Thermocouple and method of making the thermocouple and of mounting the thermocouple on a heat exchanger tube

Claim 1

A thermocouple assembly for measuring the surface temperature of a fired heat exchanger tube comprising, a cold junction end having a temperature readout instrument and a hot junction end having a temperature sensing junction member, the ends being connected by sheathed thermocouple conductors, said sheathed thermocouple conductors including an elongated tubular metal sheath, a pair of spaced thermocouple conductors within said sheath, electrical insulating material spacing and supporting said conductors within the sheath in insulating relation from each other and from the sheath, said hot junction end being defined by a thermojunction tip, said tip including a face which the conductor ends, insulation and sheath are substantially coplanar, a junction member against the face and connected to said conductors and extending from the face of said sheath and spaced from the sheath to thermally isolate the junction member from the sheath when applied to the measured surface.

Claim 18

The method of making a thermocouple assembly from a bulk length of mineral oxide insulated metal sheathed thermocouple wires, wherein the length includes an elongated tubular metal sheath, a pair of spaced thermocouple conductors within said sheath, said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, forming a thermojunction tip on an end of said length including a metal sheath having a knife-shaped edge defining a diamond-shaped face in which an opening is provided having thermocouple conductors held in spaced relation from each other and from the sheath by an insulating member including the step of making and securing a junction member to said conductors which protrudes from said face but which is sized to allow the insulating member to be exposed between the junction member and the sheath.

Claim 19

The method of making a thermocouple assembly from a bulk length of mineral oxide insulated metal sheathed thermocouple wires, wherein the length includes an elongated tubular metal sheath, a pair of spaced thermocouple conductors within said sheath, said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, forming a thermojunction tip on an end of said length including a metal sheath having a knife-shaped edge defining a diamond-shaped face in which an opening is provided having thermocouple conductors held in spaced relation from each other and from the sheath by an insulating member including the step of making and securing a junction member to said conductors which protrudes from said face but which is sized to allow the insulating member to be exposed between the junction member and the sheath.

Claim 23

The method of making a thermocouple assembly from a bulk length of mineral oxide insulated metal sheathed thermocouple wires, wherein the length includes an elongated tubular metal sheath, a pair of spaced thermocouple wires within said sheath, and said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, forming a thermojunction tip on an end of said length defining a face where the sheath, insulation and wire ends are substantially coplanar, and securing a junction member across said wires and against the insulation but in spaced relation to the sheath so that the junction member protrudes from said face.

Claim 24

The method of making a thermocouple assembly from a bulk length of mineral oxide insulated metal sheathed thermocouple wires, wherein the length includes an elongated tubular metal sheath, a pair of spaced thermocouple wires within said sheath, and said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, forming a thermojunction tip on an end of said length defining a face where the sheath, insulation and wire ends are substantially coplanar, and securing a junction member across said wires and against the insulation but in spaced relation to the sheath so that the junction member protrudes from said face.

Claim 31

The method of mounting a thermocouple assembly on the fired surface of a heat exchanger tube, wherein the tube is externally subjected to high temperature gases and carries a fluid under pressure to be heated, and wherein the thermocouple assembly includes a cold junction end having a temperature readout instrument and a hot junction end having a temperature sensing junction member, the ends being connected by sheathed thermocouple conductors, said sheathed thermocouple conductors including an elongated tubular metal sheath, a pair of spaced thermocouple conductors within said sheath, electrical insulating material spacing and supporting said conductors within the sheath in insulating relation from each other and from the sheath, said hot junction end being defined by a thermojunction tip, said tip including a face in which the conductor ends, insulation and sheath are substantially coplanar, a junction member against the face and connected to said conductors and extending from the face of said sheath and spaced from the sheath to thermally isolate the junction member from the sheath when applied to the measured surface, which method comprises, the steps of positioning the thermojunction tip on the tube surface so that the outer face of the junction member mates with said tube surface and the face is in spaced relation thereto, and applying a plurality of weld passes between the periphery of the sheath and the tube to define a void-free and leakproof weldment to prevent contact between the gases and the conductors, the number of weld passes being such that the cross section of the weldment is greater than the cross section of the sheath wall to define an unimpeded heat transfer path between the sheath and the tube, whereby the natural shrinkage of the weldment pressurizes the junction member against the tube surface, the face is in spaced relation to the tube surface and the heat energy of the sheath goes through the weldment to the tube and bypasses the junction member.

Claim 32

The method of mounting a thermocouple assembly on the fired surface of a heat exchanger tube, wherein the tube is externally subjected to high temperature gases and carries a fluid under pressure to be heated, and wherein the thermocouple assembly includes a cold junction end having a temperature readout instrument and a hot junction end having a temperature sensing junction member, the ends being connected by sheathed thermocouple conductors, said sheathed thermocouple conductors including an elongated tubular metal sheath, a pair of spaced thermocouple conductors within said sheath, electrical insulating material spacing and supporting said conductors within the sheath in insulating relation from each other and from the sheath, said hot junction end being defined by a thermojunction tip, said tip including a face in which the conductor ends, insulation and sheath are substantially coplanar, a junction member against the face and connected to said conductors and extending from the face of said sheath and spaced from the sheath to thermally isolate the junction member from the sheath when applied to the measured surface, which method comprises, the steps of positioning the thermojunction tip on the tube surface so that the outer face of the junction member mates with said tube surface and the face is in spaced relation thereto, and applying a plurality of weld passes between the periphery of the sheath and the tube to define a void-free and leakproof weldment to prevent contact between the gases and the conductors, the number of weld passes being such that the cross section of the weldment is greater than the cross section of the sheath wall to define an unimpeded heat transfer path between the sheath and the tube, whereby the natural shrinkage of the weldment pressurizes the junction member against the tube surface, the face is in spaced relation to the tube surface and the heat energy of the sheath goes through the weldment to the tube and bypasses the junction member.

Claim 37

The method of mounting a thermocouple assembly on the fired surface of a heat exchanger tube, wherein the tube is externally subjected to high temperature gases and carries a fluid under pressure to be heated, and wherein the thermocouple assembly includes a bulk length of mineral oxide insulated metal sheathed thermocouple wires having an elongated tubular metal sheath, a pair of spaced thermocouple wires within said sheath, and said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, and a thermojunction tip formed on an end of said length defining a face where the sheath, insulation and wire ends are substantially coplanar, and a junction member against the insulation and connected to said wires but in spaced relation to the sheath so that the junction member protrudes from the face, which method comprises, the steps of positioning the thermojunction tip on the tube surface so that the outer face of the junction member mates with said tube surface and the face is in spaced relation thereto, and applying a plurality of weld passes between the periphery of the sheath and the tube to define a void-free and leakproof weldment to prevent contact between the gases and the conductors, the number of weld passes being such that the cross section of the weldment is greater than the cross section of the sheath wall, whereby the natural shrinkage of the weldment pressurizes the junction member against the tube surface, the face is in spaced relation to the tube surface and the heat energy of the sheath goes through the weldment to the tube and bypasses the junction member.

Claim 38

The method of mounting a thermocouple assembly on the fired surface of a heat exchanger tube, wherein the tube is externally subjected to high temperature gases and carries a fluid under pressure to be heated, and wherein the thermocouple assembly includes a bulk length of mineral oxide insulated metal sheathed thermocouple wires having an elongated tubular metal sheath, a pair of spaced thermocouple wires within said sheath, and said mineral oxide insulating material spacing and supporting said conductors within the sheath in electrical and thermal insulating relation from each other and from the sheath, and a thermojunction tip formed on an end of said length defining a face where the sheath, insulation and wire ends are substantially coplanar, and a junction member against the insulation and connected to said wires but in spaced relation to the sheath so that the junction member protrudes from the face, which method comprises, the steps of positioning the thermojunction tip on the tube surface so that the outer face of the junction member mates with said tube surface and the face is in spaced relation thereto, and applying a plurality of weld passes between the periphery of the sheath and the tube to define a void-free and leakproof weldment to prevent contact between the gases and the conductors, the number of weld passes being such that the cross section of the weldment is greater than the cross section of the sheath wall, whereby the natural shrinkage of the weldment pressurizes the junction member against the tube surface, the face is in spaced relation to the tube surface and the heat energy of the sheath goes through the weldment to the tube and bypasses the junction member.