Abstract:
An insulation system comprising low density foam with a tensile modulus less than 5 MPa at ambient conditions and less than 10 MPa under cryogenic service conditions.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an insulation system. More particularly, the insulation system of the present invention is adapted to clad and insulate fluid transport and storage systems. 
       BACKGROUND ART 
       [0002]    The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application. 
         [0003]    Insulation cladding for pipes operating at low temperatures typically uses low density polyurethane/polyisocyanurate foam and or cellular glass sections. Typical applications for such pipe cladding are where the process pipework is required to operate at temperatures below 100° C. High quality insulation systems currently being used in deep cryogenic service to −200° C. consist of layers of prefabricated sections that are assembled piecemeal onto the pipe in a sequential manner, layer by layer or of layers of spray or pour applied insulation. High quality insulation systems installed in these manners require contraction joints between fixed points in the pipework system. The installation process requires highly skilled labour, is time consuming, wasteful of materials and access to the pipe is often limited and the time taken to complete the installation is lengthy. 
         [0004]    Installation of cold insulation is invariably one of the last major tasks to be completed on industrial projects and is a critical path activity. Time saved in the installation of the 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. 
         [0005]    Traditional cold insulation materials of cellular glass and/or low density polyurethane/polyisocyanurate 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. 
         [0006]    Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers. 
       SUMMARY OF INVENTION 
       [0007]    Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically 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. 
         [0008]    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. Functional equivalent products, compositions and methods are clearly within the scope of the invention as described herein. 
         [0009]    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. 
         [0010]    In accordance with the present invention, there is provided an insulation system comprising low density foam with a tensile modulus less than 5 MPa at ambient conditions and less than 10 MPa under cryogenic service conditions. 
         [0011]    Preferably, the tensile modulus of the low density foam is less than 3 MPa at ambient conditions and less than 6 MPa under cryogenic service conditions. 
         [0012]    In one form of the invention, the tensile modulus of the low density foam is about 3 MPa at ambient conditions and about 6 MPa under cryogenic service conditions. 
         [0013]    In a specific form of the invention, the low density foam is provided in the form of CETRAFOAM® from Cetra Technologies Pty Ltd. 
         [0014]    CETRAFOAM® is moulded using an ultra high overpack method that provides consistency in microcell size and shape throughout the product. This provides uniform density and identical mechanical and thermal properties both parallel and perpendicular to the direction of rise. The moulded product has a tough external high density skin which significantly reduces site wastage from transport and installation damage. 
         [0015]    CETRAFOAM® is specially formulated for cryogenic insulation applications from +140° C. to −200° C. The PUR/PIR formulation provides excellent fire resistance and a high tensile modulus which ensures a high Cryogenic Thermal Stress Resistance Factor (CTSR≧2). This allows CETRAFOAM® to be applied in a single layer up to thicknesses of 250 mm. 
         [0016]    CETRAFOAM® has a Tensile Modulus of 2.98 MPa at 22° C. and 5.87 at −165° C. and can withstand the thermal shrinkage stresses associated with insulating across a thermal gradient of up to 200° C. 
         [0017]    Technical data related to CETRAFOAM® are provided in Table 1. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 CETRAFOAM ® Technical Data 
               
             
          
           
               
                 Property 
                 Unit 
                 Test Method 
                 Value 
               
               
                   
               
             
          
           
               
                 Density 
                 Kg/m 3   
                 ASTM D 1622 
                 ≧45 
               
               
                 Closed Cell Content 
                 % 
                 ASTM D 2856 
                 ≧90 
               
               
                 Water Vapour Permeance 
                 μg/Ns 
                 ASTM E 96 
                 ≦4.5 
               
               
                 30° C. and 100% RH 
               
               
                 Fire Properties 
               
               
                 Maximum mean extent of burn 
                 mm 
                 BS 4735 
                 26 
               
               
                 Maximum mean extinguishing 
                 secs 
                 BS 4735 
                 ≦5 
               
               
                 time 
               
               
                 Maximum mean burning rate 
                 mm/sec 
                 BS 4735 
                 0.41 
               
               
                 Oxygen Index 
                 % 
                 GB8624-1997 
                 ≧26 
               
               
                 Coefficient Thermal Expansion 
                 mm/ 
                 ASTM D 696 
                 50-70 
               
               
                   
                 mmK × 
               
               
                   
                 10 −6   
               
               
                 Compressive Strength 
                 kPa 
                 ASTM D 1621 
                 ≧250 
               
               
                 @ 20° C. 
               
               
                 Compressive Strength 
                 kPa 
                 ASTM D 1621 
                 ≧650 
               
               
                 @ −165° C. 
               
               
                 Tensile Strength @ 20° C. 
                 kPa 
                 ASTM D 1623 
                 ≧510 
               
               
                 Tensile Modulus @ 20° C. 
                 MPa 
                 ASTM D 1623 
                 2.98 
               
               
                 Tensile Strength @ −165° C. 
                 kPa 
                 ASTM D 1623 
                 ≧380 
               
               
                 Tensile Modulus @ −165° C. 
                 MPa 
                 ASTM D 1623 
                 5.86 
               
               
                 Leachable Halides 
                 ppm 
                 ASTM C 871 
                 ≦15 
               
               
                 Thermal Conductivity @ 20° C. 
               
               
                 Fresh Blown foam 
                 W/m° K 
                 ASTM C 177 
                 0.022 +/− 
               
               
                 Aged at 21° C. for 180 days 
                   
                   
                 0.001 
               
               
                   
                   
                   
                 0.025 +/− 
               
               
                   
                   
                   
                 0.001 
               
               
                 Cryogenic Thermal Stress 
                   
                   
                 ≧2 
               
               
                 Resistance 
               
               
                   
               
             
          
         
       
     
         [0018]    It will be appreciated that the tensile modulus of the low density foam affects the tensile strength and that it is necessary to maintain a certain level of tensile strength. Preferably, the low density foam has a compressive strength above 200 kPa under ambient conditions and 500 kPa at cryogenic service temperature. More preferably, the low density foam has a compressive strength above 250 kPa under ambient conditions and 600 kPa at cryogenic service temperature. 
         [0019]    Advantageously, reducing the tensile modulus whilst maintaining the tensile strength of the low density foam reduces the brittleness at cryogenic temperature. This enables the foam to better withstand shrinkage strain imposed on the cold face of the foam in cryogenic service. 
         [0020]    Preferably, the low density foam has a compressive modulus compressive modulus at ambient temperature which can accommodate the longitudinal thermal shrinkage of the pipe without exceeding the maximum strain in the foam and also have sufficient compressive strength to withstand site applied loads such as foot traffic. 
         [0021]    Preferably, the low density foam has a compressive modulus less than 16 MPa under cryogenic service conditions. 
         [0022]    Advantageously, only one layer of the insulation system may be required to achieve desired results. 
         [0023]    The insulation system of the present invention is adapted to insulate fluid storage and transfer systems comprising fluids at depressed, ambient and elevated temperatures. 
         [0024]    The fluid storage and transfer systems may be provided in the forms of pipes, tanks, tankers, vessels and related equipment for the storage and transport of fluids such as liquid/gas hydrocarbons, liquid nitrogen, liquid hydrogen, liquid oxygen, liquid carbon dioxide and liquid ammonia. 
         [0025]    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. 
         [0026]    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 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. 
         [0027]    Cylindrical sections may be longitudinally attached to further longitudinally adjacent cylindrical sections to increase the length of the insulation system and cover greater portions of the pipe. 
         [0028]    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 does not have to be prepared at the site. Prior art insulation systems utilising cellular glass and low density foams must be constructed layer by layer at site. For cold and cryogenic applications the present invention may be applied in one single layer irrespective of the diameter of the pipe or the operating temperature of the pipe. The time and labour reduction at site will speed up the installation of the insulation and allow projects to be completed earlier. The installation cost savings and the potential additional earnings available through bringing the project online earlier are significant when compared with the cost of the insulation. 
         [0029]    The insulation system may further comprise an inner layer of resilient fibre glass blanket or cryogel blanket or solimide foam insulation material 
         [0030]    The insulation system may further comprise a vapour barrier layer. 
         [0031]    The insulation system may further comprise mechanical protection cladding. 
         [0032]    In one form of the invention, the low density foam comprises reinforcing. The reinforcing may be provided in the form of fibreglass mesh. Preferably, the reinforcing resides within the low density foam and close to both its inner and outer surfaces. Preferably the reinforcing is embedded within the low density foam during preparation of the low density foam layer. The reinforcing serves to strengthen the low density foam to better resist damage from external loads imposed on the insulation system such as foot traffic on horizontal pipework. 
         [0033]    In one form of the invention, the reinforcing mesh embedded in the low density foam has its fibres aligned in a square mesh with the fibres 90 degrees to each other with one set of fibres running longitudinally to the low density foam moulding and the other set of fibres transversely located. In this configuration, the fibreglass reinforcing mesh reduces the modulus of expansion and contraction of the low density foam to approximately that of stainless steel over the range of temperatures from −200 degrees Celsius to plus 100 degrees Celsius, namely between 15 to 20×10 −6  mm/mm/degree Kelvin which is substantially reduced from the unreinforced low density insulation foam coefficient of thermal expansion and contraction which is between 50 to 70×10 −6  mm/mm/degree Kelvin over the temperature range of −200 degrees Celsius to plus 100 degrees Celsius. 
         [0034]    Advantageously, the reinforcing reduces the effective coefficient of thermal contraction of the foam reinforcement which limits the size of the gaps between adjoining pipe sections at the cold face. The reinforcement also makes the foam tougher and better able to resist transport and handling damage. 
         [0035]    Preferably, the low density foam is a substantially closed-cell foam comprising a low-conductivity gas in the cells. In the context of the present invention, the term substantially closed cell foam shall be understood to indicate &gt;90% closed-cell foam. 
         [0036]    Advantageously, the low density foam has a relatively high resistance to heat flow compared to other types of insulation. It will be appreciated that many variables 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, CO 2 , air, hydrocarbon, or a number of other gases or combinations thereof) and how the foam is handled (dents and chips adversely affecting the resistance to heat flow). The skilled addressee will appreciate that different applications may require foams with difference resistance to heat flow. It will further be appreciated that the resistance to heat flow of the foam will have a bearing on the thickness of the foam layer in the insulation system. 
         [0037]    In one form of the invention, the insulation system further comprises a vapour barrier. 
         [0038]    In a specific form of the invention, the moulded low density foam may be installed on pipework between two fixed points without an expansion and contraction joint. 
         [0039]    Preferably, the circumferential ends of the low density insulation foam are 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. 
         [0040]    In a specific form of the invention the butt or shiplapped joints between adjacent sections are sealed with an adhesive sealant comprising a solvent free, high strength, thermosetting two component urethane adhesive. 
         [0041]    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 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 prevent through gaps and reduce heat transfer. 
         [0042]    Where provided, the shiplap joints may be sealed externally by either self-adhesive vapour barrier tape or by reinforced vapour barrier mastic. 
         [0043]    In one form of the invention, the straight lengths of pipe insulation are confined axially on the pipe between moulded insulation elements which have been bonded to the pipe. In a specific form of the invention the bonded moulded elements will be adjacent to pipe supports or pipe fittings such as elbows, Tees, flanges, valves, reducers and other fixed elements attached to the pipe. 
         [0044]    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 single layer pre-formed low density insulation foam to the fluid storage and transfer system, wherein the low density foam has a tensile modulus less than 5 Mpa at ambient conditions and less than 10 Mpa under cryogenic service conditions. 
         [0045]    Preferably, the tensile modulus of the low density foam is less than 3 MPa at ambient conditions and less than 6 MPa under cryogenic service conditions. 
         [0046]    In one form of the invention, the tensile modulus of the low density foam is about 3 MPa at ambient conditions and about 6 MPa under cryogenic service conditions. 
         [0047]    In a specific form of the invention, the low density foam is provided in the form of CETRAFOAM® from Cetra Technologies Pty Ltd. 
         [0048]    Preferably, the low density foam has a compressive strength above 200 kPa under ambient conditions and 500 kPa at cryogenic service temperature. More preferably, the low density foam has a compressive strength above 250 kPa under ambient conditions and 600 kPa at cryogenic service temperature. 
         [0049]    Preferably, the low density foam has a compressive modulus less than 16 MPa under cryogenic service conditions. 
         [0050]    Advantageously, only one layer of the insulation system may be required to achieve desired results. 
         [0051]    The fluid storage and transfer systems may be provided in the forms of pipes, tanks, tankers, vessels and related equipment for the storage and transport of fluids such as liquid/gas hydrocarbons, liquid nitrogen, liquid hydrogen, liquid oxygen, liquid carbon dioxide and liquid ammonia. 
         [0052]    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. 
         [0053]    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 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. 
         [0054]    Cylindrical sections may be longitudinally attached to further longitudinally adjacent cylindrical sections to increase the length of the insulation system and cover greater portions of the pipe. 
         [0055]    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 does not have to be prepared at the site. Prior art insulation systems utilising cellular glass and low density foams must be constructed layer by layer at site. For cold and cryogenic applications the present invention may be applied in one single layer irrespective of the diameter of the pipe or the operating temperature of the pipe. The time and labour reduction at site will speed up the installation of the insulation and allow projects to be completed earlier. The installation cost savings and the potential additional earnings available through bringing the project online earlier are significant when compared with the cost of the insulation. 
         [0056]    The method of the present invention may further comprise the step of applying an inner layer of resilient fibre glass blanket or cryogel blanket or solimide foam insulation material 
         [0057]    The method of the present invention may further comprise the step of applying a vapour barrier layer. 
         [0058]    The method of the present invention may further comprise the step of applying mechanical protection cladding. 
         [0059]    In one form of the invention, the low density foam comprises reinforcing. The reinforcing may be provided in the form of fibreglass mesh. Preferably, the reinforcing resides within the low density foam and close to both its inner and outer surfaces. Preferably the reinforcing is embedded within the low density foam during preparation of the low density foam layer. The reinforcing serves to strengthen the low density foam to better resist damage from external loads imposed on the insulation system such as foot traffic on horizontal pipework. 
         [0060]    In one form of the invention, the reinforcing mesh embedded in the low density foam has its fibres aligned in a square mesh with the fibres 90 degrees to each other with one set of fibres running longitudinally to the low density foam moulding and the other set of fibres transversely located. In this configuration, the fibreglass reinforcing mesh reduces the modulus of expansion and contraction of the low density foam to approximately that of stainless steel over the range of temperatures from −200 degrees Celsius to plus 100 degrees Celsius, namely between 15 to 20×10 −6  mm/mm/degree Kelvin which is substantially reduced from the unreinforced low density insulation foam coefficient of thermal expansion and contraction which is between 50 to 70×10 −6  mm/mm/degree Kelvin over the temperature range of −200 degrees Celsius to plus 100 degrees Celsius. 
         [0061]    Advantageously, the reinforcing reduces the effective coefficient of thermal contraction of the foam reinforcement which limits the size of the gaps between adjoining pipe sections at the cold face. The reinforcement also makes the foam tougher and better able to resist transport and handling damage. 
         [0062]    Preferably, the low density foam is a substantially closed-cell foam comprising a low-conductivity gas in the cells. In the context of the present invention, the term substantially closed cell foam shall be understood to indicate &gt;90% closed-cell foam. 
         [0063]    Advantageously, the low density foam has a relatively high resistance to heat flow compared to other types of insulation. It will be appreciated that many variables 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, CO 2 , air, hydrocarbon, or a number of other gases or combinations thereof) and how the foam is handled (dents and chips adversely affecting the resistance to heat flow). The skilled addressee will appreciate that different applications may require foams with difference resistance to heat flow. It will further be appreciated that the resistance to heat flow of the foam will have a bearing on the thickness of the foam layer in the insulation system. 
         [0064]    The method of the present invention may further comprise the step of applying a vapour barrier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0065]    Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which: 
           [0066]      FIG. 1  is a perspective view of an insulation system in accordance with a first embodiment of the present invention; 
           [0067]      FIG. 2  is a partial perspective view of the insulation system of  FIG. 1 ; 
           [0068]      FIG. 3  is a longitudinal cross-sectional view of the insulation system of  FIG. 1 ; 
           [0069]      FIG. 4  is an exploded perspective view of the insulation system of  FIG. 1 ; 
           [0070]      FIG. 5  is a longitudinal cross-sectional view of the insulation system of  FIG. 1 ; 
           [0071]      FIG. 6  is a partial longitudinal cross-sectional view of the insulation system of  FIG. 1 ; 
           [0072]      FIG. 7  is a partial longitudinal cross-sectional view of the insulation system of  FIG. 1 ; 
           [0073]      FIG. 8  is a radial cross-sectional view of the insulation system of  FIG. 1 ; 
           [0074]      FIG. 9  is an exploded perspective view of an insulation system in accordance with a second embodiment of the present invention; and 
           [0075]      FIG. 10  is a perspective view of the insulation system of  FIG. 10 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0076]    The insulation system of the present invention will now be described, by way of example only, with reference to two embodiments thereof. 
         [0077]    In  FIGS. 1 through 9  there is shown an insulation system in accordance with a first embodiment of the present invention for insulation of fluid storage and transfer systems in the form of a prefabricated insulation system comprising a layer of preformed low density polyurethane foam  10 . The preformed low density polyurethane foam  10  is provisded in the form of CETRAFOAM® from Cetra Technologies Ply Ltd. CETRAFOAM® is a 50 kg/m 3  rigid, closed cell, HCFC free PUR/PIR foam. As seen in  FIG. 1 , the insulation system is cylindrical and is adapted to encase at least a portion of a pipe  12 . As shown in  FIG. 4 , the insulation system comprises a number of complimentary moulded cylinders of varying lengths  14 ,  16  and  18 . 
         [0078]    Shiplap joints  20  are provided longitudinally and at each circumferential end of the moulded cylinders  14 ,  16  and  18  for mating with an adjacent cylinders, best seen in  FIGS. 2, 3 and 4 . 
         [0079]      FIGS. 4 and 5  depict an arrangement with cylinders  14  and  16  placed over the pipe  12  and makeup section  18  introduced to complete the insulation length required. Cylinders  14  are bonded to the pipe  12  with cryogenic adhesive  22 . If required, end cylinders  14  may be longitudinally cut into half sections to facilitate the application of the adhesive  22  between the pipe  12  and the moulded insulation  14 . 
         [0080]    A butyl rubber/aluminum vapour barrier  24  is provided on the outer surface of the insulation cylinders  14 ,  16  and  18 . The outer vapour barrier  24  is protected from mechanical damage by a metallic or rigid epoxy cladding  26 . 
         [0081]    In one special application of the present invention the outer vapour barrier is provided by a fibre reinforced epoxy or polyester or acrylic covering. 
         [0082]    The insulation system further comprises a cladding layer  28  moulded cylinder  14  with an elastomeric adhesive  30  which allows some minor radial contraction of the cylinder  14  whilst retaining the longitudinal location of the cladding  26 . 
         [0083]    A slip layer  32  is provided between the vapour barrier  24  and the outer cladding  26  as shown in  FIG. 6, 7 . The slip layer facilitates dis-bondment between the outer cladding  26  which is at ambient temp and doesn&#39;t shrink and the outer vapour barrier which is adhered to the foam insulation sections which are compressed by the longitudinal thermal shrinkage of the pipe to which they are adhered and confined between the fixed point extremities of the pipe. 
         [0084]    To allow for the axial contraction of the pipe, there is further provided a contraction/expansion joint  34  (see  FIG. 7 ) to accommodate the differential thermal expansion/contraction of the pipe  12  operating at cryogenic service conditions and the outer cladding  26  which operated at ambient temperature. 
         [0085]    The contraction/expansion joint  34  comprises the outer vapour barrier  24  over the moulded cylinder  16  and a slip layer  32  covering beneath an opening  36  in the outer cladding  26 . The opening  36  in the cladding  26  is sealed with a butyl rubber sheet  38  banded to the cladding  26  either side of the contraction/expansion joint  34 . Mechanical protection is provided by and outer cladding cover  40  which is adhered to the cladding  26  at point  15  in  FIG. 7 . 
         [0086]    Longitudinal shiplap joints  44  are provided to ensure there is no straight through joints in the single layer insulation system as shown in  FIG. 8 . 
         [0087]    In  FIGS. 10 and 11 , there is shown an insulation system in accordance with a second embodiment of the present invention. Like numerals in  FIGS. 10 and 11  denote like parts in  FIGS. 1 to 9 . 
         [0088]    As shown in  FIG. 10 , the moulded cylinder  14  is provided as two complimentary half-pipes  50 . Complimentary half-pipes  50  are thermally sealed longitudinally  52  and circumferentially  54  with cryogenic insulation material such as solvent free, high strength, thermosetting two component urethane adhesive.