High dielectric strength electric heater

Abstract

A heater assembly includes an insulative core, at least one resistive heating element wound around the insulative core along a length of the insulative core, an inner layer of dielectric medium surrounding the at least one resistive heating element and the insulative core, and insulation members arranged longitudinally along the heater assembly and surrounding the inner layer of dielectric medium. The inner insulation members defining a respective inner gap between adjacent inner insulation members. At least one coupling is disposed within at least one of the respective inner gaps between the adjacent inner insulation members, and corresponding outer insulation members are arranged longitudinally along the heater assembly and surround the inner insulation members. The corresponding outer insulation members define a respective outer gap between adjacent outer insulation members, and a portion of the at least one coupling extends within the respective outer gap between the adjacent outer insulation members.

Description

Attorney Docket No.: 0100H-000514-WO-PQAHIGH DIELECTRIC STRENGTH ELECTRIC HEATERCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U.S. Patent Application No. 63 / 694,387, filed on September 13, 2024. The disclosure of the above application is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to medium to high voltage electric heaters, and more particularly to dielectric insulation of such electric heaters.BACKGROUND

[0003] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0004] Industrial electric heaters generally heat materials such as solids, liquids, or gasses with resistive heaters that convert electrical power to heat. In some applications, the resistive heaters are submerged in the liquid or gas or the liquid or gas flows between the resistive heaters and other internal structure such as baffles. In some applications, a large amount of power is needed to bring the material to the desired temperature. For example, some applications require power greater than 1 megawatt, with some applications being in the range of 5 megawatts or greater. Typical low voltage electric heaters operate at around 700 volts but can require high electrical current (e.g., over 7,000 amps) to achieve the power required. The high current can require large and expensive power components, cables, and grounding strategies. Additionally, some industrial power sources require a step-down transformer to supply the low voltage, and dielectric isolation of the resistive heaters can be challenging.

[0005] The present disclosure addresses these and other challenges related to industrial electric heaters operating at higher voltage and / or current levels, and dielectric insulation thereof.SUMMARY

[0006] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.Attorney Docket No.: 0100H-000514-WO-PQA

[0007] In one form of the present disclosure, a heater assembly is provided that comprises an insulative core, at least one resistive heating element wound around the insulative core along a length of the insulative core, an inner layer of dielectric medium surrounding the at least one resistive heating element and the insulative core, a plurality of inner insulation members arranged longitudinally along the heater assembly and surrounding the inner layer of dielectric medium, the plurality of inner insulation members defining a respective inner gap between adjacent inner insulation members, at least one coupling disposed within at least one of the respective inner gaps between the adjacent inner insulation members, and a plurality of corresponding outer insulation members arranged longitudinally along the heater assembly and surrounding the plurality of inner insulation members, the plurality of corresponding outer insulation members defining a respective outer gap between adjacent outer insulation members, a portion of the at least one coupling extending within the respective outer gap between the adjacent outer insulation members.

[0008] In variations of this heater assembly, which may be implemented individually or in any combination: an outer sheath surrounds the plurality of outer insulation members; end seals are disposed at proximal and distal end portions of the heater assembly and disposed at least partially within the outer sheath; an outer layer of dielectric medium is disposed between the outer sheath and the outer insulation members; an intermediate layer of dielectric medium is disposed between the inner insulation members and the outer insulation members; the inner layer of dielectric medium is compacted MgO; the plurality of inner insulation members and the plurality of outer insulation members are a quartz material; a plurality of couplings are provided, wherein each of the plurality of couplings comprises a flanged portion and an extension extending radially from the flanged portion; the extension extends radially inward; the extension extends radially outward; the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the inner insulation members and the extension axially abutting at least one of the outer insulation members; the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the outer insulation members and the extension axially abutting at least one of the inner insulation members; and the flanged portion and the extension of at least one of the couplings define an L-shaped cross-section.Attorney Docket No.: 0100H-000514-WO-PQA

[0009] In another form of the present disclosure, a dielectric subassembly for a heater assembly includes a plurality of inner insulation members arranged longitudinally and defining a respective inner gap between adjacent inner insulation members, at least one coupling is disposed within at least one of the respective inner gaps, a plurality of corresponding outer insulation members are arranged longitudinally and surrounding the plurality of inner insulation members, the plurality of corresponding outer insulation members define a respective outer gap between adjacent outer insulation members, a portion of the at least one coupling extends within the respective outer gap between the adjacent outer insulation members, and a dielectric medium is disposed between the outer insulation members and the inner insulation members.

[0010] In variations of this dielectric subassembly, which may be implemented individually or in any combination: the dielectric medium is compacted MgO; a plurality of couplings are provided, wherein each of the plurality of couplings comprises a flanged portion and a radial extension extending radially from the flanged portion; the radial extension extends radially inward; the radial extension extends radially outward; the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the inner insulation members and the extension axially abutting at least one of the outer insulation members; the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the outer insulation members and the extension axially abutting at least one of the inner insulation members; the flanged portion and the extension of at least one of the couplings define an L-shaped cross-section; and the plurality of inner insulation members and the plurality of outer insulation members are a quartz material.

[0011] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.DRAWINGS

[0012] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:Attorney Docket No.: 0100H-000514-WO-PQA

[0013] FIG. 1 is a perspective view of a medium-voltage electric heat exchanger according to the principles of the present disclosure;

[0014] FIG. 2A is a schematic cross-sectional view of a heater assembly of the electric heat exchanger of FIG. 1 ;

[0015] FIG. 2B is a schematic cross-sectional view of the heater assembly of FIG. 2A with a coupling removed for clarity;

[0016] FIG. 3 is a schematic cross-sectional view of another heater assembly configured to be incorporated into the electric heat exchanger of FIG. 1 ;

[0017] FIG. 4 is a schematic cross-sectional view of another heater assembly configured to be incorporated into the electric heat exchanger of FIG. 1 ; and

[0018] FIG. 5 is a schematic cross-sectional view of yet another heater assembly configured to be incorporated into the electric heater of FIG. 1 .

[0019] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.DETAILED DESCRIPTION

[0020] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0021] Referring to FIG. 1 , an example electric heater 10 (which is in the form of a heat exchanger in this particular application) is illustrated. The electric heater 10 includes a heating portion 14, a power supply portion 18, and a neutral terminal portion 22. The heating portion 14 includes a plurality of electrical resistance heater assemblies 26 that extend parallel to a central axis 28 of the electric heater 10 between the power supply portion 18 and the neutral terminal portion 22. In the example provided, the electric heater 10 is disposed within a tube 30 having a first port or inlet / outlet 34 proximate to the power supply portion and a second port or inlet / outlet 38 proximate to the neutral terminal portion 22. The tube 30 is illustrated as transparent for clarity purposes to better illustrate the components within the tube 30. In operation, fluid is generally pumped into the tube 30 via one of the inlet / outlets and then flows through the tube 30 and comes into contact with the heater assemblies 26 until exiting via the other inlet / outlet. In the example provided, the fluid flows in the first inlet / outlet 34 and out the second inlet / outlet 38, though the flow may be reversed. ItAttorney Docket No.: 0100H-000514-WO-PQA should be understood that the term “fluid” is to be construed to include solids, liquids, gases, and plasmas, among other material states while remaining within the scope of the present disclosure.

[0022] The tube 30 includes a first shell flange 41 and a second shell flange 46. The first shell flange 41 is disposed between the power supply portion 18 and the first in let / outlet 34 and is configured to couple the tube 30 to the power supply portion 18. The second shell flange 46 is disposed between the neutral terminal portion 22 and the second in let / outlet 38 and is configured to couple the tube 30 to the neutral terminal portion 22.

[0023] A baffle 50 may also optionally be disposed within the tube 30. In the example provided, the baffle 50 is a continuous helical shape and directs the flow of the fluid along a helical flow pathway 54 between the two inlet / outlets 34, 38, though other configurations can be used. The baffle 50 can also act as a support member that supports the heater assemblies 26 relative to each other and relative to the tube 30. While illustrated and described with reference to heating a fluid flowing through the tube 30, the electric heater 10 may be used without the tube 30 in other applications such as submersion heating for example. An exemplary baffle configuration is illustrated and described in U.S. Patent No. 10,941 ,988 and its related family of patents, which are commonly owned with the present application and the contents of which are incorporated herein by reference in their entirety.

[0024] As shown in FIGS. 2A and 2B, each heater assembly 26 includes an electrically insulative core 40, a resistive heating element 42 wound around the insulative core 40, and an outer sheath 44 surrounding the resistive heating element 42. In this form, winding the resistive heating element 42 around the insulative core 40 places more of the resistive heating element 42 within the heater assembly 26 than extending the resistive heating element 42 straight through the heater assembly 26, thereby providing a higher watt density in a smaller package / assembly. Thus, the increased amount of the resistive heating element 42 along the axial length of the heater assembly 26 increases a total amount of heat that can be emitted to the outer sheath 44. The electrically insulative core 40 provides a surface around which the resistive heating element 42 may be wound through the heater assembly 26. In the example illustrated, the insulative core 40 also acts as structural support for the resistive heating element 42.Attorney Docket No.: 0100H-000514-WO-PQA

[0025] In a medium-voltage heater, such as the heater 10 operating at voltages above 2000 volts (V), for example, the resistive heating element 42 may have a tendency to electrically arc with other components of the electric heater 10 or other portions of the resistive heating element 42 without enough dielectric isolation. This electrical arcing may reduce the operating lifetime of the resistive heating element 42, and thus inhibit operation of the electric heater 10 as a whole. The unique configuration of the heater assembly 26, as set forth in greater detail below, inhibits such arcing between adjacent portions of the resistive heating element 42, and between other components of the heater 10, thereby improving the heating efficiency of the electric heater 10 and increasing its useful life.

[0026] Each heater assembly 26 further includes a plurality of inner insulation members 48a, 48b, a plurality of outer insulation members 52a, 52b, and one or more couplings 56. While only one coupling 56 is shown, it should be understood that a plurality of couplings 56 may be employed while remaining within the scope of the present disclosure. Both the inner insulation members 48a, 48b, the outer insulation members 52a, 52b, and the coupling 56 are each an electrically insulating material, thus providing additional dielectric protection to inhibit electrical arcing between the resistive heating element 42 and the outer sheath 44, or between different portions of the resistive heating element 42 and the heater assembly 26.

[0027] As shown, the inner insulation members 48a, 48b are at least partially disposed within, or are surrounded by, corresponding outer insulation members 52a, 52b, both of which are arranged longitudinally along the length of the heater assembly 26 as shown. In the example illustrated, the inner insulation members 48a, 48b are disposed within, or surrounded by, the outer sheath 44 and are axially aligned with each other. Further an inner gap 55a (best shown in FIG. 2B) is defined between adjacent inner insulation members 48a, 48b. Similarly, the outer insulation members 52a, 52b are disposed within, or surrounded by, the outer sheath 44 and are axially aligned with each other, and an outer gap 55b (best shown in FIG. 2B) is defined between adjacent outer insulation members 52a, 52b. And although the arrangement of inner and outer insulation members 48a, 48b, 52a, 52b are shown in a linear configuration, it should be understood that the inner and outer insulation members 48a, 48b, 52a, 52b are may also be curved / arcuate or take on other geometric layouts while remaining within the scope of the present disclosure.Attorney Docket No.: 0100H-000514-WO-PQA

[0028] The coupling 56 is disposed within the inner gap 55a and the outer gap 55b as shown. In one form, the coupling 56 includes a flanged portion 56a and an extension 56b that extends radially outward from the flanged portion 56a. The flanged portion 56a is thus disposed within the inner gap 55a, and the extension 56b is disposed within the outer gap 55b. In this configuration, the flanged portion 56a and the extension 56b define a tee (T) shaped cross-section. In the T shaped crosssection, one end of the flanged portion 56a axially abuts the end 59a of the inner insulation member 48a to form a joint or seam 60a between the coupling 56 and the inner insulation member 48a. Similarly, the other end of the flanged portion 56a axially abuts the end 59b of the inner insulation member 48b to form a joint or seam 60b between the coupling 56 and the inner insulation member 48b. In a similar fashion, one side of the extension 56b axially abuts the end 57a of the outer insulation member 52a to form a joint or seam 62a between the coupling 56 and the outer insulation member 52a, and the other side of the extension 56b axially abuts the end 57b of the outer insulation member 52b to form a joint or seam 62b between the coupling 56 and the outer insulation member 52b. In this way, the joint 60a between the coupling 56 and the inner insulation member 48a is staggered relative to the joint 62a between the coupling 56 and the outer insulation member 52a, so that the joints 60a, 62a are not aligned. Similarly, the joint 60b between the coupling 56 and the inner insulation member 48b is staggered relative to the joint 62b between the coupling 56 and the outer insulation member 52b, so that the joints 60b, 62b are not aligned. Thus, the joints 62a, 62b are axially staggered from the joints 60a, 60b, thereby creating a longer, or more tortuous, path for any electrical arc to travel and be dissipated before reaching the outer sheath 44. It should be understood that other shapes (and orientations) of cross-sections, such as by way of example an L-shaped cross-section (not shown) may be implemented while remaining within the scope of the present disclosure.

[0029] The inner and outer insulation members 48a, 48b, 52a, 52b, as well as the coupling 56 are made of a quartz material in one form of the present disclosure. In another form, the inner and outer insulation members 48a, 48b, 52a, 52b and the coupling 56 are made of a ceramic material, such as by way of example, boron nitride (BN), aluminum oxide (AI2O3), and / or magnesium oxide (MgO), among others. Other materials having the desired dielectric properties may also be used for both the coupling 56 and the inner and outer insulation members 48a, 48b, 52a, 52b,Attorney Docket No.: 0100H-000514-WO-PQA and each of these members (inner and outer insulation members 48a, 48b, 52a, 52b and coupling 56) need not be the same material, while remaining within the scope of the present disclosure.

[0030] In the example illustrated, the outer insulation members 52a, 52b and the inner insulation members 48a, 48b, are equal in length to each other. It should be understood, however, that the outer insulation members 52a, 52b and the inner insulation member 48a, 48b can be different lengths from each other while remaining within the scope of the present disclosure, provided the staggering as set forth above is provided with the coupling 56. Further, although only two (2) outer and inner insulation members 52a, 52b, 48a, 48b are shown, it should be understood that the heater assembly 26 can include three (3) or more outer and inner insulation members 52a, 52b, 48a, 48b while remaining within the scope of the present disclosure.

[0031] The heater assembly 26 further includes a dielectric medium 64 between the resistive heating element 42 and the outer sheath 44. The dielectric medium 64 surrounds the resistive heating element 42 to provide an electrically insulative barrier, inhibiting the electrical arcing while allowing heat from the resistive heating element 42 to reach the outer sheath 44. In one form, the dielectric medium 64 is compacted magnesium oxide (MgO), which is MgO powder compressed into a solid shape around the internal components of the heater assembly 26 as shown. Generally, the compacted MgO provides additional electrical insulation than powdered MgO because the granules of MgO are fused together into a unitary mass, increasing the density of MgO between the resistive heating element 42 and the outer sheath 44.

[0032] In one form, the dielectric medium 64 is arranged in a plurality of layers 64a (inner layer), 64b (intermediate layer), and 64c (outer layer). The inner layer 64a is radially disposed between the resistive heating element 42 and the inner insulation members 48a, 48b, the outer layer 64c is radially disposed between the outer sheath 44 and the outer insulation members 52a, 52b, and the intermediate layer 64b is radially disposed between the inner insulation members 48a. 48b and the outer insulation members 52a, 52b. Each of these layers of dielectric medium provide additional dielectric insulation and further inhibit electrical arcing from the resistive heating element 42.

[0033] In one form of the present disclosure, the plurality of inner insulation members 48a, 48b, the at least one coupling 56, the outer insulation members 52a, 52b and the dielectric medium together form a dielectric subassembly.Attorney Docket No.: 0100H-000514-WO-PQAThis dielectric subassembly may be provided separately, rather than with the heater assembly 26 and its additional components (e.g., sheath, and other components illustrated and described below) while remaining within the scope of the present disclosure.

[0034] As further shown, the heater assembly 26 further includes a pair of end seals 66 disposed at distal end portions of the heater assembly 26 within the outer sheath 44. In one form, the end seals 66 may be secured to the outer sheath 44 by welding or brazing, for example. In another form, the end seals 66 may be secured to the outer sheath 44 by bonding, swaging, or any other attachment means. The end seals 66 enclose and seal the insulative core 40, the resistive heating element 42, the dielectric medium 64, the insulation members 48a, 48b, 52a, 52b, and the coupling 56 within the outer sheath 44. The end seals 66 thus hold the components of the heater assembly 26 within the outer sheath 44 and inhibit external fluids and / or contaminants, such as water or dust, from entering the heater assembly 26. The end seals 66 each further include a sealed opening through which power pins 68 extend as shown. The power pins 68 provide electric power to the resistive heating element 42 from an external power source (not shown).

[0035] Referring now to FIG. 3, another heater assembly 126 having a different configuration of a coupling 156 according to the teachings of the present disclosure is shown. The structure and function of the heater assembly 126 is similar to the heater assembly 26 described above, apart from any exception noted below. The heater assembly 126 includes an electrically insulative core 140, a resistive heating element 142, an outer sheath 144, a plurality of inner insulation members 148a, 148b, a plurality of outer insulation members 152a, 152b, and one or more couplings 156. The structure and function of the electrically insulative core 140, the resistive heating element 142, the outer sheath 144, the plurality of inner insulation members 148a, 148b, and the plurality of outer insulation members 152a, 152b is similar or identical to the electrically insulative core 40, the resistive heating element 42, the outer sheath 44, the plurality of inner insulation members 48a, 48b, and the plurality of outer insulation members 52a, 52b, respectively, described above, and therefore, will not be described again in detail.

[0036] The coupling 156 is similarly disposed within a gap between adjacent inner insulation members 148a, 148b and a gap between adjacent outer insulation members 152a, 152b and is essentially a geometrical inverse of the couplingAttorney Docket No.: 0100H-000514-WO-PQA56 illustrated and described above. In the example illustrated, the coupling 156 abuts the inner and outer insulation members 148a, 148b, 152a, 152b. In one form, the coupling 156 includes a flanged portion 156a and an extension 156b that extends radially inward from the flanged portion 156a. In this way, one end of the flanged portion 156a axially abuts the end 157a of the outer insulation member 152a to form a joint or seam 160a therebetween and the other end of the flanged portion 156a axially abuts the end 157b of the outer insulation member 152b to form a joint or seam 160b therebetween. Similarly, one side of the extension 156b axially abuts the end 159a of the inner insulation member 148a to form a joint or seam 162a therebetween and the other side of the extension 156b axially abuts the end 159b of the inner insulation member 148b to form a joint or seam 162b therebetween. In this way, the joints between the coupling 156 and the inner and outer insulation members 148a, 148b, 152a, 152b are staggered, thereby creating a longer, or more tortuous, path for any electrical arc to travel and be dissipated before reaching the outer sheath 144.

[0037] Referring to FIG. 4, yet another heater assembly 226 having a different coupling design is illustrated according to the teachings of the present disclosure. The structure and function of the heater assembly 226 is similar or identical to the heater assemblies 26, 126 described above, apart from any exception noted below. The heater assembly 226 includes an electrically insulative core 240, a resistive heating element 242, an outer sheath 244, a plurality of inner insulation members 248a, 248b, a plurality of outer insulation members 252a, 252b, and one or more couplings 256. The structure and function of the electrically insulative core 240, the resistive heating element 242, the outer sheath 244, the plurality of inner insulation members 248a, 248b, and the plurality of outer insulation members 252a, 252b may be similar or identical to the electrically insulative core 40, the resistive heating element 42, the outer sheath 44, the plurality of inner insulation members 48a, 48b, and the plurality of outer insulation members 52a, 52b, respectively, described above, and therefore, will not be described again in detail.

[0038] In this variation, the coupling 256 has an L-shape and is disposed within a gap between adjacent inner insulation members 248a, 248b and a gap between adjacent outer insulation members 252a, 252b as shown. The coupling 256 includes a body portion 256a and an extension 256b that extends in an axial direction from an end of the body portion 156a. One end of the body portion 256a axially abuts end 257a of the outer insulation member 252a to form a joint or seam 260aAttorney Docket No.: 0100H-000514-WO-PQA therebetween and axially abuts end 259a of the inner insulation member 248a to form a joint or seam 262a. The other end of the body portion 256a axially abuts end 259b of the inner insulation member 248b to form a joint or seam 262b therebetween. The extension 256b axially abuts end 257b of the outer insulation member 252b to form a joint or seam 260b therebetween that is staggered and / or offset relative to the joint 262b. Accordingly, the joints between the coupling 256 and the inner and outer insulation members 248a, 248b, 252a, 252b are staggered, thereby creating a longer, or more tortuous, path for any electrical arc to travel and be dissipated before reaching the outer sheath 244.

[0039] Referring to FIG. 5, another heater assembly 326 is illustrated according to the teachings of the present disclosure. The structure and function of the heater assembly 326 is similar or identical to the heater assemblies 26, 126, 226 described above, apart from any exception noted below. The heater assembly 326 includes an electrically insulative core 340, a resistive heating element 342, an outer sheath 344, a plurality of inner insulation members 348a, 348b, 348c, a plurality of outer insulation members 352a, 352b, 352c and a plurality of couplings 356a, 356b. The structure and function of the electrically insulative core 340, the resistive heating element 342, the outer sheath 344, the plurality of inner insulation members 348a, 348b, 348c and the plurality of outer insulation members 352a, 352b, 352c may be similar or identical to the electrically insulative core 40, the resistive heating element 42, the outer sheath 44, the plurality of inner insulation members 48a, 48b, and the plurality of outer insulation members 52a, 52b, respectively, described above, and therefore, will not be described again in detail.

[0040] The coupling 356a is axially spaced apart from the coupling 356b and is disposed within a gap between adjacent inner insulation members 348b, 348c and a gap between adjacent outer insulation members 352b, 352c. In the example illustrated, the coupling 356a abuts the inner and outer insulation members 348b, 348c, 352b, 352c. Similarly, the coupling 356b is disposed within a gap between adjacent inner insulation members 348a, 348c and a gap between adjacent outer insulation members 352a, 352c. In the example illustrated, the coupling 356b abuts the inner and outer insulation members 348a, 348c, 352a, 352c.

[0041] In the example illustrated, each coupling 356a, 356b includes a flanged portion 359a and an extension 359b that extends radially outward from the flanged portion 359a. In this way, one end of the flanged portion 359a of the couplingAttorney Docket No.: 0100H-000514-WO-PQA356a axially abuts the inner insulation member 348b to form a joint or seam 360a therebetween and the other end of the flanged portion 359a of the coupling 356a axially abuts the inner insulation member 348c to form a joint or seam 360b therebetween. Similarly, one end of the extension 359b of the coupling 356a axially abuts the outer insulation member 352b to form a joint or seam 362a therebetween and the other end of the extension 359b of the coupling 356a axially abuts the outer insulation member 352c to form a joint or seam 362b therebetween. The joint 362a is staggered relative to the joint 360a, and the joint 362b is staggered relative to the joint 360b.

[0042] One end of the flanged portion 359a of the coupling 356b axially abuts the inner insulation member 348a to form a joint or seam 360c therebetween and the other end of the flanged portion 359a of the coupling 356b axially abuts the inner insulation member 348c to form a joint or seam 360d therebetween. Similarly, one end of the extension 359b of the coupling 356b axially abuts the outer insulation member 352a to form a joint or seam 362c therebetween and the other end of the extension 359b of the coupling 356b axially abuts the outer insulation member 352c to form a joint or seam 362d therebetween. The joint 362c is staggered relative to the joint 360c, and the joint 362d is staggered relative to the joint 360d. Accordingly, the joints between the couplings 356a / 356b and the inner and outer insulation members 348a, 348b, 348c, 352a, 352b, 352c are staggered, thereby creating a longer, or more tortuous, path for any electrical arc to travel and be dissipated before reaching the outer sheath 344.

[0043] Unless otherwise expressly indicated herein, all numerical values indicating mechanical / thermal properties, compositional percentages, dimensions and / or tolerances, or other characteristics are to be understood as modified by the word “about” or "approximately" in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

[0044] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0045] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure areAttorney Docket No.: 0100H-000514-WO-PQA intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.

Claims

Attorney Docket No.: 0100H-000514-WO-PQACLAIMSWhat is claimed is:1 . A heater assembly comprising: an insulative core; at least one resistive heating element wound around the insulative core along a length of the insulative core; an inner layer of dielectric medium surrounding the at least one resistive heating element and the insulative core; a plurality of inner insulation members arranged longitudinally along the heater assembly and surrounding the inner layer of dielectric medium, the plurality of inner insulation members defining a respective inner gap between adjacent inner insulation members; at least one coupling disposed within at least one of the respective inner gaps between the adjacent inner insulation members; and a plurality of corresponding outer insulation members arranged longitudinally along the heater assembly and surrounding the plurality of inner insulation members, the plurality of corresponding outer insulation members defining a respective outer gap between adjacent outer insulation members, a portion of the at least one coupling extending within the respective outer gap between the adjacent outer insulation members.

2. The heater assembly according to Claim 1 , further comprising an outer sheath surrounding the plurality of outer insulation members.

3. The heater assembly according to Claim 2, further comprising end seals disposed at proximal and distal end portions of the heater assembly and disposed at least partially within the outer sheath.

4. The heater assembly according to Claim 2, further comprising an outer layer of dielectric medium disposed between the outer sheath and the outer insulation members.Attorney Docket No.: 0100H-000514-WO-PQA5. The heater assembly according to Claim 1 , further comprising an intermediate layer of dielectric medium disposed between the inner insulation members and the outer insulation members.

6. The heater assembly according to Claim 1 , wherein the inner layer of dielectric medium is compacted MgO.

7. The heater assembly according to Claim 1 , wherein the plurality of inner insulation members and the plurality of outer insulation members are a quartz material.

8. The heater assembly according to Claim 1 , further comprising a plurality of couplings, wherein each of the plurality of couplings comprises a flanged portion and an extension extending radially from the flanged portion.

9. The heater assembly according to Claim 8, wherein the extension extends radially inward.

10. The heater assembly according to Claim 8, wherein the extension extends radially outward.11 . The heater assembly according to Claim 8, wherein the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the inner insulation members and the extension axially abutting at least one of the outer insulation members.

12. The heater assembly according to Claim 8, wherein the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the outer insulation members and the extension axially abutting at least one of the inner insulation members.

13. The heater assembly according to Claim 8, wherein the flanged portion and the extension of at least one of the couplings define an L-shaped cross-section.Attorney Docket No.: 0100H-000514-WO-PQA14. A dielectric subassembly for a heater assembly, the dielectric subassembly comprising: a plurality of inner insulation members arranged longitudinally and defining a respective inner gap between adjacent inner insulation members; at least one coupling disposed within at least one of the respective inner gaps; a plurality of corresponding outer insulation members arranged longitudinally and surrounding the plurality of inner insulation members, the plurality of corresponding outer insulation members defining a respective outer gap between adjacent outer insulation members, a portion of the at least one coupling extending within the respective outer gap between the adjacent outer insulation members; and a dielectric medium disposed between the outer insulation members and the inner insulation members.

15. The dielectric subassembly according to Claim 14, wherein the dielectric medium is compacted MgO.

16. The dielectric subassembly according to Claim 14, further comprising a plurality of couplings, wherein each of the plurality of couplings comprises a flanged portion and a radial extension extending radially from the flanged portion.

17. The dielectric subassembly according to Claim 16, wherein the radial extension extends radially inward.

18. The dielectric subassembly according to Claim 16, wherein the radial extension extends radially outward.

19. The dielectric subassembly according to Claim 16, wherein the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section, the flanged portion axially abutting at least one of the inner insulation members and the extension axially abutting at least one of the outer insulation members.

20. The dielectric subassembly according to Claim 16, wherein the flanged portion and the extension of at least one of the couplings define a tee (T) cross-section,Attorney Docket No.: 0100H-000514-WO-PQA the flanged portion axially abutting at least one of the outer insulation members and the extension axially abutting at least one of the inner insulation members.21 . The dielectric subassembly according to Claim 16, wherein the flanged portion and the extension of at least one of the couplings define an L-shaped crosssection.

22. The dielectric subassembly according to Claim 14, wherein the plurality of inner insulation members and the plurality of outer insulation members are a quartz material.

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