ASTM E780-17

Standard Test Method for Measuring the Insulation Resistance of Mineral-Insulated, Metal-Sheathed Thermocouples and Mineral-Insulated, Metal-Sheathed Cable at Room Temperature

SIGNIFICANCE AND USE
5.1 Thermocouples fabricated from thermocouple cable that has been contaminated by moisture or by other impurities may undergo large changes in thermoelectric properties or may fail catastrophically when exposed to high temperatures. Since such contamination usually lowers the electrical resistance between the thermoelements and the sheath substantially, measurement of the insulation resistance can provide a valuable check of insulation quality and cleanliness, and can serve as a basis for rejection of unsuitable material and unreliable components. For manufacturers in particular, low electrical insulation resistance can also be indicative of displaced thermoelements or conductors or defects in the metal sheath which will require further investigation, but all users should be aware of these potential defects when faced with an unacceptable insulation resistance measurement.  
5.2 This test method is primarily intended for use by manufacturers and users of mineral-insulated, metal-sheathed (MIMS) thermocouples or MIMS cables to verify that measured values of insulation resistance exceed specified minimum values, such as those listed in Specifications E235, E585/E585M, E608/E608M, E2181/E2181M, and E2821. Manufacturers and users should be aware, however, that when the insulation resistance is greater than 1 × 108 Ω, disagreement by an order of magnitude in the results obtained with this test method is not unusual. In addition, users of this test method should appreciate that the room temperature insulation resistance of both MIMS cables and of finished thermocouples will change during shipment, storage, and use if the end seals are damaged or defective. Consequently, values of insulation resistance determined by this test method may not necessarily be repeatable.
SCOPE
1.1 This test method provides the procedures for measuring the room temperature electrical insulation resistance between the thermoelements and between the thermoelements and the sheath, of a mineral-insulated, metal-sheathed (MIMS) thermocouple or mineral-insulated, metal-sheathed (MIMS) thermocouple cable or between the conductors and between the conductors and the sheath, of mineral-insulated, metal-sheathed (MIMS) cable used for industrial resistance thermometers. It may be used to measure the insulation resistance of bulk lengths of mineral-insulated, metal-sheathed MIMS cable previously sealed against moisture intrusion or to test a thermocouple having an ungrounded measuring junction. This method cannot be used to test a thermocouple having a grounded measuring junction unless the measuring junction is removed prior to testing, after which the thermocouple may be dealt with in the same manner as a mineral-insulated, metal-sheathed (MIMS) cable.  
1.2 This test method applies primarily to thermocouple cables and cable used for industrial resistance thermometers conforming to Specifications E585/E585M, E2181/E2181M, and E2821 and to thermocouples conforming to Specifications E608/E608M and E2181/E2181M, but may also be applied to thermocouples or MIMS cables that are suitable for use in air, whose sheath or thermoelements or conductors are comprised of refractory metals, that are tested in a dry and chemically inert environment, and that may employ compacted ceramic insulating materials other than magnesia (MgO) or alumina (Al2O3). Users of this test method should note that specifications dealing with compacted ceramic insulating materials other than magnesia or alumina, which are described in Specification E1652, are not currently available. As a result, acceptance criteria must be agreed upon between the customer and supplier at the time of purchase, or alternatively, judgment and experience must be applied in establishing test voltage levels and acceptable insulation resistance values for these types of thermocouples and MIMS cables.  
1.3 This test method may be used for thermocouples or MIMS cables having an outside...

General Information

• Status: Historical
• Publication Date: 14-Jan-2017
• ICS: 17.200.20 - Temperature-measuring instruments
• Technical Committee: E20 - Temperature Measurement
• Drafting Committee: E20.14 - Thermocouples - Testing

Standards Content (Sample)

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: E780 − 17 An American National Standard
Standard Test Method for
Measuring the Insulation Resistance of Mineral-Insulated,
Metal-Sheathed Thermocouples and Mineral-Insulated,
1
Metal-Sheathed Cable at Room Temperature
This standard is issued under the fixed designation E780; 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.
1. Scope and experience must be applied in establishing test voltage
levels and acceptable insulation resistance values for these
1.1 This test method provides the procedures for measuring
types of thermocouples and MIMS cables.
the room temperature electrical insulation resistance between
the thermoelements and between the thermoelements and the 1.3 This test method may be used for thermocouples or
sheath, of a mineral-insulated, metal-sheathed (MIMS) ther- MIMScableshavinganoutsidediameterof0.5mm(0.020in.)
mocouple or mineral-insulated, metal-sheathed (MIMS) ther- or larger.
mocouple cable or between the conductors and between the
1.4 Users of this test method should be aware that the room
conductors and the sheath, of mineral-insulated, metal-
temperatureinsulationresistanceofamineral-insulated,metal-
sheathed(MIMS)cableusedforindustrialresistancethermom-
sheathed thermocouple or MIMS cable will change during
eters. It may be used to measure the insulation resistance of
shipment, storage, or use if they are not properly sealed.
bulk lengths of mineral-insulated, metal-sheathed MIMS cable
1.5 The values stated in SI units are to be regarded as
previously sealed against moisture intrusion or to test a
standard. The values given in parentheses are for information
thermocouple having an ungrounded measuring junction. This
only.
method cannot be used to test a thermocouple having a
1.6 This standard does not purport to address all of the
grounded measuring junction unless the measuring junction is
removed prior to testing, after which the thermocouple may be safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
dealt with in the same manner as a mineral-insulated, metal-
sheathed (MIMS) cable. priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.2 This test method applies primarily to thermocouple
1.7 This international standard was developed in accor-
cables and cable used for industrial resistance thermometers
dance with internationally recognized principles on standard-
conforming to Specifications E585/E585M, E2181/E2181M,
ization established in the Decision on Principles for the
and E2821 and to thermocouples conforming to Specifications
Development of International Standards, Guides and Recom-
E608/E608M and E2181/E2181M, but may also be applied to
mendations issued by the World Trade Organization Technical
thermocouples or MIMS cables that are suitable for use in air,
Barriers to Trade (TBT) Committee.
whose sheath or thermoelements or conductors are comprised
of refractory metals, that are tested in a dry and chemically
2. Referenced Documents
inert environment, and that may employ compacted ceramic
2
2.1 ASTM Standards:
insulating materials other than magnesia (MgO) or alumina
E235 Specification for Type K and Type N Mineral-
(Al O ). Users of this test method should note that specifica-
2 3
Insulated, Metal-Sheathed Thermocouples for Nuclear or
tions dealing with compacted ceramic insulating materials
for Other High-Reliability Applications
other than magnesia or alumina, which are described in
E344Terminology Relating to Thermometry and Hydrom-
Specification E1652, are not currently available. As a result,
etry
acceptance criteria must be agreed upon between the customer
E585/E585M Specification for Compacted Mineral-
and supplier at the time of purchase, or alternatively, judgment
Insulated, Metal-Sheathed, Base Metal Thermocouple
Cable
1
This test method is under the jurisdiction of ASTM Committee E20 on
Temperature Measurement and is the direct responsibility of Subcommittee E20.14
2
on Thermocouples - Testing. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 15, 2017. Published March 2017. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1992. Last previous edition approved in 2011 as E780–06(2011). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E0780-17. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E780 − 06 (Reapproved 2011) E780 − 17
Standard Test Method for
Measuring the Insulation Resistance of Mineral-Insulated,
Metal-Sheathed Thermocouples and Thermocouple Mineral-
1
Insulated, Metal-Sheathed Cable at Room Temperature
This standard is issued under the fixed designation E780; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method provides the procedures for measuring the room temperature electrical insulation resistance between the
thermoelements,thermoelements and between the thermoelements and the sheath, of a mineral-insulated, metal-sheathed (MIMS)
thermocouple or thermocouple cable. mineral-insulated, metal-sheathed (MIMS) thermocouple cable or between the conductors
and between the conductors and the sheath, of mineral-insulated, metal-sheathed (MIMS) cable used for industrial resistance
thermometers. It may be used to measure the insulation resistance of bulk lengths of thermocouple mineral-insulated,
metal-sheathed MIMS cable previously sealed against moisture intrusion or to test a thermocouple having an ungrounded class 2
measuring junction. This method cannot be used to test a thermocouple having a grounded class 1 measuring junction unless the
measuring junction is removed prior to testing, after which the thermocouple may be dealt with in the same manner as a
thermocouple mineral-insulated, metal-sheathed (MIMS) cable.
1.2 This test method applies primarily to thermocouple cables and cable used for industrial resistance thermometers conforming
to Specifications E585/E585M and , E2181/E2181M, and E2821 and to thermocouples conforming to Specifications E608/E608M
and E2181/E2181M, but may also be applied to thermocouples or thermocoupleMIMS cables that are suitable for use in air, whose
sheath or thermoelements or conductors are comprised of refractory metals, that are tested in a dry and chemically inert
environment, and that may employ compacted ceramic insulating materials other than magnesia (MgO) or alumina (Al O ). Users
2 3
of this test method should note that specifications dealing with compacted ceramic insulating materials other than magnesia or
alumina, which are described in Specification E1652, are not currently available. As a result, acceptance criteria must be agreed
upon between the customer and supplier at the time of purchase, or alternatively, judgment and experience must be applied in
establishing test voltage levels and acceptable insulation resistance values for these types of thermocouples and thermocou-
pleMIMS cables.
1.3 This test method may be used for thermocouples or thermocoupleMIMS cables having an outside diameter of 0.5 mm (0.020
in) (0.020 in.) or larger.
1.4 Users of this test method should be aware that the room temperature insulation resistance of a mineral-insulated,
metal-sheathed thermocouple or thermocoupleMIMS cable maywill change during shipment, storage, or use.use if they are not
properly sealed.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.6 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.
2. Referenced Documents
2
2.1 ASTM Standards:
E235 Specification for Thermocouples, Sheathed, Type K and Type N, for Nuclear or for Other High-Reliability Applications
E344 Terminology Relating to Thermometry and Hydrometry
1
This test method 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 May 1, 2011Jan. 15, 2017. Published May 2011March 2017. Originally approved in 1992. Last previous edition approved in 20062011 as
E780 – 06.E780 – 06 (2011). DOI: 10.1520/E0780-06R11.10.1520/E0780-17.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
...