Standard Specification for Thermocouples, Sheathed, Type K and Type N, for Nuclear or for Other High-Reliability Applications

ABSTRACT
This specification covers the requirements for sheathed, Type K and N thermocouples for nuclear service. This specification can be used for sheathed thermocouples which are required for laboratory or general commercial applications where the environmental conditions exceed normal service requirements. The measuring junction styles for thermocouples are as follows: Style G2 (grounded) in which measuring junction is electrically connected to conductive sheaths and Style U2 (ungrounded) in which measuring junctions are electrically isolated from conductive sheaths and from reference ground. Different properties of the sheath such as integrity, cracks, voids, inclusions, surface finish, surface defect, and metallurgical structure shall be determined by performing different tests. Insulation resistance between thermoelements and the sheath shall be measured as well.
SCOPE
1.1 This specification covers the requirements for sheathed, Type K and N thermocouples for nuclear service. Depending on size, these thermocouples are normally suitable for operating temperatures to 1652 °F (900 °C); special conditions of environment and life expectancy may permit their use at temperatures in excess of 2012 °F (1100 °C). This specification was prepared specifically to detail requirements for using this type of sheathed thermocouple in nuclear environments. This specification can be used for sheathed thermocouples which are required for laboratory or general commercial applications where the environmental conditions exceed normal service requirements. The intended use of a sheathed thermocouple in a specific nuclear application will require evaluation by the purchaser of the compatibility of the thermocouple, including the effect of the temperature, atmosphere, and integrated neutron flux on the materials and accuracy of the thermoelements in the proposed application. This specification does not attempt to include all possible specifications, standards, etc., for materials that may be used as sheathing, insulation, and thermocouple wires for sheathed-type construction. The requirements of this specification include only the austenitic stainless steels and other alloys as allowed with Specification E 585/E 585M for sheathing, magnesium oxide or aluminum oxide as insulation, and Type K and N thermocouple wires for thermoelements (see Note 1).
1.2 General Design Nominal sizes of the finished thermocouples shall be 0.0400 in. (1.016 mm), 0.0625 in. (1.588 mm), 0.125 in. (3.175 mm), 0.1875 in. (4.763 mm), or 0.250 in. (6.350 mm). Sheath dimensions and tolerances for each nominal size shall be in accordance with and . The measuring junction styles for thermocouples covered by this specification are as follows:
1.2.1 Style G (grounded) Measuring junction electrically connected to conductive sheaths, and
1.2.2 Style U (ungrounded) Measuring junctions are electrically isolated from conductive sheaths and from reference ground.
1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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Publication Date
31-Oct-2006
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ASTM E235-06 - Standard Specification for Thermocouples, Sheathed, Type K and Type N, for Nuclear or for Other High-Reliability Applications
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E235 – 06
Standard Specification for
Thermocouples, Sheathed, Type K and Type N, for Nuclear
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or for Other High-Reliability Applications
This standard is issued under the fixed designation E235; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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1. Scope 1.2.2 Style U (ungrounded)—Measuringjunctionsareelec-
trically isolated from conductive sheaths and from reference
1.1 This specification covers the requirements for sheathed,
ground.
Type K and N thermocouples for nuclear service. Depending
1.3 Thevaluesstatedininch-poundunitsaretoberegarded
on size, these thermocouples are normally suitable for operat-
as the standard. The values given in parentheses are for
ing temperatures to 1652 °F (900 °C); special conditions of
information only.
environment and life expectancy may permit their use at
1.4 This standard does not purport to address all of the
temperaturesinexcessof2012°F(1100°C).Thisspecification
safety concerns, if any, associated with its use. It is the
was prepared specifically to detail requirements for using this
responsibility of the user of this standard to establish appro-
type of sheathed thermocouple in nuclear environments. This
priate safety and health practices and determine the applica-
specificationcanbeusedforsheathedthermocoupleswhichare
bility of regulatory limitations prior to use.
required for laboratory or general commercial applications
where the environmental conditions exceed normal service
2. Referenced Documents
requirements. The intended use of a sheathed thermocouple in
3
2.1 ASTM Standards:
a specific nuclear application will require evaluation by the
A262 Practices for Detecting Susceptibility to Intergranular
purchaser of the compatibility of the thermocouple, including
Attack in Austenitic Stainless Steels
the effect of the temperature, atmosphere, and integrated
E3 Guide for Preparation of Metallographic Specimens
neutron flux on the materials and accuracy of the thermoele-
E45 TestMethodsforDeterminingtheInclusionContentof
ments in the proposed application. This specification does not
Steel
attempt to include all possible specifications, standards, etc.,
E94 Guide for Radiographic Examination
for materials that may be used as sheathing, insulation, and
E112 Test Methods for Determining Average Grain Size
thermocouple wires for sheathed-type construction. The re-
E165 PracticeforLiquidPenetrantExaminationforGeneral
quirements of this specification include only the austenitic
Industry
stainless steels and other alloys as allowed with Specification
E220 Test Method for Calibration of Thermocouples By
E585/E585M for sheathing, magnesium oxide or aluminum
Comparison Techniques
oxide as insulation, and Type K and N thermocouple wires for
E230 Specification and Temperature-Electromotive Force
thermoelements (see Note 1).
(EMF) Tables for Standardized Thermocouples
1.2 General Design—Nominalsizesofthefinishedthermo-
E344 Terminology Relating to Thermometry and Hydrom-
couplesshallbe0.0400in.(1.016mm),0.0625in.(1.588mm),
etry
0.125 in. (3.175 mm), 0.1875 in. (4.763 mm), or 0.250 in.
E585/E585M Specification for Compacted Mineral-
(6.350 mm). Sheath dimensions and tolerances for each nomi-
Insulated, Metal-Sheathed, Base Metal Thermocouple
nal size shall be in accordance with Table 1 and Figs. 1 and 2.
Cable
The measuring junction styles for thermocouples covered by
E780 Test Method for Measuring the Insulation Resistance
this specification are as follows:
2 of Mineral-Insulated, Metal-Sheathed Thermocouples and
1.2.1 Style G (grounded)—Measuring junction electrically
Thermocouple Cable at Room Temperature
connected to conductive sheaths, and
E839 Test Methods for Sheathed Thermocouples and
Sheathed Thermocouple Material
1
E883 Guide for Reflected−Light Photomicrography
This specification is under the jurisdiction of ASTM Committee E20 on
Temperature Measurement and is the direct responsibility of Subcommittee E20.04
on Thermocouples.
Current edition approved Nov. 1, 2006. Published November 2006. Originally
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approved in 1964. Last previous edition approved in 2003 as E235–03. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/E0235-06. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
2
Style G and Style U measuring junctions were previously termed Class 1 and Standards volume information, refer to the standard’s Document Summary page on
Class 2 measuring junctions respectively. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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