the boot.

Preferably the incompressible compound is a gel which may be easily detached from the region of the conductors for disassembly.

The seal means is preferably a gland seal held by a threaded retainer nut in the passage. The nut may be adjustable in the passage to exert the required pressure on the seal and, when located, the nut may offer an abutment against which to locate and fix a clamping means for the insulated conductors.

The insulated conductors are preferably electrical cables, but may be electrical conductors in an oil filled conduit or optical cables.

The connection may also include a substantially rigid insert adapted to locate or receive onr or more '0' rings to seal the insert to the housing. Preferably two '0' rings are used and preferably conductors extend along the length of the insert. The use of such a separate insert facilitates reconnection without breaking any other seals, which may, for example, include use of the incompressible compound.

The invention may be applied to many types of underwater connections, such as those intended to be permanent or semipermanent and those intended to be disconnectable and reconnectable.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a cable splice according to one embodiment of the present invention .

Figure 2 is a sectional view of a penetrator according to one embodiment of the present invention.

Figure 3 is a sectional view of a multiple cable splice according to one embodiment of the present invention.

Figure 4 is a sectional view of a penetrator with demountable connections according to one embodiment of the present invention.

Figure 5 is a sectional view of a connector according to the invention.

Figure 6 is a sectional view of a gland seal arrangement including a pressure amplifier according to one embodiment of the present invention.

In the embodiment of Fig. 1 a splice has a cylindrical outer case or housing 1 of steel which houses a joint 2 between two cables 3, 4 which may be crimped or soldered or similarly joined.

A ridge or flange 5 abuts and locates a seal boot sleeve 6 within the passage. The seal boot sleeve 6 of aluminium bronze or black acetal is of circular cross-section and a groove 7 is provided adjacent and around the internal periphery of the sleeve 6 to abut the flange 5 as shown in Fig. 1. The outer surface of the sleeve 6 is shaped to follow and abut the internal shape of the housing 1. A passage 8 extends through the sleeve 6 and communicates with a passage 9 which extends through the housing 1. The sleeve broadens to the left of the passage 9 to where it abuts a gland seal 10.

A flexible seal boot 11 of circular cross section is shaped to follow the contoured inner surface of the seal boot sleeve 6. On assembly, it engages the groove 7, being retained therein by flange 5, and is located adjacent the inner surface of sleeve 6 as shown in Fig. 1.

Gland seal 10 is generally annular and contacts both the cable sheath 12 and the inside wall of the housing 1. It is located against one end of the seal boot sleeve 6 and has a tapered portion abutting a correspondingly tapered seal compression washer 13. At the left-hand end of the joint 2 the gland seal 10 and the seal boot 11 are integral. They are preferably formed from a resilient elastomeric material, e.g. monothane.

The washer 13 is formed e.g. of aluminium bronze or black acetyl and fits between the cable sheath 1 2 and the internal wall of the housing 1, which align it with seal 10. The longitudinally outer surface of the washer 1 3 is flat and is engaged by a rigid seal compression nut 14.

An internal thread 1 5 is provided in the passage and the seal compression nut 14 is screwed into the passage with the aid of a tool which engages keying holes 1 6 to effect turning.

As it is inserted, the nut 14 forces the seal compression washer 1 3 to engage the gland seal 10, and the seal boot 11, seal boot sleeve 6 and gland seal 10 become fixed against the ridge 5 and the inner wall of the housing 1.

As the nut 14 is tightened the gland seal 10 is forced against the flat end surface of seal boot sleeve 6 and tends to extrude radially, thereby gripping both the cable sheath 1 2 and the internal wall of the housing 1. By adjusting the nut 14 to a predetermined tension the gland seal 10 forms a watertight seal against both the cable sheath 1 2 and the internal wall of the housing 1.

A collet clamping nut 1 7 and cable clamping collets 1 8 are provided outside of the seal formed by gland seal 10. Clamping collets 18 are rigid sections tapered to match the angled inner surface of the collet clamping nut 1 7.

The collets 18 are also provided with a series of ridges on their inner surfaces to engage the cable 4, when collet clamping nut 1 7 is tightened and no longitudinal movement against the fixed seal compression nut 1 4 is available. The collet clamping nut 1 7 is tapered at its outer end in order to facilitate cable movement relative to the housing, and to reduce the risk of damage to the cable at its point of entry to the housing. The collet clamping nut 1 7 is provided with spanner flats to facilitate assembly and dissassembly of the cable gripping parts 1 7, 1 8.

Similar sealing and gripping arrangements are provided around the cable 3, but the gland seal 10' abuts a seal back-up ring 1 9 which is located on the corresponding side of flange 5, thereby supporting the gland seal 10 when it is put under pressure to effect sealing.

Filling passages 20 are provided in the housing 1, and may be plugged by suitable plugs 21. Through a passage 20 a compound is introduced to completely fill the cavity 22 between the joints 2, the housing 1, component parts of the sealing arrangement and the sheathed ends of the cables 3,4. The compound is liquid or gel-like and substantially incompressible and will therefore communicate a pressure exerted at one of its faces to all other of its faces. Once the compound fills the cavity 22 and is free from air bubbles the plug 21 is replaced and secured to retain the compound. A second passage is employed in the opposite wall of the housing to facilitate the exit of the air so displaced. The compound sets in about one hour to form an incompressible gel.However, the gel does not form a rigid encapsulation and once is has set it may easily be torn or cut away from the joints if the splice is disassembled.

The joints 2 and a portion of each sheathed conductor are covered by a sleeve in order to increase the conduction path length in case any foreign materials tend to facilitate conduction in the gel.

For use the splice is assembled by passing the housing 1 over one prepared cable-end with the gripping and sealing component parts in the appropriate order. The gripping and sealing components for a second cable are passed onto the prepared end of that cable in the appropriate order.

The joint is made, e.g. by crimping or by soldering, and the housing is located over the joint. The sealing component parts are fixed into the housing and tightened to effect the seals and to locate the cable.

The gripping components are then fixed in the housing and tightened against the seal compression nut 1 4 to grip and fix the cable.

The incompressible compound is then carefully introduced through a passage 20 into the cavity 22 avoiding the inclusion of air bubbles and kept there by a plug 21. If the compound is to form a gel, a suitable time must elapse before the splice is put into use.

In use, as the external pressure increases the pressure across the gland seal 10 might be expected to increase and the greater the pressure gradient across it, the more likely the seal would be to break down i.e. allow the passage of water.

However, in the present invention, as the external pressure increases, thereby increasing the pressure outside of the seal 10, the external pressure is also communicated to the boot seal 11 through passages 8 and 9. The pressure will be transferred through the boot seal 11 and the incompressible compound in cavity 22. The external pressure is thus communicated through the incompressible compound to the inside of seal 10 thereby reducing the pressure gradient which might otherwise tend to force water past the seal.

If, during assembly, any air bubbles or compressible foreign material become lodged in the cavity 22 and so also in the incompressible compound, the compound will when under pressure move to compress the inclusion thereby reducing the volume with which it occupies the cavity while itself not changing in volume. The boot seal 11, by the action of the external pressure, will follow this movement until all the voids have been filled and a small volume of water will be drawn along passages 8 and 9. The pressure exerted on and by the incompressible compound will be communicated to the internal side of the gland seal 10 and will remain subtantially equal to the external pressure.

This arrangement ensures that even if the cavity 22 is not completely filled by the incompressible compound the equalising effect it has on the pressure gradient across the gland seal 10 will still be maintained. This affords some protection from careless assembly by unskilled personnel.

There is also protection against the ingress of water which might otherwise have bypassed the gland seal 10. If, for example, there is a break in the cable sheath, outside the splice, water might penetrate the interstices of the cable and as a result of both the external pressure and capillary action might bypass the seal and enter the cavity 22.

However, with the present invention there is no pressure gradient to encourage the water to move along the cable and it will tend to reach and maintain a static position in the cable due only to capillary action.

If a cable becomes badly damaged, replacement may be easily effected by dismantling the splice in the reverse order to that in which it was assembled and finally moving the housing to one side of the joints, pulling or cutting away the incompressible compound, which in the form of a gel is easily removed.

Instead of a gel a fluid e.g. oil could be used as the incompressible compound. This could be introduced, as with the gel, after assembly of the splice through passage 20, and retained in place by plug 21.

The cable may comprise optical conductors and the joint effected accordingly, but sealed in the splice in a similar manner as that for the aforementioned electrical connection.

In the embodiment of Fig. 2, a penetrator is shown to comprise a steel housing, generally indicated by the reference numeral 23, adapted to accomodate a joint 2 between the conductors of a cable 3 and the conductors 24 of an insert 25.

The housing 23 comprises a cylindrical portion 26 and a mounting flange 27. An internal passage extends through the housing 23 and is adapted to receive the cable 3, and to accomodate sealing and retaining means as already described with reference to Fig. 1 The mounting flange 27 comprises holes 28 which are adapted to receive bolts 29 for fixing housing 23 to the wall 30. The wall 30 comprises a corresponding set of holes 31 for receiving bolts 29. A passage is arranged to extend through the wall 30 and, on assembly, to correspond to the passage in the housing 23 and to receive insert 25. The passage is countersunk on the side of the wall 30 which abuts the housing 23 in order to locate an 'O'-ring 32 against the insert 25 on assembly.

The insert 25 is a rigid non-conducting elongate body having a number of conductors 24 extending longitudinally therethrough. It is provided with a flange 33 which corresponds to a widened portion of the passage in the mounting flange 27 as shown in the Figure.

The flange 33 has a tapered portion and a lip on the side which in use is adjacent the wall 30 and which on assembly locates and retains an 'O'-ring 34 against the wall 30 and the flange 27.

To assemble the penetrator, the housing 23 and the component parts of the sealing and gripping means are slid onto the prepared end of cable 3. The conductors of the insert are connected to the cable conductors by a suitable method, e.g. soldering or crimping, and the insert is located in the passage in the wall 30 with '0' rings 32 and 34 in position. The housing 23 is moved to locate and fix the insert against the wall and is then bolted to the wall 30. The component parts of the sealing means are inserted in the penetrator passage and the seal compression nut 14 is tightened to seal and locate the cable which is subsequently gripped by the insertion and tightening of the collets.

An incompressible compound is introduced through passage 20 as in the previous embodiment. Disassembly may be effected by reversing the assembly procedure except that the gel is removed after the housing 23 is clear of the joints 2.

In use pressure equalisation will be effected as with the splice of Fig. 1. However, if the pressure within the housing fluctuates, sealing is effected by the '0' rings 32 and 34.

When the external pressure outside the wall, i.e. that on the penetrator, is greater than that within the wall the '0' rings will be deformed in one direction, and when the pressure is reversed the '0' rings will tend to be deformed in the opposite direction. By using two 'O'-rings the amount of scuffing which may take place during such reversals is reduced and the sealing life of the '0' rings increased.

By having the insert penetrating the wall, the possibility of breaking the seal if the penetrator body is damaged or broken is reduced, since such a break should still leave the insert fixed in the wall by the mounting flange 27.

In the embodiment of Fig. 3 a multiple cable splice, generally indicated by reference number 35, is adapted to house joints 2 between cables 3 and 4 within a splice housing.

Cables 3 and 4 are gripped and sealed by gripping means 36 and sealing means 37.

The gripping means 36 may be substantially as indicated by reference numerals 1 7 and 1 8 in Fig. 1 and the sealing means 37 may be substantially as indicated by reference numer als 6,8,10,11,13 and 14 in Fig. 1.

The central cavity 34 is filled with the incompressible gel after assembly to provide pressure relief.

A supporting kevlar cable 38 runs the length of conducting cable 4 and is connected through the housing 35 to a mounting block 39 which used to suspend both the cable 4 and the splice 35.

In the embodiment of Fig. 4 a demountable penetrator is shown to comprise a cylindrical steel housing, generally indicated by reference number 40 and having a mounting flange 41.

A passage extends along the length of the housing and is adapted to receive, grip and seal cables 3 and 4 in a manner substantially the same as that disclosed in Fig. 1.

The housing comprises three portions, 42 and 43, and the central flange 41. The portions 42 and 43 extend longitudinally outward on each side of the flange 41 forming one passage along their lengths.

The housing side portions 42,43 are mounted on the flange portion 41 by means of respective male and female threaded connections on the external and internal periphery of the housing portions, each being sealed by an '0' ring located therebetween.

An insert 25 with two '0' rings is provided to effect sealing between respective sides of the passage within the flange portion in the manner described previously with reference to Fig. 2.

However, in this embodiment, when a portion 42,43 of the housing is detached from the flange portion 41, the connection may be readily broken by loosening the retaining nuts 44 or 44'.

The penetrator may be disassembled either side of a wall on which the flange 41 is mounted and sealing is effected both about the connection and between the respective sides of the wall.

Further elements identified in Fig. 4 are: A. Main body C. Insert locking ring D. Insert '0' ring (outer) E. Insert '0' ring (inner) F. Primary conductor pin G. Braid continuity pin H. Cable crimp tube J. Contact disc K. Cable gland sleeve L. Sleeve/body '0' ring M. Sleeve anti-rotation screw N. Gland seal boot A 0. Seal boot sleeve P. Gland seal Q. Gland filling vent screw R. Filling compound S. Seal compression washer T. Seal compression nut U. Cable clamp V. Collet clamping nut W. Vent X. Cable to braid crimp sleeve Y. Braid insulating sleeve Z. Braid connecting cable R1. Flange '0' ring (outer) R2. Flange '0' ring (inner) C1. Body clamp ring 11. Moulded insert assembly.

Fig. 5 shows a connector which may be provided with pin or socket terminations to allow the connector to be readily disconnected and reconnected. A plug 50 is connected to a cable gland body 51 by screws 52 and sealed by '0' rings 53 and 54. A moulded insert 55 with sockets (or alternatively with pins as shown also in Fig. 5) is retained in the plug 50 by locking ring 56 and sealed by 'O' ring 57. A clamp ring 58 is provided to mate with the other half of the connector in the conventional manner.

Fig. 6 shows an embodiment of the invention in which the pressure in the incompressible compound is determined by a piston-like pressure transmission means 45 located in the passage of the housing 1 which is adapted to receive a cable to be connected.

The pressure transmission means is an elongate rigid insert, having a groove formed in and around its periphery adjacent the internal surface of the passage. The groove is adapted to locate an '0' ring in use to effect sealing between the insert 45 and the housing 1.

A spring 46 provides a biasing force between the seal compression nut 1 4 and the insert 45. This force is transmitted to the gland seal 10 through the abutment of the insert and the gland seal and ensures that there is always good contact between the two.

A portion of the insert extends adjacent the cable, through an aperture in the seal compression nut 14 and against collets 18, which form a back stop for the insert.

The gland seal 10 abuts the aforementioned incompressible compound in cavity 22 on assembly.

In use an external pressure will act on the external surface of the insert and any change in the pressure will be proportionally transmitted to the incompressible compound in cavity 22, the proportion being dependent upon the ratio of surface areas of contact with the gland seal 10 and the external surface area of the insert perpendicular to its allowed movement.

The spring 46 ensures that a pressure is always available to act on gland seal 10 which will tend to extrude radially, under such pressure, to effect sealing. Thus the incompressible compound will be maintained at a higher pressure than the external pressure so that in use there will be no tendency for the seal to be broken.

Claims (9)

1. A connection for one or more insulated conductors comprising a housing having a passage therein for receiving a prepared end of the conductor(s) to be connected, seal means arranged to be positioned around said conductor(s) and within said passage, means for filling said connection with a substantially incompressible compound so that the compound is in pressure-transmitting relation to the seal means, and means for communicating the pressure external of the connection, to which pressure one side of the seal means may be exposed, to the compound within the connection and thence to the other side of the seal means.

2. A connection as claimed in claim 1 wherein the seal means comprise a gland seal with an integral flexible impervious cylindrical boot.

3. A connection as claimed in claim 2 wherein the end of the boot is sealed to the housing and the cavity within the boot is filled with the incompressible compound, the external pressure being transmitted to the compound through a passage in the wall of the housing and thence through the flexible boot.

4. A connector as claimed in claim 1, 2 or 3 wherein the incompressible compound is a gel which may be detached from the region of the conductors for disassembly.

5. A connector as claimed in any preceding claim wherein the seal means is a gland seal held by a threaded retainer nut in the passage, the nut being adjustable in the passage to exert the required pressure on the seal and when located offering an abutment against which to locate and fix a clamping means for the insulated conductor(s).

6. A connector as claimed in any preceding claim including a substantially rigid insert adapted to locate or receive one or more '0' rings to seal the insert to the housing, the insert allowing reconnection without breaking any other seals

7. A connector as claimed in any preceding claim including a pressure amplifying arrangement adapted to maintain the pressure in the incompressible compound higher than the external pressure.

8. A connection as claimed in claim 7 wherein the pressure amplifying arrangement comprises piston means having a surface exposed to the external pressure and a surface arranged to transmit pressure to the incompressible compound.

9. Connections substantially as hereinbefore described with reference to the accompanying drawings.