AU2008233375A1

AU2008233375A1 - Pipe Insulation

Info

Publication number: AU2008233375A1
Application number: AU2008233375A
Authority: AU
Inventors: Harrill Ashley CHALLENOR
Original assignee: HARRILL CHALLENOR
Current assignee: HARRILL CHALLENOR
Priority date: 2007-10-24
Filing date: 2008-10-24
Publication date: 2009-05-14

Description

P/00/011 28/5/91 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Name of Applicant: Harrill Ashley Challenor Actual Inventor Harrill Ashley Challenor Address for service is: WRAYS Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR Invention Title: Pipe Insulation The following statement is a full description of this invention, including the best method of performing it known to me: 1 -2 "Insulation System" Field of the Invention The present invention relates to an insulation system. More particularly, the insulation system of the present invention is adapted to clad and insulate fluid 5 transport and storage systems. Background Art Insulation cladding for pipes typically uses polyurethane/polyisocyanurate foam sections. Typical applications for such pipe cladding are where process pipework is required to operate at temperatures below 200 0C. High quality 10 insulation systems currently being used in deep cryogenic service to -200 *C generally consist of layers of prefabricated sections that are assembled piecemeal onto the pipe in a sequential manner, layer by layer. The installation process requires highly skilled labour, is time consuming and access to the pipe is often limited and the time taken to complete the insulation is lengthy. 15 Traditional cold insulation materials of foamglas and/or polyurethane foam are not able to withstand the thermal gradient from cryogenic temperature on the cold face to the ambient temperature on the hot face in one layer without cracking in service. Cracks that penetrate from the inner surface to the outer surface provide a heat-in-leak path that can cause the insulation system to fail. 20 The polyurethane foam has a higher coefficient of thermal expansion and contraction than the pipe and the insulation system must be specifically designed and installed with the right vapour stops and contraction/expansion joints to allow for the differential expansion and contraction of the pipe and the insulation. It is also known to use aerogel insulation in flexible blanket form with limited 25 thickness. A cold insulation system constructed solely of aerogel blanket requires many wraps to achieve the required thickness of insulation to achieve the desired resistance to heat gain or to achieve the required outer surface -3 temperature generally set at being above dewpoint to prevent/reduce the formation of surface condensation under the design conditions. Installation of insulation is invariably the last major task to be completed on industrial projects and is a critical path activity. Time saved in installation of the 5 cold insulation is time saved on the duration of the whole project. Skilled insulation installers are difficult to find for most remote projects and reducing the skills requirement will assist in completing the insulation work earlier. The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be 10 appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia, or anywhere else, as at the priority date of the application. Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood 15 to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Disclosure of the Invention Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically 20 described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features. 25 The present invention is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally equivalent products, compositions and methods are clearly within the scope of the invention as described herein.

-4 The entire disclosures of all publications (including patents, patent applications, journal articles, laboratory manuals, books, or other documents) cited herein are hereby incorporated by reference. In accordance with one aspect of the present invention, there is provided a 5 composite insulation system for insulation of fluid storage and transfer systems comprising a first layer comprising an aerogel insulation material and a second layer comprising a low density insulation foam wherein the first layer and the second layer are adhered together prior to application of the insulation system to the fluid storage and transfer system. 10 Advantageously, only one layer of the composite insulation system is required to achieve desired results and the present invention obviates the need to add multiple layers of insulation. The insulation system of the present invention is adapted to insulate fluid storage and transfer systems comprising fluids at depressed, ambient or elevated 15 temperatures. The insulation system of the present invention is particularly adapted to insulate fluid storage and transfer systems comprising fluids at cryogenic temperatures. The fluid storage and transfer systems may be provided in the form of pipes, tanks, tankers and related equipment for the storage and transport of fluids such 20 as liquid/gas hydrocarbons, liquid nitrogen, liquid hydrogen, liquid oxygen, liquid carbon dioxide and liquid ammonia. Preferably, the insulation system is provided in the form of complimentary sections adapted to cover at least a portion of the outer surface of the fluid storage and transfer system. 25 Where the fluid storage and transfer system is a pipe, the insulation system is preferably provided in the form of a plurality of complimentary cylindrical sections adapted to cover at least a portion of the outer surface of the pipe. In one embodiment of the invention, the insulation system is provided in the form of two -5 complimentary semi-cylindrical sections adapted to cover at least a portion of the outer surface of the pipe Cylindrical sections may be longitudinally attached to further longitudinally adjacent cylindrical sections to increase the length of the insulation system and 5 cover greater portions of the pipe. Advantageously, the insulation system of the present invention reduces the work required to install insulation on industrial plants where the insulation installation is a major activity on the project critical path. This is particularly the case for cryogenic insulation. The on-site work content is reduced because the insulation 10 system does not have to be prepared at the site. Prior art insulation systems utilising low density foams must be constructed layer by layer on site, occupying significant amounts of time and related resources. The aerogel layer and the low density insulation foam layer may be adhered to each other offsite to provide a single layer composite insulation system and transported as, at least in the case 15 of pipe insulation, pre-formed semi-cylindrical sections. Reducing the on-site work will speed up the installation of the insulation and allow projects to be completed earlier. The savings and potential additional eamings available through bringing a project on-line earlier are significant when compared with the cost if the insulation. 20 In the context of the present invention, the term aerogel refers to low density solid state insulating materials derived from gels in which the liquid component of the gel has been replaced with gas. Aerogels may be prepared from different materials including silica, alumina and carbon. Silica aerogels may be prepared by mixing a silicon alkoxide precursor with 25 ethanol to provide a silicon dioxide gel (silica gel). In one embodiment of the process, the alcohol is exchanged for acetone which is replaced with liquid carbon dioxide which is then made supercritical to supercritically dry the silica gel to provide the aerogel.

-6 Advantageously, compared to low density insulation foams, aerogels exhibit no thermal shock, structural damage and degraded insulation performance and only limited thermal contraction under extremely low temperatures. Advantageously, aerogels are hydrophobic with high resistance to moisture. 5 In one form of the invention, the aerogel is reinforced with fibre. In a highly specific form of the invention, the aerogel is provided in the form of an aerogel sheet such as a blanket. Examples of aerogel blankets are those provided by Aspen Aerogels Inc. under the name Cryogel and Pyrogel. Aerogel blankets comprise silica aerogel and fibrous reinforcement. It will be 10 appreciated that the mechanical and thermal properties of the aerogel blanket may be varied upon the choice of reinforcing fibres, the aerogel matrix and additives included in the composite. As a result of the adhesion of the aerogel to the foam, the aerogel undergoes little movement relative to the foam on changes in temperature. 15 Advantageously, due to the similar coefficients of thermal expansion of the aerogel and the fluid storage and transfer system being insulated, for example, a pipe, shrinkage gaps do not open up between the components of the insulation system as is the case in multi-layer foam insulation systems. The low density insulation foam may be provided in the form of a polystyrene or 20 a urethane such as polyurethane or polyisocyanurate, or a polyolefin, a polyvinyl chloride, a polymethacrylamide, a polyethylene, a polyimide or combinations thereof. Alternatively, the low density insulation foam may be provided in the form of foamglas. Preferably, the low density insulation foam is a substantially closed-cell foam comprising a low-conductivity gas in the cells. In the context of 25 the present invention, the term substantially closed-cell foam shall be understood to indicate > 90 % closed cell foam. Advantageously, foam insulation has a relatively high resistance to heat flow compared to other types of insulation. It will be appreciated that many variables -7 affect the final resistance to heat flow of foam insulation including the initial density of the foam, the blowing gas used (for example, CFC, HCFC, HFC, C02, air, hydrocarbon, or a number of other gases or combinations thereof) and how the foam is handled (dents and chips adversely effecting the resistance to heat 5 flow). The skilled addressee will appreciate that different applications may require foams with different resistances to heat flow. It will further be appreciated that the final resistance to heat flow of the foam will have a bearing on the thickness of the foam layer in the insulation system. The thickness of the aerogel layer controls the interface temperature, the 10 interface being the region defined by the outer surface of the aerogel layer and the inner surface of the foam layer. For cryogenic use, the interface temperature should be high enough so that the temperature differential between the inner surface of the foam layer and the outer surface of the foam layer is less than 30 *C. By having a high interface temperature, the stress across the foam layer 15 is low enough so that it can be applied in one layer without the risk of cracking due to thermal stresses in the foam layer. In one form of the invention, there is provided a vapour barrier between the first layer and the second layer. The vapour barrier may be provided in the form of a multiplex vapour barrier. Preferably, the vapour barrier is bonded to the outer 20 surface of the first layer and the inner surface of the second layer. The vapour barrier may be bonded to the first layer and second layer outer surfaces utilising any means known in the art including contact adhesive. In one form of the invention, there is provided a vapour barrier on the outer surface of the insulation system. 25 In one form of the invention, the low density insulation foam comprises reinforcing. The reinforcing may be provided in the form of fibreglass mesh. Preferably, the reinforcing resides within the low density insulation foam and close to its inner surface. Preferably, the reinforcing is embedded within the low density insulation foam during preparation of the low density insulation foam 30 layer. The reinforcement serves to strengthen the low density insulation foam to -8 better resist damage from external loads imposed on the insulation system such as foot traffic on horizontal piping. In one form of the invention, the insulation system comprises at least one contraction joint in the low density insulation foam layer. Due to the thermal 5 efficiency of the aerogel layer, the composite insulation system may not shrink as much as the pipe in a longitudinal direction. In cryogenic use, the initial contraction of the cooling pipe can be accommodated within the composite insulation system without overstressing the system. Preferably, the circumferential ends of the low density insulation foam are 10 provided with joints adapted to reduce heat transfer between adjacent insulation systems. In a specific form of the invention, the joints are shiplap joints, complimentary with shiplap joints on adjacent insulation systems. Preferably, each longitudinal end of the low density insulation foam is provided with joints adapted to reduce heat transfer between the two longitudinal ends. In 15 a specific form of the invention, the joints are shiplap joints, the shiplap joint on one longitudinal ends being complimentary with the shiplap joint on an opposed longitudinal end. In use, the shiplap joints engage to reduce heat transfer. Where provided, the shiplap joints may be sealed externally by either self adhesive vapour barrier tape or by reinforced vapour barrier mastic. 20 Preferably, each longitudinal end of the aerogel layer is provided with joints adapted to reduce heat transfer between the two longitudinal ends. In a specific form of the invention, the joints are compression butt joints, cut at an off normal angle. In use, the butt joints engage to reduce heat transfer. Preferably, the circumferential ends of aerogel layer are provided with joints 25 adapted to reduce heat transfer between adjacent insulation systems. In a specific form of the invention, the joints are shiplapped compression butt joints.

-9 In accordance with a second aspect of the present invention, there is provided a method for insulating fluid storage and transfer systems comprising the steps of applying a pre-formed composite insulation system comprising a first layer comprising an aerogel and a second layer comprising a low density insulation 5 foam wherein the first layer and the second layer are adhered together prior to application of the insulation system to the fluid storage and transfer system. Brief Description of the Drawings The present invention will now be described, by way of example only, with reference to one embodiment thereof, and the accompanying drawings, in 10 which: Figure 1 is a radial cross-sectional view of a insulation system of the present invention; Figure 2 is a partially cut-away perspective view of the insulation system of Figure 1; 15 Figure 3 is a longitudinal cross-sectional view of the insulation system of Figure 1; Figure 4 is an exploded radial cross-sectional view of the insulation system of Figure 1; and Figure 5 is a partial longitudinal cross-sectional view of the insulation 20 system of Figure 1. Best Mode(s) for Carrying Out the Invention The insulation system of the present invention will now be described, by way of example only, with reference to one embodiment thereof.

- 10 In Figures 1 to 6 there is shown a composite insulation system 10 for insulation of fluid storage and transfer systems in the form of a prefabricated composite insulation system comprising an internal layer of aerogel blanket insulation 12 bonded to an outer layer of preformed polyisocyanurate foam 14. As best seen 5 in Figure 2, the insulation system is cylindrical and is adapted to encase at least a portion of a pipe 16. In the embodiment depicted, the composite insulation system 10 comprises two complimentary semicylinders 18, 20, best seen in Figure 4. A multifoil vapour barrier 22 is provided between the aerogel insulation 12 and the polyisocyanurate foam 14. 10 The aerogel insulation 12 is provided in longitudinal sections, each section being provided with tapered butt joints 24, 26 along the mating longitudinal ends 28, 30. Butt joints 32, 34 are further provided at each circumferential end of a section for mating with an adjacent section. The polyisocyanurate foam 14 is provided in longitudinal sections with a 15 contraction joint 44 in the form of aerogel at approximately the mid-point of each polyisocyanurate foam section and shiplap joints 46, 48 being provided along the mating longitudinal ends 50, 52. Shiplap joints 54, 56 are further provided at each circumferential end of a section for mating with an adjacent section. The shiplap joint 46 comprises a radially extending step 58 and the shiplap joint 20 48 comprises a radially extending step 64. The shiplap joint 54 comprises a circumferentially extending step 70 and the shiplap joint 56 comprises a circumferentially extending step 76. Multifoil vapour barrier 77 is provided between the steps 70 and 76. The semicylindrical portion of the aerogel 78 is offset from the semicylindrical 25 portion of the foam 80 such that a portion of the aerogel 82 at one longitudinal edge of the semicylinder extends past the foam 80 and a portion of the foam 84 at the opposed end extends past the aerogel 78, best seen in Figure 4. The length of the extensions 86, 88 are greater than the heights of the steps 58 and 64 so that when the pair of pre-formed complimentary semicylinders are brought -11 together such that the mating surfaces of the foam layer meet, the foam compresses the aerogel which is slightly larger than required to increase the sealing at the joint. A portion of the multifoil vapour barrier 22 at one longitudinal edge of the 5 semicylinder extends past the foam 80 and a portion of the multifoil vapour barrier 22 at the opposed end extends past the aerogel 78, best seen in figure 4. The length of the extensions are the same as those described in Figure 4 as 86, 88 so that when the pair of pre-formed complimentary semicylinders are brought together such that the mating surfaces of the foam layer meet, one multifoil 10 vapour barrier extension 86 overlays an opposed multifoil vapour barrier extension 88 to increase the sealing at the joint. The outer surface of the polyisocyanurate foam 14 is provided with a multifoil vapour barrier 85 adapted to reduce ingress of moisture into the insulation system 10, best seen in Figure 3. A taped joint seal 86 is further provided to 15 assist in joining adjacent insulation systems, best seen in Figure 5. Typically, a pipe to be insulated will have a predetermined circular external diameter, and a user (not shown), desirous of insulating the pipe would select a pair of pre-formed complimentary semicylinders with an internal bore to complement the outer diameter of the pipe and transport the pair of pre-formed 20 complimentary semicylinders to the location of the pipe. Advantageously, the semicylinders may be manufactured and stored off site. Adhesive is applied to the longitudinal ends 28, 30, 50, 52 of the semicylinders and they are bonded together. The insulation system may be clamped to the pipe with metal bands or the like. 25 Depending on the conditions within the pipe, it may be necessary to de-ice the pipe with ethanol or other de-icing agent prior to installation of the insulation system and to coat the pipe with an appropriate waxy compound to reduced condensation on the pipe. The inner surface of the insulation system may further - 12 be coated with a water curing chemical such as uncured polyurethane prior to fitting. Depending on the relative lengths of the pipe and the semicylinders, it may be necessary to add further semicylinders along the length of the pipe. Addition of 5 subsequent semicylinders is performed in the manner described above including the addition of multifoil vapour barrier 90 to the circumferential ends 32, 34, 54, 56 of the semicylinders. Advantageously, only one layer of the composite insulation system is required to achieve desired results and the present invention obviates the need to add 10 multiple layers of insulation. Operating at temperatures in the order of -200 *C, it is expected that the aerogel layer will be about 10 - 12 mm thick. Under these conditions, and in order to maintain a high interface temperature such that the difference between the interface temperature and the outside temperature is no more than 30 0C, the 15 polyisocyanurate foam layer is expected to be in the order of 70 mm thick. By having a high interface temperature, the stress across the foam layer is low enough so that it can be applied in one layer without the risk of cracking due to thermal stresses in the foam layer. The aerogel insulation has a similar coefficient of thermal expansion and 20 contraction to that of the pipe being insulated and because the interface temperature between the inner aerogel insulation blanket and the outer low density polyisocyanurate insulation is within 30 0 C of the temperature of the hot face of the insulation system, the contraction of the composite insulation is less than that of the pipe. By installing pre-formed contraction joints in the pre-formed 25 low density polyisocyanurate outer layer of the composite insulation section, the initial contraction of the cooling pipe can be accommodated within the composite insulation system without overstressing the system. The aerogel layer 12 and the polyisocyanurate foam layer 14 are adhered together and consequently, there is little movement of the two layers relative to -13 each other on cooling. Further, given that the aerogel and the pipe have a similar coefficient of contraction, the aerogel should shrink to approximately the same degree as the pipe on cooling. However, shrinkage of the aerogel is restricted by its adhesion to the foam layer. Due to the greater lengths of the 5 extensions 86, 88 relative to the heights of the steps 58 and 64, there is provided a small excess if aerogel layer adjacent the pipe surface so that when the pipe shrinks, gaps should not open up between the pipe and the aerogel layer. The invention combines the superior insulation characteristics of aerogel insulation with the jointing and vapour sealing capabilities of polyisocyanurate 10 foam insulation allowing it to be installed onto the pipe in one layer comprising two prefabricated components. It will be appreciated that the insulation system of the present may be utilised in connection with fluid storage and transfer systems other than pipes such as elbows, valves, flanged connections, tees, branches, pipe reducers and 15 expanders and other miscellaneous pipe fittings. It should be appreciated that the scope of the invention is not limited to the particular embodiment described herein.

Claims

1. A composite insulation system for insulation of fluid storage and transfer systems comprising a first layer comprising an aerogel and a second layer comprising a low density insulation foam wherein the first layer and the 5 second layer are adhered together prior to application of the insulation system to the fluid storage and transfer system.

2. A composite insulation system according to claim 1, wherein the insulation system is provided in the form of complimentary sections adapted to cover at least a portion of the outer surface of the fluid storage and transfer 10 system.

3. A composite insulation system according to claim 1 or claim 2, wherein the fluid storage and transfer system is a pipe and the insulation system is provided in the form of a plurality of complimentary cylindrical sections adapted to cover at least a portion of the outer surface of the pipe. 15

4. A composite insulation system according to claim 3, wherein the insulation system is provided in the form of two complimentary semi-cylindrical sections adapted to cover at least a portion of the outer surface of the pipe

5. A composite insulation system according to claim 3 or claim 4, wherein the cylindrical sections are longitudinally attached to further longitudinally 20 adjacent cylindrical sections to increase the length of the insulation system and cover greater portions of the pipe.

6. A composite insulation system according to any one of the preceding claims, wherein the aerogel is reinforced with fibre.

7. A composite insulation system according to any one of the preceding 25 claims, wherein the aerogel is provided in the form of an aerogel sheet. -15

8. A composite insulation system according to any one of the preceding claims, wherein the low density insulation foam is provided in the form of a polystyrene or a urethane such as polyurethane or polyisocyanurate, a polyolefin, a polyvinyl chloride, a polymethacrylamide, a polyethylene, a 5 polyimide or combinations thereof.

9. A composite insulation system according to any one of claims 1 to 7, wherein the low density insulation foam is provided in the form of foamglas.

10. A composite insulation system according to any one of the preceding claims, wherein there is provided a vapour barrier between the first layer 10 and the second layer.

11. A composite insulation system according to claim 10, wherein the vapour barrier is bonded to the outer surface of the first layer and the inner surface of the second layer.

12. A composite insulation system according to any one of the preceding 15 claims, wherein there is provided a vapour barrier on the outer surface of the insulation system.

13. A composite insulation system according to any one of the preceding claims, wherein the low density insulation foam comprises reinforcing.

14. A composite insulation system according to any one of the preceding 20 claims, wherein the insulation system comprises at least one contraction joint in the low density insulation foam layer.

15. A composite insulation system according to any one of the preceding claims, wherein the circumferential ends of the low density insulation foam are provided with joints adapted to reduce heat transfer between adjacent 25 insulation systems.

- 16 16. A composite insulation system according to claim 15, wherein the joints are shiplap joints, complimentary with shiplap joints on adjacent insulation systems.

17. A composite insulation system according to any one of the preceding 5 claims, wherein each longitudinal end of the low density insulation foam is provided with joints adapted to reduce heat transfer between the two longitudinal ends.

18. A composite insulation system according to claim 17, wherein the joints are shiplap joints, the shiplap joint on one longitudinal ends being 10 complimentary with the shiplap joint on an opposed longitudinal end.

19. A composite insulation system according to any one of the preceding claims, wherein each longitudinal end of the aerogel layer is provided with joints adapted to reduce heat transfer between the two longitudinal ends.

20. A composite insulation system according to claim 19, wherein the joints are 15 compression butt joints.

21. A composite insulation system according to any one of the preceding claims, wherein the circumferential ends of aerogel layer are provided with joints adapted to reduce heat transfer between adjacent insulation systems.

22. A composite insulation system according to claim 21, wherein the joints are 20 shiplapped compression butt joints.

23. A composite insulation system substantially as hereinbefore described with reference to the Figures.

24. A method for insulating fluid storage and transfer systems comprising the steps of applying a pre-formed composite insulation system comprising a 25 first layer comprising an aerogel and a second layer comprising a low density insulation foam wherein the first layer and the second layer are - 17 adhered together prior to application of the insulation system to the fluid storage and transfer system.