WO2016156467A1

WO2016156467A1 - Insulated hollow structure for high temperature use

Info

Publication number: WO2016156467A1
Application number: PCT/EP2016/057023
Authority: WO
Inventors: Jørgen Mikael BERTH
Original assignee: Lr Marine A/S
Priority date: 2015-03-31
Filing date: 2016-03-31
Publication date: 2016-10-06

Abstract

An insulated hollow structure (1, 1a, 1b), such as a pipe (1a) or a tank (1b), for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure (1, 1a, 1b) is provided. The insulated hollow structure (1, 1a, 1b) comprises insulation layers (3, 4) enclosing an inner wall (2) of the hollow structure (1, 1a, 1b), which insulation layers (3, 4) comprises a first inner insulation layer (3) and a second insulation layer (4). The first insulation layer (3) comprises an aerogel based insulation material which has been applied in a liquid state to a surface (2a) of said wall (2) of the hollow structure (1, 1a, 1b) and then subsequently cured after being applied, before providing a second insulation layer (4). The second insulation layer (4) is a spray foam insulation layer enclosing the first inner insulation layer (3) and the inner wall (2) of the hollow structure (1, 1a, 1b). The invention moreover relates to use of an insulated hollow structure in the maritime environment, and a method of providing an insulated hollow structure.

Description

INSULATED HOLLOW STRUCTURE FOR HIGH TEMPERATURE USE The present invention relates in a first aspect to an insulated hollow structure, in a second aspect to use of an insulated hollow structure and in a third aspect to a method of providing an insulated hollow structure.

Background

Insulation of equipment for transporting and storing fluid at high temperature has proven to be a delicate process, and different technical solutions are provided for this purpose.

However such insulation is very important for various reasons, e.g. to assure safety of persons near the insulated structure, to avoid damage of nearby equipment due to the high temperature or the like, and naturally to reduce thermal loss and thus obtain a high coefficient of utilization.

For example, WO 2008/017147 provide an insulated pipe for use at high temperatures.

Also, it is known to provide an inner insulation layer made from e.g. mineral wool or the like, and a subsequent layer of material made from e.g. polyurethane foam.

However, the presently known systems for high temperature purposes have proven to provide drawbacks in relation to obtain a sufficient and at the same time durable insulation solution, especially in harsh environments.

Moreover, different types of presently used insulation systems for high temperature purposes have shown to be space consuming.

Also, manufacturing of different types of presently used insulation systems for high temperature purposes have shown to be time consuming and difficult to conduct/provide, thus demanding skilled and experienced personnel to provide the insulation. The present invention may e.g. solve one or more of the above mentioned problems.

The invention

The invention relates to an insulated hollow structure, such as a pipe or a tank, for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure, wherein the insulated hollow structure comprises insulation layers enclosing an inner wall of the hollow structure, which insulation layers comprises a first inner insulation layer and a second insulation layer, and wherein said first insulation layer comprises an aerogel based insulation material which has been applied in a liquid state to a surface of said wall of the hollow structure and then subsequently cured after being applied, before providing said second insulation layer, and wherein said second insulation layer is a spray foam insulation layer enclosing said first inner insulation layer and said inner wall of the hollow structure. According to one embodiment the invention relates to an insulated hollow structure, such as a pipe or a tank, for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure,

wherein said insulated hollow structure comprises insulation layers enclosing an inner wall of the hollow structure, which insulation layers comprises a first inner insulation layer and a second insulation layer, wherein said first insulation layer comprises a cured liquid-applied aerogel based insulation material applied to a surface of said wall of the hollow structure, and wherein said second insulation layer is a spray foam insulation layer enclosing said first inner insulation layer and said inner wall of the hollow structure . According to one embodiment the invention relates to an insulated hollow structure, such as a pipe or a tank, for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure,

wherein said insulated hollow structure comprises insulation layers enclosing an inner wall of the hollow structure, which insulation layers comprises a first inner insulation layer and a second insulation layer, wherein said first insulation layer comprises a cured liquid-applied aerogel based insulation material applied to a surface of said wall of the hollow structure, and wherein said second insulation layer is a spray foam insulation layer enclosing said first inner insulation layer and said inner wall of the hollow structure munufactured according to the method discribed and disclosed herein.

Generally, it may be understood that the cured liquid-applied aerogel based insulation material is of the type which is applied to a surface of the wall of the hollow structure in a liquid state and then is subsequently cured after being applied, before providing the second insulation layer . The present invention provides several advantages. The feature that the insulation material has been applied in a liquid stage to a surface of the hollow structure provides that the first insulation layer provides a tight sealing that is more resistant and reliable in a harsh environment compared to insulation systems where an insulation layer is preformed/premade and then subsequently wrapped around the structure.

The present invention may be suitable for use in harsh environments such as in the maritime environment. For example, on ships, oil rigs or at harbours, the ambient air has a high humidity and concentration of salt. This environment is damaging and hard to the structure, which has an inner wall that is often made of a metal such as iron or steel, and may thus be exposed to corrosion. However the present invention provides an improved and efficient seal and at the same time insulation of the structure from for example such harsh environments.

Moreover, the present invention may provide a solution with improved insulation properties as no jointing is/are needed for the first insulation layer on the structure, such as a pipe or tank, to get the insulation layer to enclose the structure tightly. Also, the present invention provides a space saving insulation solution as the aerogel based insulation material provides a low thermal conductivity, thereby needing a reduced thickness of the first insulation layer to get temperature of the outer surface of the first insulation material reduced to a level where other insulation types can be used for the second insulation layer, which are often not resistant to temperatures above 140°C. Accordingly, the overall space consumed by the insulated structure is reduced.

Additionally, the present invention may provide an efficient way of obtaining an improved insulation at joints of the structure, e.g. in that that is fitted exactly to the individual setup of the structure of the jointing.

The present invention may also provide an advantageous, tight insulation solution for producing pre -insulated hollow structures that is/are resistant to harsh environments, also during jointing of pre-insulated hollow-structures which are insulated in accordance with aspects of the present invention. Additionally, the first insulation layer and second insulation layer, may be provided at locations of the structure such as joints and recesses that are normally hard to access adequately with the presently known insulation systems.

The hot fluid to be stored or guided may in aspects of the invention e.g. be a liquid or a gas. It may for example be superheated steam, it may be oil, tar, molten sulphur, chemicals or the like. Also, a stiff insulation system may be achieved due to the properties of the first and second insulation layers which may provide advantages in relation to the mechanical stability and durability of the insulated structure.

Additionally, the present invention provides an insulated hollow structure which may be insulated fast and cost efficiently while providing a tight and mechanically resistant insulation solution.

The present solution also provides that reduced skills may be required by a person to provide the insulated hollow structure in that it is relatively simple to obtain the insulation layers due to the way the layers are applied/provided.

It is generally to be mentioned that the spray foam insulation layer in preferred aspects of the invention is applied on/at the surface and expands and cures on/at the hollow structure as opposed to other insulation systems where the second insulation layer may be pre-formed shells such as half shells with an inner size fitting the diameter of the hollow structure to be insulated. This may provide an improved bonding directly between the first and second insulation layers without need of further layers such as adhesive layers.

It is to be understood that the aerogel based insulation material provides its insulating properties due to the insulation properties of the aerogel.

In advantageous aspects of the invention, the insulated hollow structure comprises no more than three insulation layers, preferably two insulation layers, each having a thermal conductivity factor lying in the range of 0.01-0.09 W/mK at 25°C. The second insulation layer may have an temperature operating rage up to 140°C such as up to 120°C, e.g. up to 100°C. The first insulation layer may have a higher temperature operating range, e.g. up to 180°C such as up to 200°C e.g. up to 250°C such as up to about 300°C.

In preferred aspects of the invention, the first insulation layer is applied directly on the outer surface of said inner wall of the hollow structure. The use of the aerogel based insulation material in a liquid stage may result in that a primer or inner adhesive layer on the surface of the structure may be omitted between the wall surface and the inner insulation layer.

The structure surface may thus in aspects of the invention only need to be cleansed and/or abraded, sand blasted or the like to obtain a structure surface providing an improved adhesive property compared to more smooth surfaces. This may accordingly reduce the process steps and the material types needed to obtain the insulated pipe. This may provide an improved bonding directly between the structure surface and the first insulation layer without need of further layers such as adhesive layers.

In preferred aspects of the invention, said second insulation layer is applied directly on the outer surface of said first insulation layer.

The second insulation material may thus in advantageous aspects of the invention be arranged to abut the outer surface of said first insulation layer. This may provide a bonded system where layers of material may be omitted, in that primers and/or adhesive layers between the first and second insulation layers may be omitted. However, in other aspects of the invention, such intermediate primer or adhesive layers may be provided. In advantageous aspects of the invention, said first insulation layer and said second insulation layer provides a bonded insulation system. So in preferred embodiments of the invention, both bonding directly between the structure surface and the first insulation layer and bonding directly between the first and second insulation layers are present. This may provide an improved bonded insulation system, since bonding between the varrious structures are present without the need of further layers such as adhesive layers. Also, a stiff insulation system is achieved, where the layers only to a minor extent (or not al all) can be displaced relative to each other, due to the direct bonding between both the structure surface and the first insulation layer and direct bonding between the first and second insulation layers which provide advantages in relation to the mechanical stability and durability of the insulated structure.

Bonded insulation systems may be advantageous in that they provide an improved mechanical stability. Moreover, bonded systems may also provide a more tight system that is less permeable to liquid or gas and thus less exposed to corrosion or other mechanical disintegrating, as the gas or liquid is prevented from entering between the layers (e.g.

between insulation layers, between wall and first insulation layer and/or between second insulation layer and a protection layer). This may in preferred aspects of the invention be obtained where the second insulation layer is applied directly on/at the outer surface of said first insulation layer, and the first insulation layer is applied directly on the outer surface of said inner wall of the hollow structure.

In preferred aspects of the invention, said first insulation layer may have been applied by applying a plurality of sub-layers of insulation material in a liquid stage with intermediate curing time of the respective applied sublayer before a subsequent sublayer(s) is applied.

This may be an efficient way of providing an inner insulation layer, e.g. without risking that cracks occur in the layer during curing. Thus, the first insulation layer may in aspects of the invention comprise of a plurality of such sub-layers. In aspects of the invention, the first insulation layer may consist of a plurality of such sub-layers.

In embodiments of the invention, two or more, preferably all, of said sub-layers each has a thickness of no more than 0.8mm, such as no more than 0.7mm, preferably no more than 0.6mm, e.g. no more than 0.5 or 0.55mm such as no more than 0.4 mm, e.g. between 0.3- 0.6mm.

Each of said sub-layers of the first inner insulation layer may in aspects of the invention have a thickness between 4-20% e.g. between 6-15% such as 7-12% of the overall thickness Tl of the first insulation layer. This may provide a preferred relationship between the overall thickness of the first insulation layer and the sublayers, as no cracks may occur in the sub layers while at the same time providing a sufficiently thick first insulation layer in a fast way. The first insulation layer may in aspects of the invention comprise at least four sub-layers such as at least six sub-layers, e.g. at least seven sub-layers, preferably no more than twelve sublayers such as about eight sub-layers. In aspects of the invention, the innermost sub-layer of said sub-layers may preferably abut the outer surface of the inner wall of the hollow structure. In preferred aspects, said sub-layers may be arranged directly on top of each other. Thereby a simple insulation structure may e.g. be provided where a person with reduced skills may insulate the hollow structure in a sufficient manner.

In advantageous aspects of the invention, said first insulation layer may have a thickness of no more than 10mm such as no more than 7 mm, e.g. no more than 5mm, preferably about 4mm.

It is to be understood that in preferred aspects of the invention, the first insulation layer and the second insulation layer may be arranged between the outer surface of the wall of the hollow structure, and an outer protection jacket. This provides an enhanced resistance to outer forces and/or weather conditions and thus protects the insulation layers. The protection jacket may be made from any suitable material such as a plastic material, e.g. a polyethylene material such as a High-density polyethylene (HDPE). A HDPE jacket has proven to be suitable for use as outer pipe protection jackets. In advantageous embodiments of the invention, the hollow structure is a pipe and the protection jacket is a tubular protection jacket.

The present invention may generally also have an advantage compared to for example insulation solutions where mineral wool is used as the first, inner insulation layer on a pipe, as mineral wool may be compressed when the second insulation layer is provided by a spray foam insulation such as Polyurethane foam. For example, in such aspects, the pipe with the first insulation layer is arranged to extend inside a preformed protection jacket, and then the spray foam is supplied between the outer surface of the first insulation layer and the inner surface of the protection jacket. The spray foam thus provides a compressing force towards the inner insulation layer when it expands, thereby compressing a compressible first insulation layer such as mineral wool. This may be considered unwanted as this compression may result in an unwanted reduction of the insulating property of the mineral wool.

However, the aerogel based insulation as provided by the present invention is much less compressible, and thus, the insulation properties of the first insulation layer according to aspects of the invention are maintained during expansion and curing of the second a spray foam insulation layer.

In other aspects, the hollow structure may be a tank, and the protection jacket may comprise or consist of a protection layer such as a polymeric surface protection such as a Polyurea coating.

The protection layer may not be understood as an insulation layer as opposed to the first and second insulation layers which are arranged with the goal of heat insulation.

In preferred aspects of the invention, said second insulation layer is provided by a spray foam insulation layer such as polyurethane foam. Other types of spray foam insulation may be used in further embodiments of the invention. An alternative to the PUR insulation layer may be a Polyethylene (PE) material. An alternative to the PUR insulation layer may be a Polyisocyanurate (PIR) material.

Polyurethane foam has proven to be an advantageous insulation material as it is cost efficient, effective and easy to work with. It however suffer from being vulnerable to high temperatures, such as temperatures above 140°C, but by the present invention, the first inner insulation layer provides that the temperature at the outside surface of the first insulation layer is reduced to a temperature level where e.g. polyurethane foam may be used for further insulation.

The polyurethane layer lay also have the advantage that it automatically adhere to surfaces that it comes into contact with during its expansion, and in the present case, this may result in a bonded insulation layer which may moreover, in further aspects of the invention, adhere to an outer layer such as a protection jacket. In preferred aspects of the invention, said hollow structure is a pipe, such as a metal pipe, with a wall enclosing a cavity/space for guiding said fluid having a temperature above 140°C. Preferably, the pipe is a preformed, stiff pipe, and the said insulation layers are applied after the stiff pipe has been formed.

In advantageous aspects of the invention, the structure may be a pipe, preferably comprising one or more bends such as bends with an angle less than 130°, such as less than 100°, such as about 90°, or less than 90° such as less than 80°.

Bends on pipes are difficult and time consuming to insulate properly with insulation layers of mineral wool or other types of material that are wrapped around the pipe structure. By the present invention, such bends are efficiently insulated in an easy way.

The pipe may in embodiments of the invention comprise one or more bends to extend in at least two such as at least three different directions.

The first insulation layer may in advantageous aspects of the invention have a thermal conductivity factor value k less than 0.08 W/mK at 25°C such as less than 0.06 W/mK at 25°C, e.g. about 0.055 W/mK at 25°C when cured. This may e.g. provide that a thinner player of first insulation material may be utilized to obtain a temperature of the outer surface of the insulation layer that enables use of spray foam insulation. The first insulation layer may in advantageous aspects of the invention have a thermal conductivity factor value k larger than 0.01 W/mK at 25°C such as larger than 0.03 W/mK at 25°C when dried/cured.

In preferred aspects of the invention, said first insulation layer is a silica aerogel based coating.

The second insulation layer may ion aspects of the invention have a thermal conductivity factor value k less than 0.08 W/mK such as less than 0.06 W/mK e.g. less than 0.04 W/mK e.g. around 0.03 W/mK such as about 0.02 W/mK. In aspects of the invention, the first inner insulation layer may have a thermal conductivity factor k that is higher in value than the second insulation layer's thermal conductivity. Said hollow structure may in aspects of the invention be a pipe comprising one or more tracer tubes for heating said wall of said pipe, wherein the or more tracer tubes is/are configured for guiding a heated fluid inside its cavity, so as to heat the pipe wall, and wherein the first inner insulation layer encloses the tracer tube and said pipe wall. The tracer fluid may have a temperature above 200°C such as above 250°C and may e.g. be an oil or the like.

Due to that the first insulation layer has been applied in a liquid state, it will be applied around and onto the tracer tube wall surface and the pipe wall surface. This provides that the second insulation layer may provide increased securing abilities after curing as a large part of the "free" surface of the tracer tube is provided with insolation. As the compression abilities of the first insulation layer is very limited when cured, and since the first insulation layer abut substantially whole the exposed surface of the tracer tube, the second insulation layer is able to provide a good support/securing of the tracer tube. Additionally, the second insulation layer is able to provide a good insulation around the tracer tube.

In aspects of the invention, the temperature of said fluid guided or stored in the insulated hollow structure may have a temperature above 160°C such as above 180°C, e.g. above 200°C during the storing and/or guiding in the insulated hollow structure such as above 250°C, preferably not higher than about 300°C.

The fluid to be guided in the cavity/space enclosed by the inner wall may e.g. be oil, tar or melted sulphur, and the hollow structure may thus be suitable for storing or guiding such fluid.

The combined thickness of the first and second insulation layers may in preferred aspects of the invention be between 35mm and 110mm, such as between 40mm and 70mm, preferably between 45mm and 65mm, e.g. between 55mm - 60mm. This preferably applies to aspects of the invention wherein the hollow structure is a pipe, but it may also apply to aspects of the invention wherein the hollow structure is a tank.

In an advantageous aspects of the invention, at least two of said insulated hollow structures are jointed to provide a fluid communication between spaces/cavities in the respective jointed insulated hollow structures, wherein a further layer of aerogel based insulation material which has been applied in a liquid state is provided to cover a jointing of the insulated hollow structure and to overlap an exposed part of said first insulation layer of the respective jointed structures. A spray-foam based insulation layer may then be provided between the further layer of aerogel based insulation material and a jointing jacket, which jointing jacket overlaps outer protection layers of the respective jointed, insulated hollow structures.

Generally, pre -insulating pipes and tanks may often be done in controlled environments, thereby reducing the risk of encapsulating layers that are damaging in respect of e.g.

corrosion risks.

However, when jointing pre-insulated structures, this is often done on-site due to e.g. size issues and to build complete systems. For example, piping systems and tank systems for ships are often provided in or near the maritime environment, thereby increasing the risk of contamination of surfaces and gaps during the jointing of the insulated, hollow structures. The present invention however provides insulated pipes and/or tanks that are tight and very resistant to such environments as the insulation layers encapsulate the wall of the hollow structure in a very tight manner. Thereby, the exposed parts of the first insulation layer may be overlapped by the further insulation layer, thereby providing a very tight sealing insulation layer in that the exposed, inner insulation layer of the pipes or the tank is bonded to the pipe/tank all around the structure wall, and there is thus a very low risk of water, steam, salt or the like to get in between the wall surface and the inner insulation layer, or in between the first insulation layer and the second insulation layer as these preferably are bonded together, preferably due to their characteristics.

Accordingly, the present invention may provide an advantageous, tight system that is resistant to environments, also during jointing of pre-insulated hollow-structures. The jointing of the inner walls may be provided by welding, by connecting two flanges and/or by any other suitable joining methods for joining e.g. metal pipes, tanks or the like.

The invention moreover relates to use of an insulated hollow structure in the maritime environment, which insulated hollow structure is an insulated hollow structure as described herein and according to any of claims.

Moreover, the invention relates to a method of providing an insulated hollow structure, such as a pipe or a tank, for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure, said method comprising the steps of:

applying a first insulation layer comprising an aerogel based insulation material in a liquid state to a surface of a wall of the hollow structure,

curing preferably subsequently said applied first insulation layer, and

providing a second insulation layer which second insulation layer is a spray foam insulation layer enclosing said first inner insulation layer and said wall of the hollow structure,

curing preferably subsequently said applied second insulation layer. It is generally understood that the aerogel based insulation layer may be provided by any suitable aerogel based coating that may be applied in a liquid state and then subsequently cured.

The insulation layer will be dry for touch about 2 hours from being applied. After about 3 hours, if cured at a temperature between e.g. about 20-30°C, a new layer can be applied by e.g. a spray gun. A faster curing may be obtained by curing at a higher temperature. At a curing temperature about 100-150°C, a curing time before a new layer can be applied may be reduced to about 10-15 minutes. The method may e.g. be a fast and yet effective method of providing a bonded insulated hollow structure with bonded layers, which is resistant to corrosion, space-saving and/or provides an improved insulation around curved surfaces. Other of the previously mentioned effects may also be provided by the method. Generally, by the method above, one or more of e.g. the previously described

advantages/effects may be obtained.

In one embodiment of the invention, the first insulation layer is applied directly on the outer surface of said inner wall of the hollow structure.

In one embodiment of the invention, the second insulation layer is applied directly on the outer surface of said first insulation layer. In one embodiment of the invention, the first insulation layer is applied by applying a plurality of sub-layers of insulation material in a liquid stage with intermediate curing time of the respective applied sublayer before a subsequent sublayer(s) is applied. In one embodiment the two or more, preferably all, of said applied sub-layers each has a thickness of no more than 0.8mm, such as no more than 0.7mm, preferably no more than 0.6mm, e.g. no more than 0.5 or 0.55mm such as no more than 0.4 mm, e.g. between 0.3-0.6mm. In one embodiment each of said applied sub-layers of the first inner insulation layer has a thickness (T2) between 4-20% e.g. between 6-15% such as 7-12% of the overall thickness (Tl) of the first insulation layer. In one embodiment the applied first insulation layer comprises at least four sub-layers such as at least six sub-layers, e.g. at least seven sub-layers, preferably no more than twelve sublayers such as about eight sub-layers. In one embodiment the innermost applied sub-layer of said sub-layers abuts the outer surface of said wall of the hollow structure. In one embodiment the sub-layers are applied directly on top of each other.

In one embodiment of the invention, the applied first insulation layer has a thickness (Tl) of no more than 10mm such as no more than 7 mm, e.g. no more than 5mm, preferably about 4mm.

In one embodiment of the invention, the applied first insulation layer and the applied second insulation layer are arranged between the outer surface of said wall of the hollow structure, and an outer applied protection jacket.

In one embodiment of the invention, the applied second insulation layer is a spray foam insulation layer such as polyurethane foam. In one embodiment of the invention, the hollow structure is a pipe, such as a metal pipe, with a wall enclosing a cavity/space for guiding said fluid having a temperature above 140°C. In one embodiment, the hollow structure is a pipe, comprising one or more bends such as bends with an angle (al) less than 130°, such as less than 100°, such as about 90°, or less than 90° such as less than 80°.

In one embodiment of the invention, the applied first insulation layer has a thermal conductivity factor value k less than 0.08 W/mK at 25°C such as less than 0.06 W/mK at 25°C, e.g. about 0.055 W/mK at 25°C when cured. In one embodiment the applied first insulation material has a thermal conductivity factor value k larger than 0.01 W/mK at 25°C such as larger than 0.03 W/mK at 25°C when cured.

In one embodiment of the invention, the applied first insulation layer is a silica aerogel based coating.

In one embodiment of the invention, the applied second insulation layer has a thermal conductivity factor value k less than 0.08 W/mK such as less than 0.06 W/mK e.g. less than 0.04 W/mK e.g. around 0.03 W/mK such as about 0.02 W/mK. In one embodiment of the invention, the said hollow structure is a pipe comprising one or more tracer tubes for heating said wall of said pipe,

wherein said one or more tracer tubes is/are configured for guiding a heated fluid inside its cavity, so as to heat the pipe wall, and

wherein said applied first inner insulation layer encloses said tracer tube and said pipe wall.

In one embodiment of the invention, the temperature of said fluid guided or stored in the insulated hollow structure has a temperature above 160°C such as above 180°C, e.g. above 200°C during the storing and/or guiding in said insulated hollow structure , such as above 250°C, preferably not higher than about 300°C.

In one embodiment of the invention, the combined thickness (T4) of said applied first and second insulation layers is between 35mm and 110mm, such as between 40mm and 70mm, preferably between 45mm and 65mm, e.g. between 55mm - 60mm. In one embodiment of the invention, the at least two of said insulated hollow structures are jointed to provide a fluid communication between spaces/cavities in the respective jointed insulated hollow structures,

wherein a further layer of aerogel based insulation material is applied in a liquid state to cover a jointing of the insulated hollow structure and to overlap an exposed part of said applied first insulation layer of the respective jointed structures,

wherein an spray-foam based insulation layer is applied between said further layer of aerogel based insulation material and a jointing jacket, which jointing jacket overlaps outer protection layers of the respective jointed, insulated hollow structures.

In aspects of the method, the insulated hollow structure may preferably be an insulated hollow structure according to the present invention as described and disclosed herein.

In aspects of the method, the insulated hollow structure may preferably be an insulated hollow structure according to the present invention as described and disclosed herein for use in a maritime environment such as at a harbour or at the sea on e.g. vessels such as ships or oil rigs.

Figures

Aspects of the present disclosure will be described in the following with reference to the figures in which: fig. 1 illustrates an insulated hollow structure seen in perspective according to

embodiments of the invention,

fig. 2 illustrates an insulated hollow structure with sub layers according to

embodiments of the invention,

fig. 3 illustrates an insulated hollow structure according to further embodiments of the invention,

fig. 4 illustrates an embodiment of the invention where the present invention may be advantageous

Fig. 5 illustrates an embodiment of the invention relating to providing a first inner insulation layer, Fig. 6 illustrates a cross sectional view of embodiments of the invention where a second insulation layer is applied on top of a first, inner insulation layer, Fig. 7 illustrates embodiments of the invention where a tracer tube is provided, and Fig. 8 illustrates an example of a cross sectional view of a jointing according to

embodiments of the invention.

Detailed description

Fig. 1 illustrates an insulated hollow structure 1 , in this case in the form of an insulated pipe 1 a seen in perspective, according to embodiments of the invention, but it may also be a tank lb, e.g. as described in more details later on.

The hollow structure 1, e.g. the pipe la, is suitable for guiding a fluid in having a temperature above 140°C inside the pipe in the space/cavity 7 between the pipe wall 2. The fluid is thus guided inside the space/cavity 7, and the outside surface 2a of the wall is the surface that is to be insulated by insulation layers. Accordingly, the insulation system insulating the pipe lb needs to be resistant to such high temperatures.

The wall 2 is preferably made of a metal such as iron or a metal alloy such as steel, e.g. stainless steel or any other suitable metal which is heat resistant to temperatures above 140°C.

The fluid guided or stored in the space/cavity (7) provided by the inner wall may in embodiments of the invention have a temperature above 160°C such as above 180°C, e.g. above 200°C during the storing and/or guiding in the cavity/space 7, such as above or about 250°C, preferably not higher than about 300°C.

The insulated hollow structure 1 comprises insulation layers 3, 4 enclosing the pipe wall 2 around the pipe. The insulation layers 3, 4 comprises a first inner insulation layer 3 and a second insulation layer 4 enclosing the first inner insulation layer 3 and the wall 2 of the pipe la.

The first insulation layer 3 comprises an aerogel based insulation material which has been applied in a liquid state to the outer surface 2a of the wall 2 and then subsequently cured after being applied, before providing the second insulation layer 4. This is described in more details later on. The second insulation layer 4 is a spray foam insulation layer enclosing the first inner insulation layer 3 and the wall 2 of the hollow structure 1 so that the first inner insulation layer 3 is arranged between the wall 2 and the second insulation layer 4. The first inner insulation layer 3 is resistant to very high temperatures. It may be resistant to temperatures above 140°C such as above 160°C, e.g. above 180°C, such as above 200°C, e.g. above 250° C during the storing or guiding in the space/cavity 7 in the hollow structure 1 C. However, the first inner insulation layer 3 may not be suitable for being exposed to temperatures higher than 400°C such as not higher than 350°C.

The first insulation layer 3 brings down the temperature to a temperature level where the second insulation layer 4 is useable to provide a further insulation. Accordingly, the first insulation layer 3 provide an insulation to bring down the temperature on the outer surface 3 a of the first inner insulation layer 3 to a temperature below 140°C.

According to embodiments of the invention, the first insulation layer 3 has a thermal conductivity factor value k less than 0.08 W/mK at 25°C such as less than 0.06 W/mK at 25°C, e.g. about 0.055 W/mK at 25°C when cured. The first insulation layer 3 , may in embodiments of the invention have a thermal conductivity factor value k larger than 0.01 W/mK at 25°C such as larger than 0.03 W/mK at 25°C when dried/cured.

The second insulation layer 4 is here able to take over the insulation to bring the temperature of the outer surface 4a of the second insulation layer 4 to a lower temperature level. In embodiments of the invention, the second insulation layer 4 may have a thermal conductivity factor value k (when cured) less than 0.08 W/mK such as less than 0.06 W/mK e.g. less than 0.04 W/mK e.g. around 0.03 W/mK such as about 0.02 W/mK.

The typical desired maximum temperature on the outer surface of the insulated hollow structure is preferably below 60 °C so as to obtain a surface temperature that is not harmful to persons if touching the surface with e.g. hands. However, the desired maximum temperature, seen from an energy preservation aspect is normally below 35 °C such as below 25 °C at an ambient temperature of about 15 °C to reduce heat loss. The thickness T3 of the second insulation layer 4 (e.g. measured between the surface 3a of the first insulation layer 3 and the outer surface 4a of the second insulation layer) is preferably between 30mm and 100mm such as between 40mm and 70mm, preferably between 45 an 60mm.

Preferably, the overall thickness T4 of the first and second insulation layers 3, 4 (e.g.

measured between the outer surface 2a of the wall 2 and the outer surface 4a of the second insulation layer 4) is between 35mm - 110mm, preferably between 40mm-70mm, such as between 45-65mm, e.g. between 55mm-60mm.

The thickness ratio T3/T1 between the thickness T3 of the second insulation layer 4 and the thickness Tl of the first insulation layer T3 is preferably between 9 and 20, such as between 11 and 17. For example, a first insulation layer 3 having a thickness Tl of about 4mm and a second insulation layer 4 having a thickness T3 of about 55mm will result in a T3/T1 ratio of:

Γ3 55

Tl 4

An optional protection layer 6 in the form of an outer protection jacket, such as an HDPE jacket, may in embodiments of the invention be provided to the outer surface of the hollow structure 1 to provide mechanical protection from the ambient environment and/or to provide a more water-tight enclosure.

The first insulation layer 3 and the second insulation layer 4 may thus in embodiments of the invention be arranged between the outer surface 2a of the inner wall 2 of the hollow structure 1, la, lb, and the outer protection jacket 6.

In other embodiments of the invention, the protection layer 6 may be omitted and the insulated hollow structure may thus not comprise further protection beyond the protection provided by the second insulation layer.

The second insulation 4 layer may in preferred aspects of the invention be a Polyurethane (PUR) layer, but other types of spray foam insulation may be used in further embodiments of the invention. An alternative to the PUR insulation layer may be a Polyethylene (PE) material.

In preferred embodiments of the invention, the first insulation layer 3 may, as illustrated, be applied directly on the outer surface 2a the wall 2 of the hollow structure 1, e.g. after preparing the surface 2a by cleansing and/or abrading or sand blasting the surface 2a to provide better adhesion characteristics of the surface 2a.

However, in other embodiments of the invention, which are not illustrated, a primer or adhesive may be supplied on the surface 2a of the wall 2 between the wall 2 and the first insulation layer 3 to e.g. improve adhesion properties.

In preferred embodiments of the invention, the second insulation layer 4 may, as illustrated, be applied directly on the outer surface 3 a of the first insulation layer 3, i.e. without a primer, adhesive or the like. This may however still, in embodiments of the invention, provide a bonded system where the first and second insulation layers 3, 4 are bonded to each other due to the respective properties of the first and second insulation layers, and the first insulation layer 3 is bonded to the surface 2a of the hollow structure 2. However, in other embodiments of the invention, which are not illustrated, a primer or adhesive may be supplied on the surface 3 a of the first insulation layer between the first insulation layer 3 and the second insulation layer 4 to e.g. improve adhesion properties between the insulation layers. The first and second insulation layers 3, 4 are thus preferably bonded so as to provide a tight and stiff structure where the insulation layers 3, 4 cannot be displaced relative to each other.

Fig. 2 illustrates an embodiment of the invention wherein the first insulation layer 3 is provided by a plurality of sub-layers 5a-5h. The sub-layers 5a-5h are made from the aerogel based insulation material.

Each of the sub-layers 5a-5h have been applied in a liquid state to the outer surface 2a of the wall 2 and then subsequently cured after being applied before providing the next sub-layer. For example, the first, innermost sublayer 5a may be applied in a liquid state to the surface 2a of the wall 2. The applied layer 5a is then cured, and after this, the second, subsequent sub-layer 5b is applied in a liquid state to the surface of the first sublayer 5a and then cured. Then the next, third sub-layer 5c is applied to the surface of the second, cured sublayer 5b and so, until a desired insulation property is obtained. After the outermost sub-layer 5h has been applied in a liquid state and then cured, the first insulation later 3 is ready, and the second insulation layer 4 can then be provided.

The innermost sub-layer (5a) of said sub-layers (5a-5n) may thus in embodiments of the invention abut the outer surface (2a) of said wall (2) of the hollow structure (1, la, lb).

Each of the sublayers 5a-5h may in embodiments of the invention each have a thickness of no more than 0.8mm, such as no more than 0.7mm, preferably no more than 0.6mm, e.g. no more than 0.5 or 0.55mm such as no more than 0.4mm. The ratio between the thickness of the first insulation layer 3 a compared to the sublayer thickness, also referred to as the layer/sub-layer ratio is preferably at least such as at least 8, e.g. at least 10.

For example, a fist insulation layer having an overall thickness of 4mm, where each sub- layer has an average layer thickness of 0.4mm will have an

layer/sub-layer ratio of:

Layer thickness _ 4 _ . _

sublayer thickness 0.4

As another example, a 4mm thick first insulation layer with an average sub-layer thickness of about 0,45 will have a layer/sub-layer ratio of:

Layer thickness 4 ₀ on

——— o.yy

sublayer thickness 0.45

Each of the sub-layers 5a-5h of the first insulation layer 3 may thus in embodiments of the invention have a thickness T2 between 4-20% of the overall thickness Tl of the first insulation layer 3, e.g. between 6-15% such as 7-12% of the overall thickness Tl of the first insulation layer 3. In fig. 2, eight sub-layers each having a thickness T2 together provides the overall thickness Tl of the first insulation layer 3. However, it is understood that the first inner insulation layer may comprise any suitable number of sub-layers such as at least four sub-layers 5a-5n e.g. at least six sub-layers 5a-5n, for example at least seven sub-layers 5a-5n, preferably no more than twelve sublayers such as about eight sub-layers 5a- 5n.

Accordingly, the Thickness Tl may in embodiments of the invention be provided by the sum of the thicknesses of the sublayers T2. So in the present embodiment with eight sub-layers: Tl = T2_a + T2_b + T2_C + T2_d + T2_e + T2_f + T2_f + T2_n

In preferred embodiments of the invention, the first insulation layer 3 has a thickness Tl of no more than 10mm such as no more than 7 mm, e.g. no more than 5mm, e.g. preferably about 4mm. However, it is preferred that the first insulation layer 3 has a thickness Tl of at least 2mm such as at least 3mm.

Fig. 3 illustrates an embodiment of the invention where the hollow structure 1 is a tank lb. The tank has an inlet 8 so that the hot fluid such as a liquid above 140°C can enter the tank lb and be stored in the space/cavity 7 providing a volume of the tank. The fluid can then leave the tank lb at a later point through an outlet 9. It is understood that the physical form of the tank may vary to have any suitable form, e.g. cylindrical, rectangular and/or the like. Also, it is understood that the configuration of inlet(s) and outlet(s) may vary.

The tank lb comprises a wall 2 to be insulated by a first inner insulation layer 3 and a second insulation layer as previously described. The first inner insulation layer 3 this comprises an aerogel based insulation material which has been applied in a liquid state to the tank surface 2a, and then subsequently cured, before the second insulation layer 4 is applied. The first inner insulation layer 3 may in embodiments of the invention comprise a plurality of sublayers 5a-5h as previously described, however these are not illustrated in fig. 3. The outer surface 4a of the second insulation layer 4 may in embodiments of the invention be applied with a protective layer 6 of a suitable material. This is however not illustrated in fig. 3. Such a protective layer may be provided by a substance to be applied by spraying, by brush, and then subsequently cured. The outer protection layer 6 may in embodiments of the invention (e.g. to protect a tank lb) be a Polymeric surface protection such as a Polyurea coating, which may e.g. be suitable as protection layer 6 for a tank. The Polymeric surface protection such as a Polyurea coating may be applied after application of the second insulation layer, e.g. sprayed on the surface of the second insulation layer. This coating may act as a vapour barrier and mechanical protection. The thickness of the Polymeric surface protection layer on a tank may typically be between 1mm and 7mm such as between 2mm and 5mm, e.g. about 3mm.

Fig. 4 illustrates an embodiment of the invention where the present invention may be advantageous. The insulated hollow structure 1 here comprises a pipe la with bends 14, such as about 90° (al) bends, so that the pipe /pipe system extends in different directions such as X, Y and Z directions. Bends 14 have however shown to be difficult and time consuming to insulate with the prior solutions, but the present invention provides an advantageous and yet simple solution where such bends can be efficiently insulated as the first insulation layer 3 is provided in liquid state, thus automatically adapting to the pipe shape, as will the spray foam insulation 4.

The bends may however be bends with an angle al less than 130°, such as less than 100°, such as about 90°, or less than 90° such as less than 80°.

Fig. 5 illustrates an embodiment of the invention relating to providing the first inner insulation layer 3.

In the present embodiment, the first layer is applied in a liquid state by a spray nozzle 11 to the surface 2a of the hollow structure 1, in this case a pipe la. In other embodiments of the invention, it may be applied with a brush or the like. A relative motion between the nozzle and the structure 1 is provided, either by moving the nozzle as illustrated by the arrow, or alternatively by moving the structure in its longitudinal direction while keeping the nozzle in a fixed position.

In embodiments of the invention, where the structure 1 is a pipe 1 a, the pipe 1 a may be rotated around its longitudinal direction while it is also moved in its longitudinal direction. This may e.g. be provided by drive means such as rollers (not illustrated) supporting and/or driving the pipe. This may e.g. help to provide a more even layer of insulation material. In the embodiment of the invention where the insulation material for obtaining the first inner layer 3 is applied by nozzle, the nozzle may be supplied with the aerogel-based insulation material from a storage 12.

The applying of the material by nozzle or brush or roller may in embodiments of the invention be done a plurality of time to obtain a resulting inner insulation layer 3 build up by a plurality of sub-layers as previously described. It is generally understood that the aerogel based insulation layer 3 may be provided by any suitable aerogel based coating that may be applied in a liquid state and then subsequently cured.

For example, a "AEROCOAT-300" coating product provided by TEC corporation, LTD may be used for establishing the first coating layer, which is a silica based aerogel coating material. It has a thermal conductivity about 0.055W/mK at 25°C and can be used at operating temperatures up to about 300°C.

Experiments has shown that a hot surface of a structure having a temperature about 250°C, if applied with the AEROCOAT-300 coating will reduce the outer surface temperature of the insulation layer to about 105°C in a 25°C environment if applied with an approx. 5 mm layer of AEROCOAT-300. A 4 mm AEROCOAT-300 insulation layer will reduce the temperature from 250°C to about 125°C, and a 6 mm layer to about 85°C on the surface of the insulation layer in a 25°C environment.

The mixing procedure for the aerogel based coating, in this case the "AEROCOAT-300" coating, may e.g. comprise the steps of:

• Mixing a first component, e.g. an "AEROCOAT-300A" component, for a first time period, e.g. at e.g. >500rpm

· Adding a second component, e.g. a AEROCOAT-300B component, into the first, mixed component and mixing for a second time period at e.g. >600 rpm

• Adding a further, third component, e.g. an AEROCOAT-300C component, into the above mixture of the first and second components and mixing a third time period, at e.g. >1000 rpm The time periods for mixing may each be between 3-20 minutes such as between 5 and 15 minutes e.g. about 10 minutes. The resulting mixture may then be applied to the surface 2a of the hollow structure by a spray gun with a nozzle size about 2.5mm, e.g. with an air pressure about 0.8-1.0 MPa.

The coating thickness for a sub-layer is preferably maximum about 0.5mm per coating layer, i.e. per sub-layer 5a-5h (see above).

The preferred environment temperature during coating may be above 20°C, and an air humidity about 50%.

The insulation layer will be dry for touch about 2 hours from being applied. After about 3 hours, if cured at a temperature between e.g. about 20-30°C, a new layer can be applied by the spray gun. A faster curing may be obtained by curing at a higher temperature. At a curing temperature about 100-150°C, a curing time before a new layer can be applied may be reduced to about 10-15 minutes. Another aerogel insulation material for the first insulation layer 3 may be "AEROGEL-W" coating provided by Tec Corporation, LTD. It is a silica aerogel product in the form of a water-based paste. It is heat resistant up to about 250°C, and has a thermal conductivity of about 0.015-0.020 W/mK at 25°C (dry). It may be applied by spray nozzle, roller or brush. A further example of an aerogel based coating for the first insulation layer 3 may be the "AEROCOAT 170" provided by TEC corporation, LTD.

Fig. 6 illustrates a cross sectional view of an embodiment of the invention where the second insulation layer 4 is applied on top of the first, inner insulation layer 3, in an embodiment of the invention where the hollow structure is a pipe 1 a. A nozzle 13 is arranged to provide the spray foam insulation layer 4 in the cavity between the outer surface 2a of the first, inner insulation layer 2 and the inner surface 6b of a protection jacket 6. A relative motion between the nozzle 13 and the pipe 1 a is provided while the nozzle 13 sprays the spray foam insulation into the cavity, thereby providing the second insulation layer 4 between the first insulation layer 3 and the protection jacket 6. The spray foam insulation 4 will then expand in the cavity to abut the inner surface 6b of the protection jacket 6 and the outer surface 3 a of the first insulation layer 3, and thereby provide a bonded system. It is understood that a plurality of nozzles 13 may be utilized so as to provide a more even distribution of spray foam insulation around the pipe surface 2a.

Fig. 7 illustrates an embodiment of the invention wherein the hollow structure is an insulated pipe la. A tracer tube 10 is arranged to provide a heat transfer from the tracer tube 10 to the pipe wall 12 so as to obtain heat maintenance of the pipe wall 2, thereby e.g. helping to maintain the fluid in the cavity 7 in the desired fluid state. The tracer tube 10 is thus configured to guide a hot fluid in its cavity 14 and heat of this fluid is then transferred to the pipe wall 2. The tracer tube 10 may e.g. be welded or soldered to the pipe surface 2a. The tracer tube may be made of a metal having high heat conducting abilities, e.g. a copper tube, or it may be made of stainless steel or the like.

The tracer tube 10 has a wall part 15 facing the inner pipe 2 with the cavity 7. The inner wall

2 is thus heated by the tracer tube 10. The tracer tube 10, moreover has a larger exposed wall surface 16 which abut the first insulation layer 3, e.g. by the first insulation layer 3 being applied on the exposed wall surface 16 of the tracer tube.

The first insulation layer 3 provides a tight seal in the area A of the transition between the tracer tube 10 and the pipe wall 2.

Even though only one tracer tube 10 is illustrated in fig. 7, it is understood that the hollow structure la in embodiments of the invention may comprise a plurality of tracer tubes 10, such as two, three, four or even more tracer tubes arranged around the pipe wall 2 and extending in the longitudinal direction of the inner pipe wall 2.

Fig. 8 illustrates an example of a cross sectional view of a jointing where two pipes lb are jointed and insulated according to embodiments of the present invention.

The ends 17 of the pipe walls 2 are joined by welding 18. A part of the first insulation layers

3 near the pipe ends 17 to be joined are exposed, and a bare area 19 of the surface of the inner pipe 2 between the exposed first insulation layer 3 and the ends 17 is provided to allow welding of the pipe ends 17 or to allow other types of connection methods.

After the pipe ends have been sufficiently jointed, a further layer 20 of first insulation material (e.g. an aerogel based insulation material which is applied in a liquid state as previously described, e.g. by applying several sub-layers as previously described) is arranged over the welding area 18, the bare surface 19 of the pipe and overlaps 21 the exposed part 22 of the first insulation layer 3 on the surface of the inner pipe 3. A jointing jacket 23 is then provided over the pipe ends 17 and overlaps a protection jacket 6 of the pipes 1 a, and a foam insulation layer 24 is then provided between the j ointing j acket 23 and the further layer 20 of first insulation material 3.

Alternatively, other types of insulation material, such as pre-formed PUR half shells may in embodiments of the invention be provided at the jointing 25 as the insulation layer 24 on top of the further layer 20, and then subsequently, a jointing jacket 23, such as a jointing jacket that shrink in diameter when subjected to heat, may be applied over the PUR shells.

Even though the above jointing method and result is described and illustrated with respect to jointing two pipes, it is understood that substantially the same method may be used when joining e.g. a pipe and a tank. E.g. by assuring that an insulation layer 20 overlaps 21 exposed, first aerogel-based insulation layers 3 of the tank and pipe respectfully, and then a second insulation layer 4 such as a spray foam insulation may be applied on top of that further layer.

In general, it is to be understood that the present invention is not limited to the particular examples described above but may be adapted in a multitude of varieties within the scope of the invention as specified in e.g. the claims. Accordingly, for example, one or more of the described and/or illustrated embodiments above may be combined to provide further embodiments of the invention. List

1. : Insulated hollow structure

I a : insulated pipe

lb : insulated container such as a tank

2 : wall of hollow structure such as pipe wall or tank wall forming a space/cavity

3 : first inner insulation layer

3 a : Outer surface of first inner insulation layer

4 : Second insulation layer

4a : Outer surface of second insulation layer

5a-5h : Sub-layers of first insulation layer

6 : Protection layer such as protection jacket

7 : Space/cavity of hollow structure

8 : Inlet

9 : Outlet

10 : Tracer tube

I I : Nozzle for providing first insulation layer

12 : Storage for storing aerogel-based insulation material in a liquid state

13 : Nozzle for providing second insulation layer

14: : Tracer tube cavity

15 : Tracer tube wall part facing the inner pipe

16 : exposed wall surface of tracer tube to be provided with insulation layer

17 : Pipe ends to be jointed

18 : welding jointing of pipe ends

19 : bare area of surface of the inner pipe at end to be jointed

20 : further layer of first insulation material to insulate jointing area at wall surface

21 : Part of further layer 20 overlapping exposed part 22 of first insulation layer of hollow structure at jointing

22 : exposed part 22 of the first insulation layer

23 : Jointing Jacket

24 : Second insulation layer at jointing

25 : Jointing for jointing two hollow structures.

Claims

1. A method of providing an insulated hollow structure (1, la, lb), such as a pipe (la) or a tank (lb), for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure (1, la, lb), said method comprising the steps of: applying a first insulation layer (3) comprising an aerogel based insulation material in a liquid state to a surface (2a) of a wall (2) of the hollow structure (la, lb), curing said applied first insulation layer (3), applying a second insulation layer (4), which second insulation layer (4) is a spray foam insulation layer enclosing said first inner insulation layer (3) and said wall of the hollow structure (la, lb), curing said applied second insulation layer (4).

2. A method according to claim 1, wherein said first insulation layer (3) is applied directly on the outer surface (2a) of said inner wall (2) of the hollow structure (1, la, lb).

3. A method according to claim 1 or 2, wherein said second insulation layer (4) is applied directly on the outer surface (3 a) of said first insulation layer (3).

4. A method according to any of the preceding, wherein said first insulation layer (3) is applied by applying a plurality of sub-layers (5a-5h) of insulation material in a liquid stage with intermediate curing time of the respective applied sublayer before a subsequent sublayer(s) is applied.

5. A method according to claim 4, wherein two or more, preferably all, of said applied sub- layers (5a-5n) each has a thickness of no more than 0.8mm, such as no more than 0.7mm, preferably no more than 0.6mm, e.g. no more than 0.5 or 0.55mm such as no more than 0.4 mm, e.g. between 0.3-0.6mm.

6. A method according to claim 4 or 5, wherein each of said applied sub-layers (5a-5n) of the first inner insulation layer (3) has a thickness (T2) between 4-20% e.g. between 6-15% such as 7-12%) of the overall thickness (Tl) of the first insulation layer (3).

7. A method according to any of claims 4 to 6, wherein said applied first insulation layer (3) comprises at least four sub-layers (5a-5h) such as at least six sub-layers (5a-5n), e.g. at least seven sub-layers (5a-5n), preferably no more than twelve sublayers such as about eight sublayers (5a-5n).

8. A method according to any of claims 4 to 7, wherein the innermost applied sub-layer (5a) of said sub-layers (5a-5n) abuts the outer surface (2a) of said wall (2) of the hollow structure (1 , l a, lb).

9. A method according to any of claims 4-8, wherein said sub-layers (5a-5n) are applied directly on top of each other.

10. A method according to any of the preceding claims, wherein said applied first insulation layer (3) has a thickness (Tl) of no more than 10mm such as no more than 7 mm, e.g. no more than 5mm, preferably about 4mm.

1 1. A method according to any of the preceding claims, wherein said applied first insulation layer (3) and said applied second insulation layer (4) are arranged between the outer surface (2a) of said wall (2) of the hollow structure (1 , l a, lb), and an outer applied protection jacket (6).

12. A method according to any of the preceding claims, wherein the applied second insulation layer (4) is a spray foam insulation layer such as polyurethane foam.

13. A method according to any of the preceding claims, wherein said hollow structure (1) is a pipe (la), such as a metal pipe, with a wall (2) enclosing a cavity/space (7) for guiding said fluid having a temperature above 140°C.

14. A method according to any of the preceding claims, wherein said hollow structure is a pipe (la), comprising one or more bends such as bends with an angle (al) less than 130°, such as less than 100°, such as about 90°, or less than 90° such as less than 80°.

15. A method according to any of the preceding claims, wherein said applied first insulation layer (3) has a thermal conductivity factor value k less than 0.08 W/mK at 25°C such as less than 0.06 W/mK at 25°C, e.g. about 0.055 W/mK at 25°C when cured.

16. A method according to any of the preceding claims, wherein said applied first insulation material (3) has a thermal conductivity factor value k larger than 0.01 W/mK at 25°C such as larger than 0.03 W/mK at 25°C when cured.

17. A method according to any of the preceding claims, wherein said applied first insulation layer 3 is a silica aerogel based coating.

18. A method according to any of the preceding claims, wherein said applied second insulation layer (4) has a thermal conductivity factor value k less than 0.08 W/mK such as less than 0.06 W/mK e.g. less than 0.04 W/mK e.g. around 0.03 W/mK such as about 0.02 W/mK.

19. A method according to any of the preceding claims, wherein said hollow structure is a pipe (la) comprising one or more tracer tubes (10) for heating said wall (2) of said pipe (la), wherein said one or more tracer tubes (10) is/are configured for guiding a heated fluid inside its cavity(14), so as to heat the pipe wall (2), and wherein said applied first inner insulation layer (3) encloses said tracer tube (10) and said pipe wall (2).

20. A method according to any of the preceding claims, wherein the temperature of said fluid guided or stored in the insulated hollow structure (1, la, lb) has a temperature above 160°C such as above 180°C, e.g. above 200°C during the storing and/or guiding in said insulated hollow structure (1,1a, lb), such as above 250°C, preferably not higher than about

21. A method according to any of the preceding claims, wherein the combined thickness (T4) of said applied first and second insulation layers (3, 4) is between 35mm and 110mm, such as between 40mm and 70mm, preferably between 45mm and 65mm, e.g. between 55mm - 60mm.

22. A method according to any of the preceding claims, wherein at least two of said insulated hollow structures (1, la, lb) are jointed to provide a fluid communication between spaces/cavities (7) in the respective jointed insulated hollow structures (1, la, lb), wherein a further layer (20) of aerogel based insulation material is applied in a liquid state to cover a jointing (17) of the insulated hollow structure (1, la, lb) and to overlap (21) an exposed part (22) of said applied first insulation layer (3) of the respective jointed structures (1, la, lb), wherein an spray-foam based insulation layer (24) is applied between said further layer (20) of aerogel based insulation material and a jointing jacket (23), which jointing jacket (23) overlaps outer protection layers (6) of the respective jointed, insulated hollow structures (1, la, lb).

23. An insulated hollow structure (1, la, lb), such as a pipe (la) or a tank (lb), for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure (1, la, lb), wherein said insulated hollow structure (1, la, lb) comprises insulation layers (3, 4) enclosing an inner wall (2) of the hollow structure (1, la, lb), which insulation layers (3, 4) comprises a first inner insulation layer (3) and a second insulation layer (4), wherein said first insulation layer (3) comprises a cured liquid-applied aerogel based insulation material applied to a surface (2a) of said wall (2) of the hollow structure (1, la, lb), and wherein said second insulation layer (4) is a spray foam insulation layer enclosing said first inner insulation layer (3) and said inner wall (2) of the hollow structure (1, la, lb).

24. An insulated hollow structure (1, la, lb), such as a pipe (la) or a tank (lb), for storing and/or guiding a fluid having a temperature above 140°C during the storing and/or guiding in said insulated hollow structure (1, la, lb), wherein said insulated hollow structure (1, la, lb) comprises insulation layers (3, 4) enclosing an inner wall (2) of the hollow structure (1, la, lb), which insulation layers (3, 4) comprises a first inner insulation layer (3) and a second insulation layer (4), wherein said first insulation layer (3) comprises a cured liquid-applied aerogel based insulation material applied to a surface (2a) of said wall (2) of the hollow structure (1, la, lb), and wherein said second insulation layer (4) is a spray foam insulation layer enclosing said first inner insulation layer (3) and said inner wall (2) of the hollow structure (1, la, lb) munufactured according to the method of any of claims 1 to 22.

25. An insulated hollow structure (1, la, lb) according to claim 23 or 24, wherein said first insulation layer (3) is positioned directly on the outer surface (2a) of said inner wall (2) of the hollow structure (1, la, lb).

26. An insulated hollow structure (1, la, lb) according to any of claims 23 to 25, wherein said second insulation layer (4) is positioned directly on the outer surface (3 a) of said first insulation layer (3).

27. An insulated hollow structure (1, la, lb) according to any of claims 23 to 26, wherein said first insulation layer (3) and said second insulation layer (4) provides a bonded insulation system.

28. An insulated hollow structure (1, la, lb) according to any of claims 23 to 27, wherein said first insulation layer (3) comprises a plurality of sub-layers (5a-5h) of cured insulation material.

29. An insulated hollow structure (1 , l a, lb) according to claim 28, wherein two or more, preferably all, of said sub-layers (5a-5n) each has a thickness of no more than 0.8mm, such as no more than 0.7mm, preferably no more than 0.6mm, e.g. no more than 0.5 or 0.55mm such as no more than 0.4 mm, e.g. between 0.3-0.6mm.

30. An insulated hollow structure (1 , l a, lb) according to claim 28 or 29, wherein each of said sub-layers (5a-5n) of the first inner insulation layer (3) has a thickness (T2) between 4- 20% e.g. between 6-15% such as 7-12% of the overall thickness (Tl) of the first insulation layer (3).

31. An insulated hollow structure (1 , l a, lb) according to claim 28 to 30, wherein said first insulation layer (3) comprises at least four sub-layers (5a-5h) such as at least six sub-layers (5a-5n), e.g. at least seven sub-layers (5a-5n), preferably no more than twelve sublayers such as about eight sub-layers (5a-5n).

32. An insulated hollow structure (1 , l a, lb) according to any of claims 28 to 31 , wherein the innermost sub-layer (5a) of said sub-layers (5a-5n) abuts the outer surface (2a) of said wall (2) of the hollow structure (1 , l a, lb).

33. An insulated hollow structure (1 , 1a, lb) according to any of claims 28 to 32, wherein said sub-layers (5a-5n) are arranged directly on top of each other.

34. An insulated hollow structure (l a, lb) according to any of claims 23 to 33, wherein said first insulation layer (3) has a thickness (Tl) of no more than 10mm such as no more than 7 mm, e.g. no more than 5mm, preferably about 4mm.

35. An insulated hollow structure (l a, lb) according to any of claims 23 to 34, wherein said first insulation layer (3) and said second insulation layer (4) are arranged between the outer surface (2a) of said wall (2) of the hollow structure (1 , la, lb), and an outer protection jacket (6).

36. An insulated hollow structure (l a, lb) according to any of claims 23 to 35, wherein said second insulation layer (4) is a spray foam insulation layer such as polyurethane foam.

37. An insulated hollow structure (1, la, lb) according to any of claims 23 to 36, wherein said hollow structure (1) is a pipe (la), such as a metal pipe, with a wall (2) enclosing a cavity/space (7) for guiding said fluid having a temperature above 140°C.

38. An insulated hollow structure (la, lb) according to any of claims 23 to 37, wherein said structure is a pipe (la), preferably comprising one or more bends such as bends with an angle (al) less than 130°, such as less than 100°, such as about 90°, or less than 90° such as less than 80°.

39. An insulated hollow structure (1,1a, lb) according to any of claims 23 to 38, wherein said first insulation layer (3) has a thermal conductivity factor value k less than 0.08 W/mK at 25°C such as less than 0.06 W/mK at 25°C, e.g. about 0.055 W/mK at 25°C when cured.

40. An insulated hollow structure (1,1a, lb) according to any of claims 23 to 39, wherein said first insulation material (3) has a thermal conductivity factor value k larger than 0.01

W/mK at 25°C such as larger than 0.03 W/mK at 25°C when cured.

41. An insulated hollow structure (1,1a, lb), according to any of claims 23 to 40, wherein said first insulation layer 3 is a silica aerogel based coating.

42. An insulated hollow structure (1,1a, lb) according to any of claims 23 to 41, wherein said second insulation layer (4) has a thermal conductivity factor value k less than 0.08 W/mK such as less than 0.06 W/mK e.g. less than 0.04 W/mK e.g. around 0.03 W/mK such as about 0.02 W/mK.

43. An insulated hollow structure according to any of claims 23 to 42, wherein said hollow structure is a pipe (la) comprising one or more tracer tubes (10) for heating said wall (2) of said pipe (la), wherein said one or more tracer tubes (10) is/are configured for guiding a heated fluid inside its cavity(14), so as to heat the pipe wall (2), and wherein said first inner insulation layer (3) encloses said tracer tube (10) and said pipe wall (2)·

44. An insulated hollow structure (1 , l a, lb) according to any of t claims 23 to 43, wherein said temperature of said fluid guided or stored in the insulated hollow structure (1, l a, lb) has a temperature above 160°C such as above 180°C, e.g. above 200°C during the storing and/or guiding in said insulated hollow structure (1 ,1 a, lb), such as above 250°C, preferably not higher than about 300°C.

45. An insulated hollow structure (l a, lb), according to any of claims 23 to 44, wherein the combined thickness (T4) of said first and second insulation layers (3, 4) is between 35mm and 1 10mm, such as between 40mm and 70mm, preferably between 45mm and 65mm, e.g. between 55mm - 60mm.

46. An insulated hollow structure (1 , 1a, lb) according to any of claims 23 to 45, wherein at least two of said insulated hollow structures (1 , l a, lb) are jointed to provide a fluid communication between spaces/cavities (7) in the respective jointed insulated hollow structures (1 , l a, lb), wherein a further layer (20) of cured liquid-applied aerogel based insulation material cover a jointing (17) of the insulated hollow structure (1 , l a, lb) and overlap (21) an exposed part (22) of said first insulation layer (3) of the respective jointed structures (1 , l a, lb), wherein a spray-foam based insulation layer (24) is provided between said further layer (20) of aerogel based insulation material and a jointing jacket (23), which jointing jacket (23) overlaps outer protection layers (6) of the respective jointed, insulated hollow structures (1 , l a, lb).

47. Use of an insulated hollow structure (1 , l a, lb) in the maritime environment, which insulated hollow structure (1 , l a, lb) is an insulated hollow structure according to any of claims 23 to 46.

48. Use of an insulated hollow structure according to claim 47, wherein the meritime environment can be at a harbour or at the sea on e.g. vessels such as ships or oil rigs.