ASTM E608 / E608M - 13

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

    Active Standard ASTM E608 / E608M | Developed by Subcommittee: E20.04

    Book of Standards Volume: 14.03

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    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.

    This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

    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).

    Note 1This table gives the suggested upper temperature limits for the various thermocouples in several common sheath sizes. It does not take into account environmental temperature limitations of the sheath material itself, nor does it address compatibility considerations between the thermoelement materials and the sheath containing them. The actual maximum practical temperature in a particular situation will generally be limited to the lowest temperature among the several factors involved. The purchaser should consult ASTM Manual 125 and other literature sources for further information about applications.
    Note 2The temperature limits given here are intended only as a guide to the purchaser and should not be taken as absolute values nor as guarantees of satisfactory life or performance. These types and sizes are sometimes used at temperatures above the given limits, but usually at the expense of stability or service life, or both. In other instances, it may be necessary to reduce the given limits in order to achieve adequate service.

    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.

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

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E165 Practice for Liquid Penetrant Examination for General Industry

    E220 Test Method for Calibration of Thermocouples By Comparison Techniques

    E230 Specification and Temperature-Electromotive Force (EMF) Tables for Standardized Thermocouples

    E344 Terminology Relating to Thermometry and Hydrometry

    E585/E585M Specification for Compacted Mineral-Insulated, Metal-Sheathed, Base Metal Thermocouple Cable

    E780 Test Method for Measuring the Insulation Resistance of Mineral-Insulated, Metal-Sheathed Thermocouples and Thermocouple Cable at Room Temperature

    E839 Test Methods for Sheathed Thermocouples and Sheathed Thermocouple Cable

    AWS Standards

    A5.14 Specification for Nickel and Nickel-Alloy Bare Welding Rods and Electrodes

    A5.9 Specification for Corrosion-Resisting Chromium and Chromium-Nickel Steel Welding Rods and Bare Electrodes

    ICS Code

    ICS Number Code 17.200.20 (Temperature-measuring instruments)

    UNSPSC Code

    UNSPSC Code

    DOI: 10.1520/E0608_E0608M

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