GB2174041A - Sealing device - Google Patents

Abstract

A device for sealing a spurling pipe (15) through which an anchor chain (40) passes. The device includes a member (32) which when subject to application of a force, changes its configuration to conform to the shape of the spurling pipe (15) and the chain (40) to form a seal therewith and prevent down flooding of the water into the chain locker to which the spurling pipe (15) is connected. Embodiments are disclosed in which the member is formed either from an elastomeric material or from an inflatable bag or bags. <IMAGE>

Description

SPECIFICATION Sealing device This invention relates to a sealing device, and more particularly, but not exclusively, to a device for sealing a spurling pipe through which an anchor chain passes.

In floating structures, for example ships and semi-submersible platforms, anchors are provided for restraining the structure at a partcular location.

Figure 1 shows a semi-submersible platform 1 having a platform section 2 supported relative to a pontoon 4 by means of columns 9, the pontoon 4 being submerged below the sea level 8. Two or three anchors are usually provided at each corner of the platform, each anchor being connected by an anchor chain 19 to a windlass 11, which regulates the length of anchor chain 19 paid out. The anchor chain 19 is stowed in a chain locker 13 provided in a said support column 9. The chain locker 13 is connected to the windlass 11 through a spurling pipe 15 which is provided through watertight flats 17 in the column 9.

It is a disadvantage of such an anchor chain stowage arrangement that the chain locker 13 and tube 15 can flood with sea water through opening 21.

Thus, in some stability calculations for the platform 1, the chain locker must be assumed to be full of sea water, which consequently affects stability design and requires corresponding buoyancy compensation.

There has been proposed in GB2142585A (by South Eastern Drilling Services Ltd United Kingdom) a system, for selectively sealing a chain locker. In this patent application, the spurling pipe is selectively sealed at its deck opening by a pair of opposed jaws which have profiled rubber sealing elements adapted to fit around the centre part of a link of a stud link chain, the rubber faces squeezing around the stud to form a seal. In order to be effective, the jaws must engage the flat sides of the chain link and a system is provided for sensing the orientation of the chain at the windlass, calculating the consequent chain link orientation at the pipe opening and adjusting the position of the chain so that the chain link at the pipe opening has the required orientation.

The above proposed system, however, has the disadvantage that its effectiveness is dependent upon the orientation of the chain and complicated and expensive equipment is required to ascertain and compensate for this. Furthermore, the system must be positioned at the pipe opening and is thus inflexible. The system also adds to the congestion and general complexity of the part of the platform where the windlass is disposed, where space is at a premium. Furthermore, the device is only applicable for use with stud link chains, as the jaws need to engage the centre stud to form an effective seal.

According to the invention in a first aspect there is provided a device for sealing a conduit through which a chain passes comprising sealing means arranged selectively to conform to the shape of a said conduit and a said chain and form a seal therewith irrespectively of the orientation of the said chain.

According to the invention in a second aspect, there is provided a device for sealing a conduit having sealing means defining a bore therethrough and arranged to receive a chain, the sealing means being connectable with means for changing the shape of the sealing means a first configuration in which the sealing means is arranged to allow un impeded movement of a said chain through a said bore to a variable second configuration in which the sealing means is arranged to seal with a said chain and a said conduit, the orientation of a said chain being unrestricted.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a semisubmersible platform to which an embodiment of the invention may be applied.

Figure 2 is a cross sectional drawing of a spurling pipe in which an embodiment of the invention is incorporated.

Figure 3 is a cross sectional view taken along the line 3-3' of Figure 2.

Figure 4 is a cross sectional view taken along the line 4-4' of Figure 2.

Figure 5 is a perspective view illustrating a first example of means for changing the configuration of a sealing member of the embodiment of Figure 2.

Figure 6 is a cross sectional view taken through one of the hydraulic rams shown in Figure 5.

Figure 7 is a perspective view illustrating a further example of means for changing the configuration of the sealing member of the embodiment of Figure 2.

Figure 8 is a cross sectional view taken in the direction of the arrows 8-8' of Figure 7.

Figure 9 is a perspective view of the sealing device showing detail of a protective sleeve.

Figures 10 show detail of apparatus for raising and lowering the sleeve shown in Figure 9.

Figure l lA-C shows various configurations of in- flatable bags forming part of the second embodiment of the invention.

Figure 12 is a perspective view of a containment for the second embodiment.

Figure 13 is a sectional view taken in the plane extending between line 13'-13' and the centre line of the containment of Figure 12.

Figure 14 is a plan view taken across the plane 14' of Figure 12 showing the bags uninflated.

Figure 15 is a view similar to that of Figure 14 showing the bags inflated.

Figure 16 is a block diagram illustrating the pneumatic system for the embodiment of Figures 11 to 15.

With reference to Figure 2, a first embodiment of the invention is illustrated in which a portion of the spurling pipe 15 shown in Figure 1, which connects the chain locker 13 to the windlass 11, is shown.

The pipe 15 is provided with an enlarged water tight section 30 forming a containment in which sealing means formed as a sealing member 32 is disposed. The sealing member 32 is formed from an elastomeric material, for example rubber. The member 32 has a bore 34 in the centre thereof concentric with the sides of the pipe 15. Preferably the member 32 has a hollow cylindrical form as shown more clearly in Figure 4.

Means 35 for compressing the member 32 are provided to exert a downward compressive force upon the member 32.

A first example of the compression means 35 is illustrated in Figures 5 and 6 in which hydraulic or pneumatic rams 50 are provided. The rams 50 are disposed between a fixed disc-shaped plate 52 and a movable disc-shaped 54. The sealing member 32 is disposed between the movable disc-shaped plate 54 and a further fixed disc-shaped plate 56.

As shown more clearly in Figure 6, the hydraulic or pneumatic rams 50 are connected to a source of hydraulic or pneumatic pressure through a cable or pipe 57 passing through a water tight gland 58. Exertion of force by the rams 50 in direction of the arrow A', bearing against the plate 54, which distributes the force into an even pressure, causes the member 32 to be compressed.

A further example of the compression means is illustrated in Figures 7 and 8, in which a combination of a movable cylinder 60 which is rotatable through a motor and gearing mechanism (not shown) and a fixed cylinder 62 are provided. The member 32 is disposed between the movable and fixed cylinders 60, 62 which are engaged on co-operating screw threads 64 so that rotation of the cylinder 60, relative to the cylinder 62, in the direction of arrow B', causes the cylinder 60 to approach the cylinder 62 in the direction of the arrows C', thus compressing the member 32 held therebetween.

As more clearly shown in Figure 8, a pressure plate 68 is attached to the cylinder 60 through a spacer bracket 70 so that, upon rotation of the cylinder 60, the pressure plate 68 acts directly upon the member 32. In order to ensure water tight integrity of the structure, a seal 66 is provided between the cylinder 60 and the spurling pipe 15. A further seal is formed by the elastomeric member 32 against the outer radius of the plate 68 and the fixed cylinder 62 at 72.

Returning to Figure 2, a protective sleeve 38 is also provided, having a diameter slightly less than the bore 34, the sleeve 38 being movable from a position shown by solid lines in Figure 2, to that shown by phantom lines in which position the sleeve acts to enclose the member 32 within the containment and thus protect the inner cylindrical surface of the member 32.

The sleeve 38 and an exemplary movement mechanism therefor is shown in more detail in Figures 9 and 10. As shown in Figure 9, the pipe 15 is provided with a concentric insert 72 connected to the tube 15 through a frusto conical extension 70, by welding, for example. The annular space 74, between the pipe 15 and insert 72, is used to accomodate the sleeve 38 and lifting and lowering gear 76. The lifting and lowering gear 76 is shown in more detail in Figure 10 and includes a double pulley 80 connected to the shaft 82 of a motor 78.

Two cables 84, 86 are attached to respective pulleys of the double pulley 80 and are counter wound, so that rotation of the motor shaft 82 causes both the cables 84, 86 to be either paid out or taken up. Each cable 84, 86 is routed through the annular space 74 and over respective pulleys 88, 90 which are diametrically opposed. The cables 84, 86 are then attached to the sleeve 38 at diametrically opposed positions 92, 94. Rotation of the motor shaft 82, thus causes the contra-wound cables 84, 86 to either pay out or pay in, thus lowering or raising the sleeve 38 in the direction of the arrows D'.

In use, an anchor chain 40, which may be a stud link chain as shown, or a studless chain, is disposed within the pipe 15. When it is desired to move the anchor chain 40 in or out of the chain locker, the sleeve 38 is lowered into the position shown by phantom lines, to protect the surfaces of the member 32. Once the chain has finished moving, the sleeve 38 is moved back to its non-protecting position and pressure is applied by the compression means to the member 32. Application of such pressure will cause the elastomeric material to be compressed and also to be squeezed radially. The member 32 is prevented from being squeezed outwardly by the section 30, so it squeezes in an inward radial direction so that the bore 34 is reduced in size and the sides thereof are squeezed around the chain, thus forming an axial seal in the pipe 15 against the links of the chain 40.

As the chain links are gripped by the member 32 from all sides, the sealing device is not dependent on the chain orientation.

In the preferred embodiment shown in Figure 2, the member occupies the hollow cylinder bounded by ABCD and EFGH. Axial compression as shown, would preferably reduce the height of the cylinder from AD to ID. The height AD is preferably the length of between 1.5, and 2 chain links. When compressed, the distance ID is preferably at least the length of 1 chain link.

In the alternative, the member 32 may be compressed by a radial compression applied to the outer periphery of the containment means. In this case, the outer periphery ABCD would be reduced to that indicated by JKLM.

Thus, by application of the compression means, the member 32 is compressed and forced to adopt a form in which the sides of the bore 34 grip the chain 40 thus forming a watertight seal against down flooding into the chain locker 13. When the compression means is released the elastomeric member 32 returns to its original configuration ABCD, due to its resilience.

Control of the compression means 35 may be lo cai or remote. A remote control system may be rui from each windlass or, alternatively, may be centrally controlled.

Alarm or failsafe systems may be incorporated to warn or prevent operators trying to operate the windlass with the sealing device engaged with the chain. Additionally, the sleeve 38 may be arrangec to trip switches to prevent the compression means 35 being actuated when the sleeve 38 is in the lowered position or to prevent the anchor chain 19 being moved when the sleeve 38 is in the raised position.

Although the chain tube and corresponding bore 34 of the member 32 have been shown (in Figures 3 and 4) to have a circular cross section, this is not to be construed as limitative and the member may have a bore of different cross section and may also be applicable for use with chain tubes of different cross section shapes. Also, the sealing member may be formed from a number of segments which when placed together in use have a similar form to the complete member 32 illustrated.

In a second embodiment, to be described with reference to Figures 11 to 16, the sealing means may be formed from a hydraulically or pneumatically inflatable envelope, bag or bags, having a bore through the middle thereof, so as to have the form of, for example, a toroid or hollow cylinder when inflated. The or each bag is inflated so as to grip the links of the chain in sealing engagement when it is desired to seal the chain locker, and the or each bag is deflated when it is desired to move the chain in or out of the chain locker.

In order to ensure an adequate watertight seal between a bag or bags and the links of a chain, the bag or bags must be able to expand to a form in which the spurling pipe is blocked with the bag or bags engaging the chain and containment under pressure.

For this condition to be met for a multiple bag system, it is necessary for each bag to have sufficient moveable perimeter length (i.e. arcuate dimension BC of Figure 11A-C) so that, when inflated, the bags touch along their edges from the centre line of the spurling ppe to the point on the containment at which they meet (hereinafter referred to as dimension P).

With reference to Figure 11A-C, symmetrical arrangements for 3, 4 and 5 bags are respectively illustrated. In order to ensure adequate sealing, the moveable perimeter length (BC) of each bag must be at least 2P and as the number of bags increases, the perimeter of the containment, to which the bags are attached, needs to increase correspondingly so that the moveable perimeter length of each bag remains at least 2P.

For the three bag system (illustrated in Figure 11a), the combined moveable perimeter length of the three bags must be at least 6P. As the circumference of a circular containment having radius P equals 2nP it can be seen that, for the three bag system, a circular containment to which three bags are adjacently attached can give sufficiently moveable perimeter length without requiring a complicated containment configuration such as that required for four or five bags as shown in Figures 11b and 11c.

In general, it is desirable for each bag to have a moveable perimeter length slightly in excess of the figure of 2P, so as to give the bags some reserve perimeter length with which to engage one another and the chain.

For systems employing two bags, which use a cylindrical containment, the perimeter length of each bag is significantly greater than the required dimension of 2P. Such excess perimeter length can result in creasing of the bags when in the inflated position which may lead to a reduction in watertight efficiency. Such an effect may be compensated for by using higher system pressure. This also applies to a single bag system.

With reference to Figures 12 to 17 a three-bag system, using a cylindrical containment, is shown.

With reference to Figure 12, the containment, generally designated 100, is shown installed as part of a spurling pipe 115. The containment 100 is formed in sections to allow installation with the chain in place, a suitable section of the original spurling pipe 115 being removed to allow installation.

The containment 100 includes two flanges 102, 103 which are attached to opposed ends of the spurling pipe 115. Each flange consists of two semi-annular sections 104, 105 which are connected to the spurling pipe 115 and to each other by means of welds 106.

Between the flanges, three part-cylindrical bagretaining sections 108, 110, 112 are attached, via gaskets 109. These sections are connected to the flanges and to each other to form the containment.

The maximum radius R' or the containment is not critical but is preferably greater than 1.5R where R is the radius of the spurling pipe.

Three inflatable bags 120, 122, 124 are provided within the containment 100, as illustrated in Figure 14.

The sections 108, 110, 112 are connected together via gaskets 180. Each gasket is preferably rubber moulded and includes a tapered section 182 projecting into the containment for assisting in maintaining a bag-to-bag seal at the containment wall when the bags are inflated.

Each bag 120-124 is formed from two substantially rectangular sheets of textile reinforced rubber or elastomeric material bonded together, one sheet of each bag 120-124 being provided with a respective facing 126, 128, 130, preferably formed from neoprene or other elastomeric material.

The neoprene facing 126, 128, 130 does not vary in thickness in the axial direction of the spurling pipe 115 but varies in radial thickness as shown in Figure 14 in which each facing 126, 128, 130 has points of maximum thickness 131 on either side of a central groove 129, the facing of each bag tapering towards the edges of each bag from the points of maximum thickness. The points 131 of maximum thickness of each facing 126, 128, 130 are positioned at the points of maximum required conformability when the bags are inflated. The central groove corresponds approximately in width to the width W of the chain link.

Each bag 126, 128, 130 is attached a respective section of the containment 108,110,112 by means of attachment members 132. An exemplary attachment member is illustrated in enlarged scale in Figure 14 and includes two pieces of bonded fabric/textile reinforced rubber 134, 136. Piece 136 is bonded to bag 124 and piece 134 forms a flap which includes an opening to receive a bolt 138 which is attached by means of nut 146 to section 112.

As shown in Figure 13, the position of the attachment member 132 is important to avoid limiting inflation of each bag. Generally, dimension A, taken from the edge of the bag to the point of attachment to the containment needs to be greater or equal to Try'/4 where R' is the distance to the maximum radius of the containment section. The total bag length (L) is preferably at minimum 21--2A, where I equals the chain link length, so that when inflated, the bags envelope at least two chain links.

Each bag is provided with a connector 142 to a pressurised air supply and vacuum system. An exemplary connector 142 is shown in Figure 14 and is of standard road tyre/tube design, albeit of more heavy duty construction. The connector 142 includes an air intake/discharge tube 150 sealed relative to section 108 by means of sealing gasket member 152 and being bonded to bag 120 via reinforcing member 154. The tube 150 is held in place relative to section 108 by means of nut 156 which engages with a threaded outer surface of the tube 150.

The connectors 142 from each bag 120, 122, 124 are connected to the air pressurisation/vacuum system schematicaily illustrated in Figure 16. The connectors 142 are connected together by means of pipe work 160 via reducers 162 to ensure equal airflow to all bags for near simultaneous inflation.

The pipe work 160 is connected to a two-way valve 164 which is in turn connected to a compressor 166 via an air drier 168 and accumulator 170, for providing air to inflate the air bags 120, 122, 124, and is also connected to a vacuum pump 172 for assisting in deflating the air bags 120-124 as desired. The pneumatic system is preferably automatically operated, including a remote warning and control system, located at the windlass or at a central control either for full remote operation or at minimum a visual warning to prevent operation of the windlass with the bags inflated. A branch 161 of the pipework 160 may optionally be provided to balance the system pressure in use and ensure even mass flow and hence even inflation of the bags. A pressure gauge 174 is also preferably provided to monitor system pressure.

(n use, if it is desired to seal the spurling pipe 115, the bags 120, 122, 124 are inflated by application of pneumatic pressure from the compressor 166. As the bags inflate, the neoprene faces of the bags conform to the shape of the chain 140 and to each other thus sealing the central region of the pipe 115. Also, the outer radial faces 125, 127, 129, of the bags 120, 124, 126, under action of the pneumatic pressure, mate against the containment sections 108, 110, 112 so as to effect a seal against the inner perimeter of the containment 115, with the triangular gasket sections 182 assisting in maintaining a bag-to-bag seal. In this way, inflation of the bags effects a watertight seal in the pipe 115, thus preventing downflooding into the chain locker. As the bags conform to the shape of the chain, no orientation of the chain is required in order to effect the seal.

If it is desired to move the anchor chain at any time, the air pressure is released by means of valve 164 and the air pressure is released and the air sucked out, by means of valve 164 and vacuum pump 172, to return the bags 120-124 to their deflated position as shown in Figure 14.

The protective sleeve illustrated in Figures 9 and 10 may be used with the inflatable bag embodiments.

The embodiments of the sealing device disclosed are not restricted to use in substantially vertical pipes as illustrated, but is equaliy applicable to pipes set at any angle. The closing device may also be placed at any position in or adjacent to the spurling pipe.

The device is also applicable for use in ships and other water vehicles.

Claims (38)

1. A device for sealing a conduit through which a chain passes comprising sealing means arranged selectively to conform to the shape of a said conduit and a said chain and form a seal therewith irrespectively of the orientation of the said chain.

2. A device as claimed in Claim 1 wherein the sealing means comprises at least one elastomeric sealing member.

3. A device as claimed in Claim 2 wherein the sealing member includes a bore for a said chain.

4. A device as claimed in Claim 2 wherein the sealing means comprises a plurality of said elastomeric sealing members together defining a bore for a said chain.

5. A device as claimed in any one of Claims 2 to 4 wherein the or each member is formed of rubber.

6. A device as claimed in any one of Claims 2 to 5 further comprising means for selectively compressing the at least one member into conformity with the shape of a said conduit and a said chain.

7. A device as claimed in Claim 6 wherein the compressing means comprises at least one hydraulic or pneumatic ram.

8. A device as claimed in Claim 7 wherein the compressing means further comprises a loadspreading plate disposed between the at least one ram and the member.

9. A device as claimed in Claim 6 wherein the compressing means comprises first and second compressing members within which the or each sealing member is disposed, the first and second compressing members having complementary portions arranged so that relative rotation of the compressing members causes the compressing members to approach one another and compress the sealing member.

10. A device as claimed in Claim 1 wherein the sealing means comprises at least one inflatable bag.

11. A device as claimed in Claim 10 wherein the sealing means comprises at least two said bags.

12. A device as claimed in Claim 11 wherein the sealing means comprises three said bags.

13. A device as claimed in any one of Claims 10 to 12 wherein the at least one bag is provided with an elastomeric surface for engagement with the chain.

14. A device as claimed in Claim 13 further comprising a facing providing said elastomeric surface.

15. A device as claimed in Claim 14 wherein the facing has a contoured profile.

16. A device as claimed in Claim 15 wherein the contoured profile includes an elongate groove arranged to be disposed, in use, in parallel with a said chain.

18. A device as claimed in any one of Claims 14 to 17 wherein the facing is formed from neoprene.

17. A device as claimed in Claim 16 wherein the facing tapers in thickness from each edge of the groove towards a respective edge of the facing.

18. A device as claimed in any one of Claims 14 to 17 wherein the facing is formed from neoprene.

19. A device as claimed in any one of Claims 10 to 18 wherein the or each bag is provided with a connector for connection to inflation means.

20. A device as claimed in Claim 19 further comprising inflation means arranged to be connected in use to the or each connector.

21. A device as claimed in Claim 20 wherein the inflation means comprises an air compressor, air drier and accumulator.

22. A device as claimed in Claim 20 or Claim 21 further comprising deflation means arranged to be connected, in use, to the or each connector.

23. A device as claimed in Claim 22 wherein the deflation means comprises a vacuum pump.

24. A device as claimed in Claim 22 or Claim 23 wherein the deflation and inflation means are connected to a two-way valve for connection to the or each connector.

25. A device as claimed in any one of Claims 10 to 24 wherein the or each bag includes an attachment member for attachment of the or each bag to a said conduit.

26. A device as claimed in Claim 11 or in any of Claims 12 to 25 when dependent thereupon wherein the sealing means further comprises at least one gasket member disposable between adjacent bags and arranged to contact a said conduit for assisting in effecting a seal between the bags.

27. A device as claimed in Claim 26 wherein the gasket member has a tapered cross-section.

28. A device as claimed in any of Claims 10 to 27 wherein the or each bag is formed from elastomeric material.

29. A device as claimed in any one of Claims 10 to 27 wherein the or each bag is formed from textile-reinforced rubber.

30. In combination, a conduit for receiving a chain and a device for sealing the conduit as claimed in any one of the preceding claims.

31. A combination as claimed in Claim 30 wherein the conduit includes an enlarged section for receiving the device.

32. A combination as claimed in Claim 31 further comprising a sleeve movable to confine the device within the enlarged section when the device is not in use.

33. A combination as claimed in any one of Claims 30 to 32 wherein the conduit is a spurling pipe.

34. A floating structure including a combination as claimed in any one of Claims 30 to 33.

35. A device for sealing a conduit having sealing means defining a bore therethrough and arranged to receive a chain, the sealing means being connectable with means for changing the shape of the sealing means a first configuration in which the sealing means is arranged to allow unimpeded movement of a said chain through a said bore to a variable second configuration in which the sealing means is arranged to seal with a said chain and a said conduit, the orientation of a said chain being unrestricted.

36. A sealing device substantially as hereinbefore described with reference to the accompanying drawings.

37. A combination of a conduit and a sealing device substantially as hereinbefore described with reference to the accompanying drawings.

38. The features hereinbefore disclosed, or their equivalents, in any novel selection.