EP0425339B1 - Suspension and handling device, integrated in the legs of a self elevating offshore platform - Google Patents

Description

The present invention relates to an integrated suspension and handling system for platform support legs for drilling or offshore oil production and relates more particularly to self-elevating platforms.

Platforms of this type generally have legs resting on the seabed and a hull mounted movable and adjustable in height along the legs.

The whole platform is brought into flotation to the drilling or operating site and the legs are lowered until contact with the seabed, then by resting on the legs, the hull is hoisted above from sea level, to an altitude that puts it beyond the reach of the highest waves.

The hull is therefore movable along the legs of the platform by means of lifting mechanisms integral with said hull and comprising output pinions whose bearings are integral with the hull and cooperating with racks mounted on at least part of leg length. These pinions are motorized by a plurality of for example electric motors associated with reducers whose reduction ratio is very high.

At the time of the contact of a leg with the sea bottom, at the end of the descent, the impact can be very violent taking into account the movements of the hull under the effect of the swell. These shocks reverberate in the lifting mechanisms, which very severely stress the multiple gears of the reducers.

To obtain a good behavior of the gears reducers, at the time of contact of the legs with the sea floor, it is therefore necessary to oversize them significantly or to wait for favorable climatic conditions, thus increasing the installation costs.

In order to overcome these drawbacks, there is known a leg suspension device which is constituted by a rotating balancing arm.

However, in this case, the number of twists of the balancing arm is limited, which reduces the damping stroke, and the presence of this rotating arm is dangerous for the personnel working on the platform.

Also known in FR-A-2 607 165 (cf. preamble of claim 1), a device for suspending the legs of an oil platform which comprises at least one torsion bar, one end of which is provided with 'a pinion meshing with a toothed sector mounted on the reducer and the other end of which is immobilized on the structure integral with the shell of the platform.

In this device the torsion bar or bars are arranged parallel to the axis of rotation of the drive mechanism which increases the overall size of the assembly.

The invention therefore aims to remedy the aforementioned drawbacks by creating a system for suspending the legs of a self-elevating oil platform which, while being of a relatively simple construction, makes it possible to reduce the size of the drive mechanism and the stresses due to shocks in the structure and especially in the gears of the reducers, and to carry out the installation of the platform with severe sea conditions, therefore in larger weather windows, which reduces the cost of installation.

It therefore relates to an integrated suspension and handling system for the self-elevating oil platform support legs comprising a hull mounted displaceable on the legs by means of drive mechanisms comprising at least two opposite assemblies each formed by a motor associated with at least one reduction gear driving an output pinion cooperating with opposite racks mounted on at least part of the length of the legs, said opposite assemblies of each drive mechanism being mounted articulated on a structure supporting them via at least one bearing allowing a determined angular movement of said assemblies and of each corresponding output pinion, characterized in that said motor and said at least reduction gear of each opposite assembly are housed in an energy absorption member formed by at minus a torsion sleeve used in particular when laying the legs on the seabed, and limiting the stresses due to the bending of said legs under the action of swell and wind.

• l'une des extrémités dudit manchon de torsion est entraînée en rotation par l'ensemble moto-réducteur correspondant et dont l'autre des extrémités est solidaire d'une traverse reliant deux manchons contigüs associés chacun audit ensemble moto-réducteur correspondant, chaque ensemble moto-réducteur tournant en sens inverse par rapport à l'autre ;
• le manchon de chaque ensemble moto-réducteur est formé d'au moins deux tronçons séparés par une bride intermédiaire sur laquelle est fixée l'une des extrémités de chaque tronçon,
• les brides intermédiaires des ensembles moto-réducteurs contigüs sont reliées entre elles par au moins un tirant réglable en longueur et immobilisant mutuellement lesdites brides intermédiaires en rotation,
• le manchon de chaque ensemble moto-réducteur a chacune de ses extrémités fixée sur une bride,
• le manchon de chaque ensemble motro-réducteur est fixé sur les brides par collage,
• il comporte des moyens de précontrainte en compression du manchon de chaque ensemble moto-réducteur,
• les moyens de précontrainte en compression sont formés par au moins un tirant parallèle à l'axe du manchon, dont une extrémité solidaire de la structure supportant les ensembles moto-réducteurs et dont l'autre extrémité est solidaire de la traverse reliant deux manchons contigüs.

According to other characteristics of the invention:

• one of the ends of said torsion sleeve is driven in rotation by the corresponding motor-reduction unit and the other of the ends of which is integral with a crosspiece connecting two contiguous sleeves each associated with said corresponding motor-reduction unit, each set gear motor rotating in opposite direction with respect to the other;
• the sleeve of each motor-reduction unit is formed of at least two sections separated by an intermediate flange on which one of the ends of each section is fixed,
• the intermediate flanges of the contiguous geared motor assemblies are interconnected by at least one tie rod adjustable in length and mutually immobilizing said intermediate flanges in rotation,
• the sleeve of each geared motor assembly has each of its ends fixed on a flange,
• the sleeve of each geared motor assembly is fixed to the flanges by gluing,
• it comprises means for prestressing in compression the sleeve of each motor-reduction unit,
• the compression preloading means are formed by at least one tie rod parallel to the axis of the sleeve, one end of which is secured to the structure supporting the geared motor assemblies and the other end of which is secured to the crosspiece connecting two contiguous sleeves.

• la Fig. 1 est une vue schématique en élévation d'une plate-forme pétrolière auto-élévatrice en configuration de descente des jambes.
• la Fig. 2 est une vue schématique à plus grande échelle d'un tronçon de l'une des jambes de la plate-forme, montrant un mécanisme d'entrainement de la jambe.
• la Fig. 3 est une vue en coupe selon la ligne 3-3 de la Fig. 2.
• la Fig. 4 est une vue en demi-coupe d'un premier mode de réalisation du dispositif de suspension conforme à l'invention.
• la Fig. 5 est une vue en coupe selon la ligne 5-5 de la Fig. 4.
• la Fig. 6 est une vue en demi-coupe d'une variante du dispositif de suspension suivant l'invention.
• la Fig. 7 est une vue en coupe selon la ligne 7-7 de la Fig. 6.

The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

• Fig. 1 is a schematic elevation view of a self-elevating oil platform in the descent configuration of the legs.
• Fig. 2 is a schematic view to more large scale of a section of one of the legs of the platform, showing a mechanism for driving the leg.
• Fig. 3 is a sectional view along line 3-3 of FIG. 2.
• Fig. 4 is a half-section view of a first embodiment of the suspension device according to the invention.
• Fig. 5 is a sectional view along line 5-5 of FIG. 4.
• Fig. 6 is a half-section view of a variant of the suspension device according to the invention.
• Fig. 7 is a sectional view along line 7-7 of FIG. 6.

In Fig. 1, there is schematically shown a self-elevating oil platform comprising a hull 1 movable mounted on vertical legs 2 intended to bear on the seabed 3, when the platform is in the drilling or operating position.

Each of the vertical legs 2 has, in the present case, a triangular section and it consists of three uprights 2a, connected together by a lattice of metal beams.

It ends at its lower part with a leg 4, which, in the present example, is hexagonal in shape.

The platform is also equipped, at each leg 2, with a drive and suspension mechanism 10 for the shell relative to said legs. This drive mechanism 10 makes it possible to lower the legs 2 to the contact with the seabed, then taking support on the legs, to hoist the hull 1 above the sea, to an altitude which puts it out of the reach of the highest waves.

To this end, and as shown in Figs. 2 and 3, the uprights 2a of the legs 2 are provided with diametrically opposite racks 5 disposed on a part of the length of the legs 2 and with which are intended to cooperate the output pinions 11 of the drive mechanism 10 mounted on the shell 1 For example, four output pinions can be provided for each upright 2a and each equipped with a geared motor assembly 12.

Referring now to Figs. 4 and 5, we will describe in more detail a drive and suspension mechanism 10. In these figures, there is shown in phantom the amount 2a of a leg 2 provided with two opposite racks 5.

The drive mechanism 10 comprises four geared motor assemblies 12a, 12b, 12c and 12d superimposed two by two and contiguous two by two.

Each geared motor assembly being identical, we will now describe an assembly for example 12a.

This assembly 12a comprises a motor 13, for example an electric motor, first driving a first reducer 14 at high speed and small torque, which causes a second reducer 15 for example of the epicyclic type, but at a lower speed and greater torque, on the 'slowest output shaft 16 from which the pinion 11 is keyed.

The output shaft 16 is guided at its free end by a bearing 17 of a structure 20 integral with the shell. The reduction gear 15 is articulated on the structure 20 which supports the assembly 12a by means of bearings 18a and 18b so as to allow a certain angular movement of said assembly 12a and therefore of the corresponding output pinion 11, during the descent and the laying of the leg, as we will see later.

Furthermore, the geared motor assembly 12a comprises an energy absorbing member formed by a tubular torsion sleeve 21 inside which the motor 13 and at least the reducer 14 are housed, thus making it possible to produce a compact assembly. and space-saving.

The end 21a of the sleeve 21 is fixed, for example by gluing, on a flange 22 which is itself integral with the reduction gear 15. The end 21b of the sleeve 21 is fixed, for example by gluing, on a flange 23.

Furthermore, the end 21b of the sleeve 21 is integral with a crosspiece 24 via the flange 23. This crosspiece 24 connects the sleeve 21 of the assembly 12a to the sleeve 21 of the adjoining assembly 12b, also by means of a flange 23 (Fig. 4), these two assemblies 12a and 12b being driven in the opposite direction because their respective pinion 11 meshes with the two opposite racks 5 located on either side of the upright 2a.

It is the same for the geared motor assemblies 12c and 12d, one of the ends of the sleeves 21 of which are connected together by a cross-member.

The sleeves 21 are made of an elastically deformable material such as elastomers. They can also be made of a laminated material formed by a juxtaposition of washers made of elastomer and steel washers.

To safeguard the adhesion of the bonding between the ends of the sleeves 21 and the flanges 22 and 23, in particular when the sleeves 21 tend to shorten by torsion, this is prestressed in compression for example by means of the tie rods 25 parallel to the axis of the sleeves 21. These tie rods 25 have one end secured to the structure 20 supporting the geared motor assemblies 12a, 12b, 12c and 12d and the other end secured to the crosspiece 25 connecting two contiguous sleeves.

Each movement and suspension mechanism of the hull 1 of the oil platform is therefore produced in this way.

The entire platform is therefore brought into flotation to the drilling or operating site, and the legs 2 are lowered until they come into contact with the seabed. For this, the motors 13 therefore drive, via the reducers 14 and 15, the output pinions 11 which mesh with the racks 5. During the descent of the legs 2, the motors 13 act as brakes.

When leg 2 comes into contact with the seabed at the end of the descent, the impact can be very violent, given the movements of the hull under the effect of the swell. The impact shock is transmitted by the racks 5 to the pinions 11, then to the torsion sleeves 21 via each geared motor assembly 12 in the form of a series of opposing pairs. These couples are balanced by the crosspieces 24 so that the shock is absorbed by the torsion of the two elastic sleeves 21 of the geared motor assemblies 12a and 12b and of the two elastic sleeves 21 of the motor-reducer assemblies 12c and 12d. This twist therefore allows a damping stroke of the leg 2 upwards and creates an energy absorption.

In the embodiment of Figs. 6 and 7, each torsion sleeve 21 is composed of two sections, for example a small section 21c and a longer section 21d separated by an intermediate flange 30 on which these are fixed, for example by gluing.

The flanges 30 corresponding to two contingent sleeves 21 are connected by two tie rods 31 and 32 adjustable in length and make it possible to immobilize said rotating flanges mutually.

In this case, the torsion sleeves 21 can be used for two functions.

The first function, already described with respect to the first embodiment, which consists in absorbing the shock of the pose of a leg 2 on the seabed, uses the entire length of the sleeves 21 and, in this case, the tie rods 31 and 32 are not mounted, so that the flanges 30 are free to rotate and the opposing torques are balanced by the crosspieces 24.

The second function is used when the legs 2 are placed at the bottom and the hull raised above sea level.

Indeed, a certain flexibility between the legs 2 and the shell 1 must be created to avoid concentrations of stresses when the legs 2 are stressed in bending under the action of swell and wind.

For this, only the small section 21c of the torsion sleeves 21 is used so that the flexibility is limited. The tie rods 31 and 32 are therefore installed between the intermediate flanges 30 of each motor-reducer assembly 12a, 12b, 12c and 12d.

This system is advantageous from the point of view of the cost of the installation, because it makes it possible to eliminate the interposition of elastic cushions between the structure 20 supporting the geared motor assemblies and the shell 1 of the platform, as is usual. to do so in the prior art.

It can be seen that the various arrangements which have just been described use the internal cylindrical space delimited by the tubular shape of the sleeves 21 to house the motor 13 and at least one of the reducers such as 14, which makes it possible to produce an assembly compact, space-saving, all the elements of which rotate along their axis, without creating. danger to personnel working on the platform.

On the other hand, the damping stroke is very large, because the number of torsional turns of the sleeves 21 is not limited.

In addition, the device according to the invention also makes it possible to equalize the torques between all of the reducers of the system for moving the legs relative to the hull, and thus offers the possibility of laying the platform. with more severe sea conditions, therefore in wider weather windows, which significantly reduces installation costs.

Claims (10)

1. A system for integrated suspension and handling of the support legs (2) of a self-elevating oil platform comprising a hull (1) movably mounted on the legs (2) by means of drive mechanisms (10) comprising at least two opposed units (12) each formed by a motor (13) associated with at least one reduction gear (14, 15) driving an output pinion (11) cooperating with opposed racks (5) mounted on at least part of the length of the legs (2), the said opposed units (12) of each drive mechanism (10) being mounted in an articulated manner on a structure (20) supporting them via at least one bearing (17, 18a, 18b) enabling a given angular clearance of the units (12) and of each corresponding output pinion (11), characterized in that the said motor (13) and the said at least one reduction gear (14, 15) of each opposed unit (12) are housed in a means (21) for absorption of energy - which means is formed by at least one torsion sleeve used notably at the moment when the legs (2) are placed on the ocean bed - and for limitation of the stresses due to the bending of the said legs (2) under the action of swell and wind.
2. A system in accordance with Claim 1, characterized in that one of the ends (21a) of the said torsion sleeve (21) is driven in rotation by the corresponding motor and reduction gear unit (12) and the other end (21b) of the said torsion sleeve (21) is firmly attached to a crosspiece (24) linking two contiguous sleeves (21) each associated with the said corresponding motor and reduction gear unit (12), each motor and reduction gear unit (12) rotating in an opposite direction to the other.
3. A system in accordance with Claim 2, characterized in that the torsion sleeve (21) of each motor and reduction gear unit (12) is made up of at least two sections (21c, 21d) separated by an intermediate flange (30) on which one of the ends of each section is fixed.
4. A system in accordance with Claim 3, characterized in that the intermediate flanges (30) of the contiguous motor and reduction gear units (12) are linked to one another by at least one tie rod (31, 32) which is of adjustable length and prevents reciprocal rotation of the said intermediate flanges (30).
5. A system in accordance with any one of the preceding Claims, characterized in that the torsion sleeve (21) of each motor and reduction gear unit (12) has each of its ends (21a, 21b) fixed on a flange (22, 23).
6. A system in accordance with any one of the preceding Claims, characterized in that the torsion sleeve (21) of each motor and reduction gear unit (12) is fixed on the flanges (22, 23, 30) by welding.
7. A system in accordance with any one of the preceding Claims, characterized in that it comprises means (25) for compression-prestressing the sleeve (21) of each motor and reduction gear unit (12).
8. A system in accordance with Claim 7, characterized in that the means for compression-prestressing are formed by at least one tie rod (25) parallel to the axis of the sleeve (12), one end of which tie rod is firmly attached to the structure (20) supporting the motor and reduction gear units (12) and the other end of which is firmly attached to the crosspiece (24) linking two contiguous sleeves (21).
9. A system in accordance with any one of the preceding Claims, characterized in that the torsion sleeve (21) of each motor and reduction gear unit (21) is made of elastomer or similar resilient material.
10. A system in accordance with any one of Claims 1 to 9, characterized in that the torsion sleeve (21) of each motor and reduction gear unit (12) is made of a laminated material formed by a juxtaposition of elastomer washers and steel washers.

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