GB2110871A - Protecting tube for a thermocouple - Google Patents
Protecting tube for a thermocouple Download PDFInfo
- Publication number
- GB2110871A GB2110871A GB08136293A GB8136293A GB2110871A GB 2110871 A GB2110871 A GB 2110871A GB 08136293 A GB08136293 A GB 08136293A GB 8136293 A GB8136293 A GB 8136293A GB 2110871 A GB2110871 A GB 2110871A
- Authority
- GB
- United Kingdom
- Prior art keywords
- boron nitride
- protecting tube
- thermocouple
- shell
- platinum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910052582 BN Inorganic materials 0.000 claims abstract description 45
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 45
- 239000000919 ceramic Substances 0.000 claims abstract description 16
- 239000000463 material Substances 0.000 claims abstract description 15
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims abstract description 12
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000000843 powder Substances 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 10
- LTPBRCUWZOMYOC-UHFFFAOYSA-N Beryllium oxide Chemical compound O=[Be] LTPBRCUWZOMYOC-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 238000000465 moulding Methods 0.000 claims abstract description 7
- 238000005245 sintering Methods 0.000 claims abstract description 7
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 4
- 238000007731 hot pressing Methods 0.000 claims abstract description 4
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 4
- ZCUFMDLYAMJYST-UHFFFAOYSA-N thorium dioxide Chemical compound O=[Th]=O ZCUFMDLYAMJYST-UHFFFAOYSA-N 0.000 claims abstract description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 34
- 229910052697 platinum Inorganic materials 0.000 claims description 16
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 claims description 12
- 239000011230 binding agent Substances 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 6
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 claims description 5
- 229910001006 Constantan Inorganic materials 0.000 claims description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 4
- 238000005452 bending Methods 0.000 claims description 4
- 230000015556 catabolic process Effects 0.000 claims description 4
- 230000007797 corrosion Effects 0.000 claims description 4
- 238000005260 corrosion Methods 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 150000002739 metals Chemical class 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 238000004901 spalling Methods 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- 238000010574 gas phase reaction Methods 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 claims description 3
- 229910000809 Alumel Inorganic materials 0.000 claims description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 2
- 230000002411 adverse Effects 0.000 claims description 2
- 239000004411 aluminium Substances 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 claims description 2
- 229940001007 aluminium phosphate Drugs 0.000 claims description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 2
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 2
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 2
- 239000008119 colloidal silica Substances 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 claims description 2
- 229910052749 magnesium Inorganic materials 0.000 claims description 2
- 239000000395 magnesium oxide Substances 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 239000011733 molybdenum Substances 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 229910052703 rhodium Inorganic materials 0.000 claims description 2
- 239000010948 rhodium Substances 0.000 claims description 2
- 230000035939 shock Effects 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 239000004332 silver Substances 0.000 claims description 2
- 229910052725 zinc Inorganic materials 0.000 claims description 2
- 239000011701 zinc Substances 0.000 claims description 2
- 230000008021 deposition Effects 0.000 abstract 1
- 238000000151 deposition Methods 0.000 abstract 1
- 238000003754 machining Methods 0.000 abstract 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
- G01K1/08—Protective devices, e.g. casings
- G01K1/12—Protective devices, e.g. casings for preventing damage due to heat overloading
- G01K1/125—Protective devices, e.g. casings for preventing damage due to heat overloading for siderurgical use
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
A protecting tube 10 for a thermocouple 3 comprises a shell 1 of boron nitride and a liner 2 of ceramics material. The ceramics material may be alumina, beryllia, silicon nitride, zirconia, silica, thoria, ythria or a mixture of two or more thereof. The liner may be formed by sintering or hot pressing ceramics powder, and the shell by moulding and machining, or deposition from gas. <IMAGE>
Description
SPECIFICATION
Protecting tube for a thermocouple
The invention relates to a protecting tube for a thermocouple used for measuring the temperature of very hot gases or molten metal.
Boron nitride withstands extremely high temperatures and has excellent resistance to thermal shock.
These properties make it a suitable material for protecting tubes for thermocouples, and it has found wide application in this sphere. Protecting tubes of boron nitride containing a thermocouple have been employed to measure high gas temperatures for example of helium or carbon monooxide, and temperatures of molten metals such as copper, silver, magnesium, zinc, aluminium or iron. Boron nitride is advantageous in that it does not react with such molten metal. However, the known boron nitride protecting tube has the disadvantage that boron nitride reacts with platinum, leading to breakdown of the platinum wire when boron nitride is used for the protecting tube for a platinum/platinumrhodium thermocouple. As a result, the lifetime of the platinum/platinum-rhodium thermocouple is shortened.
Although thermocouple protecting tubes made of alumina having a purity of not less than 99.5% or a composition mainly composed of molybdenum or zirconia are known, these materials are not so satisfactory for protecting tubes in that they are adversely affected by a change in temperature and often damaged or broken thereby.
The protecting tube for a thermocouple provided in accordance with this invention comprises a shell of boron nitride and a liner of ceramics material.
The boron nitride shell is preferably prepared by moulding boron nitride powders at a temperature above 1 500 C under a pressure of from 100 to 500 kg/cm2 to form a moulded block of hot-pressed boron nitride, cutting a rod having desired dimensions and shape from the moulded block, and boring the rod to form a tube. Atube having a bending strength of from about 600 to 1000 kg/cm2 can be prepared in this manner. However, the boron nitride shell may be prepared by other processes.For example, a moulded block may be prepared by mixing boron nitride powder with an inorganic binder, such aluminium phosphate or colloidal silica, or with an organic binder, such as polyvinyl alcohol or carboxymethyl cellulose, followed by moulding and then sintering under atmospheric pressure at a temperature above 1000 C, preferably above 150000.
The tube may be prepared through cutting and boring operations similar to the steps described above. Although the tube so prepared has a bending strength of about 100 kg/cm2, it may be satisfactorily used under conditions where the required strength is not so high. Otherwise, the shell may be prepared by applying a layer of boron nitride over the periphery of a core made of graphite by reacting boron trichloride and ammonia by gas phase reaction, and removing the core.
Irrespective of whether the shell is prepared by any of the aforementioned methods, it is desirable that the boron nitride constituting the shell has a density of 1.7 to 2.2 g/cm3, more preferably 1.75 to 1.85 g/cm3. The tube should desirably have good qualities of both spalling resistance and corrosion resistance, but these properties are generally contray to each other. That is, if the spalling resistance is improved, then the corrosion resistance becomes lower and vice versa. It has now been found that these two contrary properties are closely related to the density of the boron nitride used and that the two properties can be well balanced by controlling the density of boron nitride within the range above defined.
Suitable ceramics materials for the liner include alumina, beryllia, silicon nitride, zirconia, silica, thoria, yttria and mixtures of two or more thereof.
Alumina has the best properties, and is thus preferred. The liner may be prepared by sintering or hot-pressing ceramics powders with or without a binder, such as low melting point magnesia, yttria or alumina, under a pressure of from 50 to 500 kg/cm2 at a temperature above 1000"C, preferably above 1500"C. It is desirable that the shell and liner be closely contacted with each other in order to measure the temperature more precisely.
The protecting tube according to the invention may be used for the protection of a platinum/ piatinum-rhodium thermocouple, without breakdown ofthe platinum/platinum-rhodium wire as otherwise occurs when a conventional protecting tube made merely of boron nitride is used. A platinum/platinum-rhodium thermocouple protected by the protecting tube according to the invention can be repeatedly used for more than 200 times to measure the temperature of molten metals or the temperature in furnaces.
Although the protecting tube of the invention has been developed for platinum/platinum-rhodium thermocouples, it is also useful with other types of thermocouples, such as chromel-alumel, iron
Constantan and copper-Constantan thermocouples.
The invention is illustrated by the drawing, which is a diagrammatical sectional view, partly broken away, of a preferred embodiment of a protecting tube for a thermocouple according to this invention.
Referring to the drawing, a protecting tube generally denoted by reference numeral 10 comprises a shell 1 of boron nitride, and a liner 2 of ceramics material mounted in contact with the shell 1. A platinum/platinum-rhodium thermocouple 3 fitted with alumina tubes 4 is loosely inserted into the liner 2, and at the end 5 of the shell 1 the thermocouple 3 is connected, by coupling means such as a bolt-andnut unit, with terminals fixedly mounted at the open end of the protecting tube 10.
1. A protecting tube for a thermocouple, the protecting tube comprising a shell of boron nitride and a liner of ceramics material.
2. A protecting tube according to claim 1 wherein the boron nitride has a density of 1.7 to 2.2 g/cm3.
3. A protecting tube according to claim 1 or claim 2 wherein the shell is formed by moulding boron
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (9)
1. A protecting tube for a thermocouple, the protecting tube comprising a shell of boron nitride and a liner of ceramics material.
2. A protecting tube according to claim 1 wherein the boron nitride has a density of 1.7 to 2.2 g/cm3.
3. A protecting tube according to claim 1 or claim 2 wherein the shell is formed by moulding boron nitride powders at a temperature above 1 500"C under a pressure of from 100 to 500 kg/cm2 to form a moulded block of boron nitride, cutting a rod having desired dimensions and shape from the block, and boring the rod to form a cylinder.
4. A protecting tube according to claim 1 or claim 2 wherein the shell is formed by filling a mixture of boron nitride powders and binder powders in a mould, sintering the mixture at a temperature above 1500"C under atmospheric pressure to form a sintered body having a desired shape, and boring to form a cylinder.
5. A protecting tube according to claim 1 or claim 2 wherein the shell is formed by applying a layer of boron nitride over the periphery of a core made of graphite by reacting boron trichloride and ammonia by gas phase reaction, and removing the core.
6. A protecting tube according to any preceding claim wherein the ceramics material is alumina, beryllia, silicon nitride, zirconia, silica, thoria, yttria or a mixture of two or more thereof.
7. A protecting tube according to any preceding claim wherein the liner is formed by sintering ceramics powders with or without a binder at a temperature above 1000"C under a pressure of from 50 to 500 kg/cm2.
8. A protecting tube according to any of claims 1 to 6 wherein the liner is formed by hot-pressing ceramics powders with or without a binder at a temperature above 1000"C under a pressure of from 50 to 500 kg/cm2.
9. A protecting tube for a thermocouple, the protecting tube being substantially as described herein with reference to the drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08136293A GB2110871B (en) | 1981-12-02 | 1981-12-02 | Protecting tube for a thermocouple |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08136293A GB2110871B (en) | 1981-12-02 | 1981-12-02 | Protecting tube for a thermocouple |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2110871A true GB2110871A (en) | 1983-06-22 |
| GB2110871B GB2110871B (en) | 1985-09-18 |
Family
ID=10526316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08136293A Expired GB2110871B (en) | 1981-12-02 | 1981-12-02 | Protecting tube for a thermocouple |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2110871B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20170140902A1 (en) * | 2015-11-16 | 2017-05-18 | Coorstek, Inc. | Corrosion-resistant components and methods of making |
-
1981
- 1981-12-02 GB GB08136293A patent/GB2110871B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20170140902A1 (en) * | 2015-11-16 | 2017-05-18 | Coorstek, Inc. | Corrosion-resistant components and methods of making |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2110871B (en) | 1985-09-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |