Standard Active Last Updated: May 14, 2021
ASTM E608/E608M-13(2019)

Standard Specification for Mineral-Insulated, Metal-Sheathed Base Metal Thermocouples

Significance and Use

4.1 This specification describes the physical requirements of mineral-insulated, metal-sheathed base metal thermocouples and establishes suitable test criteria for their evaluation.

4.2 Standardized dimensional requirements and acceptable allowances for manufacturing variations, are given.

4.3 A set of standard tests to be applied to all thermocouples covered by this specification are described, in addition to optional tests from which applicable additional requirements may be selected.

4.4 Warning—Users should be aware that certain characteristics of thermocouples might change with time and use.

4.4.1 If a thermocouple's designed shipping, storage, installation, or operating temperature has been exceeded, the thermocouple’s moisture seal may have been compromised and may no longer prevent the deleterious intrusion of water vapor. Consequently, the thermocouple's condition established by test at the time of manufacture may not apply later after an extended period of use, and retesting may become necessary.

4.4.2 In addition, inhomogeneities can develop in thermoelements because of exposure to temperature, even in cases where the maximum exposure temperatures have been lower than the suggested upper temperature limits of Table 1. For this reason, calibration of thermocouples destined for delivery to a customer is not recommended (see S6.1).

4.4.3 Furthermore, because the EMF indication of any thermocouple depends upon the condition of the thermoelements along their entire length, as well as the temperature profile pattern in the region of any inhomogeneity, the EMF output of a used thermocouple will be unique to its installation. Because temperature profiles in calibration equipment are unlikely to duplicate those of the installation, removal of a used thermocouple to a separate apparatus for calibration is not recommended. Instead, in-situ calibration by comparison to a similar thermocouple of known accuracy is recommended.

Abstract

This specification covers the requirements for mineral-insulated, metal-sheathed base metal thermocouples for industrial or high-reliability applications. Provisions are made herein for selecting thermoelements, and insulation and sheath materials, and measuring junction configuration, thermocouple assembly length, and the type of transition or termination. This specification also includes provisions for quality assurance or verification program requirements, or both, as the purchaser's option.

Scope

1.1 This specification covers the requirements for mineral-insulated, metal-sheathed base metal thermocouples for industrial or high-reliability applications. It applies specifically to thermocouples fabricated from sheathed thermocouple material in accordance with Specification E585/E585M. The specification provides for the selection of thermoelements, insulation, sheath material, measuring junction configuration, thermocouple assembly length, and the type of transition or termination.

1.2 This specification also includes provisions for either quality assurance or verification program requirements, or both, as a purchaser’s option.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Details
Book of Standards Volume: 14.03
Developed by Subcommittee: E20.12
Pages: 8
DOI: 10.1520/E0608_E0608M-13R19
ICS Code: 17.200.20