ASTM E574-23

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: E574 − 19 E574 − 23 An American National Standard
Standard Specification for
Duplex, Base Metal Thermocouple Wire With Glass Fiber or
Silica Fiber Insulation
This standard is issued under the fixed designation E574; 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 specification sets forth the requirements for duplex, types E, J, K, N and T thermocouple wire, insulated with E-glass,
S-glass, amorphous silica fiber or polycrystalline fiber.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 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.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
E207 Test Method for Thermal EMF Test of Single Thermoelement Materials by Comparison With Reference Thermoelement
of Similar EMF-Temperature Properties
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E230/E230M Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
E344 Terminology Relating to Thermometry and Hydrometry
3. Terminology
3.1 Definitions—The definitions given in Terminology E344 shall apply to this standard.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 amorphous silica fiber, n—continuous filament of heat-insulating material whose principal constituent is amorphous silica.
3.2.2 duplex wire, n—matched pair of parallel, solid thermoelements, individually insulated (double wrap or braid) with insulating
fibers and a fiber braid of the same material overall.
This specification is under the jurisdiction of ASTM Committee E20 on Temperature Measurement and is the direct responsibility of Subcommittee E20.12 on
Thermocouples - Specifications.
Current edition approved May 1, 2019May 1, 2023. Published June 2019May 2023. Originally approved in 1976. Last previous edition approved in 20132019 as
E574 – 13.E574 – 19. DOI: 10.1520/E0574-19. 10.1520/E0574-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. 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 Conshohocken, PA 19428-2959. United States
E574 − 23
3.2.3 E-glass, n—family of calcia-alumina-silicate glasses that are used for general purposes and most electrical applications.
3.2.4 impregnate, v—to saturate the fiber insulation of wires with a high-temperature electrical insulating compound to form a
moisture barrier around the wires and to inhibit fraying of the fibers.
3.2.5 polycrystalline fiber, n—continuous polycrystalline filament of heat-insulating material whose composition is alumina, boria,
and silica in an approximate ratio of 3:1:2, respectively.
3.2.6 S-glass, n—family of magnesia-alumina-silicate glasses with a higher tensile strength and higher softening temperature than
E-glass.
4. Significance and Use
4.1 This specification presents the requirements for impregnated and non-impregnated fiber-insulated thermocouple wire for
normally accepted industrial use, but does not attempt to define such usage.
4.2 A supplement contains the requirements for insulated thermocouple wire that will be exposed to high humidity. The purchase
order or inquiry shall specify if the requirements in this supplement are required.
5. Classification
5.1 Class A–Duplex—E-glass fiber insulated, impregnated with a high-temperature electrical insulating compound and color-
coded in accordance with Specification E230/E230M.
5.2 Class B–Duplex—E-glass fiber insulated (Note 1) not impregnated and not color-coded.
5.3 Class C–Duplex—Amorphous silica fiber insulated (Note 2) not impregnated and not color-coded.
5.4 Class D–Duplex—Polycrystalline fiber insulated (Notes 2 and 3) not impregnated and not color-coded.
5.5 Class E–Duplex—S-glass fiber insulated, impregnated with a high-temperature electrical insulating compound and color-
coded in accordance with Specification E230/E230M.
5.6 Class F–Duplex—S-glass fiber insulated (Note 1) not impregnated and not color-coded.
NOTE 1—May be heat treated to retard fraying when specified in the ordering information (6.1.8).
NOTE 2—Fibers may be pre-treated with an organic compound to facilitate braiding.
NOTE 3—May be heat cleanedthermally processed after braiding to remove organic compound when specified in the ordering information (6.1.8).
6. Ordering Information
6.1 The purchase order shall specify the following information:
6.1.1 Total insulated wire length,
6.1.2 Thermocouple type,
6.1.3 Tolerance on initial values of emf versus temperature (standard or special),
6.1.4 Class of insulation (see Section 5);
6.1.5 Thermoelement diameter (see 7.1.2);
E574 − 23
6.1.6 Minimum acceptable continuous length per spool, if applicable;
6.1.7 Supplementary testing, if required (see Supplementary Requirements);
6.1.8 Special requirements (if any);
6.1.9 Deviations or special requirements not covered herein; and
6.1.10 Required documentation (see Section 9).
7. Technical Requirements
7.1 Insulated Thermocouple Wire:
7.1.1 Materials—Thermoelements shall be solid thermocouple grade materials with a smooth, bright finish (Note 4) and shall be
fully annealed prior to insulating.
NOTE 4—An optional copper-flash coating on the iron thermoelement for type J thermocouple material is permitted to prevent rusting. This coating must
be applied uniformly so that the final calibration tolerance requirement for the specific insulating material is still met.
7.1.2 Sizes—Thermoelements shall be specified in American Wire Gauge (AWG) nomenclature. Corresponding thermoelement
diameters shall be as listed in Table 1.
7.1.3 Calibration:
7.1.3.1 Standard Method—When required by the purchase order, calibration of the insulated thermocouple wire shall be performed
by one of the procedures described in Test Method E207 or E220.
7.1.3.2 Thermoelement Initial Calibration Tolerances —Standard and special tolerances on initial values of emf versus
temperature are given in Table 1 of Specification E230/E230M. The purchase order shall specify whether standard or special
tolerances are required.
7.2 Insulation Materials:
7.2.1 Individual thermoelements shall be covered with a braid, or double wrap (one wrap in each direction) of glass fibers (Classes
A and E), a braid of glass fibers (Classes B and F), or braid of fibers (Classes C and D).
7.2.2 The outer covering shall consist of a braid of the same material applied over the bare thermoelements.
7.2.3 For Classes A and E duplex thermoelements, the insulation on the individual thermoelements and the outer braid shall be
impregnated with a moisture and heat-resistant electrical insulating compound. The fibers shall be bonded sufficiently to each other
to prevent fraying under normal conditions of installation and service.
TABLE 1 Maximum Outside Transverse Dimensions of Insulated
Wire
Uninsulated Thermoelement Maximum Outside Dimensions
Diameter
Gage Nominal Classes A, B, E and
Classes C and D
(AWG) Diameter F
mm
...