EP0156682A1

EP0156682A1 - Locking device for an oil platform

Info

Publication number: EP0156682A1
Application number: EP19850400321
Authority: EP
Inventors: Pierre-Armand Thomas; Jean-Claude Naudin
Original assignee: Technip Geoproduction SA
Current assignee: Technip Geoproduction SA
Priority date: 1984-02-28
Filing date: 1985-02-21
Publication date: 1985-10-02
Also published as: FR2560246A1; DK90085D0; NO163705C; NO850762L; EP0156682B1; NO163705B; JPH0311325B2; FR2560246B1; JPS6168918A; BR8500847A; DK90085A; US4627768A; DK157498B; DK157498C; CA1228236A; CA1228236A1

Abstract

Locking device for a self-elevating oil platform comprising a shell (1) mounted displaceable on legs (2) by means of lifting mechanisms comprising output pinions cooperating with racks (3) mounted on at least part of the length of the legs (2), characterized in that it comprises a toothed part (6) forming a rack (6a) mounted on the shell of the platform, means (7) for moving said toothed part (6 ) transversely to the direction of the rack with which the device is associated to engage the teeth of said toothed part in those of the rack (3) or to disengage them from these clamping plates (13) integral with said toothed part and clamping counter plates (15) integral with said platform as well as clamping means (20) of said plates and counter plates to ensure the locking of said toothed part (6) in position in said rack.

Description

The present invention relates to offshore oil drilling platforms and relates more particularly to jack-up platforms.
The self-elevating platforms are generally arranged on legs plugged into the bottom of the drilling site and along which a shell is mounted movable by means of drive mechanisms provided with pinions cooperating with racks mounted along said legs.
When stopping the self-lifting platform, it is necessary to block it in relation to the legs in order to avoid dynamic overloads coming from the swell and stressing the legs alternately, which increases the stresses and consequently the tired.
Indeed, the hull of the platform resting on the legs by means of pinion and rack assemblies, the static reaction load is amplified by the tendency of the members to move relative to each other. to each other in a differential manner.
It follows from this that these cyclic stresses which introduce significant distortions in a trellis, generate local stresses called secondary which are in fact of the same order of magnitude as the main stresses.
To obtain good resistance to fatigue of the trellis, it is necessary to oversize the elements used in their construction.

a) L'équilibrage est assuré par butée horizontale entre deux niveaux de guides, les charges verticales étant reprises par les mécanismes auto-élévateurs.
b) L'équilibrage est réalisé par blocage vertical des membrures des treillis et par reprise de l'effort tranchant extérieur sur le guide d'appui. Les efforts verticaux de poids propre étant pris toujours par les mécanismes, dans le cas d'un système de verrouillage autonome ou par le système de verrouillage lui-même si on choisit un système auto-bloquant.

a) Balancing is ensured by stop horizontal between two levels of guides, the vertical loads being taken up by the self-lifting mechanisms.
b) Balancing is carried out by vertical blocking of the truss members and by resumption of the external shearing force on the support guide. The vertical forces of self-weight being always taken by the mechanisms, in the case of an autonomous locking system or by the locking system itself if a self-locking system is chosen.

Locking devices for existing oil platforms require significant mechanical stalls in order to make up for the play due, for example, to non-uniform depressions of the various legs of the platform in the ground.
Furthermore, the known devices are not instantly unlockable and require the intervention of a large workforce or complex equipment.
The invention therefore aims to remedy the aforementioned drawbacks of conventional devices by creating a locking device for a self-elevating oil platform which, while being of a relatively simple construction, allows rapid locking after a displacement of the platform as well as rapid unlocking either for a subsequent displacement or for a leveling up. ''
It therefore relates to a locking device for a self-elevating oil platform comprising a hull mounted movable on legs by means of lifting mechanisms comprising output pinions cooperating with racks mounted on at least part of the length of the jam bes, characterized in that it comprises a toothed piece forming a counter-rack mounted on the shell of the firm platform, means for displacing said toothed piece transversely to the direction of 1 rack with which the device is associated for engaging the teeth of said toothed part in the rack cell or disengage therefrom clamping plates integral with said toothed part and clamping counterplates integral with said platform as well as means for clamping said plates and counter plates for ensuring the locking of said toothed part in position in said rack.

- la Fig.1 est une vue schématique en plan d'une plate-forme auto-élévatrice à laquelle est appliqué le dispositif de verrouillage suivant l'invention;
- la Fig.2 est une vue en perspective d'un premier mode de réalisation du dispositif de verrouillage suivant l'invention;
- la Fig.3 est une vue en élévation du dispositif de la Fig.2 en prise avec une crémaillère d'une jambe de plate-forme;
- la Fig.4 est une coupe transversale partielle d'une plate-forme montrant un dispositif de verrouillage suivant l'invention associé à chaque crémaillère d'une jambe de plate-forme;
- la Fig.5 est une vue schématique en coupe d'une variante du dispositif de verrouillage de plate-forme suivant l'invention.

- Fig.1 is a schematic plan view of a self-elevating platform to which is applied the locking device according to the invention;
- Fig.2 is a perspective view of a first embodiment of the locking device according to the invention;
- Fig.3 is an elevational view of the device of Fig.2 engaged with a rack of a platform leg;
- Fig.4 is a partial cross section of a platform showing a locking device according to the invention associated with each rack of a platform leg;
- Fig.5 is a schematic sectional view of a variant of the platform locking device according to the invention.

In Fig.1, there is shown in plan a portion of self-elevating oil platform comprising a hull element 1 movable mounted on vertical legs 2 composed here of four frames 2a stuck in the ground of the site on which is placed the platform.
The legs 2 of the platform are provided with diametrically opposite racks 3 (Fig. 4) disposed over a part of the length of the legs 2 and with which are intended to cooperate drive mechanism output pinions (not shown) mounted on the hull 1. Six output gears can be provided per platform leg.
As can be seen in Fig.1, the shell 1 of roughly square shape has at its four corners recesses 4 each intended to receive a locking device according to the invention.
The locking device associated with a corner of the platform in FIG. 1 will now be described with reference to FIGS. 2 to 4.
This device comprises a toothed part 6 provided with a counter-rack 6a intended to cooperate with a corresponding rack 3 mounted in the leg 2.
The toothed part 6 forming a rack is movably mounted perpendicular to the rack by means of jacks 7 whose rods 8 are articulated on lateral yokes 9 of the part 6 in order to allow the engagement of the teeth of the rack 6a in those of the rack 3 when the hull is locked in position and the teeth of the counter rack 6a are removed from the rack 3 in order to unlock the hull. The rods 8 of the cylinders 7 further comprise an intermediate articulation 8a to allow compensation for the eF. displacement of the toothed part 6 on the spacing of the jacks 7.
The cylinders 10 of the jacks 7 are articulated at fixed points of the shell, not shown.
The toothed part 6 has side walls 11 perpendicular to the counter-rack 6a and defining between them a housing 12 for clamping plates 13 of rectangular shape mounted freely between the side walls 11 and held between these walls by flanges 14.
Between the plates 13 are interposed other plates 15 disposed in a mount 16 secured to the shell of the platform. They are arranged in their mounting so as to be able to move freely in a direction transverse to the direction of movement of the toothed part 6. As can be seen in particular in FIGS. 2 and 4, the plates 13 or brake plates as well as the braking counter-plates 15 are four in number.
The locking device further comprises two clamping cylinders 20 intended to apply the plates 13 and the counter-plates 15 against each other. The jacks 20 are made integral with the hull of the platform. In the present embodiment, these are hydraulic cylinders.
The body 21 of each cylinder bears against the shell by means of reaction cushions 22 made of an elastomer or even of Teflon.
The rod 23 of the actuator forming a plunger for the counter plates is lockable by means of a nut secured to a toothed wheel 24 meshing with an output pinion 25 of an electric motor 26 (FIG. 4),
As shown in this last figure, each member 2a. of the platform being equipped with two racks 3 diametrically opposite, there is provided a locking device according to the invention associated with each of these racks.
Unlike the clamping cylinders 20, the device comprises a fixed stop plate 27 constituting the equivalent of a disc brake shoe.
In the embodiment which has just been described, the braking plates 13 and the braking backing plates 15 are made of steel.
Their friction coefficients can also be increased by providing linings of friction material on the faces of said plates.
The operation of the device which has just been described is as follows.
When the platform is in the operational position or in the towing position, the main elements of the locking devices which equip the legs of the platform occupy the relative positions shown in FIG. 3. We see in this figure that the double-acting cylinders 7 cause the application of the toothed piece 6 against the corresponding rack 3, the toothed piece automatically positioning itself opposite the teeth of the rack due to the complementarity of the shapes of the teeth of the exhibits.
The part 6 carries with it the clamping plates 13 which are adjusted inside this part. These plates slide between the counter plates 15 interposed between them with a slight clearance of a few millimeters. The part 6 provided with its plates slides along a bearing face 28 of the stop 27 (Fig, 2) which acts as a brake shoe.
Once room 6 is in a position such that the teeth of the rack 7 are engaged in the corresponding teeth of the rack 3 (Fig.3). the clamping cylinders 20 are actuated and ensure the compression of the plates 13 and against the plates 15 against the stop 27 forming a jaw, the bodies of the cylinders 20 bearing against the cushions 22 made of elastomer or teflon. There is then a tightening between the plates 13 and the counter plates 15 which ensures the locking of the shell of the platform in position. Assuming that eight friction surfaces are in contact, and considering that the average coefficient of friction of steel on steel is 0.2 or even that it is 0.3 if the counter plates 15 and the stop 27 are plated with a component with a high coefficient of friction, it is obtained if F is the compression force of the jacks and V b the vertical locking force,
or
This value is given for a leg or member, which represents for cylinders whose nominal force is 750 T, V b = 4800 T or V b friction = 7200 T.
In the hypothesis of a square trellis with 11 m center-to-center distance between the members, this allows to support a dynamic moment having the following value:
or
Of course, the number of plates of the locking device can be adapted to the dynamic moment to be balanced.
When the hydraulic cylinders 2C are in action, the sets of plates 13 and counter plates 15 being tightened against the stop 27 forming a jaw and the elastomers being compressed for example by about 30 mm, the motorized nut driven by the toothed wheel 24 of the jack is wedged in the stop position on the body of the jack. The hydraulics can then be released and the reaction of the system then passes through the safety nut. The presence of the elastomer cushions 22 in this case ensures the permanence of the reaction and makes negligible the effect of low retraction of the piston when the reaction forces are taken over on the safety nut driven by the toothed wheel 24. The system is therefore completely safe and does not require a permanent supply of hydraulic fluid.
Unlocking the device occurs in the same way by reversing the procedure. The actuators 20 are actuated by applying a fluid pressure slightly higher than the setting pressure which ensures the release of the motorized safety nuts 24. These can then be unscrewed. The rods 23 of the cylinders can then be retracted causing the decompression of the elastomer cushions 22 and the plates 13 of the counter plates 15 are released. The double-acting cylinders 7 can then bring the toothed part 6 backwards to release the teeth of the counter-rack 6a relative to the teeth of the rack 3.
We then obtain the unlocking of the leg considered.
The device which has just been described presents the operating sequences which can be automated.
The locking device shown in Fig.5 is a variant of the device described with reference to Fig.2 to 4.
Like the device in FIG. 2, it comprises a toothed part 30, the toothed part of which forms a counter-rack intended to cooperate with a rack of a leg or member of the platform is not shown. In the part 30 are mounted with clearance clamping plates 31 which cooperate with clamping counter-plates 32 disposed in a fixed mount secured to the platform. The clamping counter-plates 32 bear on a stop 33 forming the brake shoe. The counter plate 32 opposite to that bearing on the stop 33, comprises bias wedges 34 intended to cooperate with the wedges 35 of complementary inclination connected together by a spacer 36 and actuated by a double-acting cylinder 37. The wedges skewers 35 bear against the shell by means of cushions 38 made of elastomer or teflon.
The operation of such a device is similar to that described with reference to FIGS. 2 to 4 with the exception of the fact that the clamping of the plates 31 and of the counter-plates 32 is ensured by biased shims 34, 35 under the action of the double-acting cylinder 37.
In order to ensure positive security of such an arrangement, the jack 37 must be provided with a motorized nut similar to that used in the clamping jacks 20 of the embodiment of FIG. 2.
Although in the variant of FIG. 5, a hydraulic cylinder 37 is used to actuate the bias wedges, it is also possible to envisage a solution of the self-locking type not using a hydraulic cylinder, by using for the control wedges biased the weight of the hull. For the descent of the hull, there would then occur a relative sliding between the wedges, which would cause the locking process.
The non-drive of the wedges would be ensured by an ordered cleat,
To ensure the unlocking of the platform, it would be necessary to cause the lifting of the hull in order to release the drive cleat, slide the shims by releasing the toothed locking part which would then be brought back by jacks analogous to the jacks 7 of the embodiment of Fig. 2.

Claims

1. Locking device for a self-elevating oil platform comprising a shell (1) mounted movable on legs (2) by means of lifting mechanisms comprising output pinions cooperating with racks (3) mounted on a part at less than the length of the legs _. (2), characterized in that it comprises a toothed part (6; 30) forming a rack (6a) mounted on the hull of the platform, means (7) for moving said toothed part (6; 30 ) transversely to the direction of the rack with which the device is associated in order to engage the teeth of said toothed part in those of the rack (3) or to disengage them from these clamping plates (13; 31) integral with said part toothed and clamping counter plates (15; 32) integral with said platform as well as clamping means (20; 34,35,37) of said plates and counter plates to ensure the locking of said toothed part (6 ; 30) in position in said rack.

2. Locking device according to claim 1, characterized in that said toothed part (6) comprises on either side of its part forming a counter-rack (6a) side walls (11) provided with flanges (14) of retaining said clamping plates (13) freely mounted in a housing (12) formed between the side walls (11) of the toothed part (6), the latter being slidably mounted against a stop plate (27) forming a brake shoe and being movable by double-acting cylinders (7) between a position in which the counter-rack (6a) is engaged with the rack (3) of the corresponding leg (2) and a posi tion in which the counter-rack (6a) is released from said rack.

3. Locking device according to one of claims 1 and 2, characterized in that the clamping means (20) of the plates (13) and against the plates (15) are constituted by at least one hydraulic cylinder whose body (21) is supported on the shell of the platform by means of shims (22) made of elastic material and the rod (23) of which is in contact with the plate (13) or against the plate (15) located at look of the jack, the plate or plate furthest from the rod (23) of the jack being in contact with the stop plate (27) forming the brake shoe.

4. Locking device according to one of claims 1 and 2, characterized in that the clamping means of the plates (31) and against the plates (32) consist of bias wedges (34) integral with a against -plate (32) and cooperating with complementary bias wedges (35) displaceable parallel to the planes of the clamping plates and counterplates (31,32) by means of a double-acting cylinder (37), the wedges displaceable by said cylinder (37) bearing against a fixed wall of the shell by means of cushions (38) made of elastic material.

5. Locking device according to one of the claims 3 and 4, characterized in that said cylinder (20) is provided with a safety device constituted by a motorized nut (24) cooperating with a thread of the rod (23) of said cylinder and intended to bear on the body (21) of the cylinder (20) to support the reaction of the clamping plates and counterplates (13,15) upon the release of the hydraulic supply pressure of said cylinder.

6. Locking device according to one of claims 1 to 5, characterized in that the plates and plywood serlage (13.15; 31.32) are made of steel.

7. Locking device according to one of claims 1 to 5, characterized in that the clamping plates and counter-plates (13,15; 31,32) are provided with linings with a high coefficient of friction.

8. Oil platform comprising a hull (1) supported by legs (2) composed or not of members (2a) and provided with racks (3) on at least a portion of their lengths of the lifting mechanisms integral with the hull having output pinions cooperating with the racks (3), characterized in that at least one locking device according to any one of claims 1 to 7 is provided, associated with each leg or leg frame of the platform form.