SUBSEA SUPPORT ARRANGEMENT

Abstract: A subsea support arrangement (10) (Fig. 1) for a submerged body (13), suspended from a surface vessel by umbilical (27) and moveable horizontally by thrusters (26), includes a post or pile (14) upstanding from the sea bed having a profiled axial recess (14) in the top and, on the body, support means including a hydraulic ram (12). The ram has a cylinder (17) fixed to the body and a piston shaft (20) rotatable in the cylinder and extendable along support axis (19) carrying a profiled plunger or pin (21) which is extended to seat in the recess (14) and support the body thereon, the pin and recess absorbing vertical and lateral loads, and rotation between piston and cylinder forming a rotational bearing. Alternatively (Fig. 3) the cylinder is fixed with respect to the piston and mounted in a housing about which the body can rotate and which sits on the post to give vertical support, the plunger providing only lateral support. Furthermore (Figs. 6 to 8), resilient fingers (56) may depend from the housing into the recess and be wedged against the recess wall by the plunger to provide also resistance to lifting of the body. An underside recess (25) and guide channel (29) permits the body to be manoeuvred laterally by thrusters (26) into correct disposition above the post (14) for extending the ram and extending the fingers.

Description: SUBSEA SUPPORT ARRANGEMENT This invention relates to support arrangements for mobile submerged bodies and particularly but not exclusively to arrangements for supporting submersible bodies with lifting capabilities to form subsea cranes. In subsea hydrocarbon production it is known to use remotely operated submersible vehicles (ROVs) to perform subsea tasks involving, for example, the replacement of parts on sea bed structures. Such ROVs have a limited, ability to carry and manipulate parts due partly to their own requirements for operating power and control. It is common for such an ROV to operate in conjunction with a cage-like garage to which it is tethered, the cage providing transport between a surface vessel and the work site for the ROV and any parts to be replaced by the ROV and power and control to the ROV. Such a cage-like garage may be positioned on the sea bed or disposed above it, being a 'free-flying' arrangement including station keeping propulsion and buoyancy control means, a buoyant arrangement tethered to anchors or suspended by an umbilical from a surface vessel. Difficulties which occur with such arrangements in respect of replacing parts of a subsea structure involve buoyancy changes to the ROV and possibly the cage entailed by transferring the parts. Such buoyancy changes limit the ability of such systems to effect replacement of heavy items and in the past such replacement has involved lifting and lowering easily replaced items from a surface vessel, using the ROV for guidance, or returning the complete structure to the surface for dismantling. Even this fall-back has disadvantages in respect of relative motion between the subsea structure and surface vessel due to wave motion and is limited to conditions of calm that may entail a considerable period of delay and lost hydrocarbon production. To avoid this dependency of a suspended lifting arrangement on surface vessel motion whilst enabling a lifting capacity to be used that is not constrained by the buoyancy change limitations of freely-flying arrangements, it is possible to set down a moveable submerged body on an upwardly extending member formed on or near the subsea structure and overhanging it and to use the body as a crane to transfer heavy objects to and from the structure. A suitable body may comprise a specially constructed crane device or may comprise an ROV or conveniently a cage-like ROV garage adapted to carry a lifting boom as well as transport replacement parts and a tethered ROV to assist in the replacement. However, other purposes can be served by having a submerged body supported at the sea bed and it is to be understood that the present invention is not limited to the support of a particular form of body supported for a particular purpose, nor to the provision of certain features additional to the fundamental ones which may be used in specific circumstances to give a preferred arrangement. Any moveable submerged body which may be moved to such an upstanding member to be supported thereon will be capable of horizontal motion by means of positioning thrusters and will either be a buoyancy controlled freely moving body capable of vertical motion by buoyancy changes or thrusters or a body suspended from a surface vessel and moveable vertically by intentional surface vessel control and unintentional surface vessel motion. Despite the apparent simplicity of the operation of setting down a moveable body on an upstanding member and supporting it thereon, the hostile environment of the sea on vulnerable parts and the exertion of forces on the body by sea currents and performance of tasks by the supported body dictate a relatively precise and positive support engagement between the body and upstanding member protected prior to engagement. It is an object of the present invention to provide a subsea support arrangement for a moveable submerged body which permits the body to undertake tasks involving forces on the body not feasible with an unsupported body. According to one aspect of the present invention a subsea support arrangement for a moveable submerged body comprises an upstanding member having a recess therein extending for predetermined distance in a vertical direction and on the body, support means adapted to rest on the upstanding member and including a part insertable into the recess to provide lateral support between the support means and the upstanding member. According to another aspect of the present invention a method of supporting a moveable submerged body with respect to the sea bed comprises providing an upstanding member with a vertically extending recess therein fixed with respect to the sea bed, providing on the body support means including a hydraulic ram having a cylinder and a piston, reciprocable with respect to the cylinder along a downwardly extending support axis and carrying a plunger insertable into the recess of the upstanding member, disposing the body, with the ram retracted, with the support axis substantially aligned with the recess in the upstanding member and extending the ram to locate the plunger in the recess and support the body on the upstanding member by way of the support means and provide lateral support for the body by way of the plunger and recess wall. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partly cut away perspective view of a first embodiment of a support arrangement according to the present invention showing a moveable submerged body approaching an upstanding member on which it is to be supported, Figure 2 is a sectional elevation through the support arrangement of Figure 1 showing the body supported on the upstanding member, Figure 3 is a sectional elevation through a second embodiment of support arrangement according to the invention including support means set down upon an upstanding member for support thereby and immediately after setting down thereon, Figure 4 is a sectional elevation through the arrangement of Figure 3 showing the body fully supported on the upstanding member against lateral motion, Figure 5 is a sectional elevation through a third embodiment of support arrangement according to the invention disposed as Figure 3, Figure 6 is a sectional elevation through the arrangement of Figure 5 disposed as for Figure 4, Figure 7 is a sectional elevation through a fourth embodiment of support arrangement according to the invention, being a modification of, and disposed as, the arrangement of Figure 5, and Figure 8 is a sectional elevation through the arrangement of Figure 7 disposed as for Figure 4. Referring to Figures 1 and 2 a support arrangement 10 in accordance with the present invention comprises two parts, an upstanding member 11 fixed with respect to the sea bed and support means 10* , comprising at least a hydraulic ram 12, carried by a moveable submerged body 13 to be supported on the upstanding member. The upstanding member 11 conveniently comprises a post or pile of circular cross section forming a vertically extending projection of a subsea structure or sunk into the sea bed. The upper end of the member has a recess, conveniently called a socket recess 14, which extends for a predetermined distance along its vertical longitudinal axis. The socket recess is conveniently circular in cross section and has at its end and part way along its length changes in diameter defined by chamfered shoulder guide and support 15 and guide shoulder 16, the length L of recess of least diameter between guide shoulder 16 and the end of the recess having a significance discussed hereinafter. In the body 13 the support means 10' is manifested by the hydraulic ram 12 which comprises an elongate cylinder 17 fixed to the body and a piston 18 reciprocable therein along a support axis 19 extending substantially though the centre of gravity of the body and vertically with respect to the desired attitude of the supported body. The piston 18 has a shaft member 20 extendable from the piston downwardly along the support axis and carrying at the end a part or plunger insertable into the support recess 14. The plunger comprises a profiled pin 21 cooperable with the support recess 14, having a wide portion 22 adjacent the shaft 20 and a narrow end portion 23 separated therefrom by a chamfered shoulder 24 having the same profile as the guide and support shoulder 15 to seat thereon. The narrow end portion has a diameter slightly less than the narrowest part of socket recess 14 to form a sliding fit therein and, with the pin shoulder 24 or recess shoulder 15, a lateral load bearing surface against the recess wall. The cylinder 17 is conveniently mounted in an upper portion of the body to keep the raised pin protected within the body and may be of such a length that the lowered pin on the extended ram is above the centre of gravity of the body, in which case the lower part will then require a location recess, such a shown at 25. The body includes horizontal manoeuvring thrusters 24 to permit motion in at least two orthogonal directions and is suspended by an umbilical 27 from a surface vessel (not shown). The surface vessel is provided with motion compensation means by which vertical motion of the vessel is largely decoupled from the suspended body leaving a vertical position variation of —H which may, with modern equipment, be reduced to the order of —1 metre in force 7 seas. Control means 28 operates to provide hydraulic power to the ram 12 and receives signals to effect such control either from the surface vessel by way of umbilical 27 or, possibly, directly from transducers, shown as being provided by force or displacement sensor 28' or television cameras 28". To support the body on the upstanding member the submerged body is basically moved to a position with the support axis 19 aligned with the support recess 15 and the ram 12 above the member by no more than the extension length of the piston shaft. This may be done by an operator on the surface vessel observing the position of the body and post on a television camera 28' . The operator signals the control means 28 to extend the ram and insert the pin into the recess 14. It will be appreciated to ensure full entry into the recess with a potential body vertical uncertainty of 2H the ram must have at least this extension. The shoulder 16 acts as a guide for the . iarrow portion 23 of the pin guiding it into the wider part of the recess and the guide shoulder 16 guides it into the narrow portion of the recess which it penetrates until the pin shoulder 24 seats on the shoulder 15. At such time the ram will experience the weight of the body and this may be detected to limit ram extension. The cylinder pressure may be reduced to permit the cylinder, and the body, to move relative to the pin in accordance with the unco pensated motion of the suspending vessel. At this time the suspension umbilical may be slackened to decouple the body from motion of the surface vessel leaving it support solely by means of the pin 21 in recess 14. It will be appreciated that the pin 21 in recess 14 forms a support transferring vertical and lateral loads of, and on, the body into the upstanding member. If the body is self-contained and well balanced there may be little lateral loading if the support axis extends through the centre of gravity of the supported body as well as suspensed body. However, if the equilibrium of the body is to be disturbed, say by removing a heavy object therefrom or using it as a crane with winch and boom 29 to lift a heavy object, then the lateral forces between body and upstanding member are transmitted by way of the narrow portion 23 of the pin. The length L of the portion is chosen having regard to the magnitude of anticipated forces. Clearly, because of such ability to accommodate lateral forces by a pin of suitable dimensions, it is not essential for the supprt axis 19 to extend through the centre of gravity of the suspended body nor for the centre of gravity to be below the pin in the position it assumes in the supported body and such constraints apply only insofar as it is desired to dispose the unextended ram above the upstanding member for extension. The arrangement may include locating means comprising the aforementioned recess 25 which may have vertically tapered, that is, conical, walls to act as a funnel for a body lowered onto the upstanding member to guide the pin to a position above the recess 14 or, as shown in Figures 1 and 2, a recess 25 having boundaries of slightly larger diameter than the upstanding member, to receive it therein correctly disposed with respect to the support axis 11, and a tapered guide channel 30 extending laterally thereof to a side of the body. The depth of recess 25 and guide channel 30 is at least the vertical uncertainty 2H of the suspended body, although it will be appreciated that for a free flying body it may be less. In operation the suspended body is lowered from the surface vessel to one side of the upstanding member and adjacent the top thereof as observed by an attendent television camera 28". The positioning thrusters 26 are then operated to move the (vertically oscilatory) body laterally towards the upstanding member so that it is captured in the guide channel 30 and the lateral thrust maintained to locate it in the recess 25 and maintain it there until the ram 12 has extended and positioned the pin 21 in the recess 14. The camera 28" may be remote from the body on an attendant submersible or in the body and trained upon the recess 25 to observe capture of the post 11 therein. Alternatively a transducer 28' may respond directly to capture the post in the recess 25. The signals of transducer or camera need not go via the surface operator but may directly cause control means 28 to extend the ram. The insertable part, that is, the pin 21, may be disposed in the recess so as not to rotate therein and the body may be equally fixed with respect to rotation relative to it about the support axis so as to be fixed with respect to the upstanding member. For such function the wide portion 22 of the pin may be partly or totally omitted so that the body may be set down on the top of the upstanding member to provide the vertical support for the body, the pin 21 effectively then providing only lateral support by way of the recess walls. However, rotation of the body relatively to the upstanding member about the support axis may be desirable, particularly where the supported body is used as a crane mentioned above, to effect slewing thereof. It will be appreciated that the engagement between the pin and the socket recess, particularly by way of the tapered support shoulders, provides a high resistance to relative rotational motion. The ram 12 may be arranged such that the piston and cylinder are relatively rotatable about the support axis 19 whereby the support axis also becomes a rotational axis between the body 13 and part of the support means, the cylinder, and another part of the support means, the piston and plunger. To effect such rotational motion the body 13 may be provided with drive means having a driven member engageable with a circular wall portion of the arrangement operationally fixed with respect to the sea bed, the driven member being rotatable with respect to the body to rotate the body with respect to the upstanding member. The circular wall portion may be formed as a toothed ring adapted to mesh with a toothed driven member or the driven member may be adapted to make, and be biased into, frictional engagement with the wall portion to effect the rotation. In the embodiment shown in Figures 1 and 2, advantage is taken of the circular cross section of the upstanding member 11 and drive means 31 in the body includes a driven member 32 in the form of a roller biased into frictional contact with the outer wall of the upstanding member when the body is supported thereon. The driven member, in conjunction with other such roller members arrayed about the upstanding member provides rotation of the body and may provide additional lateral support if the bias is of sufficient force, for example being provided by further hydraulic ram means 33. Referring now to Figures 3 and 4 these show in sectional elevation similar to Figure 2 a second embodiment of the invention in which the support arrangement 35 permits rotation of a supported submerged body 13 with respect to the supporting upstanding member 11. The upstanding member 11 has a vertically extending recess 36 the walls of which are uniformly tapered and preferably, at the lower portion 36' thereof the taper is a conical one. Support means 37 carried by the body has a housing 38 including an apertured floor portion 39 adapted to seat on the upper end of the upstanding member 11 and a circular cylindrical side wall 40 at an upper end of which is carried a toothed gear ring 41 of drive means 42 described hereinafter. The circular side wall 40 also carries bearing means 43 on which is supported the body 13 and on which the body can rotate relative to the support means housing. The housing 43 also contains a hydraulic ram 44 comprising a cylinder 45 fixed with respect to the support means housing and a piston 46 reciprocable therein along a support axis 47 extending substantially through the centre of gravity of the body and its support means by control means 48 instructed from the surface by an operator or directly by tranducers (not shown) as outlined above. The piston is attached to a shaft member 49 extending downwardly along the support axis and at the end of which is carried a conically tapered plunger 50 displaceable with the piston 46 and forming a part of the support means insertable into the recess 36 when the support means housing is disposed seated on the upstanding member 11 as illustrated. To assist in centralisation of the support axis 47 with respect to the recess 36 the floor 39 of the housing may have downwardly projecting location lugs 51. The drive means 42 comprises in addition to the aforementioned toothed ring gear 41 comprises a drive motor 52 and an intermediate toothed driven member 53 both carried by the housing and in permanent mesh with the ring gear. Such a drive means provides a more positive drive than the frictional arrangement described above although it will be appreciated that such could be used if desired. In particular the disposition of the body and support means housing enables the drive ring or corresponding frictional engagement drive position to be provided on the housing and carried by body rather than on the upstanding member with reliance upon installation alignment and possibly operating environment conditions to effect drive. The body 13 may have a guide channel 30, as described above, in the lower surface thereof to assist in locating the support means, housing 38, above the upstanding member. A surface operator, observing the disposition of parts by a television camera (not shown), causes the body to be lowered onto the upstanding member followed by instruction to the control means 48 to extend the ram 44 to drive the plunger 50 into recess 36, providing by engagement between the plunger and recess walls lateral support for the body seated on the upstanding member by means of the support means housing, as shown in Figure 4. The piston 46 is not necessarily rotatable with respect to the cylinder 45 as both the housing containing the cylinder and the plunger are rotationally fixed with respect to the upstanding member in operation, rotation or slewing of the body with respect to the upstanding member being accommodated by way of bearings 43 between housing and body. It will be appreciated that if such rotational motion of the body with respect to upstanding member is not required the drive means 42 and the bearing 43 support between body and housing 38 may be omitted. Referring now to Figures 5 and 6, which correspond largely to Figures 3 and 4 and in which identical integers are given identical reference numbers, a third embodiment 55 of a support arrangement in accordance with the present invention is shown. This differs from the arrangement 35 described above in that the support means 37 has depending from the floor 39 thereof a plurality of pliable, and preferably, resilient, fingers 56 arrayed about the support axis 47 and forming a conically tubular funnel from the periphery of the floor aperture through which the plunger 50 descends. The array of fingers is of such dimensions as to locate freely into the support recess of the upstanding member as the body and support means is lowered onto it, there now being a requirement for greater vertical clearance between the body and top of upstanding member to effect the seating operation. After seating of the support means housing upon the upstanding member the ram 44 is extended to drive the plunger 50 into the support recess within the array of fingers 56 forcing them radially outwards with respect to the support axis 47 and wedging between the plunger and recess wall to provide additional lateral support between the recess wall and the floor of the support means housing, as shown in Figure 6. To release the body from the upstanding member, the ram 44 is contracted to withdraw the plunger and the fingers 56 are biased by their resilience away from the recess walls permitting the body and its support means to be raised clear of the upstanding member. It will be appreciated that the fingers need not be resilient but merely pliable in the outwardly radial direction provided that they are initially radially contracted to be inserted into the recess, that when the plunger is removed there is little frictional or other resistance to their being withdrawn from the recess by axial motion of the support means with respect to the upstanding member and that some means is provided of radially contracting them again before they are inserted into the recess of an upstanding member. Clearly the provision of radially resilient fingers provides a most convenient arrangement and also permits by suitable engagement between the resilient fingers and recess walls the ability to impede axial motion of support means relative to the upstanding member, that is, lifting of the body, when the plunger is installed. As the resilient fingers operatively make and break contact with the recess wall by radial motion the recess walls and outer surfaces of the fingers may be provided with a high degree of resistance to relative surface movement in the direction removing the fingers from the recess. This may be provided by cooperating projection and recesses, such by friction between suitably treated surfaces of the fingers and recess walls or by exaggerating the surfaces into one or more shoulders on the recess wall having abutment surfaces facing downwardly into the recess and cooperating outer surfaces of the fingers having abutment surfaces facing upwardly. Figures 7 and 8, corresponding substantially to Figures 5 and 6 respectively, illustrate one form of such modified arrangement 60 in which the recess 36 in the upstanding member 11 is provided with a re-entrant portion 36' defining a peripheral shoulder 61 having a generally downwardly facing abutment surface 62 and the outer surfaces of the resilient fingers 56 are provided with shoulders 63 having cooperating generally upwardly facing abutment surfaces 64. It will be appreciated, and figure 7 illustrates, that the resilient fingers and shoulders 64 thereof are biased to assume a radial dimensions with respect to the support axis 46 that permits their axial insertion into and removal from the recess with the plunger removed, but that when the plunger 50 is inserted into the recess, as shown in Figure 8, the fingers are displaced radially and the abutment .surfaces 62 and 64 of shoulders 61 and 63 overlap to provide a latch or inhibition of relative axial movement between the support means and upstanding member which would permit unwanted lifting of the body. Clearly, where the ram is retracted the resilience of the fingers biases them out of engagement with the wall and permits raising of the body and support means.

Claims: Claims : 1. A subsea support arrangement for a moveable submerged body comprising an upstanding member fixed with respect to the sea bed having a recess therein extending for a predetermined distance in a vertical direction and, on the body, support means adapted to rest on the upstanding member and including a part insertable into the recess to provide lateral support between the support means and the upstanding member. 2. A subsea support arrangement as claimed in claim 1 in which the support means includes a hydraulic ram comprising an elongate cylinder, a piston reciprocable therein along a support axis extending downwardly through the body and a shaft member connected to the piston and extending along the support axis, a plunger carried on an end of the shaft member comprising said insertable part and control means operable to displace the piston along the support axis so as to insert the plunger into the recess to provide lateral support between the support means and the upstanding member by way of the recess wall. 3. A subsea support arrangement as claimed in claim 1 or claim 2 in which said insertable part is adapted to be disposed in the recess so as not to rotate therein and the supported body is rotatable with respect to at least part of the support means, rotationally fixed with respect to the insertable part, about the support axis. 4. A subsea support arrangement as claimed in claim 3 in which the piston and cylinder are fixed against relative rotation about the support axis and said cylinder is contained within a housing on which the body is supported for rotation about the support axis. 5. A subsea support arrangement as claimed in claim 4 in which the floor of the housing is adapted to rest on top of the upstanding member. 6. A subsea support arrangement as claimed in any one of the preceeding claims in which the part of the support means insertable into the recess of the upstanding member also comprises a plurality of pliable fingers extending downwardly of the support means and arrayed about the support axis, each of said fingers being radially displaceable by the insertion of the plunger into the recess to be wedged between the plunger and the recess wall. 7. A subsea support arrangement as claimed in claim 6 in 5 which the pliable fingers are resilient. 8. A subsea support arrangement as claimed in claim 6 in which the outer surfaces of at least some of the fingers and the wall of the recess are provided with interengaging surface profiles operable to inhibit movement of wall engaging fingers 10 out of the recess. 9. A subsea support arrangement as claimed in claim 8 in which the recess in the upstanding member contains a reentrant portion with a downwardly facing shoulder and at least some of said resilient fingers have on their radially outer surfaces 15 upwardly facing shoulders adapted to align with the downwardly facing recess shoulders upon insertion of the fingers into the recess and latch the radially displaced fingers therewith against upward motion of the support means with respect to the upstanding member. 20 10. A subsea support arrangement as claimed in any one of claims 1 to 3 in which the recess has portions of different cross sectional dimensions separated by upwardly facing shoulders and the plunger comprises a pin of corresponding profile arranged to sit upon said shoulders when inserted into the recess. Z5 11. A subsea support arrangement as claimed in claim 10 in which the shoulders are tapered along the recess. 12. A subsea support arrangement as claimed in claim 10 or claim 11 when dependent on claim 3 in which the ram cylinder is fixed with respect to the body and the piston is rotatable with 30 respect to the cylinder about the support axis to permit rotation of the body with respect to the support member. 13. A subsea support arrangement as claimed in any one of the preceding claims including a location recess in the underside of the body dimensioned to accommodate an upper portion of the 35 upstanding member. 14. A subsea support arrangement as claimed in claim 13 in which the body includes a guide channel between the location recess and a side wall of the body to permit the body to be moved laterally to accommodate the upper portion of the upstanding member within the location recess. 15. A subsea support arrangement as claimed in claim 14 in which the guide channel is convergent towards the location recess. 16. A subsea support arrangement as claimed in any one of claims 13 to 15 in which cross sectional dimensions of the location recess are of the same order of magnitude as the upstanding member to locate the support axis with respect to the recess of the upstanding member prior to extension of the piston member. 17. A subsea support arrangement as claimed in any one of claims 13 to 16 in which the moveable submerged body is suspended from a surface vessel and subjected to vertical excursions and the depth of the location recess and extension of the ram is not less than the maximum vertical excursion of the suspended body. 18. A subsea support arrangement as claimed in any one of claims 3 to 17 when dependent on claim 3 in which the rotatable body includes drive means having a driven member engageable with a circular wall portion of the arrangement operationally fixed with respect to the sea bed and rotatable with respect to the body to rotate the body with respect to the upstanding member. 19. A subsea support arrangement as claimed in claim 18 in which the circular wall portion is at the periphery of the support means. 20. A subsea support arrangement as claimed in claim 18 in which the circular wall portion is formed at the outer surface of the upstanding member. 21. A subsea support arrangement as claimed in any one of claim 18 to 20 in which the circular wall portion is formed as a toothed ring gear adapted to mesh with a toothed driven member. 22. A subsea support arrangement as claimed in any one of claims 18 to 20 in which the driven member is adapted to make frictional engagement with the surface of said circular wall portion and the drive means includes bias means operable to press the driven member into engagement with the circular wall portion. 23. A subsea support arrangement as claimed in any one of the preceding claims in which the upstanding member is a post. 24. A subsea support arrangement as claimed in claim 2 or any claim dependent on claim 2 in which the support axis is arranged to extend through the centre of gravity of the moveable submerged body. 25. A subsea support arrangement substantially as herein described with reference to, and as shown in, Figures 1 and 2, or Figures 3 and 4, or Figures 5 and 6, or Figures 7 and 8 of the accompanying drawings. 26. A method of supporting a moveable submerged body with respect to the sea bed comprising providing an upstanding member • with a vertically extending recess therein fixed with respect to the sea bed, providing on the body support means including a hydraulic ram having a cylinder and a piston, reciprocable with respect to the cylinder along a downwardly extending support axis and carrying a plunger insertable into the recess of the upstanding member, disposing the body, with the ram retracted, with the support axis substantially aligned with the recess in the upstanding member and extending the ram to locate the plunger in the recess and support the body on the upstanding member by way of the support means and provide lateral support for the body by way of the plunger and recess wall. 27. A method as claimed in claim 26 comprising forming the plunger as an elongate pin dimensioned to cooperate with the recess and provide vertical support for the body on the upstanding member by way of the piston. 28. A method as claimed in claim 26 or claim 27 comprising forming the ram such that the piston is rotatable relative to the cylinder about the support axis and the cylinder is fixed with respect to the body and rotating the body with respect to the upstanding member by way of rotation within the ram between the body and the pin. 29. A method as claimed in claim 26 comprising forming on the support means downwardly dependent fingers displaceable radially with respect to the support axis by axial displacement of the plunger along the support axis upon ram extension, lowering the body and support means towards the upstanding member such that the fingers locate in the recess and extending the ram to displace and wedge the fingers against the recess wall. 30. A method as claimed in claim 29 comprising providing the radially resilient fingers and recess wall with cooperable projections and recesses and causing displacement of the fingers by the ram to latch the shoulders into cooperation and prevent upward motion of the body with respect to the upstanding member. 31. A method as claimed in any one of claims 26 to 30 comprising providing a location recess in the bottom of the body to accommodate an upper portion of the upstanding member in alignment with the support axis and a guide channel between the recess and a side of the body and disposing the body with respect to the upstanding member by moving it laterally with respect to the upper position of the upstanding member, capturing said portion in the guide channel and moving the body to locate the portion in the location recess for extension of the ram. 32. A method of supporting a moveable submerged body with respect to the sea bed substantially as herein described with reference to Figures 1 and 2 or Figures 3 to 8 of the accompanying drawings.

Inventors: CHAPMAN IAIN MCLEAN, LOGAN WILLIAM ALLAN DEMPSTER, CHAPMAN, IAIN, MCLEAN, LOGAN, WILLIAM, ALLAN, DEMPSTER
Applicants: FSSL LTD, MOBIL OIL CORP, FSSL LIMITED, MOBIL OIL CORPORATION
Application year: 1989
Main classification: B63C11
IPC codes: B63C11, E21B41