ROGERS, Robert, Charles (5 Bay Road, Wormit Fife DD6 8LU, GB)
CANNELL, David (Whitecairn, Culsalmond, Insch Aberdeenshire AB52 6UU, GB)
ROGERS, Robert, Charles (5 Bay Road, Wormit Fife DD6 8LU, GB)
| Claims 1. A swivel assembly comprising at least: (a) a first connector piece having a shaft; (b) a second connector piece having a hollow body for receiving the shaft of the first connector piece; (c) one or more bearings between the first and second connector pieces to allow rotation thereinbetween; (d) lubricant surrounding at least one of said bearings; and (e) a lubricant-pressure adjuster. 2. A swivel assembly as claimed in claim 1 the shaft includes an enlarged head. 3. A swivel assembly as claimed in claim 1 or claim 2 wherein the hollow body includes a restricted neck portion. 4. A swivel assembly as claimed in any one of the preceding claims having at least one roller bearing. 5. A swivel assembly as claimed in any one of the preceding claims wherein the lubricant-pressure adjuster is able to adjust the pressure of the lubricant within the swivel assembly between the shaft of the first connector piece and the hollow body of the second connector piece including at least one bearing thereinbetween, optionally including all bearings thereinbetween. 6. A swivel assembly as claimed in any one of the preceding claims wherein the lubricant-pressure adjuster is pressure-moveable, continuously moveable, or both, following any change in pressure on the lubricant from pressure around or otherwise ambient to the swivel assembly. 7. A swivel assembly as claimed in any one of the preceding claims wherein the lubricant-pressure adjuster comprises one or more of the group comprising: piston, plug, cap, hose, diaphragm, membrane, float, blade and bladder. 8. A swivel assembly as claimed in any one of the preceding claims wherein the lubricant-pressure adjuster is biased or includes a biaser, adapted to alter the pressure-adjusting effect of the lubricant-pressure- adjuster on the lubricant. 9. A swivel assembly as claimed in any one of the preceding claims wherein the swivel assembly includes one or more lubricant chambers. 10. A swivel assembly as claimed in claim 9 wherein the lubricant chamber(s) includes a body of lubricant on which the lubricant-pressure adjuster applies pressure. 11. A swivel assembly as claimed in claim 10 wherein the lubricant chamber(s) includes a body of lubricant on which the lubricant-pressure adjuster adjusts the pressure of the lubricant within the swivel assembly. 12. A method of adjusting the pressure of lubricant in a swivel assembly as defined in any one of claims 1 to 11 , the method comprising at least the step of: (a) moving the lubricant-pressure adjuster to adjust the pressure of lubricant surrounding at least one of said bearings in the swivel assembly. |
Swivels and their uses are well known. Swivels are commonly used to bring or connect together two other items and allow rotation
thereinbetween, often under tension. Examples of such items include umbilicals, cables, lines, drills, wires and the like, and the present invention is not limited by the nature of the connected items.
Swivels are used in many environments. This can include harsh working environments such as being underground, underwater, or even both. For example, US6637969 describes a swivel for use with horizontal directional drilling techniques for product installation, which allows a pipe string to rotate during drilling of the bore therefor. As stated therein, "The bore may be exposed to drilling fluids such as a mixture of water, bentonite and polymers known in the industry as "mud". The liquid or mud can be destructive of the bearing seals and bearings typically found in
commercially available swivels. Bearings may fail, not only from
degradation or loss of lubrication due to seal failure, but also from heavy bending force loads on the swivel."
EP0649996 A1 also shows a swivel for use in a harsh environment, which can include combined underground boring and cable pulling.
Swivels can also be used for the deployment and recovering rigging of subsea constructions, such as those used in the oil and gas exploration and production industries. Such uses include underwater deployment, where changes in the ambient pressure around the swivel can also affect the swivel seals to a detrimental effect, especially when being used to lift or move heavy loads, sometimes being hundreds of tonnes.
It is an object of the present invention to provide an improved swivel for use in harsh environments, in particular for use underground or underwater.
Thus, according to one aspect of the present invention, there is provided swivel assembly comprising at least:
(a) a first connector piece having a shaft;
(b) a second connector piece having a hollow body for receiving the shaft of the first connector piece;
(c) one or more bearings between the first and second connector pieces to allow rotation thereinbetween;
(d) lubricant surrounding at least one of said bearings; and
(e) a lubricant-pressure adjuster.
In this way, variation in the ambient pressure around the swivel assembly can be compensated for during use, and/or variation in the lubricant pressure can be achieved to hinder the ingress of unwanted material such as debris to the area or areas between the first and second connector pieces including the bearings.
The first connector piece may have any suitable size, shape and design. It may be formed from a suitable material or combination of materials, and may be a single integral piece or formed from a number of conjoined pieces. Generally, the first connector piece includes one or more components or features to allow its connection to a suitable item, including but not limited to eyes, hooks, threads or threaded portions.
The shaft of the first connector piece may also have any suitable size, shape or design, whilst being related to the size, shape and design of the hollow body of the second connector piece. Optionally, the shaft includes an enlarged head, such a head either being integrally formed or conjoined with the remainder of the shaft or a shaft support surface. Preferably, the shaft includes at least one transverse edge, more preferably at least one shoulder or at least one set of shoulders relative to the longitudinal axis of the shaft.
The second connector piece may have any suitable size, shape and design, being the same or different to that of the first connector piece, at least in terms of outward appearance and/or outer diameter. It may be formed from a suitable material or combination of materials, and may be a single integral piece or formed from a number of conjoined pieces.
Generally, the second connector piece includes one or more components or features to allow its connection to a suitable item, including but not limited to eyes, hooks, threads or threaded portions
The hollow body of the second connector piece may also have any suitable size, shape or design, whilst being related to the size, shape and design of the shaft of the first connector piece. Optionally, the hollow body includes a restricted neck portion.
Preferably, the hollow body includes at least one transverse edge, more preferably at least one shoulder or at least one set of shoulders relative to the longitudinal axis of the hollow body. Preferably, the first and second connector pieces have the same or similar outer diameter or dimensions at or near their point of rotation. The swivel assembly includes one or more bearings. Each bearing may be the same or different to any and each other bearing. Each bearing may be in-line with or co-axial the longitudinal axis of the swivel assembly, or one or more bearings may be angled thereto. One or more bearings may also be tapering or tapered.
Suitable bearings for use between connector pieces of a swivel assembly are known in the art, and include ball bearings, plane bearings, roller bearings and the like. Angled bearings for use in swivels to allow for rotational movement between connector pieces, and optionally to take into consideration tensile loading between the first and second connectors, are also known in the art. Examples are shown in US6637969 and
EP0649996, and the present invention is not limited by the nature, number, size or design of the bearings. Preferably, the swivel assembly of the present invention includes at least one bearing between a transverse edge such as a shoulder of the shaft of the first connector piece, and a transverse edge such as a shoulder within the hollow body of the second connector piece. The swivel assembly may include one or more plane or planer bearings to consider compression forces which may occur during use of the swivel assembly.
The lubricant preferably surrounds all bearings between the first and second connector pieces. The lubricant for use in the present invention may comprise any suitable material or combination of materials, including but not limited to one or more of the group comprising: oil or grease. Suitable grades of oil and grease for use in swivels and optionally under high load conditions, are known in the art and are not further described herein.
The lubricant-pressure adjuster for use in the swivel assembly of the present invention may be any component, unit, apparatus or device, or combination of same, able to adjust the pressure of the lubricant where it is located within the swivel assembly. This may include the internal area or areas within the swivel assembly between the shaft of the first connector piece and the hollow body of the second connector piece, generally including at least one bearing thereinbetween, optionally including all bearings thereinbetween.
Preferably, the lubricant-pressure adjuster, or at least a portion of the lubricant-pressure adjuster, is pressure-moveable, continuously moveable, or both, in response to or in anticipation of any change in pressure on the lubricant from pressure around or otherwise ambient to the swivel assembly.
Alternatively or additionally, the lubricant-pressure adjuster provides a necessary or desired over-pressure or under-pressure to the lubricant in comparison with the pressure around or otherwise ambient to the swivel assembly.
The lubricant-pressure adjuster may comprise one or more of the group comprising: piston, plug, cap, diaphragm, hose, membrane, float, blade and bladder. The lubricant-pressure adjuster may comprise one or more moveable parts, portions or components moveable relative to the remainder, such as a housing. Alternatively, the lubricant-pressure adjuster is wholly or substantially moveable.
Optionally, the lubricant-pressure adjuster is biased or includes a biaser, adapted to alter the pressure-adjusting effect of the lubricant-pressure- adjuster on the lubricant, optionally also in relation to the ambient pressure around the swivel assembly.
The swivel assembly of the present invention may also include one or more lubricant chambers. Said lubricant chamber(s) may include a body of lubricant on which the lubricant-pressure adjuster can or does applies pressure, more preferably on which it adjusts the pressure of the lubricant within the swivel assembly of the present invention.
The swivel assembly of the present invention may include one or more lubricant fill points, and/or one or more lubricant vent points or ports. This can allow for the options of flushing through the assembly and to ensure no gas pockets remain.
The swivel assembly of the present invention may also include one or more debris caps able to allow access to the inside of the swivel for the removal of debris, in particular larger particles.
According to a second aspect of the present invention, there is provided a method of adjusting the pressure of lubricant in a swivel assembly as defined herein, the method comprising at least the step of: (a) moving the lubricant-pressure adjuster to adjust the pressure of lubricant surrounding at least one of said bearings in the swivel assembly.
An embodiment of the present invention will now be described by way of example only and with reference to the accompanying diagrammatic drawings in which:
Figure 1 is a cross-sectional view of a first swivel assembly according to an embodiment of the present invention; and
Figure 2 is a cross-sectional view of a second swivel assembly according to the present invention.
Referring to the drawings, Figure 1 shows a first swivel assembly 2 as a first example of the present invention. The first swivel assembly 2 has a first connector piece 4 having a shaft 6, and a second connector piece 8 having a hollow body 10 for receiving the shaft 6 of the first connector piece 4. Not shown in Figure 1 are the remaining portions of the first and second connector pieces 4, 8. These remaining portions are labelled areas A and B in Figure 1 , and may include one or more components or features such as eyes, hooks, threads or threaded portions, able to connect each of the first and second connector pieces 4, 8 to other items. As described hereinabove, such other items include many possible items depending upon the intended use and environment for the swivel assembly, including but not limited to the deployment and recovery rigging for subsea constructions and structures. Thus, the swivel assembly may be a separate unit or may be integral with a sea-going vessel crane or crane hook. Whilst some sea-going vessels can have cranes designed to take up loads of up to 45 tonnes, many subsea constructions or structures are significantly heavier, being up to 450 tonnes. With heavier loads, there is increased tension at or in the lifting lines, points or means, such as wires or ropes, and it is generally intended to ensure that there is no turning or twisting of such wires, etc. either prior to or during the deployment or lifting (or other movement) of such constructions or structures.
Use in deep water present further problems. Ambient pressures in deep water can force sea water into the body of a swivel, which leads to an acceleration of the corrosion, as well as providing the potential for debris to enter the swivel. Both of these conditions lead to damage to the swivel. It may be possible to fully seal a swivel, or at least the cavity of the swivel, against a high ambient pressure such as that found in deep water.
However, if there is a leak into the swivel, then on recovery of the swivel from the deep water, the now high internal pressure in the swivel can lead to a potentially dangerous situation. In addition, dramatic pressure changes within the swivel could lead to a hydraulic 'lock', which could result in the swivel no longer rotating and thus not working.
The present invention seeks a more universal solution to variable situations, uses and environments that a swivel may be used in, including but not limited to varying ambient pressure. The swivel assembly of the present invention can be used at high loads of up to 450 tonnes, as well as being useable in deep water.
Referring again to Figure 1 , the shaft 6 of the first connector piece 4 has an enlarged head portion 6a, and a restricted neck portion 6b between the head portion 6a and the remainder of the first connector piece 4. Between the outer surface of the head portion 6a and the neck portion 6b is a first transverse edge 6c, generally in the form of a circumferential shoulder. The hollow body 10 of the second connector piece 8 has a first portion 10a being of a corresponding size to the enlarged head portion 6a of the shaft 6 of the first connector piece 4, with a first cavity 14 thereinbetween, and a restricted neck portion 10b, again having a size corresponding to the neck portion 6b of the shaft 6, with a second cavity 16 thereinbetween.
The dimensions, relative dimensions, and spatial relationships, etc. of the features shown in Figure 1 are diagrammatic only, and are shown for the purposes of best illustrating an example of the present invention. No direct interpretation of the dimensions, relative dimensions, and spatial relationships, etc as shown in Figure 1 are intended. For example, the sizes of the first and second cavities 14, 16 would generally be smaller to provide a tighter fit between the shaft 6 and the hollow body 10.
Between the head portion 10a and the neck portion 10b of the hollow body 10 in Figure 1 , the hollow body 10 also has a transverse edge 10c, in the form of an internal circumferential shoulder.
Between the transverse edge 6c of the shaft 6 and the transverse edge 10c of the hollow body 10, there is located a roller bearing 12 to allow rotation between the shaft 6 (and the first connector piece 4) and the hollow body 10 (and the second connector piece 8).
Roller bearings are known in the art and generally comprise a number of bearing elements within a casing. Bearing elements that are rollers are generally able to withstand significantly more force that ball bearings, and optionally the roller bearing 12 is tapered to increase the ability of the swivel assembly to accommodate substantial tensile or axial loadings to which it may be subjected. The swivel assembly 2 may include one or more further bearings between one or more portions or parts of the first connector piece 4 and the second connector piece 8. These can include roller, ball or planer bearings, to assist the rotational allowance or movement between the first and second connector pieces 4, 8.
Between the shaft 6 and the hollow body 10 are first and second cavities 14 and 16. The second cavity 16 extends laterally or transversely beneath the furthermost extent of the second connector piece 8 into a third cavity 18 where the ends of the first and second connector bodies 4, 8 directly meet, and typically there are one or more seals (diagrammatically represented by seals 20 in Figure 1) in this region, which seals 20 still allow rotational movement between the first and second connector pieces 4, 8. In the region of the second connector piece 8 extending away from the hollow body 10, there is a fourth cavity 22. Between the outside surface of the second connector piece 8 and the fourth cavity 22, there is a filling vent and/or port 24 and a debris cap 26. Within the fourth cavity 22, and optionally in line with the debris cap 26, there is a lubricant-pressure adjuster 28 moveable within the fourth cavity 22 as described hereinafter.
Within all of the above described cavities 14, 16, 18 and 22, there is a lubricant 30. Suitable lubricants for use in swivel assemblies, in particular for allowing rotation between two connector pieces, are known in the art, and can include various grades of oil and/or grease. The nature, lubrication ability and properties of the lubricant are not further described.
The lubricant 30 can be provided through the filling port 24 in a manner known in the art. The filing port 24 may be securely sealable by a plug or the like, or may itself be a self-sealing filling nozzle or the like, and the filing port 24 may be integral with or removable from the second connector piece 8. The lubricant 30 surrounds the roller bearing 12, and any other bearings within the various cavities described between the first and second connector pieces 4, 8.
The fourth cavity 22 includes a lubricant chamber 32, within which the lubricant-pressure adjuster 28 can act on lubricant 30 housed within. That is, the lubricant-pressure adjuster 28 is moveable within the lubricant chamber 32.
The lubricant-pressure adjuster 28 may have any suitable size, shape or design, and be formed from any component or assembly of components, generally comprising at least one moveable component able to provide a pressure-changing force on the lubricant 30 within the lubricant chamber 32, (and thus also throughout all connected lubricated areas between the first and second connector pieces 4, 8). Figure 1 shows the lubricant- pressure adjuster 28 in the form of a solid block, and the skilled man is aware of suitable alternatives being a membrane such as a bladder, a diaphragm or piston.
Figure 1 also shows movement of the lubricant-pressure adjuster 28 along a single longitudinal axis, preferably being the same central axis of the debris cap 26. Alternatively, a suitable lubricant-pressure adjuster may include a moveable component moveable in more than one dimension.
Optionally, the lubricant-pressure adjuster 28 may be biased either directly or indirectly, so as to provide a biased-pressure force on the lubricant 30. For example, one or more springs could be located between the non- lubricant side of a moveable component of the lubricant-pressure adjuster 28, and a fixed or secured surface of the second connector piece 8, so as to apply a positive or negative pressure on the lubricant 30.
In use, once the swivel assembly 2 is formed, lubricant 30 can be provided through the filling vent 24 to fill the cavities between the first and second connector pieces 4, 8, optionally with a lubricant overpressure. The pressure-adjusting force of the lubricant-pressure adjuster 28 can be predetermined or otherwise adjusted to achieve the desired pressure of the lubricant 30 once the filling port 24 is closed.
The pressure-adjusting ability of the lubricant-pressure adjuster 28 may be achieved in a number of ways, such as the nature, size and design of the lubricant-pressure adjuster 28, optionally in comparison with the size, nature and design of the lubricant chamber 32, and/or the nature and pressure of any material between the non-lubricant side of the lubricant- pressure adjuster 28 and a fixed or secured surface of the second connector piece 8, and/or any biasing of the lubricant-pressure adjuster 28, etc.
Where the lubricant 30 is provided with an over-pressure compared with the ambient pressure around the swivel assembly 2 during use, the entry of ambient fluid or other material is hindered by the already greater lubricant pressure within the swivel assembly. Where the swivel assembly 2 may be used in a changing ambient pressure environment, such as underwater, and more particularly at a changing water depth, the ambient pressure around the swivel assembly 2 will change. However, the lubricant-pressure adjuster 28 can
accommodate any such ambient pressure change, in particular
compensate for the change in the ambient pressure, so as to reduce variation in the pressure of the lubricant 30 with the cavities between the first and second connector pieces 4, 8, and preferably to wholly or substantially maintain a constant lubricant pressure during the changing ambient pressure.
Thus, movement of the lubricant-pressure adjuster 28 allows pressure of the lubricant 30 to be compensated during operation of the swivel assembly 2 at varying ambient pressure, in particular during the lowering and raising of the swivel assembly 2 under water.
In this way, the lubricant is pressure-compensated, i.e. maintained at a desired pressure such as ambient pressure, (or above or below such ambient pressure if previously set as such) during varying ambient pressure changes, such as lowering or raising through a water column. This can compensate variations in ambient pressure during operation or deployment of the swivel assembly 2, such as during the deployment of recovery of underwater and subsea constructions and structures.
The debris cap 8 as shown in Figure 1 allows access to the lubricant- pressure adjuster 28 if necessary or desired, as well as allowing a larger port for the drainage or removal of debris within the cavities between the first and second connector pieces 4, 8 if desired or required. Figure 2 shows a more graphically detailed second swivel assembly 40 according to the present invention. The swivel assembly 40 has a first connector piece 42 having an integral shaft 44 comprising an upper shaft portion 44a and a lower shaft portion 44b with a central aperture 44c. The lower portion 44b is secured to the first connector piece 42 in a manner known in the art, such as by welding or complementary threading, optionally with a final security pin therethrough.
The second swivel assembly 40 also comprises a second connector piece 46 having a hollow body 48 for receiving the shaft 44 of the first connector piece 42.
Similarly to Figure 1 , not shown in Figure 2 are the remaining portions of the first and second connector pieces 42, 46 connectable to other items. Such remaining portions are labelled areas A and B in Figure 2, as with Figure 1.
Within the hollow body 48 of the second connector piece 46 is a threaded section 50 which can be connected to the outer shell of the hollow body 48 during assembly of the second swivel assembly 40 after location of the shaft 44 and bearing 56 into the hollow body 48.
The upper shaft portion 44a has an enlarged middle section, and so includes a transverse circumferential edge to create a first shoulder 52. The top edge 54 of the threaded section 50 provides a transverse edge in relation to the hollow body 48. Between the first shoulder 52 and the threaded section top edge 54, there is located a suitable roller bearing 56 to allow rotation of the first and second connector pieces 42, 46
thereinbetween. The second swivel assembly 40 includes plane bearings 58 between a second circumferential shoulder of the upper shaft portion 44a and an upper internal circumferential shoulder 59 of the hollow body 48. Between the components of the first connector piece 42 and the
components of the second connector piece 46 are a number of cavities (shown in black in Figure 2) filled with a lubricant as discussed
hereinabove. The lubricant surrounds the roller bearing 56 and the plane bearings 58.
In the second connector piece 46 is a filling vent 60. Between the filling vent 60 and the interior of the hollow body 48, there is a fluid chamber 62. At one end of the fluid chamber 62 is a lubricant-pressure adjuster 64 comprising a pressure-compensating piston or a pressure-compensating bladder, able to provide pressure on the lubricant in the fluid chamber 62, and thus provide pressure on all the lubricant within all the cavities shown in Figure 2.
On the opposite side of the lubricant-pressure adjuster 64 from the fluid chamber 62 is a debris filter cap 66.
At the region between the meeting of the first and second connector pieces 42, 46 are two circumferential seals 68 arranged in a manner known in the art to allow movement thereinbetween, whilst sealing the conjunction.
A filling port 70 in the shell of the hollow body 48 allows for filling the lubricant into the cavities in the swivel assembly 40 and flushing through of lubricant in conjunction with the filling vent 60. The pressure-adjusting ability of the lubricant-pressure adjuster 64 shown in Figure 2 is similar to the lubricant-pressure adjuster 28 shown in Figure 1. Movement of the lubricant-pressure adjuster 64 can compensate for changes in the ambient pressure around the second swivel assembly 40, and thus maintain proper operation of the lubricating ability and properties of the lubricant in the second swivel assembly 40 during changes to the ambient pressure. This can be such as during deployment of the second swivel assembly 40 from a first to a second underwater depth, in particular between a sea surface and a deep underwater deployment.
Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.
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