Sheathed Thermocouple

Abstract

A sheathed thermocouple component has at least a sheath housing with at least one thermocouple and electrical insulation therein. The sheath housing has an outer diameter and a wall thickness relative to a cross section of the at least one thermocouple, and a ratio of the wall thickness to the outer diameter is in the range of 0.17 to 0.45. Such a sheathed thermocouple component can be manufactured efficiently and has a number of advantageous uses.

Claims

1. A sheathed thermocouple component, comprising a sheath housing with at least one thermocouple and electrical insulation therein, wherein the sheath housing has an outer diameter and a wall thickness relative to a cross section of the at least one thermocouple, and a ratio of the wall thickness to the outer diameter is in the range of 0.17 to 0.45.

2. The sheathed thermocouple component according to claim 1, wherein the ratio of the wall thickness to the outer diameter is in the range of 0.35 to 0.42.

3. The sheathed thermocouple component according claim 1, wherein a radial insulation distance of the at least one thermocouple from the sheath housing is less than the wall thickness of the sheath housing.

4. The sheathed thermocouple component according to claim 1, wherein the sheath housing is made of a material that has a tensile strength (R.sub.m) of at least 350 N/mm.sup.2 at a temperature of 700 C.

5. The sheathed thermocouple component according to claim 1, wherein the sheath housing is made of a material that has a thermal conductivity of at least 20.0 W/mK.

6. The sheathed thermocouple component according to claim 1, wherein the sheath housing includes a material from the following group: nickel-chromium steel, stainless steel.

7. The sheathed thermocouple component according to claim 1, wherein the electrical insulation includes a material from the following group: aluminum oxide, magnesium oxide.

8. The sheathed thermocouple component according to claim 1, wherein the outer diameter is less than 3.0 millimeters.

9. The sheathed thermocouple component according to claim 1, wherein the sheath housing has at least one inner layer and an outer layer, the inner layer and the outer layer being metallic.

10. A method for manufacturing a sheathed thermocouple rod, comprising: a. providing an assembly having at least a sheath housing with at least one thermocouple and electrical insulation therein, wherein the sheath housing has an outer diameter and a wall thickness relative to a cross section of the at least one thermocouple, and a ratio of the wall thickness to the outer diameter is in the range of 0.17 to 0.45, b. deforming the assembly, wherein the outer diameter and the wall thickness are reduced, and the ratio of the wall thickness to the outer diameter remains in the range of 0.17 to 0.45.

11. A method for determining a hot gas temperature that is at least occasionally at least 600 C. or at least 900 C. comprising providing the sheathed thermocouple component according to claim 1.

12. A method for determining a temperature in a corrosive medium comprising providing the sheathed thermocouple component according to claim 1.

13. A method for determining a temperature in a fluid stream that varies over time with regard to pressure and temperature medium comprising providing the sheathed thermocouple component according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The invention and the technical background are explained in greater detail below with reference to the figures. The figures show exemplary embodiments, to which the invention, however, is not limited. In the interest of clarity, it is pointed out that the technical features illustrated in the figures may be extracted and also optionally combined with features of other figures and/or the description without taking further technical features in the same figure. If there is a technical need to combine characteristics of one technical feature with those of another technical feature, this is explicitly noted herein, so that these features may otherwise be freely combined.

[0063] The figures schematically show the following:

[0064] FIG. 1: shows one design of a sheathed thermocouple component,

[0065] FIG. 2: shows a sequence of the method for manufacturing a sheathed thermocouple rod, and

[0066] FIG. 3: shows another design of a sheathed thermocouple component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] FIG. 1 shows a sheathed thermocouple 1 in cross section. The sheathed thermocouple component 1 is radially surrounded or enclosed by an outer sheath housing 2. On the end-face side, the thermocouple 3 may extend beyond both end faces of the sheath housing 2. At the top, FIG. 1 shows the connection for the evaluation electronics system, and at the bottom shows the measuring point in the area of the welded wires or tip. In this regard, the thermocouple extends through the cylindrical sheath housing. The at least one thermocouple 3 is positioned at a distance from the sheath housing. This is achieved in particular with electrical insulation 4. The electrical insulation 4 may be made from one material and/or from multiple electrically insulating materials. In the present case, the electrical insulation is designed, for example, in the manner of a coating on the thermocouple 3, and in addition an air gap is provided. However, it is also possible for the indicated interior of the sheath housing to be completely filled with (a single piece of) electrical insulation. The spaced-apart arrangement of the at least one thermocouple 3 and the sheath housing 2 may be illustrated in particular with reference to the radial insulation distance 7. The thermocouple 3 may have a wire diameter 11. With regard to the sheath housing 2, the wall thickness 6 is also indicated. In the present case, the wall thickness 6 is constant over the entire axial extension of the sheath housing 2, but this is not absolutely necessary. In addition, the outer diameter 5 is specified by the sheath housing 2. In the present case, the sheath housing is cylindrical over the entire axial extension, but this is not absolutely necessary. In the sheathed thermocouple component 1 schematically shown here, a ratio of the wall thickness 5 to the outer diameter 6 is to be maintained in the range of 0.17 to 0.45.

[0068] In the sheathed thermocouple 1 shown, the opposite sides or ends are to be closed gastight according to the above discussion, so that the thermocouple and the electrical insulation are accommodated and enclosed gastight in the sheath housing 2.

[0069] FIG. 2 illustrates the basic manufacture of a sheathed thermocouple rod or a sheathed thermocouple sensor with steps a, b, c, and d.

[0070] According to step a, an assembly 9 having at least one sheath housing 2 with at least one thermocouple 3 and electrical insulation 4 therein is initially provided. The outer diameter or the interior space of the sheath housing 2 is selected in particular in such a way that a precise, desired arrangement of the thermocouple and electrical insulation therein is made possible. The opposite sides or ends are also closed airtight before they undergo a subsequent drawing process.

[0071] In step b, the assembly is subsequently drawn once or multiple times, resulting in a cross-sectional reduction that accordingly decreases the outer diameter and tapers the wall thickness. At the conclusion of step b, the ratio of the wall thickness 6 to the outer diameter 5 is still in a value range of 0.17 to 0.45. An annealing process may be carried out afterward or between multiple drawing processes.

[0072] According to step c, the assembly 9 may then be cut to length with the desired axial extension, so that a sheathed thermocouple rod is present.

[0073] After the cutting to length, the opposite (hot and cold) sides or ends may once again be machined and subsequently closed gastight as explained above.

[0074] Completion to form a functional sensor may take place in a further step d, for example by providing the mounting 13 for fixing the measuring probe and/or for connecting to a measurement evaluation unit, on one side of the sheathed thermocouple component. On the opposite side a cap 12 may be mounted at or on the sheathed thermocouple component to provide better protection for the measuring point.

[0075] Such a sheathed thermocouple is preferably used for determining a temperature in its hot, corrosive, optionally pressure-pulsing gas stream 10.

[0076] FIG. 3 shows another design of a sheathed thermocouple component 1. This design essentially corresponds to the disclosure in FIG. 1, to which reference is made in full. In this case, however, the sheath housing 2 is designed with two layers, namely, a (metallic) inner layer 14 and a (metallic) outer layer 15. The outer layer 15 completely covers the inner layer 14 for protection from the surroundings, at least in the area in which the sheathed thermocouple component is exposed to the medium whose temperature is to be monitored. This medium is preferably exhaust gas.

LIST OF REFERENCE NUMERALS

[0077] 1 sheathed thermocouple component

[0078] 2 sheath housing

[0079] 3 thermocouple

[0080] 4 insulation

[0081] 5 outer diameter

[0082] 6 wall thickness

[0083] 7 insulation distance

[0084] 8 sheathed thermocouple rod

[0085] 9 assembly

[0086] 10 gas stream

[0087] 11 wire diameter

[0088] 12 cap

[0089] 13 mounting

[0090] 14 inner layer

[0091] 15 outer layer