A HANG-OFF DEVICE FOR AN END FITTING OF A SUBSEA TUBULAR

Abstract

A hang-off device for an end fitting of a subsea tubular, including: an annular latch mounting member having a throughbore; a plurality of latches pivotally mounted on the annular latch mounting member and configured for engagement with an end fitting of a subsea tubular passing through the throughbore and being pivotable between engaged and disengaged positions; a frangible retaining member to retain at least one of the latches in the engaged position; and a housing having a throughbore, defining a longitudinal axis of the device and aligned with the throughbore of the latch mounting member, and one or more recesses configured to receive a portion of the latches when in their engaged positions; the annular latch mounting member is displaceable in the longitudinal direction relative to the housing, and the device includes spring means for biasing the latch mounting member and the recesses in the housing away from each other.

Description

TECHNICAL FIELD OF INVENTION

The present invention relates generally to the field of subsea tubulars and manifolds, and more particularly, to the field of subsea tubular connections of flexible umbilicals to a fixed structure including devices for limiting the bend of the flexible tubulars or umbilicals. In particular, the present invention relates to an improved hang-off device for an end fitting of a subsea tubular, which is adapted for intervention-less installation of marine equipment such as, for example, a bend-stiffener for cables connecting to Floating Offshore Wind (FOW) facilities, and which permits disconnection in the event of excessive tension in the subsea tubular.

BACKGROUND

In subsea operations, it is often required to use a string of tubulars, also called a ‘riser’, to connect equipment on the seafloor with a fixed structure above, such as, for example, an offshore floating platform or a vessel. The string of tubulars or riser usually includes conduits or a plurality of conduits used for safe transport of material (e.g. hydrocarbon production fluid, such as, crude oil or gases). The string of tubulars or risers may include cabling or control lines so as to allow remote control of any equipment from the surface structure (i.e. the platform or vessel).

FIG. 1 shows an example of a typical setup for subsea operation, where production fluid is transferred from at least one subsea well 10 to a floating production, storage and offloading unit 20, also referred to as FPSO 20. Also, wind turbines 95 of an FOW (floating offshore wind) may be connected via subsea cables 97. A flexible riser 30 (string of tubulars) is used to transports the production fluid from the well 10, or a seabed production field in case of multiple wells, to the FPSO 20 via turret 40 installed on the FPSO 20. In order to protect the flexible riser 30 from excessive cyclic bending, for example, due to movement that may be caused by waves, current or wind, or which may simply be caused by the movement of the FPSO 20, one or more bend stiffeners 50 (only one connection is shown in FIG. 1) are typically used at the junction where the flexible riser 30 enters the fixed structure (i.e. through an ‘I’- or ‘J’ tube 60).

Often, the bend stiffener 50 is installed to the ‘I’- or ‘J’-tube 60 via a releasable connector assembly 70. The releasable connector assembly 70 may comprises a male connector member 72 that is fitted to the bend stiffener 50, and a female connector member 74 that is fitted to the ‘I’- or ‘J’-tube 60. During installation, the male connector member 72 is attached to the bend stiffener 50 and an end-fitting 32 of the riser 30 is located within and attached to the male connector member 72. In particular, the end-fitting 32 of the riser 30 is moved through the bend stiffener 50 into the throughbore of the male connector member 72 and locked into place by, for example, a cam device, a simple clamp mechanism 78, a latch mechanism or any other suitable interlocking mechanisms (not shown). The end-fitting 32 of the string of tubulars 30 is typically installed to the male connector member 72 in a workshop.

The assembly (i.e. riser 30, end-fitting 32, bend stiffener 50 and male connector member 72) is then transported to a desired subsea location and pulled towards and into connection with the female connector member 74 using a wire line 80 that is attached to the end-fitting 32 of the riser 30. Once the male connector member 72 is correctly positioned within the female connector member 74, it is retainingly interlocked with the female connector member 74, forming a secure connection between the bend stiffener 50 and the ‘I’ or ‘J’ tube 60. After locking the male connector member 72 inside the female connector member 74, the end-fitting 32 is released from engagement with the male connector portion 72 and the riser 30 is drawn up and through the bend stiffener 50 and the ‘I’- or ‘J’-tube to be fixed into place at the FPSO 20.

Often, the locking and unlocking of the male and female connector members 72, 74, as well as the release of the riser end-fitting 32 from engagement with the male connector member 72, is done through external intervention, such as, for example, subsea divers 90 or Remotely Operated Vehicles (ROV's) 92. In order to at least minimise the time and/or costs, as well as potential risks when using subsea divers 90 or ROV's 92, currently available connector assemblies have been since been improved to also use remotely operable latch-mechanisms and/or end-fitting release mechanisms.

The releasable coupling between the male connector member and the female connector member is typically realised using pivoting latch arms (see latch arm 76 in FIG. 1) that are mounted to the female connector member and which are configured to contactingly engage with a lip or shoulder portion of the male connector member, so that the male connector member is ‘hanging’from the radially inwardly projecting latch arms.

However, for this type of coupling engagement, any relative movement between the male connector member and the female connector member can impose substantial stress onto the latch arms, as well as, the engaging lip or shoulder portion of the male connector member. In particular, any axial dislocation between the male connector member and the female connector member, when engaged, may ‘rock’ the lip or shoulder portion up and down when sitting on respective latch arms, thus, repeatedly hammering the latch arms up to the point of potential failure. Further, currently available latch mechanisms may allow for small relative movement between the male connector member and the female connector member (e.g. caused by movement of the floating structure, wave or wind movement transmitted to the string of tubulars, or even the pressurised fluid pumped through the conduit(s)), but at the cost of an increased risk of damage due to fatigue and wear from recurring high pressures, shear stresses, imbalanced engagement and/or continuous movement between contacting surfaces between the male and female connector member.

The subsea tubular is subject to continuous changes in applied load. It is therefore desirable for the end fitting and the I- or J-tube to be disconnected automatically on application of an excessive load, in order to prevent damage. However, it is also desirable for such automatic disconnection to be able to withstand an increased load, greater than a nominally excessive level, which is only applied momentarily, to ensure that disconnection only occurs when an excessive load is applied for a period of time sufficient for damage to occur otherwise.

SUMMARY OF THE INVENTION

In accordance with the present invention, a hang-off device for an end fitting of a subsea tubular comprises:

• • an annular latch mounting member comprising a throughbore;
  • a plurality of latches pivotally mounted on the annular latch mounting member, the latches being configured for engagement with an end fitting of a subsea tubular passing through the throughbore and being pivotable between engaged and disengaged positions;
  • a frangible retaining member configured to retain at least one of the latches in the engaged position; and
  • a housing comprising a throughbore, defining a longitudinal axis of the device and aligned with the throughbore of the latch mounting member, and one or more recesses configured to receive a portion of the latches when in their engaged positions;
  • wherein the annular latch mounting member is displaceable in the longitudinal direction with respect to the housing and the device further comprises spring means for biasing the latch mounting member and the recesses in the housing away from each other.

Such a device allows the latches to pivot to their disengaged positions, and thereby disengage the end fitting, on application of an excessive force to the subsea tubular sufficient to overcome the bias of the spring means, but the provision of the frangible retaining member will ensure that if an increased load, greater than the level which would normally be sufficient for disengagement of the latches, is applied only momentarily, the latches will still be retained in their engaged position. However, if the increased load on the tubular continues to be applied, the fuse bolt will shear, allowing the latches to pivot to their disengaged positions, thereby disengaging the end fitting.

Preferably, the hang-off device comprises a plurality of frangible retaining members, each configured to retain a latch in the engaged position.

Preferably, each of the latches is provided with a frangible retaining member configured to retain it in the engaged position.

Preferably, the or each frangible retaining member is secured to a latch and to a portion of the housing.

The or each frangible retaining member may comprise a fuse bolt.

The hang-off device may comprise a plurality of springs for biasing the latch mounting member and the recesses in the housing away from each other.

The plurality of springs may comprise a plurality of compression springs.

Each of the compression springs may be mounted in a spring housing.

The latches may be configured to be pivotable to the engaged position by engagement with an end fitting of the subsea tubular as it moves through the throughbore of the annular latch mounting member.

Each of the latch members may comprise a projection configured to engage with a recess in the end fitting of a subsea tubular as it moves through the through bore of the annular latch mounting member.

Each of the latch members may comprise a hooked end portion configured to engage with a recess in the housing when in the engaged position.

The hang-off device may comprise a tubular housing.

The housing may comprise a plate member which carries the one or more recesses.

Preferably, the plate member is annular.

The plate member may be formed from a plurality of assembled portions.

The annular latch mounting member may be formed from a plurality of assembled portions.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows an example of a typical offshore setup for producing hydrocarbons from a subsea well and transferring the fluids to and from a FPSO via a flexible riser, wherein the riser is protected by a bend stiffener at the point of entering an ‘I-’ or ‘J-tube’ of the FPSO;

FIG. 2 is a perspective view of an embodiment of a hang-off device for an end fitting of a subsea tubular in accordance with the present invention, shown fitted to an ‘I-tube’;

FIG. 3 is a perspective view of the hang-off device of FIG. 2, shown to a larger scale;

FIG. 4 is a side view of the hang-off device of FIG. 2;

FIG. 5 is a plan view of the hang-off device of FIG. 2;

FIG. 6 is a cross-section through the hang-off device of FIG. 2, looking in the direction of arrows A-A of FIG. 5;

FIG. 7 is a cross-section through the hang-off device of FIG. 2, looking in the direction of arrows B-B of FIG. 4;

FIG. 8 is a cross-section through the hang-off device of FIG. 2, looking in the direction of arrows C-C of FIG. 5;

FIG. 9 is a cross-section through the hang-off device of FIG. 2, looking in the direction of arrows E-E of FIG. 5;

FIG. 10 is a vertical cross-section through the hang-off device of FIG. 2, shown fitted to an ‘I-tube’, in an engaged mode;

FIG. 11 is a vertically sectioned perspective view through the hang-off device shown in FIG. 10;

FIG. 12 is a vertical cross-section through the hang-off device of FIG. 2, shown fitted to an ‘I-tube’, in a disengaged mode;

FIG. 13 is a vertically sectioned perspective view through the hang-off device shown in FIG. 12.

DETAILED DESCRIPTION

The described example embodiment relates to hang-off device for an end-fitting used with a subsea connector assembly. However, the invention is not limited to subsea applications and may be used for any other type of couplings connecting two tubular components using a wire or cable.

Certain terminology is used in the following description for convenience only and is not limiting. The words ‘right’, ‘left’, ‘lower’, ‘upper’, ‘front’, ‘rear’, ‘upward’, ‘down’, ‘downward’, ‘above’, ‘below’, ‘uphole’ and ‘downhole’ designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted (e.g. in situ). In particular, the designated directions used in the description are with respect to the equipment installed within the arrangement so as to provide a connection between the FPSO and the subsea well/reservoir. In particular, the terms ‘top’, ‘upper’ and ‘uphole’ refer to the side of the equipment directed towards the surface when in situ, the terms ‘bottom’, ‘lower’ and ‘downhole’ refer to the side of the equipment directed towards the seabed or seafloor when in situ. The words ‘inner’, ‘inwardly’ and ‘outer’, ‘outwardly’ refer to directions toward and away from, respectively, a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description.

Further, as used herein, the terms ‘connected’, ‘attached’, ‘coupled’, ‘mounted’ are intended to include direct connections between two members without any other members interposed therebetween, as well as, indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.

The term ‘bend stiffener’ may refer to any one of a bend-stiffener, -restrictor or -limiter. The terms ‘fixed structure’, ‘turret’, ‘I-tube’ and ‘J-tube’ may be used interchangeably. A ‘riser’ is understood to mean any string of tubulars or umbilicals suitable to operatively connect the subsea well or any other seafloor equipment with the fixed structure, e.g. a FPSO vessel.

Further, unless otherwise specified, the use of ordinal adjectives, such as, ‘first’, ‘second’, ‘third’ etc. merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.

Through the description and claims of this specification, the terms ‘comprise’ and ‘contain’, and variations thereof, are interpreted to mean ‘including but not limited to’, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality, as well as, singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract or drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

An embodiment of hang-off device 110 in accordance with the present invention is illustrated in the drawings. In FIGS. 2 and 11 to 16 the hang-off device 110 is shown coupled to the upper end of an ‘I-tube’ 112 and in conjunction with an end fitting 114 attached to one end of a subsea tubular 115.

As best seen in FIGS. 2 to 10, the hang-off device 110 comprises an annular split plate 116 to the lower end of which a split flange interface 118 is connected coaxially by means of a plurality of bolts 120 extending through the flange interface 118 into the lower end face of the annular split plate 116. The flange interface 118 is secured to a corresponding flange 113 at the upper end of the I-tube 112 by a plurality of identical securing bolts 119. A coaxially mounted tubular funnel mount 122 comprising four identical equally angularly spaced support legs 124 defining four identical apertures 126 is secured to the upper face of the annular split plate 116 and supports a coaxial frusto-conical funnel 128 at its upper end.

An annular latch mounting member in the form of a split annular mounting plate 130 is mounted coaxially with the annular split plate 116, split flange interface 18, tubular funnel mount 122 and frustoconical funnel 128 and together they define a longitudinal through passage or throughbore 132. The annular mounting plate 130 is retained by a split annular clamp 134 located around its periphery.

Each of the annular split plate 116, annular split flange interface 18, tubular funnel mount 122, annular mounting plate 130 and annular clamp 134 is formed from two semi-annular portions to facilitate assembly, but each may alternatively be formed in one piece, as will be explained.

The annular mounting plate 130 carries four pairs of identical planar parallel mounting flanges 136, 138, each pair supporting a pivot pin 140 by means of which a latch in the form of a hang-off collet 142 is pivotally mounted. The mounting flanges 136, 138 are secured to the upper face of the annular mounting plate 130 by means of bolts 139 passing through apertures in the mounting plate and being received in threaded bores in the undersurface of each flange 136, 138 (FIG. 8).

Each of the hang-off collets 142 is generally hook-shaped and is pivotally mounted at pivot pin 140 adjacent an upper end. Each collet 142 is provided with a radially inwardly-directed projection 144 at its upper end and a hook portion 146 at its opposite end. Each collet 142 is pivotable between a first, engaged position shown in FIGS. 6, 11, 12 and 15 in which the projection 144 is engaged with a corresponding recess 148 in an outer face of an end fitting 114 and the hook portion 146 is hooked under a complementarily-shaped peripheral overhang 150 at the upper end of the split plate 116 and a second, disengaged position shown in FIGS. 13, 14 and 16 in which the projection 114 is disengaged from the recess 148 in the end fitting 114 and the hook portion 146 is disengaged from the peripheral overhang 150. It will also be observed that the inner face of each collet 142 is shaped to receive the outer periphery of the annular mounting plate and the upper end of the split plate 116 when in the first, engaged position.

Each collet 142 is retained in its engaged position by means of a fuse bolt 154 which passes through a bore 156 in the collet and is threadedly received in a threaded bore 158 in the peripheral face of the annular mounting plate 130. Each fuse bolt 154 is also prevented from inadvertent disengagement by means of a socket head cap screw 160 which engages with the head of the fuse bolt 154.

Eight identical preloaded spring assemblies 162 extend between the upper face of the annular split plate 116 and the annular mounting plate 130 and bias the annular mounting plate 130 away from the annular split plate 116 to retain the collets 142 in their engaged position. Each spring assembly 162 comprises a tubular spring case 164 within which a securing bolt 166 is coaxially mounted and whose lower end is threadedly received in a complementarily threaded aperture 168 provided in the upper face of the split plate 116.

A compression spring 170 is located around each spring sleeve 166 and is preloaded to a set level. The lower end of each spring 170 is seated in an annular recess 172 in the upper face of the split plate 116 and the upper end of the spring is retained by an upper end face 173 of the tubular spring case 164. The lower end of the spring case is of an increased external diameter and is retained by an overhanging shoulder portion 178 of aperture through which the spring case passes. The springs therefore bias the annular mounting plate upwards, i.e. in a direction away from the split plate 116.

However, it should also be noted that the fuse bolts 154 are configured to resist a higher load than that required to overcome the preloading of the springs 170, as will be explained.

In use, the end fitting 114 at one end of a subsea tubular 116 is pulled through the I-tube 112 and the annular split plate 116, annular split flange interface 18, tubular funnel mount 122, annular mounting plate 130 and annular clamp 134 are assembled around it by sliding the halves of the various units together. In this assembly, the collets 142 will be in their first, engaged position and the fuse bolts 154 will also be fitted. The end fitting 114 is thereby retained in the I-tube by the collets 142. The assembled hang-off device 110 is then secured to a flange 113 at the upper end of the I-tube 112 by means of the securing bolts 119.

The subsea tubular 116 is subject to continuous changes in applied load. The preload applied to the compression springs 170 minimises the effect of fatigue on the assembly from the constant changes in tension applied to the tubular 116. The preload applied to the compression springs 170 typically corresponds to at least 85% of a defined emergency release load. When the load applied by the compression springs is exceeded by the load applied to the tubular 116 (and by extension to the collets 142) for an extended period of time, the springs are compressed which disengages the hook portions 146 of the collets from the peripheral overhangs 150. However, the fuse bolts 154 form a backup in case of a sudden, very brief load (e.g. if the tubular 116 is snagged temporarily) which momentarily exceeds the emergency release load. In such circumstances, the fuse bolts will prevent the collets 142 from pivoting to their second, disengaged positions and will allow the system to return to the normal state once the temporary increased load is relieved. However, if the load is applied other than very briefly, the fuse bolts 154 are designed to shear, which will then allow the collets 142 to pivot to the second, disengaged positions, as shown in FIGS. 13 and 14, resulting in disengagement of the end fitting 114 from the I-tube 112 and allowing it to move downwardly through the I-tube.

The present invention thereby results in automatic disengagement of the end fitting from the I-tube 112 in the event of application of a load to the subsea tubular 116 which exceeds a predetermined emergency release load, but also prevents such automatic disengagement if the applied load only briefly exceeds the load at which disengagement would normally occur.

The invention is not restricted to the details of the foregoing embodiments.

For example, although in the above embodiments the unit is assembled around the end fitting 114 after it has been pulled through the I-tube 112, the split components may instead be provided as complete (non-split) units. In that case, it would be assembled at the top of the I-tube 112 before the end fitting 114 is pulled through, in which case the collets 142 would be in the second, disengaged position (without the fuse bolts 154 fitted) and held back from the throughbore 132 to allow the end fitting to pass. It would then be necessary to compress the springs 170 by approximately 10 mm (using removable studs and nuts) to enable the hooked end portions 146 to engage with the overhangs 150. The fuse bolts 154 would then be fitted.

Claims

1. A hang-off device for an end fitting of a subsea tubular, comprising:

an annular latch mounting member comprising a throughbore;

a plurality of latches pivotally mounted on the annular latch mounting member, the latches being configured for engagement with an end fitting of a subsea tubular passing through the throughbore and being pivotable between engaged and disengaged positions;

a frangible retaining member configured to retain at least one of the latches in the engaged position; and

a housing comprising a throughbore, defining a longitudinal axis of the device and aligned with the throughbore of the latch mounting member, and one or more recesses configured to receive a portion of the latches when in their engaged positions;

wherein the annular latch mounting member is displaceable in the longitudinal direction with respect to the housing and the device further comprises spring means for biasing the latch mounting member and the recesses in the housing away from each other.

2. A hang-off device according to claim 1, comprising a plurality of frangible retaining members, each configured to retain a latch in the engaged position.

3. A hang-off device according to claim 2, wherein each of the latches is provided with a frangible retaining member configured to retain it in the engaged position.

4. A hang-off device according to claim 1, wherein the or each frangible retaining member is secured to a latch and to a portion of the housing.

5. A hang-off device according to claim 1, wherein the or each frangible retaining member comprises a fuse bolt.

6. A hang-off device according to claim 1, comprising a plurality of springs for biasing the latch mounting member and the recesses in the housing away from each other.

7. A hang-off device according to claim 6, comprising a plurality of compression springs.

8. A hang-off device according to claim 7, wherein each of the compression springs is mounted in a spring housing.

9. A hang-off device according to claim 1, wherein the latches are configured to be pivotable to the engaged position by engagement with an end fitting of the subsea tubular as it moves through the throughbore of the annular latch mounting member.

10. A hang-off device according to claim 9, wherein each of the latch members comprises a projection configured to engage with a recess in the end fitting of a subsea tubular as it moves through the through bore of the annular latch mounting member.

11. A hang-off device according to claim 1, wherein each of the latch members comprises a hooked end portion configured to engage with a recess in the housing when in the engaged position.

12. A hang-off device according to claim 1, comprising a tubular housing.

13. A hang-off device according to claim 1, wherein the housing comprises a plate member which carries the one or more recesses.

14. A hang-off device according to claim 13, wherein the plate member is annular.

15. A hang-off device according to claim 14, wherein the plate member is formed from a plurality of assembled portions.

16. A hang-off device according to claim 1, wherein the annular latch mounting member is formed from a plurality of assembled portions.