FR2771703A1 - MOORING DEVICE FOR A FLOATING STRUCTURE - Google Patents

Abstract

The hull (2) of the floating structure (1) is traversed by a vertical axis well (3) in which a turret (7) is rotatably mounted around the vertical axis (10) of the well (3). Mooring lines (8) are each connected by their upper part to a connecting member (17, 18). Each of the connecting members (17, 18) comprises a key (17) housed in a notch (16) of radial direction in a peripheral part of a horizontal table (14) constituting the lower part of the turret (7). The key (17) is suspended from the turret (7) by means of a tie rod (18). The key (17) to which a mooring line (8) is connected is movable in a radial direction relative to the table (14) of the turret (7) and relative to the internal wall of a bearing (15 ) arranged coaxially in the lower part of the well (3).

Description

The invention relates to a mooring device for a floating structure

  and in particular for a boat used for drilling at sea or

  for the exploitation of oil or gas wells underwater.

  Boats known for drilling at sea or for the ex-

  exploitation of oil or gas wells having a wellhead at the bottom of a sea or ocean. It is necessary to secure these boats so that the boat does not drift during drilling or

  the operation of a well, for example under the effect of currents or wind.

  There are known boat mooring systems used for the ex-

  offshore petroleum exploitation, the hull of which is crossed by a vertical shaft opening into the open air at its upper part, at the level of an upper deck of the boat and, at its lower part, in the body of water on which floats the boat, at the bottom of the hull, below the waterline. The vertical well can be used in particular to pass the drill string or the operating pipes of the well through the hull of the boat, towards the bottom of the body of water on

which floats the boat.

  There are known devices for mooring boats comprising a

  vertical shaft wells passing through the hull, which include a turret available

  placed in the well in a substantially coaxial arrangement with respect to the well which is rotatably mounted, via its upper part, on

  the hull of the boat, around the vertical axis of the well.

  Mooring means such as mooring lines constituted by chains are connected to the turret and are distributed around the axis of the turret, so as to oppose the drift of the turret, under the effect of transverse forces exerted on the boat. Because the turret is held in place, the boat, which is connected via a bearing to the upper part of the turret, is held against the transverse forces, so that any drift is avoided Of the boat. The boat can only turn around the axis of the turret, because it is rotatably mounted

  relative to the turret via the upper bearing.

  When the mooring lines which have a lower part extending towards the sea or ocean floor are connected by their upper part, directly to the lower part of the turret which is

  generally produced in the form of a circular horizontal table

  created with a certain radial clearance in the lower part of the vertical shaft, all of the transverse forces and torques exerted by the boat on the

  turret maintained by the mooring lines is transmitted by the upper bearing

  laughing which must therefore be designed in a massive and very resistant.

  It is possible to make part of these efforts take up again by the table constituting the lower part of the turret, by placing against the internal surface of the vertical well, in its lower part opposite the table, a bearing coaxial with the well and at the table through which the table

  can come to rest against the vertical well of the hull of the boat, under the eff-

  of transverse efforts. However, in this case, the bearing and the lower part

  higher of the vertical well undergo impacts or forces which can be the cause of a bending of the body of the turret and a deformation of the bearing,

for example by ovalization.

  It may therefore be preferable to liaise with the higher parties.

  res mooring lines with the turret, by means of

  link pivotally mounted on the turret around a horizontal axis, ma-

  to be able to move each in a radial direction of the green well

  tical and turret, under the effect of the forces exerted by the lines of moor-

  rage to come to bear on a lower bearing of the tank well. However

  in this case, the torque exerted by the mobile boat in rotation around

  from the axis of the vertical well is transmitted to the mooring lines, via

  diary of the connecting members articulated on the turret, so that these or-

  hinged connecting hinges which undergo the torque risk of deforming and

to be damaged.

  The object of the invention is therefore to propose a mooring device for a floating structure having a hull traversed by a well with a vertical axis, comprising a turret disposed in the well and rotatably mounted by its upper part on the hull of the floating structure, around the vertical axis of the well, mooring means distributed around the axis of the turret, each having a lower part extending towards the bottom of a body of water on which the floating structure and an upper part connected to a connecting member mounted to move in a radial direction relative to the well and to the turret, this device making it possible to re-

  take the transverse forces and the torque exerted by the flow structure-

  aunt, without risk of damage to the connecting members of the mooring means. For this purpose, each of the connecting members comprises a key housed in a notch of radial direction in a peripheral part of a horizontal table constituting a lower part of the turret, so that the key to which is connected at least one means of mooring is movable in a radial direction relative to the turret table and

  relative to the inner wall of the vessel well.

  Preferably, the key is pivotally suspended from the turret, by means of at least one tie rod having axes of articulation hinged to the turret and to the key, in a horizontal direction. we will describe, by way of examples, with reference to the appended figures, several modes

  for producing a mooring device according to the invention of a utility boat

  se for oil exploitation at sea.

  FIG. 1 is a schematic view in elevation and in section through

  tielle of a boat comprising a mooring device according to the invention.

  Figure 2 is an elevational view in section through a vertical plane

  of the part of a mooring device according to the invention and according to a pre-

  mier embodiment arranged in the vertical well of the boat.

  Figure 3 is a sectional view along 3-3 of Figure 2.

  Figure 4 is a sectional view similar to the view of Figure 2

  of an alternative embodiment of the mooring device.

  Figure 5 is an elevational view in partial section along 5-5

  of FIG. 6 of the upper part of an articulated connecting member of the device

positive mooring.

  Figure 6 is a top view of the upper part of the device.

  articulated link shown in Figure 5.

  Figure 7 is a top view and in section through a horizontal plane

  of the lower part of an articulated connecting member of the securing device

  rage. Figure 8 is a sectional and elevational view along 8-8 of the

figure 7.

  In Figure 1, there is shown a boat provided with a mooring device according to the invention, generally designated by the reference

1.

  The boat 1 has a hull 2 crossed by a vertical well 3

  the upper part of which opens into the open air, at the level of an upper deck

rieur 4 of hull 2 of boat 1.

  The vertical well 3 opens, at its lower part, through the bottom

  of the hull 2 of boat 1, in the sea water 5 on which the boat floats

sheet 1.

  Sea water 5 fills the vertical well 3, up to a level 6 cor-

  corresponding to the waterline of the boat.

  In the case of a boat 1 used for petroleum exploitation, the height in the axial direction of the central part of the hull 2 and therefore the length of the well in the axial direction are of the order of 30 meters. The

  well has a diameter of the order of 7 to 8 meters.

  The boat mooring device 1 comprises a turret 7 of generally cylindrical shape arranged coaxially inside the well 3 and mooring lines 8 connected to connecting pieces at the lower end of the turret 7, as will be explained

  thereafter with reference to FIGS. 2 and 3.

  Each of the mooring lines 8 which is constituted by a set of very long chains (several kilometers or more

  tens of kilometers) is made up of very large links

large mass.

  Each of the mooring lines 8 has a lower part 8a extending towards the bottom 9 of the sea 5 which is made up of chains which are generally secured to anchoring means on the sea bottom

  9, at their end part resting on the bottom of the sea.

  Each of the lines 8 has an upper end portion 8b

  which is connected to a connecting member at a lower end portion

  turret 7, as will be described below.

  The anchor lines 8 are distributed around the axis 10 of the ver-

  tical 3, so as to maintain the turret 7 in a position

  substantially fixed relative to the bottom 9 of the sea 5.

  In the embodiment shown in FIGS. 2 and 3, the device

  positive mooring comprises three anchor lines each consisting of four chains, the upper end parts of which are connected to connecting members at the level of the lower part of the turret 7, in three zones distributed around the axis 10 of the turret and the vertical shaft 3, the positions of which are located 120 from one another around the axis 10. The turret 7 comprises an upper table 11 constituted by a rigid circular structure of great thickness, perpendicular to the vertical axis

  10 of the turret, by means of which the turret 7 is mounted

  tative on the upper part of the hull 2 of the boat, around the axis 10

  vertical well 3, using a roller crown 12. The crown

  lets 12 is fixed via a support 12a on the upper part

  of the hull 2 of the boat, the support 12a comprising an an-

  ring which is fixed by screwing on the upper part of the shell 2,

  around the upper end of the well 3.

  The roller crown 12 comprises a set of rollers

  ment 13a with horizontal axes mounted on the internal lower part of the crown 12, on which the upper table 11 of the turret comes to rest

  7. The rolling crown 12 also includes a set of ga-

  runners 13b with horizontal axes fixed on the upper part

  dull crown 12, coming to bear on the upper surface of the table 11. Finally, the crown 12 comprises a set of rollers 13c with vertical axes fixed on the internal cylindrical surface of the crown 12 coming into contact with the external cylindrical edge of the upper table 11. In this way, the upper table 11 is perfectly maintained and guided in rotation about the axis 10 of the vertical well 3. In the case where the rolling diameter of the roller crown 12 can be limited to a value of around 7 meters, the roller crown

  can be made in one piece. On the other hand, in the case where the dia-

  roll meter of the crown 12 is greater than 7 meters, it may be necessary to produce the roller crown 12 in several sectors which

  are assembled and fixed on the support 12a.

  The lower end part of the turret 7 is constituted by a

  circular table 14 at which the upper ends of the lines

  anchor genes 8 are connected to connecting members in the manner which

will be explained later.

  The diameter of the table 14 is substantially less than the inside diameter of the well 3, so that there remains a free space of a certain width between the peripheral edge of the table 14 and the internal surface of the

lower part of the well 3.

  A support bearing 15 is fixed, in a coaxial arrangement, against the internal surface of the well 3, in its lower part, opposite the table 14. However, there remains a radial clearance of the order of 30 mm between the outer peripheral surface of the table 14 and the inner bearing surface of the bearing 15. The turret 7 is produced in a circular hollow form, so that one can pass inside, in the vertical direction , tubes or pipes from the upper part of the hull 2 of the boat,

towards the bottom of the sea.

  The table 14 constituting the lower part of the turret 7 comprises,

  in its peripheral part, three notches 16 of radial direction open out

  edge on the outer peripheral surface of the table 14 and extending following

  for the entire thickness of the table 14.

  The notches 16 are arranged in three zones of the table 14, the positions of which are located 120 from one another around the axis 10 of

turret 7.

  In each of the notches 16 of the peripheral part of the table 14 is disposed a key 17 to which the ends of the

  chains constituting an anchor line 8.

  The key 17 has a width in the circumferential direction a little less than the width of the notch 16, so that the key 17 is mounted freely inside the notch 16, which allows it to move in the radial direction of the turret 7, towards the internal surface of the bearing 15 fixed to the lower part of the well 3, opposite the table 14. In addition, the key 17 has a length in the direction

  radial less than the radial length of the notch 16, so that the classification

  vette has a certain radial clearance inside the notch 16, between the rear surface 16a of the notch 16 and the internal surface 15a of the

level 15.

  Each of the keys 17 is suspended from the upper table 11 of

  the turret 7, by means of a suspension tie rod 18.

  The suspension tie rod 18 is mounted articulated at one of its ends.

  tees on the upper table 11 and at its other end on the key 17,

  around respective horizontal axes 18a and 18b.

  As can be seen in FIGS. 5 and 6, the upper table 11 of

  the turret 7 is crossed by an opening 19 of rectangular shape

  forced at the periphery by a frame 20 of rectangular current section.

  Inside the frame 20, are arranged in transverse directions

  versales, T-shaped suspension plates 21 which are welded

  on the frame 20. The suspension plates 21 delimit suc-

  stops inside the frame 20 in each of which can be pivotally mounted a link 38 consisting of two parallel arms 38a and 38b

  suspended from a shaft 22 mounted and stopped in rotation between two plates 21.

  The spacing between the arms 18a and 18b is maintained by a spacer tube

23 engaged on the shaft 22.

  Each of the tie rods 18 mounted pivoting about a horizontal axis inside the frame 20 ensures the suspension of a key 17 in which

  are received and fixed the ends of the chains of an anchor line 8.

  In the case where each of the anchor lines has four chains

  nes, the key 17 is suspended from the upper table 11 of the turret 7, by means of four links 18 each comprising two arms

  38a and 38b parallel to each other and arranged with a certain spacing.

  As can be seen in FIGS. 7 and 8, the key 7 is produced in the form of a box of substantially parallelepiped shape having an external wall 17a directed towards a bearing and sliding surface 15a of the bearing 15, the shape of which in cylinder portion corresponds to the shape of

  the bearing surface of the bearing 15 disposed opposite.

  The key 17 also has walls 17b parallel to each other

  and substantially perpendicular to the support wall 17a of the key.

  The walls 17b delimit between them successive spaces in

  each of which penetrates the lower end part of a link 38.

  The walls 17b are interconnected and held by ribs

res 24.

  Each of the walls 17b has, at its rear end opposite the support wall 17a, a recess for the engagement of two ends

  shaft 25 integral with the body 26 of a chain guide device tu-

bular 27.

  On the shaft ends 25 are engaged the lower end portions

  laughing arms 38a and 38b of a link 38 which are crossed by openings for passage of the shaft ends 25. The body 26 of the chain guide device against which the end portions of the arms 38a and

  38b come into support constitutes both a spacer maintaining the

  arm 38a and 38b and a circular support.

  The shaft ends 25 are held in half bores (cut

  diametral) on the walls 17b, by caps 28 comprising the other of-

  mid-bore and fixed by screws on the walls 17b.

  In this way, each of the rods 18 arranged in an es-

  space between two successive walls 17b is hingedly connected to the key 17 and to the chain passage device 27 of tubular shape which

  is fixed in an opening passing through the body 26.

  The rods 38 which are fixed by their lower part, in an articulated manner, to the key 17, around a common horizontal articulation axis

29 constitute a tie rod 18.

  As can be seen, in particular in FIG. 8, the chain guiding devices 27 or "fairleads" are produced in tubular form and successively comprise a frustoconical part for engaging a chain and a coaxial cylindrical part engaged in the opening of the body 26 in a direction 30 inclined relative to the horizontal plane. The angle

  of inclination of the axes of the fairleads 27 is at least equal to 20.

  Each fairlead 27 has a diametrically widened end flange 31 in its end part located at the rear of the link 38. On the flange 31 is fixed a slide 32 on which is slidably mounted, in a direction perpendicular to the axis of fairlead 27, a wedge 33 having a central opening in which is housed the lower part of the first link of the anchoring chain 34, in the position of

  blocking of the shim 33, as shown in FIG. 8.

  The wedge 33 can be moved between a low out of service position in which the wedge 33 is in abutment on the lower part of the slide 32 constituting a bearing heel and a high service position shown in FIG. 8 in which the wedge 33 locks chain 34 of

the mooring line.

  When the wedge 33 is in its out-of-service position, the outlet opening of the fairlead 27, at the flange 31, is free, so that

  can move the chain inside the fairlead, by pulling in the direction

  tion 30 to ensure the tension of the anchor line, for example in use

  sant a winch carried by the hull 2 of the boat.

  When the chain has been hoisted into the fairlead, the shim 33 is moved

  in its high service position in which the shim 33 ensures the blocking

  cage of part of a link of the chain 34 introduced into the wedge 33, by

  through a bearing surface.

  Each of the chains 34 introduced into a guide fairlead 27

  connected to the key 17 is tensioned and then blocked by an analog stop piece

to stop 33.

  The upper end of the anchor line, the fairlead and the landing are immersed in the body of water on which the boat 2 floats. As a result, the part 33 is not accessible and its movements between its out position service and its service position are achieved using a motor

  remotely controlled, for example from the upper deck of the boat.

  When the fixing has been carried out, as indicated above, of the assembly

  ble of the chains 34 of the anchor line 8 connected to the key 17, the key 17 is biased in the radial direction towards the internal surface

  1 5a from the bearing 15 coaxial to the well 3 of the shell 2.

  As shown in Figure 7, the vertical side surfaces

  radial direction of the notch 16 of the table 14 are covered each

  one of an anti-friction lining 14a or 14b. The key 17 is slidably mounted between the linings 14a and 14b, practically without play, so that the key 17 returned in the radial direction by the mooring line

  8 can only move in the radial direction, and that the surface ex-

  dull front wall 17a of key 17 comes to bear against internal surface 15a of bearing 15 covered with an anti-friction lining 15c

  constituting a sliding surface of the keys during the displacements

  relative elements in rotation of the boat and the turret.

  The inclination of the anchor lines 8, which corresponds to the angle of inclination

  origin of the axis 30 of the fairleads 27, is chosen so that a preponderant part of the horizontal component of the force exerted by the mooring lines is exerted directly on the internal surface of the bearing 15 integral

from the hull well.

  The angle of the axis 30 of the fairleads with the horizontal plane can be

between 20 and 80.

  A certain fraction of the vertical force exerted by the weight of the mooring line is also exerted directly on the internal surface of the bearing

15.

  This significantly reduces the forces transmitted to the table

  upper 11 of the turret 7, by means of the tie rod 18.

  The fact that each rod of the tie rod 18 is articulated at one of its ends on the upper table 11 of the turret 7, around a horizontal axis 18a, allows displacement by pivoting in the radial direction

  of the key 17 in the direction of the internal surface 15a of the bearing 15. When-

  that the boat is stressed by transverse forces, the support

  keys against the surface 15a of the bearing 15 prevents impacts from occurring

  duize between the table 14 of the turret 7 and the bearing 15 of the well 3 and between the rear surface of the keys and the rear surface of the notches 16. Due to its articulation around the axis 29 parallel to the axis of articulation 18a des

  rods 38 on the turret 7, the key 17 can be oriented so as to

  nir in perfect support against the internal surface 15a of the bearing 15. This improves the transmission of forces between the mooring lines and the hull of the

  boat. In addition, the key 17 is mounted practically without play inside.

  laughter of the notch 16 of the table 14, so that all of the couples exerted on the turret 7, due to the couples exerted by the shell 2 are

  taken from table 14, and transmitted directly to the mooring lines

  rage 8. This avoids transmitting torques to the upper bearing 12 of

turret 7.

  The torques are taken up by mooring lines 8, directly at

  level of the lower table 14, via the keys 17, the lines

  mooring pins 8 and the notches 16 of the table 14 in which the keys are placed being distributed around the axis 10 common to the

  vertical well 3 and turret 7.

  The keys 17 are made of a material resistant to corrosion.

  seawater, such as a nickel alloy or ferritic silicon iron. The keys 17 are mounted completely free inside the notches 16 of the table 14 and have only a latitude of movement in

the radial direction.

  In FIG. 4, an alternative embodiment of the arrangement is shown.

  mooring sitive. The corresponding elements in FIGS. 2 and 4 bear the same references with, however, the exponent '(prime) with regard to

  the elements of the variant embodiment shown in FIG. 4.

  The mooring device is similar, in its general structure, to the mooring device described with reference to FIG. 2 and comprises a turret 7 'rotatably mounted by means of a crown 12' inside the

  well 3 'passing through the hull 2' of a boat.

  The lower table 14 'of the turret 7' has notches 16 'into each of which is inserted a key 17'. The notches 16 'and the keys 17' are distributed around the axis 10 'common to the turret 7'

  and to the well 3 'and each of the keys 17' is integral with the upper part

8 'mooring line.

  One can use for example three mooring lines 8 'connected to three keys 17' mounted in notches 16 'of the table 14' to 120 around

from the axis 10 'of the turret 7'.

  The notches 16 'in the same way as the notches 16 of the dis-

  positive shown in Figure 2 have a length in the radial direction

  greater than the radial length of the keys 17 ′, so that the keys

  your 17 'are mounted with a certain clearance between the rear surface 16'a of the notch 16' and the internal surface 15'a of the bearing 15 'secured to the

  internal surface of the well 3 'in its lower end part.

  The keys 17 'are mounted articulated at the end of tie rods 18' which may be constituted, as before, by a set of

  rods parallel to each other and each consisting of two parallel arms

  the the. Unlike the embodiment shown in FIG. 2, the

  tie rods 18 'for suspension of the keys 17' are not fixed to the upper table

  upper 11 'of the turret 7', at their upper part, but on ears 35

  integral with the body of the turret 7 ′ and arranged 120 from one another

  around the axis 10 'of the turret. In this way, the upper axis 18 ′ of articulation of the tie rod 18 ′ on the turret 7 ′ is at a level substantially lower than the level of the upper table 11 ′. This avoids the use of very long rods (for example of the order of 30 m), the ears 35 and the axes 18'a being placed a few meters above the lower table 14 '. On the other hand, the pivot angle of the tie rods 18 'for obtaining the support of the keys 17' on the bearing 15 'is greater than the pivot angle in the case where the upper articulation of the tie rod is placed at the

upper level of the turret.

  The operation and the advantages of the mooring device according to the embodiment variant are substantially identical to the operating mode.

* ment and the advantages of the device described above.

  In particular, the mooring lines 8 'distributed around the axis 10'

  recall the keys 17 'in the radial direction, against the

  inner face 15'a of the bearing 15 '.

  During transverse movements of the boat, this avoids all

  impact of the rear part of the keys 17 'on the internal surface 16'a of the

check mark 16 '.

  In addition, the couples exerted on the turret 7 ′ are taken up directly-

  by the mooring lines 8 ', at the level of the lower table 14', from the

  the fact that the keys are mounted practically without play in the housings

16 'ches.

  The articulation of the keys 17 'around a horizontal axis 29' to the ex-

  lower end of the tie rod 18 'allows an orientation of the key which comes

  in contact through its entire front surface with the internal surface 15'a of the

link 15 '.

  The invention therefore generally makes it possible to avoid transmitting excessive forces or torques to the upper bearing of the turret 7 ′ and any risk of impact between the attachments of the mooring lines and the

lower part of the turret.

  The invention is not limited to the embodiments which have been described.

  crits. This is how one can use any number of mooring lines themselves made up of any number of chains or cables placed in parallel and connected to a key mounted mobile in the

  radial direction relative to the turret.

  In all cases, however, the mooring lines are regularly distributed around the axis common to the hull well and the turret, so as to take up the torques and transverse forces exerted on the boat and through it on the turret kept immobile by the

mooring lines.

  The tie rods can consist of one or more rods

  rigid arranged in parallel or by one or more rods or cables

  wheat arranged substantially vertically and connected to one of their ends

  tees at one part of the turret and at their other end at a key.

  The tie rods can be connected to the turret, in any area

  than the turret, depending on its height, depending on the characteristics re-

  sought for the mooring device.

  The tie rods constituted by rods or cables could be connected, by their upper part, to the hull of the boat, instead of being connected

  with the turret, to ensure the suspension of the keys.

  The keys could also be mounted sliding in a

  radial direction on a horizontal part of the lower table of the

  real; in this case, the keys would be both housed between two surfaces

  these lateral radial direction of the table and resting on the table. In

  in all cases, the keys can only move in the direction

  dial and are integral in rotation with the turret.

  The mooring lines can be connected in any way

  that at the keys, the use of fairleads, as described, allows

  both to ensure effective guidance of the upper part of the components

mooring lines.

  The invention applies not only to boats used in the context of underwater petroleum exploitation but also in the case of any floating structure used for petroleum exploitation at sea or in any other form of activities at sea in which it is necessary

  to immobilize a floating structure, on the surface of the sea or ocean.

Claims (10)

  1.- Mooring device for a floating structure (1) having a hull (2, 2 ') crossed by a well (3, 3') of vertical axis, comprising a turret (7, 7 ') arranged in the well (3, 3 ') and rotatably mounted by its upper part (12, 12') on the hull (2, 2 ') of the floating structure (1) around the vertical axis (10, 10') of the well (3, 3 '), mooring means (8, 8') distributed   around the axis (10, 10 ') of the turret (7, 7') each having a lower part   lower extending to the bottom of a body of water (5) on which floats the floating structure (1) and an upper part connected to a connecting member (17, 18, 17 ', 18') mounted movably in a radial direction relative to the   well (3, 3 ') and turret (7, 7'), characterized in that each of the or-   connecting hoses (17, 18, 17 ', 18') includes a key (17, 17 ') housed   in a notch (16, 16 ') of radial direction in a peripheral part   as a horizontal table (14, 14 ') constituting a lower part of the turret (7, 7'), so that the key (17, 17 ') to which is connected at least one mooring means (8 , 8 ') is movable in a radial direction relative to the horizontal table (14, 14') and relative to the internal wall   (15a, 15'a) of the lower part (15) of the tank well (3, 3 ').   2.- Device according to claim 1, characterized in that the lower part of the tank well (3, 3 ') comprises a bearing (15, 15') fixed against the internal surface of the lower part of the tank well ( 3, 3 '), in a coaxial arrangement.   3.- Device according to claim 2, characterized in that a surface (15a, 15'a) of the bearing (15, 15 ') directed towards the inside of the well of   tank (3, 3 ') is covered with an anti-friction lining.   4.- Device according to any one of claims 1 to 3, ca-   characterized by the fact that each of the keys (17) is mounted with practically no play between two lateral surfaces in the radial direction of the notch (16) and with a certain play in the radial direction relative to a rear surface (16a, 16 ' a) of the notch (16, 16 '), so that the key (17, 17') has a certain clearance in the radial direction between a rear surface (16a, 16'a) of the notch (16, 16 ') and the internal wall (15a, 'a) from the well (3).   5.- Device according to claim 4, characterized in that the lateral surfaces of the radial direction of the notch (16) are covered with an anti-friction lining (14a, 14b).   6.- Device according to any one of claims 1 to 5, ca-   characterized by the fact that the key (17, 17 ') is suspended in a pi-   voting to the turret (7, 7 '), by means of at least one tie rod (18, 18') having hinge pins articulated to the turret (7, 7 ') and to the key (17, 17 '), horizontal direction, 7.- Device according to claim 6, characterized in that each of the tie rods (18, 18') connected to a key (17, 17 ') consists of a plurality of rigid rods ( 38) parallel to one another articulated at one of their ends or lower end on the key (17), around a common horizontal axis (29) and at their upper part, on the turret (7) around an axis horizontal (18a) parallel to the articulation axis (29) of the rods on the key (17).   8.- Device according to claim 7, characterized in that   each of the links (38) consists of two arms (38a, 38b) parallel them between them.   9.- Device according to any one of claims 7 and 8, ca-   characterized by the fact that a guide tube (27) of a mooring chain (34) is connected to the key (17) and to the lower end of each of the rods (38) of the tie rod (18).   10.- Device according to claim 9, characterized in that   each of the guide tubes (27) of a mooring chain (34), or   mards, comprises an end flange (31) crossed by an opening for passage of the mooring chain (34), at the exit of the fairlead (27) and a   block (33) for blocking the chain (34) movable between an out-of-service position   vice allowing the free passage of the mooring chain (34) through the fairlead (27) and a blocking position of the mooring chain (34) by compared to the fairlead (27).   11.- Device according to any one of claims 1 to 10,   characterized by the fact that it has three mooring lines (8) and three   bolts (17) each inserted in a notch (16) of the horizontal table (14) of the turret (7), distributed at 120 around the axis (10) of the turret (7) and of the vertical well (3) . 12.- Device according to claim 11, characterized in that each of the mooring lines (8) comprises four chains (34) arranged   parallel to each other and connected to a key (17).