ASTM B389-81(2020)

Standard Test Method for Thermal Deflection Rate of Spiral and Helical Coils of Thermostat Metal

SIGNIFICANCE AND USE
5.1 This test method simulates, to a practical degree, the operation of the thermostat metal coil.  
5.2 The thermal deflection properties of a coil may vary from lot-to-lot of thermostat metal material. This method is useful for determining the optimum thickness and length of the material for a given deflection specification.  
5.3 This method is useful as a quality test to determine acceptance or rejection of a lot of thermostat metal coils.
SCOPE
1.1 This test method covers the determination of the thermal deflection rate of spiral and helical coils of thermostat metal.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
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 become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, 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.

General Information

• Status: Published
• Publication Date: 30-Sep-2020
• ICS: 29.120.20 - Connecting devices
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.10 - Thermostat Metals and Electrical Resistance Heating Materials

Relations

• Refers: ASTM E77-14 - Standard Test Method for Inspection and Verification of Thermometers
• Effective Date: 01-May-2014
• Refers: ASTM E77-07 - Standard Test Method for Inspection and Verification of Thermometers
• Effective Date: 01-Dec-2007
• Refers: ASTM E77-98(2003) - Standard Test Method for Inspection and Verification of Thermometers
• Effective Date: 01-Nov-2003

Overview

ASTM B389-81(2020) – Standard Test Method for Thermal Deflection Rate of Spiral and Helical Coils of Thermostat Metal outlines a reliable procedure to determine the thermal deflection rate of thermostat metal coils in spiral and helical forms. This standard method simulates the operational response of thermostat metal coils by measuring their angular displacement as temperature changes. By providing a consistent way to assess performance and compare batches or vendors, this standard underpins quality control, material selection, and design optimization in industries that use thermostat metals.

Key Topics

• Test Method Scope: Defines the evaluation of the thermal deflection rate for spiral and helical coils made from thermostat metals.
• Deflection Rate Calculation: Specifies how to record the angular rotation corresponding to set temperature changes, using dedicated specimen holders and measurement apparatus.
• Coil Types: Covers both spiral coils (wound strip on itself) and helical coils (wound with the strip width parallel to the axial length), both of which are prevalent in thermostat applications.
• Quality Assessment: Allows for determination of coil suitability, including acceptance or rejection of material batches.
• Simulation of Operation: The method closely mirrors real-world functioning by exposing coils to controlled temperature environments and measuring their physical response.
• Standardization: Provides inch-pound units as the standard, with SI conversions for reference.
• Material Optimization: Helps determine optimal coil dimensions (thickness, length) for a specified thermal deflection characteristic.

Applications

ASTM B389-81(2020) is vital for manufacturers, quality assurance teams, and engineers in industries relying on accurately performing thermostat metals. Key applications include:

• Design of Thermal Actuators: Critical for engineers selecting materials and dimensions for thermostat coils that must respond predictably to temperature changes.
• Production Quality Control: Used as a lot qualification tool to ensure consistent thermal behavior across production batches of thermostat metals.
• Material Sourcing: Assists purchasers in verifying supplied thermostat metal matches required specifications for thermal deflection, reducing performance variability in end products.
• Failure Analysis: Provides a standardized basis for diagnosing performance issues related to coil deflection rate in service.
• Research and Development: Supports optimization of composite structures in thermostat metals to achieve desired thermal activity.

Thermostat metals and their coils find applications in temperature regulators, household thermostats, automotive devices, and industrial temperature-sensitive controls, making the accurate measurement of thermal deflection essential for safety, efficiency, and reliability.

Related Standards

To ensure comprehensive compliance and accurate measurement, ASTM B389-81(2020) references and relates to several standards:

• ASTM E77: Test Method for Inspection and Verification of Thermometers. Vital for ensuring temperature measurement accuracy when testing thermal deflection rate.
• ASTM Annual Book of Standards: For information on referenced standards and up-to-date procedures.
• International Trade Compliance: Developed under the World Trade Organization (WTO) guidelines for standardization, supporting harmonization in global materials testing.

Other related standards may include those covering composite thermostat materials, calibration techniques, and universal quality management for metals.

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By adhering to ASTM B389-81(2020), organizations benefit from standardized, repeatable testing for the thermal deflection rate of thermostat metal coils, driving product dependability and compliance throughout the supply chain. This standard is essential for anyone involved in the manufacture, quality control, or application of spiral or helical thermostat metal coils.

Standards Content (Sample)

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.
Designation: B389 −81 (Reapproved 2020)
Standard Test Method for
Thermal Deflection Rate of Spiral and Helical Coils of
Thermostat Metal
This standard is issued under the fixed designation B389; 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 differing expansivities of the components, tends to alter its
curvature when its temperature is changed.
1.1 Thistestmethodcoversthedeterminationofthethermal
3.2 thermal deflection rate, n—the ratio of angular rotation
deflection rate of spiral and helical coils of thermostat metal.
to temperature change. It is a measure of the coil’s thermal
1.2 The values stated in inch-pound units are to be regarded
activity. It may have the units of angular degrees per degree
as standard. The values given in parentheses are mathematical
Fahrenheit, or Celsius, and is expressed by the equation
conversions to SI units that are provided for information only
D=(A −A )/(T −T ) where A and A are angular positions
2 1 2 1 2 1
and are not considered standard.
at temperature T and T respectively.
2 1
1.3 This standard does not purport to address all of the
3.3 spiral coil, n—a part made by winding strip on itself.
safety concerns, if any, associated with its use. It is the
Fig. 1 and Fig. 2 show typical spiral coils, which can be wound
responsibility of the user of this standard to become familiar
with the low-expansive side inside or outside, mounted on the
with all hazards including those identified in the appropriate
specimen holder.
Safety Data Sheet (SDS) for this product/material as provided
3.4 helical coil, n—a part made by winding strip in a form
by the manufacturer, to establish appropriate safety, health,
wherein the plane of the width of the strip is parallel to the
and environmental practices, and determine the applicability
axial length. Fig. 3 shows a typical helical coil, which can be
of regulatory limitations prior to use.
wound with the low-expansive side inside or outside, and
1.4 This international standard was developed in accor-
right-hand or left-hand, mounted on the specimen holder.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4. Summary of Test Method
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4.1 The test for thermal deflection rate of spiral and helical
Barriers to Trade (TBT) Committee.
coils consists of measuring the angular rotation that a coil
undergoes in response to a known temperature change.
2. Referenced Documents
2.1 ASTM Standards: 5. Significance and Use
E77 Test Method for Inspection and Verification of Ther-
5.1 This test method simulates, to a practical degree, the
mometers
operation of the thermostat metal coil.
5.2 The thermal deflection properties of a coil may vary
3. Terminology
from lot-to-lot of thermostat metal material. This method is
3.1 thermostat metal, n—a composite material, usually in
useful for determining the optimum thickness and length of the
the form of sheet or strip, comprising two or more materials of
material for a given deflection specification.
any appropriate nature, metallic or otherwise, that, by virtue of
5.3 This method is useful as a quality test to determine
acceptance or rejection of a lot of thermostat metal coils.
This test method is under the jurisdiction of ASTM Committee B02 on
6. Apparatus
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
B02.10 on Thermostat Metals and Electrical Resistance Heating Materials.
6.1 Temperature Bath—A stirred liquid bath or uniformly
Current edition approved Oct. 1, 2020. Published October 2020. Originally
heated enclosure in which the specimen and mounting fixture
approved in 1962. Last previous edition approved in 2016 as B389 – 81 (2016).
DOI: 10.1520/B0389-81R20.
can be placed shall be used. An adjustable heating source is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
desirable for maintaining the specimen at the desired tempera-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
tures with a variation in temperature throughout the specimen
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. not to exceed 0.5°F (0.3°C).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B389 − 81 (2020)
and the top end allowed to rotate freely with a temperature
change. Preferably the end of the coil with the center tab shall
be considered the bottom and secured by clamping or press-
fitting the tab into a slotted arbor similar to that described in
6.4.1 for spiral coils.The depth of the slot shall be such that the
full height of the tab shall be held. If the coils do not have a
center tab, the arbor shall contain provisions for attaching the
coil with screws, rivets, or by welding. A transmission pointer
can be affixed to the top end. The center line of the coil, the
transmission pointer, and the protractor shall coincide.
6.4.3 Deviations from these procedures of holding may be
necessary when simulating the mounting used in the device for
which the coil was designed, or in cases where coils are press
fitted on arbors. In these cases, the details of mounting should
be mutually agreed upon between the manufacturer and the
purchaser.
6.5 Transmission Pointer:
6.5.1 Spiral Coils—To the outer end of the spiral coil shall
be attached a pointer that will transmit the rotation of the coil
so that it can be read on the protractor. The pointer shall be of
lightweight construction and attached to the coil by suitable
means so that the movement of these portions of the coil that
do not normally contribute to the movement of the coil with a
temperature change shall not influence the rotation of the
pointer. The pointer, when using the fixture shown in Fig. 1,
shall be so positioned that its tip shall ride slightly above the
divisions of the protractor, but shall not touch the protractor at
any time during the test. The pointer, when using the fixture
shown in Fig. 2, shall be of sufficient length so that the top may
FIG. 1 Spiral Coil
protrude from the bath when the coil is submerged.The pointer
f
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