Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~'~9'~:853
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Device for the assembly or
mechanical reinforcement and
anti-corrosion treatment of
elements of submerged structures
and assembly and treatment
process associated ~ith it.
The subject of the invention is a device for the fix-
ed assembly or mechanical reinforcement of component
elements of submerged structures, such as branch junc-
tions, such as there are, for example on "off-shore"
drilling platforms. The subject of the invention is also
a process for the fixed assembly, or mechanical reinfor-
cement and anti-corrosion treatment of such elements of
structures, and a device for carrying out the said pro-
cess.
All submerged structures, for example bridge piers,
dykes, barrages or "off-shore" drilling platforms, are
sooner or later subject to the effects of corrosion.
Such effects occur particularly on all the metal parts
submerged in an ocean environment, and depending on the
amount of corrosion the result is often a mechanical
weakening of the structure as a bhole. The strength of
the structure and its useful life are thereby reduced.
The anti-corrosion treatments carried out hitherto
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make use of techniques which are virtually manual. In
fact, the most common solution is to employ the services
of divers or men wearing pressure suits ~ho coat by hand
the elements to be treated, for example with paints,
resins, or cements, under several metres or tens of met-
res of water. Such techniques carried out under diffi-
cult conditions are very costly, dangerous to the per-
sonnel and usually of inadequate effectiveness.
In addition to the harmful effects attributable to
corrosion, such submerged structures undergo the conse-
quences of various mechanical stresses, such as, for ex-
ample, gravity, the repeated impact of the waves, the
pressure of underwater currents or pulls exerted on an-
choring points. Off-shore drilling platforms are struc-
tures which are relatively sensitive in this respect in
terms of both their construction and their exposure to
the natural elements. Under the effect of the swell over
long periods, component elements, such as branch junc-
tions, are continua(ly subjected to tensile, compressive
and even sheering or tortional forces. These branch junc-
tions, because they usually have several welds, are points
of weakness which it is advisable to check regularly and,
if necessary, protect and even reinforce, these operations
being difficult and indeed dangerous at great depths.
Although simulations on mock-ups or by means of theo-
retical models are possible and, where appropriate,
6 1~2853
make it passible to identify the weakest points of such
structures in advance, the number and variety of the
effects, to which branch junctions of submerged drilling
platforms may be subjected, are such that, in practice,
it is only possible to act after the event, that is to
say once the structure has been in operation, after a
more or less protracted period of submersion.
To carry out the fixed assembly or mechanical rein-
forcement and anti-corrosion treatment of component ele-
ments of submerged structures, such as, for example,
branch junctions, it is important for a person skilled
in the art to have available technical solutions which
are easy to put into practice and are safe and reliable.
This is achieved advantageously by means of the device
according to Claim 1, adopting the process as indicated
in Claim 2.
It was found, in fact, that the dev;ce according to
the ;nvention could advantageously be used for the fixed
assembly or mechanical reinforcement and anti-corrosion
treatment of component elements of highly complex struc-
tures, such as branch junct;ons of supporting elements,
beams or tubes, for example supporting off-shore dril-
ling platforms.
~ t was noted, in particular, that such elements ass-
embled by means of the device according to the invention
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could withstand tensile or compressive forces clearly
higher than, sometimes more than double~ those ~hich
assemblies produced by means of the current techniques
withstood, before undergoing deformation or expe~iencing
weld fractures.
The accompanying Figures illustrate by way of exam-
ple one of the embodiments of the device according to
the invention.
Figure 1 partially shows one of the embodiments of the
device according to the invention and an embodi-
ment of the device for carrying out the process
according to the invention.
figure 2 shows one of the embodiments of the device ac-
cording to the invention.
Figure 3 is a sectional view through a particular embodi-
ment of the device according to the invention.
Figure 4 is a sectional view through another particular
embodiment of the device according to the inven-
tion.
In the embodiment illustrated in the abovementioned
Figures, the device according to the invention is desig-
ned for the fixed assembLy or mechanical reinforcement
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and anti-corrosion treatment of a branch junction compo-
sed of a main tubular element 1 and of a secondary tub-
ular element 2 one of the ends of which is fixed to the
surface of the said element 1. Such an embodimeht is in
no way limiting.
According to the invention the device comprises a
collar 3 3 fastened to the secondary element 2 later-
aLly (Figure 4) or at its end tFigures 1 to 3). The said
collar is composed of a first portion 3 fixed to the ele-
ment 2 and shaped so as to surround at least part of the
main element 1 and of at least one second portion 3 if
appropriate several interacting collar segments 3 shaped
so as to be fastened to the first portion 3 and forming
with the latter a collar 3 3 surrounding the element 1
with some play. The portions 3 and 3 can be secured to
one another by any suitable means 12, such as for example
bolts rivets or welding spots.
If the collar portion 3 is fastened to the end of the
element 2 ~Figure 3) fastening is usual~y carried out by
means of a weld. If the colLar portion 3 is fastened to
the sides of the element 2 (figure 4) the said portion
can be extended for example in a form 13 encasing the
said element 2 over part of its outer surface; in such a
case fastening can be carried out by means of clamping
clips 14.
lZ92853
According to the invent;on, the collar 3, 3' shaped so
as to surround the main element 1 with some play In fact,
such play is necessary in order to make it possible to in-
troduce elastic polymerized material 4 which once in con-
tact with alL the metal surfaces to be treated, can thus
exert its full anti-corrosion effect. It is also expedient
if the mass 4 is distributed uniformly on either side of
the collar 3, 3', in order to ensure good distribution of
the mechanical stresses to ~hich the assembly as a whole is
subject. The play provided bet~een the outer surface of the
element 1 and the inner surface of the collar 3, 3' can
vary, according to circumstances, from several millimetres
to several centimetres; it will usually ~e near the thick~
ness of the metal sheets used for constructing the elements
1 and 2 and the collar 3, 3'.
As mentioned, the portions of elements 1 and 2 inter-
acting with the collar 3, 3' are set in a mass of elas-
tic polymeri2ed material 4, (figure 2). According to
the invention, th;s is a homogeneous mass, the modulus
of elasticity of which can be adjusted as desired, as a
function of the mechanical stresses to be withstood.
Such adjustment is within the scope of a person skilled
in the art: the particular aim of this will be to avoid
introducing hard spots in the submerged structure as a
whole.
To carry out the fixed assembly or mechanical
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reinforcement and anti~corrosion treatment of elements, such
as those described above, the foLlowing operations are
conducted in a submerged environment, the assumed sit-
uation being one in ~hich the weld initially connecting
the element 2 to the surface of the element 1 has given
way and the end portion of the element 2 has been sawn
or abraded (Figure 3):
- a first collar portion 3 is fastened to the sawn or
abraded end of the element 2 usually by means of a
weld, the portion 3 being shaped so as to surround at
least part of the element 1. This operation can be re-
peated several times if the branch junction has sev-
eral secondary branches;
- a second colLar portion 3' is subsequently fastened to
the first portion 3 by suitable means 12. If approp-
riate, according to the configuration of the location
to be treated, severa( interacting collar portions 3'
can be assembled together and fastened to the first
portion 3 in order to obtain the desirèd collar 3, 3'.
Of course, the shape and arrangement of al( the com-
ponent elements of the collar 3, 3' are designed in
such a way that the collar surrounds the element 1
with the predetermined play;
- finally, a liquid composition generating an elastic
polymerized material 4 is poured into an enclosure 5
surrounding the assembly formed by the collar 3, 3'
and by the portions of elements 1 and 2 interacting
with this.
1292~3S;3
In a situation where ~he device according to the inven-
tion is intended more particularly for the mechanical re-
inforcement and anti-corrosion protection of branch junc-
tions, in which the secondary element 2 remains welded to
the main element 1, for example the following operation
can be carried out (see Fig.4):
- a first collar portion 3 is used for such purposes, or
if appropriate several first portions, extended by a
form in the shape of a casing 13. This extension 13 is
shaped so as to be laid laterally against the outer
surface of the element 2 near the end welded to the
element 1;
- the said collar portion 3 is fastened to the element
2 by means of its extension 13, for example clamping
clips 14 ensuring that this assembly is fixed together;
- a second collar portion 3' is subsequently fastened to
the first portion 3, the collar so formed being shaned
so as to surround the element 1 with the desired play;
- finally, the liquid composition generating elastic
polymeri~ed material 4 is poured in, as mentioned above.
According to the invention, the said liquid composi-
tion has a density higher than that of the ambient liquid
medium. ~y suitable means which will be described below,
it is conveyed to the lower region of the inner space of
the enclosure 5, the latter then being filled progres-
sively from the bottom, the liquid composition expelling
the water from the said space upwards at the rate at which
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it flows in. This procedure avoids undesirable mixing
of the liquids present, which may lead to the forma-
tion of emulsions and possibly defects in the homogen-
eity of the mass 4, once it has been polymerized:
As mentioned above, the liquid composition generating
the elastic polymerized material has a density higher
than that of the ambient liquid medium. The density is
adjusted in the customary way by means of products found
in the trade. The said liquid composition also has the
characteristic of polymerizing without shrinkage under
the conditions of the ambient medium: it is because of
this that it is possible to guarantee good adhesion of
the polymer to the treated element, for example metal or
concrete, and consequently the best possible anti-corro-
sion protection and mechanical reinforcement. Moreover,
the liquid composit;on is des;gned to generate an elas-
tic polymer;zed mass, preferably a polymerized mass,
the modulus of elasticity of which can be adjusted as
desired as a function of the mechanical reinforcement
effects required.
The liquid composition used can advantageously be
two-component mixtures generat;ng epoxy resins or poly-
urethanes, ;f appropriate mixed with various additives,
such as, for example, ballast substances, polymerization
retarders or dyes. The essential objective is to obtain a
liquid composition which polymerizes under water and
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the characteristics of which can be adapted at any time
to the requirements mentioned above: a person skilled in
the art can arrive at this easily by means of products
found in the specialized trade.
The abovementioned enclosure S is also part of the
invention: it is used as a means for carrying out the
process described above. The subject of the invention is,
more specifically, a device comprising preformed shutter-
ing elements 6,7,8, etc. which can be assembled together
round the point to be treated, to form an enclosure 5
open at the top and having, on some of its faces, ducts
9,10, etc~ closely matching the periphery of the ele-
ments 1 and 2 interacting with them, and possessing
means (11) for conveying the liquid composition to the
lower region of the space delimited by the said enc(osure.
The detail of a particular embodiment of such a
device tsee F;gùre 1) and its use according to the inven-
tion will be described belaw. Each of the shutter;ng ele-
ments 6,7,8, etc. has, on at least some of its edges,
one or more recesses arranged so as to co;nc;de with
one or more correspond;ng recesses in the adjacent shut-
tering element, thus forming ducts, 9, 10, etc., the axis
of symmetry of which is usually represented by the edge
common to two elements assembled together. The said ducts,
9, 10, etc. are shaped so as to match closely the peri-
phery of the elements 1 and 2 of the submerged structure.
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Such preforming does not present any special problem,
since it can be carried out on land with great accuracy
from construction drawings of ~he structure to be trea-
ted.
According to circumstances, the periphery of the ducts
9, 10, etc. can be equipped with elastic gaskets intended,
among other things to compensate imperfections in con-
struction or preforming. Such gaskets can also be arran-
ged on the edges, by means of which the shuttering ele-
ments are to interact with one another.
The device also possesses means making it possible to
fasten together the assembled shuttering elements 6,7,
8, etc. Any suitable known means, such as , for example,
a catch, a clip, a screw system or a bolt system, can be
used for such purposes. The said means would be designed
to ensure either temporary or permanent assembly of the
shuttering eléments, as required.
The device also has means 11 making it possible to con-
vey a polymerizable liquid composition to the lower region
of the space delimited by the enclosure S. The means 11
used can be, for example, an injection pump connected to a
pipe, the lo~er end of which opens out near the bottom of
the enclosure S on the inside of this. The simplest solu-
tion involves using a flexible hose of sufficient diameter
which conveys the liquid composition from the surface.
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The device is installed as follows. First, rigidly
preformed shuttering elements 6,7,8, etc. are brought
level with a point on the structure to be treated and are
subsequently assembled together at least 2 by 2 by means
of their edges, in order to form round the point to be
treated an enclosure 5 which is open at the top and some
of the faces of which allow elements 1 and 2 of the
structure to pass through the ducts 9,10 etc. Once the
said elements have been fastened to one another, and once
the assembly has thus been fixed together round the point
of the structure to be treated, the space delimited by the
enclosure 5 is filled with a liquid composition
polymeri~ing without shrinkage.
According to circumstances, to make it possible to
release the shuttering elements easily from the poly-
merised mass 4, the inner face of these can be lined be-
forehand with a polymer sheet or film having lo~ adhesion
re~ative to the mass 4, for example a polyester sheet.
Again according to circumstances, the shuttering
elements 6,7,8 etc. can be reinforced by means of brackets
or struts arranged according to the mechanical stresses
to be experienced. The said elements, to make it easier
to handle them in a liquid medium, will preferably be
made of a material having a density essentially near
that of the ambient liquid medium: appropriate for this
are simple or composite materials, such as, for example,
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high-density wood or polyester reinforced with glass
fibres, if necessary suitably ballasted by metal elements.
If expedient, steel shuttering elements can also be
used, in which case these are held in suspension by means
of floats or, as far as possible, retained from the surface
by means of cables or any other suitable means. Where the
treatment of metal submerged structures is concerned, a so-
called "sandwich" structure is then obtained (metal/polymer/
metal), and this also contributes to the mechanical rein-
forcement of the assembly, the shuttering elements used
then being left in place.
