FR3130010A1 - Thermal insulation piece for double-walled tank, method for producing the insulation piece and double-walled tank equipped with several insulation pieces - Google Patents

Abstract

The invention relates to a thermal insulation part intended to be placed in a space located between two walls of a double-walled tank, the space being provided so that the vacuum is formed therein, the thermal insulation part comprising a stack of several layers of film (12) interposed with layers of fibers (14), the different layers (12, 14) being held together. The invention also relates to a method of manufacturing the assembly part and a double-walled tank comprising several insulation parts. Figure for the abstract: Fig. 1

Description

Thermal insulation piece for double-walled tank, method for producing the insulation piece and double-walled tank equipped with several insulation pieces

The invention relates to the thermal insulation of tanks which may contain liquefied gases, in particular natural gas, hydrogen, oxygen, nitrogen, argon, etc. The invention is not limited to liquefied gases and the tanks concerned can contain any type of fluid, even solid particles in suspension in a fluid.

To date, the liquefied gas market is growing strongly. Transport and storage takes place in thermally insulated tanks. Reservoirs are notably present in gas production units, in storage places, for transport, for example in the form of a tank mounted on a truck, and in places of use.

Mobile liquefied gas tanks, for example to equip a truck or a ship, generally include a double wall with a fairly high vacuum in the space between the two walls in order to limit heat exchange by convection. The walls are for example made of stainless steel for the inner wall and of carbon steel for the outer wall.

In order to limit the exchange of heat by radiation, a thermal insulator is placed between the walls. For a cylindrical tank, the installation of the insulation can be done by wrapping several layers of insulation around the internal wall. The assembly is then inserted into the outer wall. Then the walls are welded and the vacuum is created between the two walls.

Wrapping is a delicate operation to perform. The wrapping operation poses particular difficulties in controlling the number of layers put in place and positioning the layers in non-cylindrical areas such as around pipes allowing the gas to be introduced into and extracted from the tank. In the case of maintenance, the repair of parts of the thermal insulation is also problematic. In fact, the wrapping is generally carried out without interruption over the entire tank. A local repair then forms a discontinuity in the thermal insulation.

The invention aims to overcome all or part of the problems mentioned above by proposing in particular a new process for producing thermal insulation placed in a double-walled tank.

To this end, the subject of the invention is a thermal insulation part intended to be placed in a space located between two walls of a double-walled tank, the space being provided so that the vacuum is created there, the thermal insulation piece comprising a stack of several layers of film interposed with layers of fibers, the different layers being held together.

Advantageously, at least one edge of the insulating part reveals the different layers, so as to allow the air present in the layers of fibers to escape from the insulating part when the vacuum is created.

Advantageously, the different layers are held together by means of assembly components passing through all the layers forming the insulation part.

The thermal insulation part advantageously comprises local reinforcements of the outer layers of the insulation part at the level of the assembly components.

The thermal insulation part advantageously comprises at least one local fixing layer of the hook-and-loop type fastened to an outer layer of the insulation part by means of the assembly components.

The thermal insulation part advantageously comprises two opposite outer faces each formed of a layer of film, a covering zone configured to be arranged under another insulation part, in the covering zone, the different layers being folded over them -same together so that a first one of the outer faces of the insulation part is found in the position of a second of the outer faces of the insulation part.

The invention also relates to a method for manufacturing an insulation part, the method linking the following steps:
a - From a roll made up of a couple of a layer of film and a layer of interdependent fiber, unroll on a plate several couples on top of each other by superimposing them and respecting the order of the layers of the finished insulation piece to form a stack of layers,
c - Simultaneously cut the different pairs to the dimensions of the insulation piece to form edges,
e - Fix the different pairs near the cut edges.

Advantageously, the manufacturing method comprises between steps a and c, a step b of local reinforcement of the edges.

Advantageously, the manufacturing method comprises, between steps c and e, a step d of placing a local fixing layer of the hook-and-loop type fixed to an outer layer of the stack.

Advantageously, during step a, the pairs are each arranged so that the fiber layer faces the plate, the method comprising, after step e, a step f of turning over the stack of fixed layers, removal of an outer layer of fiber, and local reinforcement of the edges.

Advantageously, the manufacturing method comprises, after step f, a step g of local folding of all of the fixed layers to reveal the zone of overlap and of fixing of the assembly in the zone of overlap.

The invention also relates to a double-walled tank comprising an inner wall and an outer wall, a space being provided between the inner wall and the outer wall, space in which several pieces of insulation according to the invention are arranged edge to edge or overlapping, the space being kept under vacuum.

The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, description illustrated by the attached drawing in which:

there shows an example of a stack of layers forming a thermal insulation part according to the invention;

there shows an example of a tank equipped with several pieces of thermal insulation as shown in the ;

there represents an example of a thermal insulation part according to the invention;

there represents several pieces of insulation assembled on a wall of the tank of the ;

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FIGS. 5a to 5g illustrate an example of a process for manufacturing an insulation part according to the invention.

For the sake of clarity, the same elements will bear the same references in the various figures.

There shows in partial section a stack 10 of layers forming a thermal insulation piece intended to be placed in a space located between two walls of a double-walled tank. As mentioned above, double-walled tanks are commonly used to contain liquefied gases therein. The space located between the two walls is kept under vacuum in order to limit heat transfer by convection in this space. Thermal insulation is therefore intended to reduce heat transfer by radiation.

The stack 10 comprises several layers 12 of film based on metallic material such as an aluminum film. The film can also be thermoplastic, thermosetting or based on any type of material that can give the insulation the flexibility required to cover the internal wall of the tank. Between the layers of film 12, the stack 10 comprises intermediate layers of fibers 14 woven or nonwoven. On the , four layers 12 and three spacer layers 14 are shown by way of example. It is of course possible to produce a stack 10 having a greater or lesser number of layers. Typically, it is possible to produce thermal insulation parts having between five and thirty-five layers.

There shows an example of a tank 20 with a double wall. More specifically, the tank 20 comprises an internal wall 22 inside which is stored the fluid contained in the tank 20 and an external wall 24 forming the outer envelope of the tank 20. The two walls 22 and 24 can be made made of alloy steel. For example, for a gas tank, it is common to make the inner wall 22 of stainless steel to avoid any reaction with the gas contained. It is also common to make the outer wall 24 of carbon steel for its high mechanical strength.

Several thermal insulation parts are arranged in a space 23 provided between the two walls 22 and 24. The various insulation parts are made flat, as will be seen below, and shaped on the internal wall 22. By example for a tank 20 of cylindrical shape extending around an axis 26, to cover the cylindrical part of the internal wall 22, it is possible to provide several insulation parts of flat and rectangular shape during their manufacture. The length of the rectangle being substantially equal to the circumference of the cylindrical part around the axis 26. The various rectangular insulation pieces are wound around the cylindrical part and arranged edge to edge or partially superimposed. In the example shown, three pieces of insulation 28, 30 and 32 surround the cylindrical part of the internal wall 22. To cover the ends 34 and 36 of the internal wall 22, ends substantially perpendicular to the axis 26, several pieces insulation can be arranged on each of the ends, the parts 38 and 40 on the first end 34 and the parts 42 and 44 on the second end 36. The different insulation parts can be arranged edge to edge. However, it is preferable to arrange the various pieces of insulation in partial overlap in order to limit heat losses through any gaps between the pieces of insulation.

For manufacturing constraints of the various insulation parts and for shape constraints of the internal wall 22, it is possible to provide other shapes of the insulation parts. For example, to surround the cylindrical part, it is possible to provide rectangular insulation pieces whose length is only equal to a fraction of the circumference of the cylindrical part. Several pieces of insulation are then necessary to complete the circumference of the cylindrical part. Similarly, to cover the ends 34 and 36, the curved shapes of these ends and the presence of orifices, such as a tube 46 allowing the filling and emptying of the fluid from the reservoir 20 may require special cutouts of the insulation parts. . Accesses other than the tube 46 can be provided in the internal wall 22, requiring special cutouts of the insulation parts.

The outer wall 24 is arranged around the insulation parts after they have been placed on the inner wall 22. For the placement of the outer wall 24, it is possible to slide a cylindrical part 48 along the axis 26 around the insulation parts 28, 30 and 32 put in place on the internal wall 22. Ends 50 and 52 of the external wall 24 are then fixed in a sealed manner to the cylindrical part 48, for example by gluing or welding . After closing the outer wall 24, the vacuum is created there in order to limit as much as possible the heat transfer by convection between the two walls 22 and 24. A pumping valve can be provided for this purpose in the outer wall 24.

there represents an example of a thermal insulation piece 60 formed from the stack 10 of several layers of film 12 between each of which is placed a layer of fiber 14. The different layers 12 and 14 are held together, by example by means of assembly components passing through all the layers 12 and 14. The assembly components can be staples 62 and 64, as shown in the . Any other means such as rivets, threads forming a seam can also be used to hold the different layers 12 and 14 secured to each other. The material of the assembly components is chosen to have a low thermal conductivity in order to avoid the formation of thermal bridges crossing the thermal insulation part 60. At least one of the edges of the insulation part 60 must reveal the different layers, so as to allow the air present inside the insulation part and in particular in the layers of fibers 14 to escape from the insulation part 60 when the vacuum is created after mounting several insulation pieces between the walls 22 and 24. On the , the edge 66 is completely open and the different layers 12 and 14 remain accessible there from the outside of the insulation part 60. The different staples 62 and 64, and in general any type of crossing assembly components form discrete, i.e. non-continuous, attachments. Using several assembly components to discontinuously attach the layers 12 and 14 to each other allows air to circulate between the various assembly components and therefore the possibility for the air to be evacuated during installation. space vacuum 23.

The layers of film 12 can be very thin, for example of the order of a few micrometers, which makes them fragile. The risk of tearing is particularly high. The staples 62 and 64 or any type of assembly components generate incipient fractures when crossing the different layers and in particular the layers of film 12. To limit the embrittlement of the insulation part 60 in line with the staples 62 and 64, it is possible to equip the insulation part 60 with local reinforcements of the outer layers of the insulation part 60 in the vicinity of the staples 62 and 64. It is for example possible to arrange a self-adhesive film along the perimeter of the insulation piece 60. Along the edge 66, two reinforcements 68 and 70 appear. The reinforcement 68 is arranged on the upper outer layer of film 12sup and the reinforcement 70 on the lower outer layer of film 12inf. The two outer layers 12inf and 12sup each form one of the outer faces of the insulation piece 60. The staples 62 and 64 can pass through the reinforcement as for example for the reinforcement 70 in the lower layer 12inf. Alternatively, the reinforcement can cover the staples as for the reinforcement 68 placed in the upper layer 12sup.

In the space 23, several insulation pieces are arranged to cover the internal wall 22. On the , seven different pieces are represented. They can all have the same stack of layers 12 and 14 as the insulation part 60 represented on the . External dimensions may vary from one piece of insulation to another. These dimensions are defined according to the geometry of the walls to be covered. In a tank, it is possible to arrange the various pieces of insulation edge to edge. However, this type of arrangement can leave gaps between neighboring insulation pieces. More or less significant gaps may appear depending on the manufacturing tolerances of the walls and the insulation parts. To avoid these openings, it is advantageous to provide partial overlapping of the neighboring insulation pieces. To achieve good thermal insulation by radiation and by conduction, it is advantageous to prevent a lower layer from coming into contact with an upper layer. In other words, if a temperature gradient exists from the coldest at the level of the internal wall 22, for example due to the presence of a cold gas in the reservoir 20, towards the hottest at the level of the external wall 24, the due to its contact with the ambient air, this same gradient is found from the lower film layer 12inf in contact with the internal wall 22 to the upper film layer 12sup in contact with the external wall 24. At the level of the local superposition of two neighboring insulation pieces, to avoid having a lower film layer 12inf in contact with an upper film layer 12sup, the insulation piece 60 can have an overlap zone 72 in which the different layers 14 and 16 are folded together so that the lower layer 12inf is found in the position of the layer 12sup, that is to say on the side of the upper layer 12sup. The designations upper layer 12sup and lower layer 12inf are conventional and it is of course possible to carry out the fold in the other direction.

There shows an example of placing several insulation parts 60-1, 60-2 and 60-3 on the internal wall 22. The three insulation parts 60-1, 60-2 and 60-3 are similar to the insulating part 60 described using the . The second piece of insulation 60-2 is arranged on the internal wall 22 so as to cover the overlap zone 72 of the first piece of insulation 60-1 and so on. Thus through the various insulation parts, the thermal gradient is always established in the same direction perpendicular to the internal wall 22.

On the overlap zone 72 of the first piece of insulation 60-1, the second piece of insulation 60-2 can simply be placed. It is possible to fix the various insulation pieces on the internal wall 22 in order to prevent them from moving in the space 23 provided to accommodate them. Alternatively, or in addition, it is advantageous to fix two neighboring pieces of insulation together at the level of the overlap zone 72. This fixing can for example be carried out by means of adhesive tapes 74 which can be laid out flat covering the outer layers 12sup of two adjacent insulation pieces as shown in the at the level of the covering of the insulation parts 60-1 and 60-2. Alternatively, it is possible to arrange a double-sided adhesive tape 76 between the faces in contact of two neighboring insulation pieces in the overlap zone 72, as shown in the between the outer layers 12inf of the two pieces of insulation 60-2 and 60-3. An advantage of this double-sided adhesive tape 76 is to reveal the different layers 12 and 14 on the edges of the respective insulation parts 60-2 and 60-3.

Alternatively to the adhesive tape, it is possible to set up a hook-and-loop fastener. This type of attachment comprises two layers each intended to be attached to one of the insulation pieces, one comprising a pile and the other hooks intended to adhere to the pile. On the , a hooked layer 78 is placed near the edge 66 and a pile layer 80 is placed at the level of the overlap zone 72. Advantageously, the hooked layer 78 is fixed to the outer layer 12inf by means of the clip 62 and the velvet layer 80 is fixed to the outer layer 12inf by means of the clip 64. Thus a single method of fixing makes it possible to fix the layers 12 and 14 between them and the layers either with hooks 78 or with velvet 80 .

Layers 78 and 80 can also be used to attach insulation piece 60 to wall 22, in which case one of layers 78 or 80 is attached to insulation piece 60 and the other layer is attached to wall 22. .

In the overlap zone 72, a reinforcement 82 is arranged on the outer layer 12inf. The reinforcement 82 accommodates the two ends of the clip 64. Still in the overlap zone 72, it is also possible to place a reinforcement 84 on the outer layer 12sup.

FIGS. 5a to 5g illustrate an example of the manufacturing process for the insulation part 60. The insulation part 60 is produced flat on a plate 90. After production, the insulation part 60 is shaped on the internal wall 22. The different layers 12 and 14 can be supplied in the form of a roll 92 formed by a pair 94 of a layer of film 12 and a layer of fiber 14 integral with each other. This type of roller can also be used to wrap tanks. The workstation is mainly composed of the plate 90 and a support 96 holding the roller 92 in position relative to the plate 90 and configured so that an operator can place several pairs 94 of layers on the plate 90.

During a first step a, represented on the , the operator unrolls a first pair 94 on the plate 90, the layer of fiber 14 of this pair 94 being for example arranged facing the plate 90. This first pair 94 is cut to a dimension greater than that of the insulation part once finished. Still during this first step a, the operator unrolls several pairs 94 by superimposing them on top of each other, respecting the order and the number of layers to form the finished insulation part 60. After unrolling each pair 94, the operator makes a cut. The different pairs are cut substantially to the same dimension.

During a second step b optional and represented on the , the operator has the reinforcements 70 on the last layer of film 12 visible. These reinforcements 70 can be positioned to reinforce areas of the last layer 12 in line with the edges of the finished insulation part 60. To ensure this positioning, the last layer can be marked with the dimensions of the insulation part 60. This marking can be carried out by means of a pattern. To hold the layers together, it is possible to place on the stack of layers 94 weights, providing pressure and holding the layers in place by adhesion.

During a third step c, the operator simultaneously cuts the different pairs to the dimensions of the insulation piece 60 to form the edges 98 thereof. This cutting step is represented on the . A cutting tool 100 is used for this purpose. If reinforcements 70 are present, the cut is made along the reinforcements 70.

Then, during an optional fourth step d and represented on the , the operator locally sets up the self-gripping type fixing layers and in particular the layer with hooks 78 on the reinforcements 70 if they are present.

During a fifth stage e represented on the , the fixed operator, for example by means of staples 62, the various pairs 94 in the vicinity of the edges 98 cut. When reinforcements 70 and layers with hooks 78 are present, stapling is done through them.

Then, during a sixth optional step f and represented on the , the operator returns the stack made on the plate 90, then removes the visible layer of fibers 14 and places the reinforcements 68 to cover the staples 62.

Finally, during a seventh step g optional and represented on the , the operator produces the overlap zones 72. More specifically, the operator locally folds the stack produced, arranges the pile layers 80 if necessary and fixes the assembly by means of staples 64 crossing the stack twice. of layers, also twice the reinforcement 82, the reinforcement 84 and the pile layer 80.

Claims (12)

Thermal insulation part intended to be placed in a space (23) located between two walls (22, 24) of a tank (20) with double walls, the space (23) being provided so that the vacuum there is produced, the thermal insulation piece (60) comprising a stack of several layers of film (12) interposed with layers of fibers (14), the different layers (12, 14) being held together. Thermal insulation piece according to claim 1, in which at least one edge (66) of the insulation piece (60) reveals the different layers (12, 14), so as to allow air present in the layers of fibers (14) from escaping from the insulating piece (60) when the vacuum is created. Thermal insulation part according to one of the preceding claims, in which the various layers (12, 14) are held together by means of assembly components (62, 64) passing through all the layers (12, 14 ) forming the insulation piece (60). Thermal insulation part according to Claim 3, comprising local reinforcements (68, 70, 82, 84) of the outer layers (12inf, 12sup) of the insulation part (60) at the level of the assembly components (62, 64). Thermal insulation part according to one of Claims 3 or 4, comprising at least one local fixing layer of the hook-and-loop type (78, 80) fixed to an outer layer (12inf) of the insulation part (60) by means of the assembly components (62, 64). Thermal insulation part according to one of the preceding claims, comprising two opposite outer faces each formed of a layer of film (12inf, 12sup), an overlap zone (72) configured to be placed under another insulation part (60), in the overlap zone (72), the different layers (12, 14) being folded back on themselves together so that a first of the outer faces (12inf) of the insulation part ( 60) is found in the position of a second of the outer faces (12sup) of the insulation piece (60). Method of manufacturing an insulation part (60), according to one of the preceding claims, linking the following steps:
a - From a roll (92) formed by a pair (94) of a film layer (12) and a fiber layer (14) which are integral, unroll on a plate (90) several pairs ( 94) on top of each other by superimposing them and respecting the order of the layers (12, 14) of the finished insulation part (60) to form a stack (10) of layers,
c - Simultaneously cut the different pairs (94) to the dimensions of the insulation piece (60) to form edges (98),
e - Fix the various pairs (60) in the vicinity of the edges (98) cut out. Manufacturing process according to claim 7, comprising between steps a and c, a step b of local reinforcement of the edges (98). Manufacturing method according to one of Claims 7 or 8, comprising between steps c and e, a step d of placing a local fixing layer of the self-gripping type (78, 80) fixed to an external layer (12inf) of the stack (10). Manufacturing process according to claim 9, in which, during step a, the pairs (94) are each arranged so that the fiber layer (14) faces the plate (90), the process comprising after step e , a step f of turning over the stack (10) of fixed layers (12, 14), removing an outer layer of fiber (14), and locally reinforcing the edges (98). Method of manufacturing according to claim 10 of an insulation part (60) according to claim 6, comprising after step f , a step g of local folding all of the fixed layers to reveal the overlap zone (72 ) and fixing the assembly in the overlap zone (72). Double-walled tank comprising an inner wall (22) and an outer wall (24), a space (23) being provided between the inner wall (22) and the outer wall (24), space in which several pieces of insulation ( 28, 30, 32, 38, 40, 42, 44) according to one of claims 1 to 6 are arranged edge to edge or overlapping, the space (23) being kept under vacuum.