WO2012030909A2

WO2012030909A2 - Configurations and methods for heat trace insulation

Info

Publication number: WO2012030909A2
Application number: PCT/US2011/049888
Authority: WO
Inventors: Vaughn Barnes; Brett Miller
Original assignee: Thermal Structures, Inc.
Priority date: 2010-08-31
Filing date: 2011-08-31
Publication date: 2012-03-08
Also published as: WO2012030909A3

Abstract

A composite insulating structure comprises a reflective non-interlocking layer and two or more flexible and curable layers that include a preferably high-performance insulating material to provide substantial flexibility for installation while allowing the structure to be cured to form a fluid impervious and preferably rigid barrier layer. It is further preferred that the reflective non-interlocking layer faces the heat trace and thus avoids entanglement of insulating material with the heat trace while providing a first thermal barrier against heat loss.

Description

CONFIGURATIONS AND METHODS FOR HEAT TRACE INSULATION

[0001] This application claims priority to our co-pending U.S. provisional application with the serial number 61/378,758, which was filed August 31, 2010.

Field of the Invention

[0002] The field of the invention is devices and methods of insulating structures, and especially structures comprising one or more heat traces.

Background of the Invention

[0003] Heat traces are well known in the art and are commonly used in various pipe and other containment systems to maintain or raise the temperature of the conduit, vessel, and contents thereof. In most embodiments, heat traces are configured as electrical heating elements that are in close contact with a pipe or other containment system, which is then covered with a thermal insulation to reduce heat losses from the heat trace and the pipe.

[0004] Where the heat traces also need protection from fluid ingress and/or where the insulating material requires structural protection, most trace heating systems are permanently encased in the thermal insulation. For example, pipelines are often spiral wrapped into fiberglass mats that are then coated with a sealant to permanently enclose and affix the insulation material. Alternatively, insulating foam is formed over a pipe structure and then sealingly encapsulated with a composite or non-composite material to so form a permanent barrier for the pipe and heat trace system. While such systems are suitable for at least some installations, various disadvantages remain. For example, such installation is often time consuming as multiple processing steps are required and as the inner insulating layer typically requires an at least temporary retaining structure. Also, removal of the insulating structure will in many cases jeopardize the integrity of the heat trace on the pipe due to the intimate engagement of the insulating material with the heat trace.

[0005] Alternatively, a layer of an electroconductive polymer may be placed around a pipe that is heated by resistance heating of the polymer and that is encased in a second insulating layer as described, for example, in WO2006097765A1 or U.S. Pat. No. 4,429,213. While such structures often allow simplified installation where the layers are formed from pre-cast elements, seams and joints must be sealed to avoid fluid ingress and thus add to the installation time. Still further, where the layers are formed in situ, multiple installation steps are once more required.

[0006] To simplify installation and removal of heat traces, dedicated and modular form- fitted heating and insulation elements are used as described, for example, in U.S. Pat. No.

7,919,733. Here, heat traces are installed on brackets that engage with a fluid conduit, and the brackets and the fluid conduit are then surrounded by an insulation jacket. Installation of such systems is often simple and can be done by untrained personnel. However, as the heat traces are not in contact with the conduit, but retained by the bracket, heating efficiency is often reduced. Moreover, due to the modular structure, numerous seams and joints are present, each of which are a potential point of fluid ingress.

[0007] U.S. Pat. No. 6,070,615 describes a pipe system in which a fluid conduit is coupled to a heat trace that is wrapped in a foil to dissipate heat from the heat trace to an outer metal pipeline. A sensor disposed between the foil and the outer pipeline is then used to detect leaks or fire. While such system typically allows for secure fluid transfer of noxious chemicals, installation is once more time consuming. Moreover, where insulation is desired, such insulation is provided to the outer metal pipeline.

[0008] Consequently, even though various methods for insulating heat traces on pipes and other conduits are known in the art, all or almost all of them suffer from one or more disadvantages. Therefore, materials and methods of thermal insulation of heat traces would be desirable that allow for easy and quick installation/removal in the field by even unskilled workers. Moreover, such systems should also provide insulating properties superior to those provided by systems in which a pipe and heat trace are wrapped with a fiberglass mat.

Summary of The Invention

[0009] The inventive subject matter is drawn to materials and methods of thermal insulation of a fluid conduit or other containment structure in which a flexible material is installed in segments and cured on site to a final insulator that forms a fluid impervious structure. Most preferably, the flexible material encloses a (preferably flexible) low k-factor insulator and has a heat-reflective and non-interlocking layer to prevent entanglement with the heat trace and to provide a first heat-retaining structure. Upon installation (preferably by wrapping the flexible insulating material around a conduit), the flexible insulating material is cured to a final shape, which can be readily uninstalled without risk of damage to the heat trace. Thus, contemplated materials combine several heretofore mutually exclusive characteristics: Flexibility, fluid impermeability, ease of installation, high performance insulation, and non-entanglement with the heat trace.

[0010] In one especially preferred aspect of the inventive subject matter, an insulated fluid containment structure that includes a fluid containment device (e.g., pipe, manifold, tank, etc.) that has an outer surface to which a heat trace is coupled that heats a fluid within the containment device. Contemplated insulated structures further comprise a composite insulating structure that includes a reflective non-interlocking layer coupled to a first flexible carrier, a second flexible carrier, and a flexible insulating material between the first and second flexible carriers. Most preferably, the first and/or second flexible carriers comprises a curable material that can form a fluid impervious barrier layer upon curing, and the composite insulating structure is coupled to the fluid containment device such that the heat trace is enclosed by the outer surface and the reflective non-interlocking layer, which in turn is at least partially surrounded by the first and second flexible carriers.

[0011] In particularly preferred aspects, the reflective and non-interlocking layer comprises or is formed from a fiberglass layer having a metallized surface (e.g., spray coated) or metal layer (e.g., metal film), wherein the fiberglass layer may also include a heat-curable material. Similarly, it is preferred that the first and second flexible carriers comprise fiberglass and that the curable material is a heat-curable material. Consequently, it is also preferred that the reflective non-interlocking layer is coupled to the first flexible carrier via the curable material.

[0012] While not limiting to the inventive subject matter, it is generally preferred that the flexible insulating material has a k- factor of equal or less than 0.4 and even more preferably equal or less than 0.3 Btu in/hr ft2 °F. Thus, suitable flexible insulating materials include fiberglass, mineral wool, an elastomeric foam, and/or a synthetic polymer (e.g., closed cell foams).

[0013] To further facilitate installation, it is contemplated that the composite insulating structure is configured as a blanket, which is most preferably shaped and configured into a predetermined geometry to so conformingly fit a known geometry of the fluid containment device. Additionally, or alternatively, the blanket may also have seam or split that is configured to allow removal of the composite insulating structure after curing. Most typically, multiple composite insulating structures are coupled t a single fluid containment device, preferably such that the composite insulating structures are coupled to each other via the curable material to form a fluid impervious barrier layer upon curing.

[0014] Therefore, and viewed from a different perspective, the inventor also contemplates a method of insulating a fluid containment device having a heat trace, in which in one step first and second composite insulating structures (as described above) are provided as well as a fluid containment device having an outer surface to which a heat trace is coupled. In another step, the outer surface is at least partially surrounded with the first and second composite insulating structures such that the heat trace is disposed between the outer surface and the reflective and non-interlocking layers of the first and second composite insulating structures. In yet another step, the first and second compound insulating structures are then cured (preferably heat-cured) to form a continuous fluid resistant composite insulating structure.

[0015] As already noted above, it is generally preferred that the composite insulating structures are configured as a blanket, and/or comprise or are manufactured from silicone coated fiberglass. In still further preferred methods, the composite insulating structures comprise a flexible insulating material having a k- factor of equal or less than 0.4 Btu in/hr ft2 °F. Thus, suitable flexible insulating material include fiberglass, mineral wool, an elastomeric foam, and a synthetic polymer.

[0016] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

Brief Description of The Drawing

[0017] Figure 1 is a schematic illustration of an insulated fluid containment structure according to the inventive subject matter.

[0018] Figure 2 is a schematic illustration of a composite insulating structure configured as a blanket according to the inventive subject matter.

[0019] Figure 3 is a schematic illustration of an insulated fluid containment structure having multiple composite insulating structures. Detailed Description

[0020] The inventive subject matter is drawn to configurations and methods of insulating a fluid containment structure having an external heat trace. Contemplated configurations and methods provide ordinarily mutually exclusive characteristics in which flexibility, fluid impermeability, ease of installation, high performance insulation, and non-entanglement with the heat trace are combined into a single material.

[0021] Most preferably, a pipe or other fluid containment structure is thermally coupled to a heat trace, which is then enclosed with a thermal insulation blanket comprising a thermally insulating inner portion and a heat curable outer portion. Additionally, a reflective and non- interlocking layer is included in the blanket and proximally positioned to the heat trace to so provide a first layer of heat loss protection while preventing the (preferably high

performance) insulation material to become entangled with the heat trace. Thus, use of numerous low k-factor materials is possible while providing a simplified method of installation. Indeed, as the insulating blankets are initially pliable, they can be installed in a very simple manner over pipes and even structures with complex surface geometry. Once properly positioned, the blankets are then cured to form a (preferably rigid) insulation structure that is not only resistant to fluid ingress, but also less thick than otherwise known insulation.

[0022] As used herein, the term "k-factor" refers to a thermal conductivity factor, which is a measure of heat in Btu that passes through one square foot of a homogeneous substance, 1 inch thick, in an hour, for each degree F temperature difference. The lower the k-factor, the higher the insulating value. As also used herein, the term "flexible" refers to the property of a material where that material can be substantially deformed (e.g., deformed from a flat to a rolled-up or angled configuration) employing manual force without breaking or otherwise damaging the material. For example, a silicone coated or impregnated fiberglass sheet or a thin latex sheet are considered flexible. In contrast, a 2mm thick polycarbonate plate would not be considered flexible under the scope of this definition, because polycarbonate plates can typically not be substantially deformed without breaking. As still further used herein, the term "rigid" refers to the property of a material that is harder or less pliable than a flexible material and that will retain the shape of the material in a configuration where the same shape of flexible material would deform (e.g., under the force of gravity or influence of heat). As also used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously.

[0023] Therefore, in one preferred aspect of the inventive subject matter, an insulated structure is contemplated that comprises a pipe, manifold, tank, or other fluid containment device with an outer surface to which a heat trace is coupled. Most typically, the heat trace will be in direct contact with the fluid containment device to allow heating of a fluid within the containment device. Contemplated insulated structures further comprise a composite insulating structure that includes a reflective non-interlocking layer coupled to a first flexible carrier, a second flexible carrier, and a flexible (preferably low k-factor) insulating material between the first and second flexible carriers. Most preferably, the first and/or second flexible carriers comprises a curable material that can form a fluid impervious barrier layer upon curing, and the composite insulating structure is coupled to the fluid containment device such that the heat trace is enclosed by the outer surface and the reflective non-interlocking layer, which in turn is at least partially surrounded by the first and second flexible carriers.

[0024] Figure 1 exemplarily depicts an insulated fluid containment structure 100 comprising a pipeline 1 10 to which a heat trace 120 is coupled. Composite insulating structure 130 surrounds the pipeline 1 10 such that aluminized layer 132 forms a reflective and non- interlocking layer (preferably directly) above the heat trace 120 and outer surface of the pipeline 1 10. Most preferably, the aluminized layer is directly formed (or deposited) onto flexible composite carrier 134 that is preferably formed from heat-curable silicone coated fiberglass. A second flexible carrier 136, typically formed from heat-curable silicone coated fiberglass, is then used to sealingly enclose low k-factor insulating material 138, which is preferably a flexible composite material (e.g., ceramic fiber paper encapsulated between layers of high temperature woven textile, quilted by lock stitching in one-inch squares). Using such configurations, it should be appreciated that very thin, but highly insulative materials can be made that are very easy to install as the materials are preferably provided as blankets or pre-cut sections, and as the material is flexible enough to allow simple manual installation. Once installed, the composite insulating structure is then heat cured to form a final fluid impervious and typically rigid structure. [0025] An exemplary blanket configuration is schematically depicted in Figure 2 where the blanket 200 has a perforation 210 (or cut line) along which the blanket can be partially separated to allow shaping into a desired form. Similarly, perforation 220 can be in the shape of a window (or otherwise shaped access point) to allow simplified removal once the blanket is installed and cured. Of course, it should be recognized that multiple blankets can be used to form a final insulated fluid containment structure as is exemplarily and schematically depicted in Figure 3. Here, a pipe 301 is wrapped in three, typically partially overlapping blankets 310A, 310B, and 3 IOC that are cured to form a continuous insulation layer around the pipe. Most advantageously, it should be appreciated that the curing not only cures the individual composite insulating structures, but also joins the structures together to form a fluid impervious seal.

[0026] With respect to the fluid containment device it should be recognized that all known such devices are deemed suitable so long as such devices have an outer surface to which a heat trace is coupled. For example, suitable devices include gas and liquid pipes, pipes for toxic or otherwise dangerous good, air conduits, tanks, reservoirs, manifolds, valve stems, etc. Thus, it should be noted that the fluid containment device is not limited to a specific shape. Indeed, all shapes are deemed appropriate for use here and include cylindrical shapes, rectangular shapes, complex shapes, and even irregular shapes.

[0027] Similarly, it should be recognized that the nature of the heat trace is not critical. For example, suitable heat traces include those that are directly coupled to the fluid containment device or those that are proximally positioned thereon. Moreover, the heat trace may be configured as a wire, a blanket, or sleeve, etc., so long as the heat trace is suitable to a heat fluid within the fluid containment device. Therefore, the operating temperature of the heat trace may be at least 50 °C, at least 100 °C, at least 250 °C, at least 500 °C, at least 750 °C, or even higher.

[0028] Consequently, it is noted that the choice of the insulating material will predominantly depend on the operating temperatures of the heat trace and/or a requirement that the composite insulating structure should be fire proof. Most preferably, the insulating material is a low k-factor insulating material (e.g., k-factor equal or less than 0.4 Btu in/hr ft² °F, more preferably equal or less than 0.3 Btu in/hr ft² °F, and most preferably equal or less than 0.25 Btu in/hr ft² °F). Thus, and viewed from a different perspective, various insulating materials are deemed suitable for use herein and include various synthetic polymers (e.g., phenolic foam, polystyrene, polyurethane, polyisocyanurate, etc), carbonaceous materials (e.g., compressed exfoliated graphite, various refractory carbides and nitrides, vermiculite, etc.), inorganic materials (e.g., fiberglass, mineral wool, cellular glass, ceramics, etc.), and any reasonable combination thereof. Still further, it should be noted that suitable insulating materials may be in various processed or raw forms, and may therefore be compounded with a carrier, woven, quilted, powdered, etc.

[0029] Consequently, it should be appreciated that the insulating material may be configured as a flexible material (e.g., as a fabric or tape) or as a rigid material (e.g., as ceramic tile). While it is generally preferred that the insulating material is flexible, it should be noted that the insulating material may also be configured to allow at least some flexibility. For example, where a ceramic is used as the insulating material, the ceramic may be provided as a plurality of small tiles that can freely move relative to each other, or as a pattern of interconnected tiles. Thus, it should be appreciated that high-performance insulating materials may be used that would otherwise not be suitable for wrapping or other simple manual installation.

[0030] Regardless of the type of insulating material, it is generally preferred that the insulating material is at least partially, and more preferably entirely enclosed within flexible carriers that are most preferably coupled together to so retain the insulating material in place during installation and after curing. There are numerous flexible carriers known in the art, and all of such carriers are deemed suitable for use herein. However, it is particularly preferred that the carriers are formed from or comprise an insulating material. Therefore, especially preferred carriers may comprise or be manufactured from similar or even the same materials as the above insulating material. It is further generally preferred that the carrier is configured such that the carrier is flexible, for example, in form of a blanket, a tape, or other pre-shaped structure. Thus, especially suitable carriers will be configured as generally flat carriers having a thickness of between 0.5 mm and 1cm, and more typically between 1 mm and 5mm (for example, carriers may be fiberglass or Teflon mats). Where suitable, multiple layers of carrier material may be used to form a composite carrier, for example, to increase mechanical strength or thermal resistance.

[0031] In especially preferred aspects of the inventive subject matter, the carriers are coupled together by chemical or mechanical means to (preferably hermetically) enclose the insulating material, and most preferably by gluing or heat-curing together silicone coated carriers. Thus, it should be noted that the step of heat curing silicone coated (or otherwise impregnated) carriers not only allows formation of a fluid impervious structure, but also allows to seal together separate composite insulating structures to so form a single fluid impervious compound structure. However, numerous alternative manners of coupling together the carriers are also deemed suitable, and appropriate manners include UV curing, radiation curing, chemical bonding via one or more adhesives, and mechanical coupling (e.g., sewing, stitching, snap- or hook-and-loop fasteners etc.).

[0032] In further preferred aspects, at least one side of at least one carrier is further modified such as to include a reflective and non-interlocking layer. The term "reflective and non- interlocking" when used in conjunction with a layer refers to the layer as being capable of reflecting at least 25%, more typically at least 50%, even more typically at least 75%, and most typically at least 90% of radiant heat while at the same time having a surface that will not interlock with a heat trace. Therefore, particularly suitable reflective and non-interlocking layer will include planar or curved surfaces, corrugated or undulating surfaces, which are most preferably metallic. For example, suitable reflective and non-interlocking layers include metal films (typically less than 1mm thickness), or may a surface of the carrier onto which a metal layer has been deposited or otherwise formed (e.g., via cold spray coating, vapor deposition, etc.).

[0033] Thus, it should be recognized that the insulating material and the composite insulating structure will typically be suitable not only for reduction of heat loss from the fluid containment device, but also for thermal insulation where a fluid and/or the fluid containment device is on fire (e.g., due to malfunction of the heat trace or chemical reaction of the contents of the fluid containment device). Additionally, it should be appreciated that the composite insulating structure will also provide a fluid impervious barrier to the heat trace and fluid containment device. Moreover, it should be noted that where curing is heat curing or UV curing, a simple process step can be used on site to finish installation of even complex geometries.

[0034] For example, where the composite insulating structure is configured as a multi-layer blanket, a non-woven insulating material layer is encased on the 'cold' side with one thin layer of silicone impregnated fiberglass, while the 'hot' side is encased with two or more layers of silicone impregnated fiberglass. The contact surface of the 'hot' side is then finished with an additional layer of silicone impregnated fiberglass that has a heat reflective layer (e.g., aluminum coating) coupled thereto. The heat trace and containment structure is then positioned proximal to the heat reflective layer of the 'hot' side . As the silicone material is not fully cured, it should be appreciated that the so formed blanket will readily conform to various surface geometries without use of excessive force or tailoring. Moreover, and as noted before, upon curing a strong and fluid resistant structure is achieved that does not entangle with the heat trace and that can therefore be readily installed and removed from the containment structure without requiring any significant skill. Moreover, it should be appreciated that contemplated structures allow use of low k- factor materials and as such substantially reduce the thickness of the insulating layer. For example, typical composite insulating structures may be configured as a blanket and may have a thickness of equal or less than 2 cm, more typically equal or less than 1 cm, and even more typically equal or less than 5 mm.

[0035] Although many applications of contemplated insulating structures are contemplated, it is especially preferred that the structure is configured as a blanket that is shaped and configured to thermally insulate a pipe or conduit of a known contour, geometry, and features (as would be found on a manufactured system requiring trace heating). Using the known geometry of the pipe, a blanket is then manufactured that conformingly fits the contours and features of the pipe. Most preferably, the blanket will be made with a seam or split in one or more places on the blanket so that it can be easily installed and uninstalled over the pipe and trace heating element.

[0036] It is conceivable that for a given manufactured system such as a fuel conditioning unit, numerous blanket configurations would be necessary to insulate a heat trace system. Once manufactured the blankets can be easily installed and uninstalled in the field by unskilled persons, with greatly reduced chance of incorrect installation. Temporary attachment methods prior to heat curing could be reusable or disposable straps such as zip ties, or any other means suitable and desirable to the end user. Alternatively, or additionally, field customizable versions of the blanket can be made that would comprise of one or more standard lengths and contours and that can be pieced together for non manufactured applications in a simple and effective manner.

[0037] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C .... and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

Claims

CLAIMS What is claimed is:

1. An insulated fluid containment structure comprising:

a fluid containment device having an outer surface to which a heat trace is coupled to allow heating of a fluid contained within the fluid containment device;

a composite insulating structure that comprises (i) a reflective and non-interlocking layer that is coupled to a first flexible carrier, (ii) a second flexible carrier, and (iii) an insulating material disposed between the first and second flexible carriers;

wherein at least one of the first and second flexible carriers comprises a curable material that allows formation of a fluid impervious barrier layer upon curing; and wherein the composite insulating structure is coupled to the fluid containment device such that the heat trace is enclosed by the outer surface and the reflective and non- interlocking layer, and such that the reflective and non-interlocking layer is at least partially surrounded by the first and second flexible carriers.

2. The insulated fluid containment structure of claim 1 wherein the reflective and non- interlocking layer comprises a fiberglass layer having a metallized surface.

3. The insulated fluid containment structure of claim 2 wherein the fiberglass layer further comprises a heat-curable material.

4. The insulated fluid containment structure of claim 1 wherein the reflective and non- interlocking layer comprises a fiberglass layer and a metal layer.

5. The insulated fluid containment structure of claim 1 wherein the first and second flexible carriers comprise fiberglass and wherein the curable material is a heat-curable material.

6. The insulated fluid containment structure of claim 1 wherein the reflective and non- interlocking layer is coupled to the first flexible carrier via the curable material.

7. The insulated fluid containment structure of claim 1 wherein the insulating material is flexible and has a k- factor of equal or less than 0.4 Btu in/hr ft² °F.

The insulated fluid containment structure of claim 1 wherein the flexible insulating material has a k-factor of equal or less than 0.3 Btu in/hr ft² °F.

The insulated fluid containment structure of claim 1 wherein the flexible insulating material comprises at least one of fiberglass, mineral wool, an elastomeric foam, and a synthetic polymer.

The insulated fluid containment structure of claim 1 wherein the composite insulating structure is configured as a blanket.

The insulated fluid containment structure of claim 10 wherein the blanket is shaped and configured into a predetermined geometry to conformingly fit a known geometry of the fluid containment device.

The insulated fluid containment structure of claim 10 wherein the blanket has seam or a split that is configured to allow removal of the composite insulating structure after curing.

The insulated fluid containment structure of claim 1 wherein the fluid containment device is a pipe, a tank, or a manifold.

The insulated fluid containment structure of claim 1 further comprising at least a second composite insulating structure, wherein the composite insulating structure and the second composite insulating structure are coupled to each other via the curable material to so form the fluid impervious barrier layer upon curing.

A method of insulating a fluid containment device having a heat trace, comprising:

providing a first and second composite insulating structure according to claim 1 and a fluid containment device having an outer surface to which a heat trace is coupled; at least partially surrounding the outer surface with the first and second composite

insulating structures such that the heat trace is disposed between the outer surface and the reflective and non-interlocking layers of the first and second composite insulating structures; and

curing the first and second compound insulating structures to form a continuous fluid resistant composite insulating structure.

16. The method of claim 15 wherein the step of curing is heat-curing.

17. The method of claim 15 wherein the first and second composite insulating structures are configured as a blanket.

18. The method of claim 15 wherein the first and second composite insulating structures comprise silicone coated fiberglass.

19. The method of claim 15 wherein the first and second composite insulating structures comprise a flexible insulating material having a k-factor of equal or less than 0.4 Btu in/hr ft² °F.

20. The method of claim 15 wherein the flexible insulating material comprises at least one of fiberglass, mineral wool, an elastomeric foam, and a synthetic polymer.