Mineral insulated cable having reduced sheath temperature

Patent metadata

Field	Value
Publication number	US-10076001-B2
Application number	US-201313931863-A
Country	US
Kind code	B2
Filing date	Jun 29, 2013
Priority date	Jul 5, 2012
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A mineral insulated heating cable for a heat tracing system. The heating cable includes a sheath having at least a first, and optionally a second layer, wherein the thermal conductivity of the second layer is greater than a thermal conductivity of the first layer. In addition, the first and second layers are in intimate thermal contact. The heating cable also includes at least one heating conductor for generating heat and a dielectric layer located within the sheath for electrically insulating the heating, conductor, wherein the sheath, heating conductor and dielectric layer form a heating section. In addition, the heating cable includes a conduit for receiving the heating section. Further, the heating cable includes a cold lead section and a hot-cold joint for connecting the heating and cold lead sections. In addition, a high emissivity coating may be formed on the first layer.

First claim

What is claimed is:

1. A mineral insulated heating cable for a heat tracing system, comprising:
a sheath;
at least one heating conductor located, within the sheath;
a dielectric layer located within the sheath for electrically insulating the heating conductor, wherein the sheath, heating conductor and dielectric layer form a heating section;
a conduit, wherein a full length of the heating section is located within the conduit, the conduit defining an internal cavity sized to create a gap separating the heating section from an interior surface of the conduit along the full length of the heating section so that heat generated by the heating section is transferred to the conduit by radiation;
a cold lead section; and
a hot-cold joint for connecting the heating and cold lead sections, wherein the hot-cold joint is located at least partially within the conduit.

2. The mineral insulated cable according to claim 1 , wherein the conduit is corrugated.

3. The mineral insulated cable according to claim 1 , wherein the conduit has corrosion resistant properties.

4. The mineral insulated cable according to claim 1 , wherein a surface area of the interior surface of the conduit is at least 2.5 times greater than an outer surface area of the heating section.

5. The mineral insulated cable according to claim 1 , wherein the heating section is sealed within the conduit to provide isolation from environmental conditions.

6. The mineral insulated cable according to claim 5 , wherein the heating section is sealed by affixing plugs to respective openings in the conduit.

7. The mineral insulated heating cable according to claim 1 , wherein the sheath includes at least one first layer having a first thermal conductivity and at least one second layer having a second thermal conductivity that is greater than the first thermal conductivity.

8. The mineral insulated heating cable according to claim 7 , wherein the conduit is corrugated.

9. The mineral insulated heating cable according to claim 7 , wherein the first layer has corrosion resistant properties.

10. The mineral insulated heating cable according to claim 7 , wherein the first layer is fabricated from Alloy 825.

11. The mineral insulated heating cable according to claim 7 , wherein the second layer is fabricated from copper.

12. The mineral insulated heating cable according to claim 7 , wherein the first layer is in intimate thermal contact with the second layer.

13. The mineral insulated heating cable according to claim 7 , wherein a thickness of the second layer is greater than approximately 10% of a thickness of the sheath.

14. The mineral insulated heating cable according to claim 7 , wherein the first layer is at least approximately 0.002 inches thick.

15. The mineral insulated heating cable according to claim 7 , wherein the second layer has a thermal conductivity of greater than approximately 20 W·m −1 ·K −1 .

16. The mineral insulated heating cable of claim 7 further including at least one fin in thermal contact with the heating section.

17. The cable of claim 1 further including a high emissivity coating applied to the sheath, the coating having an emissivity value of at least 0.6.

18. The cable of claim 1 wherein the sheath includes an outer surface that is oxidized to form an oxidized layer.

19. The cable of claim 1 wherein the sheath includes an outer surface that is subjected to a black anodizing process to form an anodized layer.

20. The cable of claim 1 wherein at least a portion of the sheath has a thermal conductivity greater than 20 W·m −1 ·K −1 .

21. The cable of claim 1 wherein the sheath includes material with a thermal conductivity of at least approximately 400 W·m −1 ·K −1 .

22. The cable of claim 1 wherein the cable includes at least two heating conductors, each heating conductor having a first end and a second end, wherein the second ends of the heating conductors are joined and sealed to provide isolation from environmental conditions.

23. The cable of claim 1 further including a bus wire, wherein the heating conductor extends from a first end to a second end, and wherein the first end of the heating conductor is connected to the bus wire at the hot-cold joint.

24. The cable of claim 1 wherein the conduit extends between closed ends, and wherein the cold lead section extends past one of the closed ends.

25. The cable of claim 24 further including a fitting, wherein the fitting closes one of the closed ends of the conduit, and wherein the cold lead section extends through the fitting.

26. The cable of claim 25 wherein the fitting is brazed, welded, or compression fit into the conduit to seal the conduit from environmental conditions.

27. The cable of claim 1 wherein the cold lead section extends out an end of the conduit.

28. The cable of claim 27 wherein:
the hot-cold joint is situated within the conduit;
the heating section extends from one end of the hot-cold joint; and
the cold lead section extends from an opposing end of the hot-cold joint.

29. The cable of claim 1 further including a bus wire connected to an end of the heating conductor at the hot-cold joint.

30. The cable, of claim 29 wherein the bus wire extends through the cold lead section.

31. The cable of claim 1 further including a conduit plug having a first conduit plug section that is smaller than a second conduit plug section such that the conduit plug has a stepped plug configuration, wherein:
the hot-cold joint includes a first joint section that is smaller than a second joint section such that the hot-cold joint has a stepped joint configuration; and
the first conduit plug section and the first joint section are sized to fit within the conduit.

Assignees

• Pentair Thermal Man Llc
• Nvent Services Gmbh

Inventors

• Becker Paul
• Ling Fuhua
• Liu Ningli
• White Lawrence Joseph
• Martin Ii Louis Peter
• Finlayson Scott Murray
• Beres James Francis
• Kleinehanding Marcus

Classifications

• H05B3/08 Primary

  having electric connections specially adapted for high temperatures · CPC title

• H05B2203/011

  Heaters using laterally extending conductive material as connecting means · CPC title

• H05B3/02 Primary

  Details · CPC title

• H05B3/56

  Heating cables · CPC title

• H05B3/50

  heating conductor arranged in metal tubes, the radiating surface having heat-conducting fins · CPC title