Batteries: thermoelectric and photoelectric – Thermoelectric – Having housing – mounting or support
Patent
1988-05-19
1991-08-27
Nelson, Peter A.
Batteries: thermoelectric and photoelectric
Thermoelectric
Having housing, mounting or support
136234, 1362361, 136239, H01L 3502
Patent
active
050430238
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a mineral-insulated, metal-sheathed (MIMS) thermocouple cable, and to thermocouples made from such cable.
The manufacture of MIMS cable is well known. The components consist of a metallic sheath and two thermoelements (thermocouple conductors) insulated from each other, and the sheath, by a compacted ceramic-oxide-insulation material. The components are assembled under clean, dry conditions and by a process such as drawing, swaging or rolling, the sheath diameter is reduced to compact the ceramic and fill the available space. The assembly is further reduced in diameter to the desired size, an overall reduction in diameter of 10 to 1 being common. Before diameter reduction the assembly may be evacuated, annealed and or back-filled with an inert gas.
Thermocouples are temperature-measuring sensors. They are fabricated from MIMS cable by cutting to the required length, welding the thermoelements together at one end of the cable to form the `hot junction` and welding extension leads to the other. Insulating powder is packed in around the hot junction to avoid an air pocket in the completed product, and the MIMS section of the thermocouple is then sealed by welding in some sheathing alloy over the hot junction and, for example, providing a suitable potting compound at the other.
Conventional base-metal MIMS cables are produced with sheaths of inconel or stainless steel and with thermoelements of one of the five internationally-standardised thermocouple types (types E,J,K, N and T: letter designations of the Instrument Society of America).
Of the two types suitable for high-temperature use (types N and K) the type N alloys have well-defined compositions whereas those for the type K alloys are not defined. The main requirement for the positive and negative type K thermoelements is that, as a matched pair, the relationship between their net emf and temperature should agree with the relevant internationally-accepted reference equations (such as BS4937, ASTM E230) within defined limits of error.
The present invention is directed to providing an improved MIMS thermocouple cable, and to thermocouples made from such cable.
A thermocouple cable according to the invention has a positive and a negative thermoelement conforming to the standard emf-temperature specification for type K thermocouples, a sheath through which the thermocouples extend, and compacted ceramic insulating the thermoelements from each other and from the sheath; the sheath comprising an oxidation-resistant alloy having a thermal coefficient substantially the same as that of the negative thermoelement and a melting point in excess of 1300.degree. C.
The alloy of which the sheath is formed may be a nickel based alloy, although other alloys such as cobalt based alloys can be used. The nickel based alloy preferably is a nickel-chromium alloy, a particularly preferred alloy being one containing 13 to 15 wt. % chromium, 1 to 2 wt. % silicon with the balance most typically principally comprising nickel. The nickel-based alloy preferably contains substantially no manganese; while manganese, if present, should be less than 0.1 wt. %.
The nickel-based alloys for the sheath may contain elements such as magnesium to enhance their oxidation resistance, and refractory metals such as niobium, tungsten, tantalum or molybdenum to enhance physical properties of the sheath, such as its strength. Nicrosil (nominally 14.2 wt. % silicon and the balance essentially nickel) is an example of a suitable alloy for the sheath.
The positive and negative thermoelements are to be of alloys conforming to the standard emf-temperature specification of type K thermocouples. The thermoelements preferably are of respective alloys such that they conform to such specification to within .+-.0.75% of temperature, most preferably to within .+-.0.375% of temperature. The thermoelements should be of alloys meeting above 1300.degree. C.; the alloys preferably comprising nickel-based alloys. In the case of the positive thermoelement, the alloy preferably comprises 9 to 1
REFERENCES:
patent: 2691690 (1954-10-01), Poch et al.
patent: 2859264 (1958-11-01), Troy
patent: 2909428 (1959-10-01), Spooner et al.
patent: 3673003 (1972-06-01), Starr
patent: 3776781 (1973-12-01), Starr
patent: 3820983 (1974-06-01), Starr
patent: 3913058 (1975-10-01), Nishio et al.
patent: 3942242 (1976-03-01), Rizzolo
patent: 4018624 (1977-04-01), Rizzolo
patent: 4415758 (1983-11-01), Lacoste et al.
patent: 4492809 (1985-01-01), Dahlberg
patent: 4778537 (1988-10-01), Thom et al.
patent: 4834807 (1989-05-01), Burley
Metals Handbook, 9th Ed., vol. 3, pp. 700-703.
Burley et al., Advanced Instrum., vol. 3, 1978, pp. 209-219.
Wang et al., Advanced Instrum., vol. 3, 1978, pp. 235-254.
Bentley, Materials Australasia, Jul./Aug. 1986, pp. 16-18.
Bentley et al., Sci. Instrum., 1986, pp. 262-268.
Commonwealth Scientific and Industrial Research Organization
Nelson Peter A.
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