Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
7~813
A SEALING SYSTF~ FOR USE 0~ AN OFFSHORE PLATFORM
AND A ~ETHOD OF APPLYING THIS SEALING SYSTEM
On offshore platforms, in particular on offshore platforms
for the production of crude oil or gas, it is necessary to
separate so-called safe areas from so-called classified areas,
in order to prevent the passage of oil, gas, vapour, smoke and
flames.
For this purpose gaps between units on the platform or
gaps between said units and parts of the platform have to be
sealed. Said units are for example equipment-containing modules
which are generally used on offshore platforms.
According to a known system, the said gaps are closed by
tack-welding steel strips or plates to adjacent units or to
units and adjacent parts of the platform, whereafter sealing
strips of rubber or of a similar material are bonded by means
of a suitable adhesive to adjacent units or to units and ad-
jacent parts of the platform. The welding of the steel strips
or plates is time-consuming and the sealing strips tend to
deteriorate rather quickly, so that frequent maintenance is
necessary.
It is an object of the invention to provide an improved
sealing system and an improved method of applying said sealing
system, having the advantage that the sealing system can be
installed in a shorter period of time than that required for
the known sealing system. This means not only that the cost of
installing the improved sealing system is lower than the cost
of installing the known sealing system, but also that large
cost savings are obtained due to the fact that the down time of
the production platform is reduced substantially.
1~ 813
According to the invention a sealing system for sealing a
gap between units on an offshore platform, or between said
units and parts of the offshore platform, comprises a barrier
of polyurethane foam, foamed in-situ, and arranged in the eaP~
at least part of the surface of said barrier being covered with
a coating of a fire-protective material.
In a suitable embodiment of the above invention, a pre-
fabricated plate of which a side is covered with a coating of
fire-protective material is present in the gap and the barrier
of polyurethane foam, foamed in-situ, is arranged against a
side of the prefabricated plate which is not covered with the
fire-protective material. If desired, the plate is made of
polyurethane foam.
A method of applying the above sealing system co~prises,
according to the invention, cleaning and drying the walls of
the gap, supplying polyurethane-forming components to the gap
and allowing the polyurethane to foam in-situ so that a barrier
of polyurethane foam is formed in the gap and covering at least
part of the surface of the barrier with a coating of fire-
protective material.
A preferred embodiment of this method comprises, accordingto the invention, first placing in the gap a prefabricated
plate of which a side is covered with a coating of fire-pro-
tective material, supplying the polyurethane-fo~ming components
to the gap at a side of the plate which is not covered with the
fire-protective material, and allowing the polyurethane to foam
in-situ so that a barrier of polyurethane foam i5 formed in the
gap and covering at least part of the surface of the barrier
with a coating of fire-protective material.
The invention will be explained with reference to the
drawings, wherein
Figure 1 shows schematically a side view of a deck of an
offshore platform on which a number of units are arranged;
Figure 2 shows a first embodiment of the proposed sealing
system in cross-section;
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Figure 3 shows~ a second embodiment of the proposed sealing
system in croas-secti`on;
Figure 4 shows a third embodiment of the proposed sealing
system in cross-section;
Figure 5 shows a fourth embodiment of the proposed sealing
system in cross-section;
Figure 6 shows a fifth embodiment of the proposed sealing
system in cross-section;
Figure 7 shows various steps a, b, c, d, e, f, g, h of the
method of applying the sealing system according to the invention.
In figure 1, a deck, for example the cellar-deck, of an
offshore platform is indicated by the reference numeral 1. On
the deck 1 a number of units 2, such as prismatic modules con-
taining equipment, are arranged. On top of the modules 2 further
modules 2a are arranged. I beams 5 are secured to the bottom
walls of the modules 2 and 2a, so that gaps 3a are present
between the modules 2 and the deck 1 and gaps 3b are present
betweenthe modules 2 and 2a. Furthermore, gaps 3c are present
between the modules 2 and gaps 3d are present between the
modules 2a.
It is necessary to arrange a sealing system in the gaps
3a, 3b, 3c and 3d, in order to isolate a safe area from a
classified area on the platform. For this purpose, the sealing
system according to the invention is used.
In the figures 2 through 7 a wall of a unit 2 is indicated
by the reference numeral 7 and a wall of another unit, of a
deck or of some other element of the platform is indicated by
the reference numeral 8. Between the walls 7 and 8 a gap 9 is
present.
In the gap 9 the sealing system according to the invention
is arranged.
In figures 2 and 3, a simple embodiment of the sealing
system according to the invention is shown. In figures 2 and 3
polyurethane-forming components are supplied to the gap 9,
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preferably by spraying, whereafter the polyurethane is allowed
to foam in-situ, so that a barrier 10 is formed in the gap 9.
In the embodiment of figure 2 the outer surface at one side of
the barrier 10 is~covered with a fire-protective coating 11. In
the embodiment of figure 3, the outer surfaces at both sides of
the barrier 10 are covered with coating 12,respectively 13, of
fire-protective material. In both embodiments, it is possible
to arrange a prefabricated plate (not shown) in the gap before
starting the spraying operation, which plate can be removed
after the spraying operation has been completed.
In figures 4 and 5, the sealing system comprises a pre-
fabricated plate 15 for example made of a rigid polyurethane
foam, covered at one side with a coating 16 of fire-protective
material, arranged in the gap 9 and a barrier 18 of polyurethane
foam, foamed in-situ, arranged in the gap 9 at the side of the
plate 15 which is not provided with fire-protective material.
The outer surface of the barrier 18 is covered with a coating
17 of fire-protective material. The only difference between the
embodiments as shown in figures 4 and 5 is that, in the embodiment
according to figure 5, the outer surface of the barrier 18 is
trimmed, so that a flat outer svrface is obtained before the
application of the coating 17 of fire-protective material.
The embodiment of the sealing system as shown in Figure 6
will now be aescribed in detail.
A prefabricated plate 15 of polyurethane foam pre-sprayed
at one side with a coating 16 of fire-protective material is
arranged in the gap 9. The plate 15 is made of a low density,
fire-retarded, grade of rigid closed cell polyurethane foam,
for example having a density of 29 kg/m3 and a compressive
strength of 172 kN/m3. Such a polyurethane t`oam is available
from Coolag Ltd, Charleston, Glossop, Derbyshire, England. The
coating 16 of fire-protective material is for example Thermo-
Lag 290 (a registered trade mark and marketed by T.S.I. Inc. of
St. Louis, Missouri, U.S.A.) which is a low temperature,
117~3
subliming, water-based, mastic for the protection of com-
bustible building- and insulating materials. The thickness of
the coating 16 is for example 6 mm.
Before applying coating 16 the surface o~ the polyurethane
plate 15 must be prepared by vacuum cleaning to remove dust,
followed by priming with a suitable primer. ~hen the coating 16
of fire-protective material is Thermo-Lag 290 a recommended
primer is Thermo-Lag 351 primer (a registered trade mark and
marketed by T.S.I. Inc. of St. Louis, Missouri, U.S.A.). In
lO fieure 6 the layer of primer is indicated by the reference
numeral 25. After the coating 16 of Thermo-Lag 290 has been
applied, for example by spraying, the outer surface of the
coating 16 is finished by applying a protective coating 26 of
Thermo-Lag 350 top coat (a registered trade mark and m&rketed
by T.S.I. Inc. of St. Louis, Missouri, U.S.A.).
The plate 15 with the coatings 25, 16, 26 is prefabricated
and cut to the proper size before it is inserted into the gap 9.
After the plate 15 has been properly positioned in the gap 9
as shown, polyurethane-forming co~ponents are sprayed against
20 the walls 7 and 8 and against the side 27 of the plate 15, which
is not provided with a fire-protective oating. The poly-
urethane is allowed to foam in-situ. If the height of the gap 9
is between 25 and 75 mm, a single spray operation is sufficient,
but for a height of the gap 9 between 75 and 200 mm three or
25 four spray operations are necessary.
In the embodiment according to figure 6 four spray oper-
ations are necessary, so that four layers 28, 29, 30, 31 of
polyurethane foam are applied. Together these layers form the
barrier 18. The foam is made by reacting a polyol system with
MDI (4,4'-diphenylmethane diisocyanate). The polyol system is a
spray polyurethane foam formulation known as SS 215 ( a re-
gistered trade mark and marketed by the "Baxenden Chemical Company"
of Lancashire, England), which is specially formulated as a
cold weather spray system which has good adhesion to steel in
,.
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the region +0.5 to 7 C. It is a fire-retarded grade of poly-
urethane foam, haying a densit~ in the region of 30 to 40 ke/m3
which can be easily cut and worked by means of hand tools. The
foam forms a good bond to the polyurethane foam plate 16 and
to the walls 7 and 8. The rheological properties of the rising
foam are such that it can flow into and plug any imperfections
and openings between the plate 15 and the walls 7 and 8. See in
this connection the opening 32 which is filled by the poly-
urethane foam of the layer 30.
On top of the surface of the layer 30 of polyurethane foam
a layer 33 of primer is applied, for example Thermo-Lag primer
351. Then the final layer 31 of polyurethane foam is applied.
Since the sprayed polyuretbane foam will overfill the gap 9,
it is necessary to cut the layer 31 in order to obtain a flat
surface 34 before the fire-protective coating is applied. Then
the cut flat surface 34 of polyurethane foam is primed with
Thermo-Lag 351 primer, a fire-protective coating 35 of Thermo-
Lag 290 is applied to the surface 34 and to the walls 7 and 8
in the manner as shown in figure 6, and firally the outer
surface of the coating 35 is finished by applying a protective
coating 36 of Thermo-Lag 350 top coat.
For safety reasons the safe area on the platform is pres-
surized to prevent gas, smoke or flames to pass from the
classified area to the safe area. The sealing system according
to the invention is able to resist a pressure difference of up
to 1 ata.
It is observed that if the prefabricated plate 15 of rigid
polyurethane foam~ has to be placed in curved sections, the
plate is provided with saw cut9 to allow the plate to negotiate
curvature. The saw cuts are arranged at the side of the plate
which is not provided with fire-protective coating.
In figure 7a through h, various steps of a method of
applying a barrier according to the invention are shown.
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In figure 7a, the walls 7 and 8 are dried by means of
compressed air and in figure 7b the said walls 7 and 8 are
further dried by means of a rag. Before the drying of the walls
7 and 8 it is necessary to clean the walls in order to remove
grease and/or dirt.
The prefabricated plate 15 of rigid closed cell poly-
urethane foam, provided at one side with a coating of fire-
protective material 16, is fitted in the gap 9 (see figure 7c).
Then the polyurethane-forming components are sprayed (see
figure 7d) into the gap 9 against the walls 7 and 8 and against
the side of the plate 15 which is not covered with fire-protect-
ive material. The polyurethane is allowed to foam in-situ, so
that a barrier 18 is formed and a good bond is obtained between
the barrier 18, the walls 7 and 8 and the plate 15. After the
spraying and foaming operation, the outer side of the barrier 18
is trimmed (see figure 7e) by means of a suitable cutting tool,
so that a flat outer surface 20 of the barrier 18 is obtained,
whereafter the cut flat surface 20 is covered with a suitable
primer, for example by spraying (see figure 7f). Then a coat-
ing 21 of fire-protective material is applied to the surface 20
by means of a spraying method (see figure 7g). Finally, a top
coat 22, for example a suitable paint, is sprayed on top of the
coating 21 of fire-protective material (see figure 7h).
