KR20210075173A - How to weld a fluid-tight membrane in a tank - Google Patents

Abstract

The present invention relates to a method for welding a fluid-tight insulating tank membrane, comprising: at least two metal strakes (1,2) of the fluid-tight membrane, at least two metal weld supports, a pair of inner rollers, a pair of With an outer roller, each one of the weld supports inserted between the adjacent raised edge by the inner roller and the outer roller is simultaneously seam welded with each of the two adjacent raised side edges.

Description

How to weld a fluid-tight membrane in a tank

The present invention aims at the production of fluid-tight and insulated tanks for the maritime transport of liquefied gas or cryogenic liquids, more specifically for the transport of liquefied natural gas (LNG) or liquefied petroleum gas (LPG) with a high methane content. These tanks can also be installed on land or in floating storage structures.

The present invention here relates to the welding of fluid-tight membranes of such tanks, and the present invention more particularly proposes a solution for performing optimal welding between two adjacent strakes of the membrane and two anchor flanges, These two successive metal strakes have a raised edge and a weld between the two successive metal strakes made at the level of these raised edges.

Hereinafter, the terms "anchor flange" and "weld support" refer to the same functional component that provides a means of securing the membrane (strake) to the insulation and serves as a weld support secured to each of two adjacent strakes. They may be used interchangeably to indicate.

For example, in FR 2798358, FR 2709725, FR 2549575, a tank is known as a tank for storing or transporting liquefied gas at low temperature, where each fluid-tight membrane, particularly the primary fluid-tight membrane, is a product mounted in the tank. It is in contact with and consists of a thin metal plate supported by an insulating barrier. These metal sheets are interconnected in a fluid-tight manner to provide a fluid-tightness of the tank.

1 shows a known method of fixing the metal plate to an insulating barrier in a tank of this type. In this FIG. 1 , the upper surface 101 of the insulating barrier comprises a groove 102 extending from the support surface 101 within the thickness of the insulating barrier. The groove 102 has, within the thickness of the insulating barrier, a retaining area formed by an undercut 103 extending parallel to the support surface 101 . The undercut (103) extends at the level of one end of the groove (102) opposite the support surface (101) within the thickness of the insulating barrier, the groove (102) being inverted, the base of which is formed by the undercut (103). It has a true "T" shaped cross section. An "L" shaped anchor flange 104 is inserted into the groove 102 . The anchor flange 104 has in this way a base 105 received in the undercut 103 to hold the anchor flange 104 on the insulating barrier in a direction perpendicular to the support surface 101 . The anchor flange 104 further comprises an anchor branch 106 having a lower portion connected to the base 105 and an upper portion 108 projecting above the support surface 101 .

Two metal plates 109 are disposed on each opposite side of the anchor flange 104 . Each of these metal plates 109 has a planar central portion 110 on which a support surface 101 is supported (for ease of reading the support surface 101 and the metal plate 109 are shown spaced apart in FIG. 1 ). ). These metal plates 109 also have raised side edges (referred to herein as raised edges 111 ). The raised edge 111 of each of the two adjacent metal plates 109 is welded to each side of the anchor branch 106 of the anchor flange 104 .

The raised edge 111 thus forms a bellows with the anchor flange 104 to absorb forces associated with shrinkage of the fluid-tight membrane, for example during loading of a cryogenic liquid into a tank.

However, anchor flanges 104 of this kind constitute a fixed attachment point for each raised edge 111 . Anchor flanges 104 are loaded in two opposite directions by raised edges 111 and remain substantially static in the tank. Consequently, the anchoring of the raised edge 111 to the support surface 101 via the anchor flange 104 is substantially fixed in a direction perpendicular to the raised edge 111 . Therefore, the flexibility of the fluid-tight membrane is limited.

This is why the use of two anchor flanges is proposed in FR 3054872. Each of the two anchor flanges has the function of securing each one of the two adjacent strakes for its function.

However, the junction between the raised edges of two adjacent strakes comprises four thicknesses of material (two raised edges of the strake and two anchor flanges) that are welded together in a fully fluid-tight manner. Now considering that attaching two strikes to two anchor flanges is particularly difficult, especially considering the thickness of the protruding edges of the strike and anchor flanges, and moreover, considering that the purpose is to maintain a high degree of flexibility or elasticity, in particular It is particularly difficult at these junction levels in a way that can absorb the load.

When two adjacent respective strakes disclosed in FR 3054872 are welded to each anchor flange, the method of welding two adjacent strakes is not sufficiently effective or fast.

The present invention aims to ameliorate the disadvantages of the prior art by proposing a particularly effective solution for forming a weld between two adjacent strakes when each adjacent strake is welded to an anchor flange connecting it or attaching it to a thermal insulation. do it with

Through various studies and analyzes, the applicant has been able to quickly form between adjacent/continuous strakes of membranes through respective anchor flanges, which are technically simple to implement and perfect welds, i.e., fully fluid-tight welds of very high mechanical strength. found a solution there.

Accordingly, the present invention relates to a method of welding a fluid-tight and insulating tank membrane, wherein the fluid-tight insulating tank comprises an insulating body comprising at least one fluid-tight metal membrane and at least one insulating barrier adjacent the membrane. but:

- at least two metal strakes of the fluid-tight membrane supported by the support surface of the insulating barrier take the form of a profile part comprising a planar central portion lying on the support surface and two raised side edges projecting from the support,

- at least two metal weld supports supported by an insulating barrier project from the supporting surface between two adjacent raised side edges of two adjacent strakes;

The method according to the invention is characterized by:

- at least one pair of inner rollers, each having a first circular section, are inserted between the two metal welded supports, so that each said circular section of each inner roller is respectively in contact with said metal welded support,

- a pair of outer rollers each having a second circular section is arranged such that each said circular section of each outer roller is in contact with each adjacent raised edge of said metal streak,

- there are seams that are simultaneously welded in a fluid-tight manner, two by two due to the inner and outer rollers, each of the raised side edges of the two metal strakes adjacent to each of the metal weld supports being said sandwiched between adjacent raised edges.

According to a preferred embodiment, the inner roller and the outer roller are arranged in line along the axis x'x in FIG. 3 . In this case the first circular sections of each inner roller also contact each other. This embodiment will be described below with reference to the accompanying drawings. In this embodiment, one current flows between all inner and outer rollers.

Nevertheless, it can be expected that the inner rollers are not in contact. In this case, there are two pairs of rollers, each consisting of an outer roller and an inner roller. In this embodiment, a distinct current flows through each pair of inner/outer rollers by means of each of the two pairs of inner/outer rollers, while welding is still performed simultaneously or similarly on the two raised edge/metal weld support assemblies. Moreover, these two pairs of inner/outer rollers are longitudinally offset (relative to the direction of movement of the seam welding device), ie not actually aligned with each other.

Thanks to this method according to the invention, welds of optimum quality can now be produced automatically, which significantly reduces the time for installing fluid-tight insulating tanks. Therefore, productivity is improved. Moreover, the welding method according to the present invention can achieve the mechanical continuity and fluid-tightness of the weld bead, and the length of the welded raised edge can be obtained without stopping or re-starting due to the electrical continuity, and the two welding supports are The two raised edges are fused together at the weld level.

Furthermore, with the method according to the invention, each of the two raised edge/weld support assemblies is welded simultaneously (simultaneously).

Numerous tests have been performed to evaluate the quality of the weld between each anchor flange and the strake (raised edge), and these tests are particularly important for impact resistance, tensile resistance/bending resistance/compression resistance and resistance to thermal gradients (anchor flange and ridged edge). The joints between the strakes exhibit mechanically good weld quality (especially no traces of the material forming the inner rollers) at the level of always being fluid-tight.

"Seam welding" is a technique in which parts are assembled by applying an electric current (continuous or non-continuous application of electric current) and pressing a knurl (here an outer roller in the embodiment detailed below) against the surface to be welded. means welding.

Other advantageous features of the invention are briefly described below:

- prior to seam welding, using a spreader device, each of the adjacent raised edges of the strake and each metal weld support are moved away from each other to form a space for inserting a pair of inner rollers;

- according to a preferred embodiment of the present invention, it is preferred that the diameter of the first circular section of the two inner rollers is the same, and that the diameter of the second circular section of the two outer rollers is also the same,

- According to one preferred embodiment of the invention, the diameter of the first circular section of the two inner rollers is smaller than the diameter of the second circular section of the two outer rollers.

Here, the outer roller may have a smaller diameter than the inner roller, but in this case the life of the outer roller may be reduced, especially because the rollers are subjected to greater wear, and for a greater reason, the current passes through the outer roller first (in the two rollers, each outer roller will alternately form the input terminal of the electric circuit if the polarity of the current is preferably changed),

- the inner roller, preferably the outer roller, is also preferably cooled during welding, although in an embodiment of this kind this cooling is preferably carried out by circulating a refrigerant fluid in said roller;

- the at least one metal weld support (preferably both) preferably consists of an anchor flange, fixing the fluid-tight membrane to the insulating barrier of the thermal insulation;

- in this embodiment, according to one possibility provided by the present invention, the anchor flange is L-shaped and comprises a length portion and a lower portion interconnected with an insulating barrier, the lower portion of the anchor flange is an insulating barrier of thermal insulation It is preferred to extend parallel to the central portion of the metal strake in the recess of the;

- According to a preferred embodiment of the present invention, before welding each raised said edge to one of said metal welding supports, said metal welding supports are fixed to each other by welding in a fluid-tight manner.

Therefore, as shown in the accompanying Figure 7, the joint of two adjacent strakes and two metal anchor flanges has a profile or W-shaped cross section due to various spot welding. That is, this kind of bond has a double bellows function which imparts a high elasticity allowing the fluid-tight membrane to withstand or absorb a fairly high thermal gradient, which is reflected by particularly significant (thermal) shrinkage at this level.

- seam welding of two adjacent each of said raised edges and of each said weld support at a speed between 1 m/min and 2.5 m/min (inclusive) per minute, preferably at a speed of 1.5 m/min It is preferred to perform;

- according to an embodiment of the invention, the raised edge and preferably also the metal weld support are made of Invar® or steel containing at least 20% manganese, preferably at least 25% manganese, even more preferably 28% manganese manufactured;

- according to one embodiment, the thickness of the raised edge and preferably also the thickness of the weld support is between 0.5 and 0.8 mm (mm), preferably 0.7 mm;

- in this embodiment, during seam welding, the current is from 2.5 to 4 kiloamps (inclusive), preferably from 3 to 3.5 kiloamps (inclusive), the pressure exerted by each outer roller against each raised edge is in the range of 2 to 3.5 bar, preferably 2.6 to 2.9 bar;

- according to another embodiment, the thickness of the raised edge and preferably also the thickness of the metal weld support is 0.9 to 1.2 mm, preferably 1 mm;

- in this embodiment, during seam welding, the current is 3 to 4 kiloamps (inclusive), preferably 3.3 to 3.7 kiloamps (inclusive), and the pressure exerted by each outer roller against each raised edge is in the range of 3.5 to 5.5 bar, preferably 4 to 5 bar;

- During seam welding, the welding current preferably does not flow continuously, said current preferably flowing at a constant frequency from 60% to 80% of the time.

The present invention also relates to a system for welding fluid-tight and insulating tank membranes, the system comprising a seam welding device comprising two knurls, optionally means for holding the knurls against the surface to be welded. and a wall of fluid, wherein the sealed and insulated tank comprises:

- two metal strakes adjacent to the fluid-tight membrane and supported by the supporting surface of the insulating barrier of the wall of the fluid-tight insulating tank, said metal strakes from a planar central portion resting on said supporting surface and said supporting surface two metal strakes in the form of a profile part comprising two raised side edges that project; and

- two metal weld supports projecting from the support surface between two adjacent raised side edges of two adjacent strakes and supported by an insulating barrier;

According to the system according to the invention, the welding device comprises:

- a pair of inner rollers, each having a first circular section adapted to be inserted between two metal welding supports, the circular sections of the inner rollers being in contact with each other and each adapted to contact against said metal welding support; inner roller;

- preferably a spreader device in which each raised edge of the strake and the metal weld support moves away from each other to allow insertion of said pair of inner rollers;

- a pair of outer rollers, each having a second circular section, the circular section of each outer roller being adapted to contact the respective raised edge of each adjacent strake; and

- Preferably, cooling means for cooling the inner roller, preferably also the outer roller;

The inner and outer rollers allow simultaneous seam welding of each of the two adjacent lateral raised edges to each of the metal weld supports interposed between the adjacent raised edges.

It should be noted that all features described above in connection with the welding method according to the invention have been found to apply to the welding system briefly described above.

It should be noted here that the welding apparatus according to the invention is capable of applying currents from classical frequencies such as 50 Hz (hertz) to high frequencies, i.e. over a very wide frequency range, such as at least 1 kHz (kilohertz) and up to 2 kHz or more. do. Thus, the spot weld produced while applying an electric current between the two outer rollers/knurls is very close along the welding line, as a result of which the fluid-tightness and mechanical strength of the welding line are particularly improved.

The present invention relates to a fluid-tight and insulating tank integrated into a support structure, the present invention comprising at least one fluid-tight insulating membrane composed of a plurality of metal strakes and at least one insulating barrier adjacent the membrane. including a body,

- two or more metal strakes of the fluid-tight membrane supported by the supporting surface of the insulating barrier take the form of a profiled part comprising a planar central portion lying on the supporting surface and two raised side edges projecting from the supporting surface; ;

- At least two metal weld supports projecting from the supporting surface between the adjacent two raised side edges of two adjacent strakes and supported by an insulating barrier project are welded to each other in a fluid-tight manner by spot welding.

In the tank according to the invention, two adjacent raised respective side edges of two adjacent metal strakes and each said metal weld support interposed between said adjacent raised edges are fluid-tight two by two. by two) are seam welded together.

The formation of a weld between the strake (raised edge) and the anchor flange is clearly known per se from document FR 3054872, but with the method according to the invention the spot weld has a cross-section of a different shape than the prior art. In fact, if we place a pair of inner rollers on the side (adjacent) of the anchor flange and the placement of knurls (or outer rollers) on the side of the protruding edge of the strike, the cross section of the spot weld is on the side of the strike, i.e. during welding. It has a substantially elliptical (not strictly symmetrical as in the prior art) shape, such as the ridges (projections or bosses) found on the side where the knurls (outer rollers) are placed. Assuming that two identical knurls placed on opposite sides of the spot weld are used, the spot weld has a symmetrical shape. These cross-sections have slightly different shapes, so that the attached figure 7 is not representative with respect to this shape feature of the spot weld - compared to the prior art there is obviously no negative result with respect to the quality of the spot weld formed by the method of the present invention. Allows spot welding to be distinguished from spot welds formed by other welding processes. Thus, a tank of this kind, having all the above-mentioned characteristics and characterized by at least one spot weld formed by a pair of "outer/inner rollers", is a tank in which the outer rollers have a shape and/or size (diameter) relative to the inner rollers. There is novelty in that it is different from

It should also be noted that, thanks to the device and the welding method according to the invention, it is equally possible to modify the +/- polarity of the outer rollers alternately at the required frequency. This causes the polarity of the outer rollers/knurls to be alternated so that the heat dissipation due to the Joule effect (resistance to current) between the outer roller pair due to electrical energy is dissipated in the form of heat, thereby reducing the path of residual (electrons) Considering that, the first outer roller forming the input terminal for electric current is subjected to greater heat (because it will be subjected to higher current) than the second and final outer rollers forming the outer terminal for electric current.

Finally, the present invention also relates to a vessel for transporting cold liquid products, said vessel comprising a double hull as briefly described above arranged in the double hull and a fluid-tight insulated tank.

The vessel according to the invention advantageously comprises at least one fluid-tight insulated tank, as described above, said tank comprising two successive fluid-tight barriers, the primary barrier being the product loaded in the tank and a second barrier in contact with the other is disposed between the primary barrier and the supporting structure and preferably constitutes at least a portion of the tank wall, these two fluid-tight barriers being disposed between two insulating barriers or primary barrier supporting structures It is constructed alternately with a single insulating barrier.

Tanks of this kind are generally referred to as integral tanks in the International Maritime Organization (IMO) codes, for example tanks of type NO 96®.

The tank is preferably loaded with liquefied natural gas (LNG) or liquefied gas (LG).

According to one embodiment, the present invention also provides a method for loading or unloading a vessel of the above type, wherein the fluid is routed through an insulating pipe to or from a tank of the vessel or from it to a floating or terrestrial storage facility or therefrom.

According to one embodiment, the present invention also provides a fluid delivery system, said system comprising a ship, an insulated pipe arranged in such a way as to connect a tank installed in the hull of the ship to a floating or onshore storage facility, and a tank of the ship or a pump for driving a fluid flow through an insulated pipe to or from a floating or above-ground storage facility.

The following description is provided by way of non-limiting example only with reference to the accompanying drawings.
1 is a cross-sectional view of a prior art metal fluid-tight metal membrane anchor flange secured to an insulating barrier of a fluid-tight insulating tank;
Figure 2 is a cross-section of two metal membrane anchor flanges, the two anchor flanges being welded together before being inserted into the insulation, this Figure 2 shows the tank at two adjacent strake levels prior to application of the welding method according to the present invention; shows the wall part of
3 is a view from above of two anchor flanges and two raised edges of adjacent strakes, showing specific elements for implementing the welding method according to the invention;
Fig. 4 is a front view repeating the elements of 3 also in the vertical plane X'X.
Fig. 5 is a schematic view of some elements of a welding apparatus according to the invention, showing in particular a spreader apparatus for separating a raised edge and an anchor flange to position a pair of inner rollers to perform seam welding;
Fig. 6 is a front view of Fig. 5 on the plane P;
7 is a cross-sectional view repeating the elements seen in FIG. 2 of a fluid-tight insulating tank wall part after carrying out a welding method according to the invention;
8 is a schematic cross-sectional explanatory view of a methane tanker ship tank and a terminal for loading/unloading the tank.

In the following description reference is made to a fluid-tight membrane in relation to a fluid-tight insulating tank. A tank of this kind contains an interior space filled with combustible or non-combustible gas. The gas is especially liquefied natural gas (LNG), i.e. a gas containing predominantly methane with small proportions of one or more hydrocarbons such as ethane, propane, n-butane, i-butane, n-pentane, i-pentane, neopentane and nitrogen. may be a mixture of The gas may also be ethane or liquefied petroleum gas (LPG), ie a mixture of hydrocarbons produced from petroleum refining and containing essentially propane and butane.

A fluid-tight membrane is usually placed on a supporting surface formed as an insulating barrier of the tank. The fluid-tight membrane comprises, on the one hand, a strip of sheet metal forming strakes disposed on a support surface and on the other hand an elongate weld support connected to the support surface and extending parallel to the sheet metal strip for at least a portion of the length of the sheet metal strip. It has a repeating structure that contains alternately. The sheet metal strip includes raised side edges disposed and welded to an adjacent weld support. This kind of construction is used, for example, in methane vessel tanks of type NO 96® sold by the applicant.

At the level of the fluid-tight thermally insulated tank, which is not fully represented in the accompanying drawings, the raised edges of the strakes are preferably arranged in the longitudinal direction perpendicular or parallel to the longitudinal direction of the vessel. Accordingly, the raised edge constitutes the bellows so that the contractile force in the longitudinal direction of the vessel or in the transverse direction perpendicular to the vessel can be absorbed. Sheet metal strips and weld supports are blocked at the corners in the manner described, for example, in WO 2012/072906 or FR2724623 documents.

According to one embodiment, the fluid-tight membrane (streak), one of the fluid-tight membranes or the fluid-tight membrane may be made of a metal selected from stainless steel, aluminum, Invar®, i.e. the coefficient of expansion is generally an iron and nickel or manganese content in the range between 1.2 X 10 ^-6 and 2 X 10 ^-6 K ^-1 (including the boundary values) of at least 20% or at least 28%, the coefficient of expansion between 7 and 9 X 10 ^{− It} can be made of metals selected from iron alloys with a high manganese content, on the order of 6 K ^-1. According to one embodiment ^{, a material having a coefficient of thermal contraction of less than 16 X 10 -6} /K is selected for applications in which the liquid gas is at a temperature between -45 °C and -100 °C.

2 to 7 show between two adjacent metal strakes 1 , 2 of the fluid-tight membrane of the tank wall and two weld supports 3 , 4 fixed to the thermal insulation barrier 5 of the thermal insulation of the tank wall. A drawing of a wall of a fluid-tight insulating tank at the level of the connection is shown. A thermal insulation barrier 5 of this kind is formed by juxtaposed thermal insulation elements. For example, suitable thermal insulation members are described in document W02012/072906. This insulating barrier 5 of thermal insulation may be formed in one or more thicknesses which deal with the function of insulating the contents of the tank from the surrounding environment. Materials that may be present in this type of insulation include, for example, polyurethane foam, polystyrene or polymer foam such as polyethylene, preferably low density polyethylene (LDPE), manufactured glass wool, loose glass wool, melamine foam, airgel, matte or loose polyester filler in the form of

The insulation is generally fixed to a supporting structure not shown in the accompanying drawings, for example a ship or barge, by means of a retaining member. Here, each heat insulating member forming the heat insulating body has a rectangular parallelepiped shape composed of two large faces or principal faces and four small faces or lateral faces. More specifically, adjacent metal strakes 1 , 2 lie on the support surface 10 of the thermal insulation (or thermal insulation barrier 5 ). The support surface 10 is formed by the upper surface of the insulating barrier 5 . The weld supports 3 , 4 are fixed to the insulating member of the thermal insulation barrier 5 of the thermal insulation body.

For fixing the weld supports 3 , 4 to the insulation, the upper surface of the insulation (insulation barrier 5 ) comprises a groove 11 whose cross section is in the shape of an inverted "T". The upper portion of the insulating barrier 5 may include a plywood or a composite material in which the groove 11 is formed. The holding region 12 extends into the thickness of the insulating barrier 5 of insulating insulation parallel to the supporting surface 10 . The welded supports 3 , 4 are slid into the groove 11 of the insulation. The welding supports 3 , 4 are thus slidably fixed on the insulation 5 or inside the insulation 5 in the longitudinal direction of the welding supports 3 , 4 .

The holding region 12 may extend equally in a direction generally oblique to the support surface 10 , and may possibly include components parallel to the support surface 10 . Here, as can be seen in FIG. 2 , the holding region 12 is formed by two undercuts 13 , 14 extending from respective opposite sides of the groove 11 at the level of the lower end of the groove 11 . .

The weld supports 3 , 4 preferably consist of two metal anchor flanges of the same shape and type (material). The metal anchor flanges 3 , 4 are essentially symmetrical with respect to a plane perpendicular to the support surface 10 and parallel to the longitudinal direction of the groove 11 . Each metal anchor flange 3 or 4 includes an anchor branch 22 and an "L"-shaped cross-section including a base 21 . The base 21 corresponds to the lower part of the metal anchor flange 3 , 4 , while the anchor branch 22 corresponds to the longitudinal part of the same metal anchor flange 3 , 4 .

The base 21 of each metal anchor flange 3 , 4 is received in a respective undercut 13 , 14 or recess of the groove 11 . The base 21 of the metal anchor flanges 3 , 4 extends parallel to the support surface 10 . The lower portion of the anchor branch 22 of one of the metal anchor flanges 3 or 4 is coupled to the other anchor branch 22 of the metal anchor flange 3 or 4 . According to one possibility provided by the invention, the lower part of the anchor branch is thus welded to each other by means of a welding line 23 of 22 of the two metal anchor flanges 3 , 4 . This weld line 23 is preferably accommodated or positioned within the thickness of the insulating barrier 5 (the embodiment shown in FIGS. 2 to 4 ) while the weld line 23 is located at the level of the support surface 10 , or supports It may be located slightly above the surface 10 . The upper part of the anchor branch 22 of each of the metal anchor flanges 3 , 4 projects from the support surface 10 into the tank interior in the groove 11 .

That is, two adjacent metal strakes 1 , 2 are disposed on the support surface 10 on opposite sides of each of the weld supports 3 , 4 . Each metal streak 1 , 2 has a planar central portion 6 , 7 . Each metal strake 1 , 2 has two raised edges 8 , 9 located along two opposite longitudinal edges of the planar central portion 6 , 7 . A single raised edge 8 , 9 of each of the two metal strakes 1 , 2 is shown in FIGS. 2 to 4 . The protruding edges 8 , 9 project against the support surface 10 .

2 shows two adjacent strakes 1 , 2 , 6 , 7 , 8 , 9 , a central part 6 , 7 , their raised edges 8 , 9 , and two anchor flanges 3 , 4 (spot welds). fixed to each other at the level of 23), and various elements (1, 2, 3, 4, 5, 6, 7, 8, 9), including the insulation 5 before application of the welding method of the present invention. shows the arranged state.

3 and 4 showing the same element in two views or two cross-sections, the welding method and welding apparatus according to the invention comprises two respective raised edges 8 and 9 and two welding supports. Two outer rollers 30, 31 are used abutting two inner rollers 32, 33 which are disposed or placed between (3, 4). The continuity of the material is thus from the welding device to the knurl, from one of the outer rollers 30 or 31 to the other outer roller 30 or 31 , ie one of the raised edges 8 or 9, then the weld support. one of (3 or 4), then a pair of inner rollers 32, 33, and then again another (or second) weld support 3 or 4, another raised edge 8 or 9 and a third outer exists for the current path to the rollers 31 or 32 . These elements 3 , 4 , 8 , 9 , 30 , 31 , 32 , 33 cause the welding device to move through the outer rollers 30 , 31 towards the pair of inner rollers 32 and 33 on each outer roller ( Applying a pressure 34 of 2 to 5.5 bar directed at 30 , 31 is brought into contact with an application of current enabling resistance welding.

In order to produce a linear movement 35 of the welding device along the weld line, the outer rollers 30 , 31 and the inner rollers 32 , 33 are respectively rotated by the device in opposite directions of rotation, i.e. in some cases half It rotates clockwise and in other cases clockwise.

The inner rollers 32 and 33 may be mounted to rotate freely so as to be rotationally driven by the forward movement of the outer rollers 30 and 31 and the pressure 34 applied by the outer rollers. The inner rollers 32 , 33 may also be rotationally driven by the welding device like the outer rollers 30 , 31 .

As can be seen in the accompanying drawings, the inner rollers 32 , 33 preferably have a diameter smaller than the diameter of the outer rollers 30 , 31 so that the two welds were previously spaced apart from each other by the spreader device 36 . Supports (3 or 4) - can be easily positioned between raised edge (8 or 9) assemblies.

In one non-limiting exemplary embodiment, the diameter of the outer rollers 30, 31 is 30 mm (mm), while the diameter of the inner rollers 32, 33 is 14 mm. Accordingly, as can be seen in particular in FIG. 3 , the distance between the two metal weld supports 3 , 4 should be 28 mm to accommodate the inner rollers 32 , 33 . In this configuration, the weld supports 3 , 4 have, for example, a length of 40 mm from the support surface 10 of the insulation 5 (the length projecting from the support surface 10 ). The weld supports 3 , 4 have a length greater than the height of the raised edges 8 , 9 , ie the weld supports 3 , 4 protrude above the protruding edges 8 , 9 , for example by a few millimeters. do. A seam weld line is usually created on the order of a few millimeters from the top edge of the raised edges 8, 9, for example between 4 mm and 8 mm at that edge. Of course, the different sizes of the raised edges 8, 9 of the metal welding supports 3, 4 or the diameters of the rollers 30, 31 and 32, 33 may be achieved so that the target position of the inner rollers 32, 33 is achieved and the seam It indicates that the weld can be effectively formed without deterioration of the elements 3, 4, 8, 9 to be welded to each other or without deterioration of the elements used to perform the seam weld.

According to one possibility offered by the present invention, not shown in the accompanying drawings, the attachment of the raised edge 8 or 9 and the weld support 3 or 4 by seam welding can be performed according to the general welding technique of the seam weld line. This can be supplemented, for example, by spot welding located at a higher level (above). The spot weld line is preferably located at the upper edge level of the raised edge 8 or 9 .

In FIGS. 5 and 6 other elements of the welding device can be seen, in particular the pressure roller 37 and the spreader device 36 .

The compression roller 37 is supported by studs 38 secured to a welding apparatus not shown in full in the accompanying drawings. Their function is a metal weld support 3, 4 and two raised edges 8, 9 before and after the passage of rollers 30, 31, 32, 33, followed by rollers 30, 31, 32, 33. ) consists of pressing two by two on each opposite side, since they are all connected or fixed to the welding device and follow the same along the raised edge 8, 9 and the metal welding support 3, 4 Because they are moving in the same direction at the same speed. There are four pressing rollers 37, all including a rotating device 39 at the lower end which provides easy guidance of the welding device by the operator. The rotating disk 39 of these pressure rollers 37 can be freely rotated or rotationally driven through each stud 38 by one or more motive forces present in the welding apparatus.

Guide rollers not shown in the accompanying drawings have the same function of supporting the movement or movement of the welding device along the weld line to be produced. These guide rollers typically consist of wheels mounted or rotationally driven for free rotation by at least one motor or the like in a welding apparatus and supported on planar central portions 6 , 7 of strikes 1 , 2 .

Rotating the pressure rollers 37 and/or the guide rollers may provide assistance to the operator operating the welding device, on the one hand assisting the movement of the welding device and on the other hand allowing the device to move at a constant speed. This will directly affect the quality and consistency of the seam weld line.

In an embodiment selected to illustrate the present invention, the spreader device 36 shown in FIG. 5 has a substantially conical cross-section from the front to the back of the punch, or substantially at the spacing required to position the inner rollers 32,33. It takes the form of a punch having the width or length of the base only of the corresponding circle. This spreader device 36 connected or attached to the welding device is arranged in front of the inner rollers 32, 33 so that when the welding device moves forward, the point at the end of the spreader device 36 is a metal welding support ( 3 , 4 ), each raised edge 8 , 9 being spaced apart from each other by a distance that allows the position or passage of the inner rollers 32 , 33 .

In FIG. 5 , a portion of the raised edge 8 and a portion of the metal weld support 3 are represented as transparent, so that the profiled shape of the spreader device 36, a flared portion at a point in its front end, is visible. In the embodiment shown in the accompanying drawings, the spreader device 36 is constituted by manual mechanical means, ie is moved due to the action of the welding device or during movement, has a conical cross-sectional shape and two welding supports 3 , 4 . The penetrating ends space the raised edges 8 , 9 and the weld supports 3 , 4 apart by the distance necessary to position the inner rollers 32 , 33 . Of course, prior to the seam welding operation, other means for keeping the raised edges 8 , 9 and the weld supports 3 , 4 spaced a predetermined distance may be used independently of the welding apparatus or by their inherent performance and/or by several means. It is to be expected whether these separation movements are formed by mechanical or electrical/electronic processing processes.

Preferably, a system for cooling the rollers is provided for each of the two pairs of inner rollers 32,33 and outer rollers 30,31 to dissipate or dissipate energy due to resistance to the passage of electric current. become (also welded). This type of cooling system, not shown in the accompanying figures, may consist of channels formed in rollers that circulate a refrigerant fluid such as one or more components of the glycol (water + glycol mixture) or hydrofluorocarbon (HFC) series. Of course, the choice of this refrigerant fluid and the flow rate in the roller channels are particularly related to the current used to create the seam weld.

In the context of the present invention, the choice of current and pressure applied by the knurls (outer rollers 30 , 31 ) is determined after several experiments to ensure optimal seam welding. Current and pressure ranges (eg, expressed in bars) follow what was previously described for defined material thicknesses and properties.

In view of the operation of the welding device according to the invention, many configurations can be considered for the polarity of various elements for carrying out the welding operation.

Furthermore, according to one possibility provided by the present invention, the polarity of the two outer rollers is determined at a frequency necessary to periodically modify the function of these two rollers as input and output terminals of the current supplied by the welding device. It can be noted that it may be subject to change. Thus, the seam weld line is identical on each side (spot welds on each of the two raised edges - the weld support assembly has a substantially identical cross-section), and heating by the Joule effect causes these rollers (the rollers that form the current input terminals) ) is split between the two outer rollers instead of experiencing one of them more/intensively.

The raised edges 8 , 9 of the strakes 1 , 2 have a thickness of 0.7 mm (mm) at least at the level of the anchor branch 22 which is welded to the corresponding raised edge, as the anchor flanges 3 , 4 . Of course, the thickness of the raised edges 8 , 9 can in this way be greater than the thickness of the anchor flanges 3 , 4 , which causes a higher current to be imposed. The different thicknesses can be equally chosen for the raised edges 8 , 9 and the anchor flanges 3 , 4 , likewise the raised edges 8 , 9 ( strikes 1 , 2 ) and the anchor flange 3 , 4) The constituent materials or properties of the materials are different from each other.

As can be seen in FIG. 7 , once the welding method according to the invention is used, the raised edge 8 , 9 of each of the two adjacent metal strakes 1 , 2 is a respective metal anchor forming a weld support. It is welded to the flanges (3, 4). More specifically, each raised edge 8 , 9 is welded on top of a single metal anchor flange 3 , 4 by means of a weld line 40 , 41 .

For producing the fluid-tight insulating tank fluid-tight membranes described above, the techniques described above can be used in other types of tanks, such as on-ground installations, or fluid-tight membranes for LNG tanks in floating structures such as, for example, methane tankers, etc. can be used to configure

Referring to FIG. 8 , a cross-section of a methane tanker 70 shows a prismatic, general-shaped, fluid-tight insulated tank 71 mounted on the double hull 72 of the ship. The walls of the tank 71 include a primary fluid-tight barrier adapted to contact the LNG contained in the tank, a secondary fluid-tight barrier disposed between the ship's primary fluid-tight barrier and the double hull 72 and , two insulating barriers disposed respectively between the primary fluid-tight barrier and the secondary fluid-tight barrier and between the secondary fluid-tight barrier and the double hull 72 .

Loading/unloading pipes 73 arranged on the upper deck of the vessel in a manner known per se can be connected by suitable connectors to sea or port terminals to transport LNG cargo to or from tank 71 . .

FIG. 8 shows an example of a marine terminal comprising a loading and unloading station 75 , a submersible pipe 76 and a ground facility 77 . The loading and unloading station 75 is a stationary offshore installation comprising a moving arm 74 and a tower 78 . The moving arm 74 supports a bundle of insulated flexible tubes 79 that can be connected to the loading/unloading pipe 73 . The directional movement arm 74 adapts to all methane tanker loading gauges. A connecting pipe, not shown, extends into the tower 78 . The loading and unloading station 75 enables the loading and unloading of the methane tankers 70 from or to the above-ground facility 77 . The ground installation comprises a liquefied gas tank 80 and a connecting pipe 81 connected by a submersible pipe 76 to the loading/unloading station 75 . The submersible pipe 76 allows the transfer of liquefied gas between the loading/unloading station 75 and the ground facility 77 over a large distance, for example 5 km, so that the methane tanker 70 can be transported to shore during loading and unloading operations. to stay away from

A pump mounted on the vessel 70 and/or a pump installed on the ground installation 77 and/or a pump installed on the loading/unloading station 75 are used to generate the pressure required to transport the liquefied gas.

While the present invention has been described with reference to a plurality of specific embodiments, it is not intended to be limited in any way thereto, and it is intended to include all technical equivalents and combinations of the described means provided that such equivalents and combinations fall within the scope of the invention as defined in the claims. It is clear that

Use of the verbs "comprise" or "comprise" and their conjugates does not exclude the presence of elements or steps other than those specified in a claim.

Reference signs between parentheses in the claims should not be construed as limiting the claims.

1, 2: Strike 3, 4: Welding support
5: Insulation barrier 11: Groove
13, 14: undercut 22: anchor branch
21: base 23: welding line

Claims (19)

A method of welding a fluid-tight insulating tank membrane comprising:
The fluid-tight insulating tank comprises an insulating body having at least one fluid-tight metal membrane and at least one insulating barrier (5) adjacent said membrane,
- two or more metal strakes 1 , 2 of a fluid-tight membrane supported by a supporting surface 10 of the insulating barrier 5 , with a planar central portion 6 , 7 lying on the supporting surface 10 and the supporting surface takes the shape of a profile part comprising two raised side edges (8, 9) projecting from (10),
- at least two metal weld supports 3 , 4 supported by an insulating barrier 5 have a support surface between two adjacent raised side edges 8 , 9 of two adjacent strakes 1 , 2 11) protruding from
- at least a pair of inner rollers 32 , 33 each having a first circular cross section are inserted between the two metal welding supports 3 , 4 so that each said circular cross section of each inner roller 32 , 33 is each in contact with the metal welding support (3, 4),
- a pair of outer rollers 30 , 31 each having a second circular cross-section, each said circular cross-section of each outer roller 30 , 31 being each adjacent ridge of said metal streak 1 , 2 disposed in contact with the edges (32, 33);
- there is a seam that is simultaneously welded two by two in a fluid-tight manner due to the inner rollers 32, 33 and the outer rollers 30, 31, the metal welding support 3, 4) A welding method, characterized in that the raised side edges (8, 9) of the two metal strakes (1,2) adjacent to each are sandwiched between the adjacent raised edges, respectively. The method of claim 1,
A welding method, characterized in that the circular cross-sections of each of said inner rollers (32, 33) further contact each other. 3. The method according to claim 1 or 2,
Prior to seam welding, using a spreader device 36, the adjacent respective raised edges 8, 9 of the strakes 1, 2 and each metal weld support 3, 4 are applied to the inner rollers 32, 33) Welding method, characterized in that moved apart from each other to form a space for inserting the pair. 4. The method according to any one of claims 1 to 3,
Welding method, characterized in that the diameters of the first circular cross-sections of the two inner rollers (32, 33) are equal to each other and the diameters of the second circular cross-sections of the two outer rollers (30, 31) are preferably equal. 5. The method according to any one of claims 1 to 4,
A welding method, characterized in that the diameter of the first circular cross-section of the two inner rollers (32, 33) is smaller than the diameter of the second circular cross-section of the two outer rollers (30, 31). 6. The method according to any one of claims 1 to 5,
Welding, characterized in that during welding, the inner roller (32, 33) and preferably the outer roller (31, 31) are also cooled by circulating a refrigerant fluid in the roller (30, 31, 32, 33) Way. 7. The method according to any one of claims 1 to 6,
characterized in that at least one weld support (3 or 4), preferably two weld supports (3, 4), is provided with anchor flanges for fixing the fluid-tight membrane to the insulating barrier (5) of the thermal insulation. welding method. 8. The method of claim 7,
The anchor flange is L-shaped and includes a longitudinal portion 22 and a lower portion 21 interlocked with the thermal insulation barrier 5, wherein the lower portion 21 of the anchor flanges 3 and 4 is a A welding method, characterized in that in the recesses (13, 14) of the insulating barrier (5) it extends parallel to the central part (6, 7) of the metal strakes (1,2). 9. The method according to any one of claims 1 to 8,
characterized in that prior to welding each raised edge (8, 9) to one of the metal weld supports (3, 4), the metal weld supports (3, 4) are fluid-tightly welded to each other welding method. 10. The method according to any one of claims 1 to 9,
A welding method, characterized in that the seam welding of each of the two adjacent raised edges and of each one of said weld supports is carried out at a speed of 1 m/min to 2.5 m/min, preferably at a speed of 1.5 m/min. 11. The method according to any one of claims 1 to 10,
Characterized in that the raised edges (8, 9) and preferably the metal weld supports (3, 4) are formed of steel or Invar containing at least 20% magnesium, preferably at least 25% magnesium. welding method. 12. The method of claim 11,
The thickness of the raised edges 8 and 9, and preferably also the thickness of the weld support, is 0.5 millimeters to 0.8 millimeters (mm), preferably 0.7 mm, and during seam welding, the current is at least 2.5 kiloamps and not more than 4 kiloamps. , preferably not less than 3 kiloamps and not more than 3.5 kiloamps, and the pressure applied to each raised edge 8, 9 by the respective outer rollers 30, 31 is not less than 2 bar and not more than 3.5, preferably not less than 2.6 bar. Welding method, characterized in that not more than 2.9 bar. 12. The method of claim 11,
The thickness of the raised edge (8, 9) and preferably the thickness of the metal welding support (3, 4) is 0.9 millimeters or more and 1.2 millimeters (mm) or less, preferably 1 mm, and during seam welding, the current is 3 A kiloampere or more and 4 kiloampere or less, preferably 3.3 kiloampere or more and 3.7 kiloampere or less, and the pressure exerted by each of the outer rollers 30, 31 on each raised edge 8, 9 is 3.5 bar or more and 5.5 bar or less, preferably A welding method, characterized in that preferably 4 bar or more and 5 bar or less. 14. The method according to any one of claims 1 to 13,
A welding method, characterized in that during seam welding, the welding current does not flow continuously, and the current flows preferably between 60% and 80% of the time at a constant frequency. A welding system for welding a fluid-tight insulating tank membrane comprising:
The welding system comprises a seam welding apparatus having two knurls 30, 31, optionally means for holding the knurls 30, 31 against a surface to be welded, and a wall of a fluid-tight insulating tank. However, the fluid-tight insulation tank,
- two metal strakes (1,2) adjacent to a fluid-tight membrane, supported by a support surface (10) of an insulating barrier (5) of the wall of a fluid-tight insulating tank, said support surface (10) Two metal strakes 1 , 2 taking the form of a profiled part comprising a planar central portion 6 , 7 lying on the surface and two raised side edges 8 , 9 projecting from the support surface 10 . ; and
- two metal weld supports 3 projecting from the support surface 10 between the two adjacent raised side edges 8 , 9 of the two adjacent strakes 1 , 2 and supported by an insulating barrier 5 . , 4); including,
The welding device is
- a pair of inner rollers (32, 33) each having a first circular cross-section adapted to be inserted between two metal welding supports (3, 4), the circular cross-sections of which are in contact with each other and a pair of inner rollers (32, 33) each adapted to contact a respective one of the metal weld supports (3, 4);
- Preferably, each raised edge (8, 9) and metal support (3, 4) of said strake (1, 2) move apart from each other to insert a pair of inner rollers (32, 33) spreader device 36;
- a pair of outer rollers (30, 31) each having a second circular cross-section, the circular cross-section of each said outer roller (30, 31) being adapted to abut the respective raised edge of each adjacent strake, a pair of outer rollers 30 and 31;
- preferably comprising cooling means for cooling the upper inner roller (32, 33) and preferably also the outer roller (30, 31),
Due to the inner rollers 32, 33 and the outer rollers 30, 31, each metal weld support 3, 4 sandwiched between the adjacent raised edges 8, 9 has two respective adjacent side raised edges ( 8, 9) at the same time seam welding, characterized in that the welding system. A fluid-tight insulating tank comprising at least one fluid-tight metal membrane composed of a plurality of metal strakes (1,2) and an insulation comprising at least one insulating barrier (5) adjacent said membrane. , a fluid-tight insulated tank integrated into a support structure,
- at least two metal strakes (1,2) of the fluid-tight membrane supported by the support surface (10) of the insulating barrier (5) have a planar central portion (6, 7) lying on the support surface (10) and It takes the form of a profiled part comprising two raised side edges (8, 9) projecting from the support surface (10),
- at least two metal weld supports (3, 4) supported by the insulating barrier (5), between two adjacent raised side edges (8, 9) of two adjacent strakes (1, 2) said support surface Protruding from (10), two metal welding supports (3, 4) are welded to each other in a fluid-tight manner by spot welding,
Each of the two adjacent raised side edges 8 and 9 of the two adjacent metal strakes 1 and 2 and the respective metal weld supports 3 and 4 sandwiched between the adjacent raised edges 8 and 9 are seam welded. Fluid-tight insulation tank, characterized in that welded to each other in a fluid-tight manner by two by two (two by two) by. A vessel (70) for transporting cryogenic liquid products, the vessel (70) comprising a double hull (72) and a fluid-tight insulating tank (71) of claim 16 arranged in the double hull. A fluid transport system comprising:
The system is
The vessel (70) of claim 17,
Insulation pipes 73, 79, 76, 81 arranged in such a way that the tank 71 installed in the hull of the ship is connected to the floating storage facility or the onshore storage facility 77 and the floating storage facility through the insulation pipe or a pump for driving the flow of fluid from the onshore storage facility to the tank of the vessel or from the tank of the vessel to the floating storage facility or the onshore storage facility. In the method of loading or unloading the vessel (70) of claim 17,
The fluid is transferred from the floating storage facility or onshore storage facility 77 to the vessel's tank 71 or from the vessel's tank 71 through the insulated pipes 73 , 79 , 76 , 81 to the floating storage facility or the onshore storage facility. A method of loading or unloading a vessel, characterized in that it is routed to.

Images