ASTM E608/E608M-13
Standard Specification for Mineral-Insulated, Metal-Sheathed Base Metal Thermocouples

Standard No.
ASTM E608/E608M-13
Release Date
2013
Published By
American Society for Testing and Materials (ASTM)
Status
Replace By
ASTM E608/E608M-13(2019)
Latest
ASTM E608/E608M-13(2019)
Scope

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).

TABLE 1 Suggested Upper Temperature Limits for Sheathed Thermocouples
Note 1—This 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 2—The 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.