EP0336811A1 - Heavy duty support and method for its use - Google Patents

Abstract

The invention relates to a heavy-duty support which can experience slight deformation when it is being subjected to load. This support consists of a plurality of studs (3), each comprising at least one flat hydraulic jack (4) known per se, the jacks of the various studs being associated with a hydraulic circuit (5-7) making it possible, as desired, to isolate them and to put them in communication with one another when the support is being subjected to load. <IMAGE>

Description

The invention relates to heavy load supports, that is to say generally of the order of several thousand tonnes, supports which are slightly deformable during their loading and which are interposed vertically between a base and the heavy load supported.

It applies in particular to offshore drilling platforms comprising a rigid horizontal deck which rests on several pillars.

During the construction of such a platform, the deck is gradually loaded and it is subjected to slight bending due to the fact that its zones comprised between the pillars and cantilevered beyond these pillars tend to sag from the areas below the pillars.

It is therefore advisable to interpose between the pillars and the apron a support arranged so as to make possible the flexions of the apron because, if this is not the case, the stresses which result therefrom can cause local deterioration or breakage of said apron and / or said pillars.

In the known embodiments, the supports of the kind in question generally consist of bodies made of a material capable of undergoing plastic deformations.

The deformations of these bodies are irreversible, which is a drawback when the support does not reach its final deformed state until after an irregular evolution.

In addition, the manufacturing tolerances of said bodies are difficult to comply with so that they exhibit behavior which is difficult to predict with precision when they are subjected to very high loads: in particular they may be subject to unwanted crushing after a period of less than the desired lifetime for the load supported.

The invention aims, among other things, to remedy these drawbacks.

To this end, the supports of the kind in question are essentially characterized according to the invention in that they comprise a plurality of studs each composed of at least one hydraulic flat cylinder suitable for vertical and bending deformations and means for horizontal stop, the different studs being distributed in locations, of the base, in which the load imposes vertical deformations of different amplitudes on them, and the jacks of the different studs being associated with a hydraulic circuit allowing them to communicate between them during the loading of the support, so as to permanently apply in all these jacks the same pressure making possible their diversified vertical deformations, and to isolate them from each other

The above flat hydraulic cylinders are each composed, in a manner known per se, by a sealed capsule filled with liquid and formed by two metal discs bordered by a peripheral channel and welded head to tail along their edges.

In advantageous embodiments, use is also made of at least one of the following arrangements:
at least one of the studs is associated with a flat surface allowing the relative horizontal sliding between the stud and the supported load and with special horizontal stop means for limiting the amplitude of this relative sliding,
- at least one of the studs is extended vertically by a receptacle of variable volume filled with a material likely to play successively two distinct roles, namely a first role corresponding to the closing of the receptacle, for which the material which it contains behaves like a non-deformable block, and a second role, associated with the opening of an orifice evacuation into the receptacle, for which said material lends itself to evacuation from the latter, said receptacle being associated with means making it possible to successively play the filling material its two roles above.

The invention also relates to the methods allowing the progressive loading of supports of the genre in question.

These processes are essentially characterized in that, firstly, the interior volumes of the flat cylinders of the various studs are placed in communication with one another and in that, when the load supported has taken its final form, the different cylinders of a hardenable product.

In an interesting embodiment, after a first mutual communication of the different jacks, each of these jacks is isolated during a certain loading period; after which, they are put in communication again to allow them to take the form imposed by the deformations of the load supported: after which, these cylinders are again isolated, this cycle being repeated several times before the cylinders are blocked in their forms final.

As for the pads associated with receptacles with emptying content mentioned above, they can be replaced even after the content of their cylinders has hardened by following the following operations: the receptacle associated with said pad is emptied of its material. filling, the hydraulic circuit connected to the pad is disconnected, this pad is released laterally, it is replaced by an entire new pad associated with a receptacle of the above type filled with its filling material, but with its empty flat cylinder, and the latter is loaded so as to give it a degree of swelling identical to that of the flat cylinder comprised by the original stud.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

• La figure 1, de ces dessins, montre en coupe axiale verticale selon I-I, figure 2, un plot constitu­tif d'un support établi conformément à l'invention.
• La figure 2 montre le même plot en plan vu de dessous selon II-II, figure 1.
• Les figures 3 et 4 sont des coupes partielles semblables à la figure 1 et pour lesquelles le plot se trouve respectivement en son état le plus expansé ver­ticalement et en son état le plus écrasé.
• La figure 5 montre schématiquement en plan une portion du support ci-dessus faisant apparaître une plu­ralité de ses plots constitutifs.
• Les figures 6 et 7 montrent schématiquement en coupe verticale un ensemble de ces plots pour respecti­vement deux états de déformation différents de la charge supportée.
• Les figures 8 à 11 montrent schématiquement un ensemble de plots du genre ci-dessus mettant en oeuvre un perfectionnement de l'invention qui permet leur rem­placement individuel, ces quatre figures correspondant à quatre étapes successives du remplacement de l'un de ces plots.
• La figure 12 montre en coupe partielle un plot mettant en oeuvre une variante du perfectionnement pré­cédent.

In what follows, a preferred embodiment of the invention will be described with reference to the accompanying drawings in a manner which is of course not limiting.

• Figure 1 of these drawings shows in vertical axial section along II, Figure 2, a stud constituting a support established in accordance with the invention.
• FIG. 2 shows the same plot in plan seen from below along II-II, FIG. 1.
• Figures 3 and 4 are partial sections similar to Figure 1 and for which the stud is respectively in its most vertically expanded state and in its most flattened state.
• Figure 5 shows schematically in plan a portion of the above support showing a plurality of its constituent studs.
• Figures 6 and 7 show schematically in vertical section a set of these pads for respectively two different deformation states of the supported load.
• Figures 8 to 11 schematically show a set of studs of the above kind implementing an improvement of the invention which allows their individual replacement, these four figures corresponding to four successive stages of the replacement of one of these studs.
• Figure 12 shows in partial section a stud implementing a variant of the previous improvement.

The support considered here is assumed for example interposed between a pillar 1 of an offshore drilling platform and the deck 2 of this platform.

The pillar 1 is in particular in the form of a large diameter crown, - this diameter can for example be between 15 and 20 m -, delimited above by a horizontal bearing surface in the form of an annular crown from 1 to 2 m radial thickness.

As we know, the deck 2 above is gradually loaded on site, which leads to slightly deform it since some of its areas, not located directly above the pillars, tend to sag slightly with respect to those located directly above these pillars: this results in a slight vertical bending of said deck and the support must be designed so as to absorb the corresponding deformations.

To this end, the support in question is constituted by a plurality of studs 3 - generally several dozen - placed side by side on the crown defining the upper span of each pillar 1.

Each pad 3 comprises at least one flat hydraulic cylinder 4 of a type known in itself, that is to say an airtight capsule full of liquid formed by mutual welding, along their edges, of two metal discs surrounded by a channel.

The set of two channels applied one against the other of a capsule forms a peripheral bead 8.

The internal volume of each capsule can be placed in communication, through a line 5 controlled by a valve 6, with the internal volumes of the others capsules and possibly with a pump 7 or other device making it possible to adjust the pressure of the liquid throughout the circuit.

In the preferred embodiment illustrated in Figures 1 to 4, the number of flat cylinders 4 included by each pad 3 is two.

The lower jack 4 is placed on a base 9 itself surrounded by a peripheral groove 10 suitable for receiving the bead 8 of this lower jack and extended by a vertical rising edge 11.

On this lower jack is placed a wafer 12 itself surrounded by an annular clearance 13 serving as upper housing for the bead 8 above, said wafer being housed with a slight horizontal clearance inside the flange 11.

The upper cylinder 4 is in turn placed on the upper face of the wafer 12, which has a peripheral clearance 14 suitable for receiving the bead 8 of this upper cylinder.

A flat-bottomed cover 15 covers said upper cylinder 4 and successively has at its periphery a groove 16 overlapping the bead 8 of the upper cylinder 4 and a vertical descending flange 17 externally closing said groove 16 and surrounding the wafer 12 with little horizontal play.

A sheet 18 of polytetrafluoroethylene (pTFE) covers the flat upper face of the cover 15.

Furthermore, the underside of the deck 2 has above each pad 3 a plate 19 coated below with a sheet 20 of stainless steel suitable for resting directly on the sheet 18 and abutments 21 are attached around the plate 19, clean to cooperate horizontally with facing spans 22 of the cover 15 in order to limit the horizontal races of mutual sliding of the two sheets 18 and 20, that is to say those of the deck 2 relative to the studs 3.

FIG. 1 represents the various components of these studs 3 in their average position: in particular, the degree of filling with liquid of the two cylinders 4 is medium so that each of these cylinders can be further expanded vertically, as visible in FIG. 3 , or on the contrary crushed (figure 4) compared to this average position.

The mounting also makes it possible to give the cover 15 a slight inclination relative to the base 9.

For purely illustrative purposes, the amplitudes of the possible adjustments with such a stud, from the average position of its components, and for an external diameter of each flat cylinder of the order of 40 cm, are of the order of ± 15 mm for vertical deflections, of the order of ± 0.003 radians for angular deflections and of the order of ± 30 mm for horizontal glides.

FIGS. 1 and 5 also show square plates 23 provided on the pillars 1 to serve as bases for the studs 3.

The loading of the support described above is as follows.

Initially the valves 6 are all open, the flat cylinders 4 are all loaded with liquid so as to have a state of swelling average tell that that shown in Figures 1 to 6 and the deck 2 --or at least its underside of scope - is straight and horizontal.

From this situation, the deck is deformed during the progressive loading of the platform and it comes to occupy a deformed position such as the curved one shown diagrammatically in C in FIG. 7.

This new shape of the apron corresponds deformations of the various flat cylinders 4 constituting the pads 3 of the support.

For example, some of these jacks are then expanded vertically, as is the case for the two middle studs in Figure 7, while others are on the contrary slightly flattened and inclined (see the two extreme studs in Figure 7).

These new expanded, crushed and / or inclined shapes are taken very simply and automatically by the jacks because of their great deformability due to their filling with liquid and their mutual communication.

When the deformation of the deck 2 has ceased to evolve, it may be advantageous to block the various jacks in the final shapes which they have then acquired.

To this end, the liquid contained in these cylinders is replaced by a hardenable product such as a cement grout or a resin.

The loaded and slightly deformed apron 2 is then supported in a perfectly balanced manner all along the bearing surface of the pillar 1 without creating any excessive local stress.

According to an advantageous variant, the loading of the jacks 4 is carried out in several successive cycles.

We start by putting these cylinders in mutual communication so as to exactly balance the pressures of the liquid in them.

Then they are isolated from each other by closing the valves 6.

It is only then, after a first loading phase, that the valves are opened again so as to restore communication between the jacks, which allows the assembly to automatically adapt to new local conditions. dump, each cylinder then taking the deformed position corresponding both to the deformation of the deck 2 to its plumb and to the balancing of the pressure in all of the cylinders.

Then the cylinders are again isolated from each other by closing the valves 6.

It is only after several of these opening and closing cycles of the valves that the deformation of the bulkhead has become final and that the jacks are then blocked in the manner described above.

This variant has the advantage of minimizing the drawbacks due to the possible creation of a leak in the hydraulic supply circuit of the jacks.

Indeed, the periods during which the cylinders are put in mutual communication are very short and lend themselves to easy monitoring and, during other periods, during which the cylinders are isolated, possible leaks cannot affect at most only one cylinder, which represents only a very small fraction of the total supported load, so that the support provided collectively by all the cylinders is practically not disturbed and that the repair is easy.

FIGS. 8 to 12 illustrate an improvement making it possible to individually replace each pad 3 even after the contents of its (or its) jack (s) 4 have hardened.

According to this improvement, each stud 3 is mounted on a base formed by a receptacle 24 of variable internal volume initially filled with a material 25 capable of successively fulfilling two distinct roles, namely:
a first role corresponding to the closure of the receptacle 24, for which the material 25 which it contains behaves like a non-deformable block,
- And a second role, associated with the opening of a discharge orifice in the receptacle for which said material 25 lends itself to evacuation from the latter.

In the embodiment of FIGS. 8 to 11, the receptacle 24 is a rigid container with vertical side walls placed under the pad 3, the base 9 of which is fitted together in this container and the filling material 25 is sand.

As long as the tank is closed, the pad 3 rests on the sand 25 present in the tank, sand which behaves like a single non-deformable block.

To empty the tank, it suffices to clear sufficiently large openings in its wall and to introduce a sufficiently powerful jet of water or air through these openings.

According to the variant shown diagrammatically in FIG. 12, the filling material 25 is no longer sand, but a material - such as for example an epoxy pitch resin - capable of hardening at room temperature and of being transformed by heating so as to become easily eliminable, this transformation possibly being in particular a liquefaction: the calories necessary for such a heating can be brought to said material using an electric resistance 26 embedded in it and connected to a suitable electric current source 27.

In either case, the replacement of a damaged stud with a new stud can be easily obtained by the following operations.

Initially, the assembly composed by the pad 3, with the content of its hardened jack 4, and by the tank 24 filled with material 25 has a maximum overall height.

This set participates in supporting heavy load 2, but only for a small fraction of this load, which can however reach a few hundred tonnes.

To clear this block, it is necessary to reduce said height.

To this end, the material 25 is removed from the container 24 through at least one opening (not shown) in the wall of this container, according to arrow F (FIG. 9), preferably using a washing jet. suitable, after having made said material removable if necessary, in particular by heating.

Emptying this tank brings stud 3 into it according to arrow G.

The pipes 5 which terminated at the stud 3 considered are then disconnected, in particular at the level of the nearest valve 6 (FIG. 10) and the stud-tank assembly considered is released laterally.

Then, in place of this assembly, there is a new assembly in which the jack 4 is in its deflated state (FIG. 11), which gives the overall height of this assembly a value less than the vertical distance between the base. 1 and charge 2 at the location considered.

Finally, the circuit 5 is connected to the jack 4 of the new assembly and the latter jack is loaded at the pressure sufficient to establish vertical contact between the new pad 3 and the load 2 (arrow H, FIG. 11) so that this pad participates to support this load in the same proportion as each of the other studs.

As a result of which, and whatever the embodiment adopted, there is finally a support for heavy loads slightly deformable during their loading whose constitution, implementation and advantages result sufficiently from what precedes.

As it goes without saying, and as already follows from the above, the invention is not limited in no way to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular:
- those where the number of superimposed flat cylinders included in each stud would be greater than two and for example equal to three, the horizontal stop means of course being adapted accordingly,
- those where a cushion of elastic material such as Neoprene would be interposed between at least one of the studs 3 and the structure which carries it (1) or the heavy mass which it supports (2), such a cushion being able to replace the sliding contact elements (18,20) or be provided in addition to these elements,
- And those where the flat cylinders are arranged in inclined planes, for example according to the side facets of an inverted pyramid, instead of being horizontal.

Claims (6)

1. Heavy load support slightly deformable during loading, vertically interposed between a base (1) and said load (2), characterized in that it comprises a plurality of studs (3) each composed of at at least one hydraulic flat cylinder (4) suitable for vertical and bending deformations and horizontal stop means (11,12,17), the various studs being distributed in locations, of the base, in which the load imposes vertical deformations of different amplitudes, and the jacks of the different studs being associated with a hydraulic circuit (5-7) allowing them to communicate with each other when the support is loaded, so as to apply continuously in all these jacks the same pressure making possible their diversified vertical deformations, and isolating them from each other. 2. Support according to claim 1, characterized in that at least one of the studs (3) is associated with a flat surface (18,20) allowing the relative horizontal sliding between the stud (3) and the supported load (2 ) and to special horizontal stop means (21, 22) to limit the amplitude of this relative sliding. 3. Support according to any one of claims 1 and 2, characterized in that at least one of the studs (3) is extended vertically by a receptacle (24) of variable volume filled with a material (25) capable of successively play two distinct roles, namely a first role corresponding to the closing of the receptacle (24), for which the material (25) which it contains behaves like a non-deformable block, and a second role, associated with the opening of an evacuation orifice in the receptacle for which said material (25) lends itself to evacuation from the latter, said receptacle being associated with means making it possible to make the filling material play its two roles above successively 4. A method of loading a support according to any one of the preceding claims, characterized in that, firstly, the internal volumes of the flat cylinders (4) of the various are put into communication with each other studs (3) and in that, when the supported load (2) has taken its final form, the various jacks are filled with a hardenable product. 5. A method of charging a support according to claim 4, characterized in that after a first mutual communication of the different jacks, each of these jacks is isolated during a certain charging period; after which, they are put in communication again to allow them to take the form imposed by the deformations of the supported load; after which, these jacks are again isolated, this cycle being renewed several times before the jacks are locked in their final shapes. 6. Method for replacing a support stud established according to claim 3, even after hardening of the contents of its flat cylinder, characterized by the following operations: the receptacle (24) associated with said stud (3) is emptied of its material filling (25), the hydraulic circuit (5) is disconnected connected to the pad, this pad is released laterally, it is replaced by the assembly of a new pad associated with a receptacle of the above type filled with its filling material , but with its empty flat cylinder, and the latter is loaded so as to give it a degree of swelling identical to that of the flat cylinder comprised by the original stud.

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