ASTM E771-90(1996)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: E 771 – 90 (Reapproved 1996)
Standard Test Method for
Spontaneous Heating Tendency of Materials
This standard is issued under the fixed designation E 771; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.3 Exothermic reaction under test conditions is a positive
indication of spontaneous heating tendencies of a material.
1.1 This test method covers a small-scale laboratory proce-
Negative test results indicate the absence of detectable spon-
dure to determine the self heating tendency of liquid and solid
taneous heating behavior under the experimental conditions
chemicals by exposure to elevated temperatures in air in a
imposed, but should not be regarded as conclusive for all
controlled semi-adiabatic system.
conditions, particularly those which may be considered adia-
1.2 This standard does not purport to address all of the
batic.
safety concerns, if any, associated with its use. It is the
4.4 The spontaneous heating behavior of a material is
responsibility of the user of this standard to establish appro-
affected by such factors as available surface area, availability
priate safety and health practices and determine the applica-
of oxygen to the test specimen, humidity, sample moisture
bility of regulatory limitations prior to use.
content, packing density, the test temperature, and loss of
2. Terminology exothermic heat to the surroundings.
2.1 Definitions:
5. Apparatus
2.1.1 spontaneous heating or self heating, n—an exother-
5.1 General—The complete apparatus (see Fig. 1), consists
mic reaction of a material due to slow or incomplete reaction
of a test chamber with a sample well and auxiliary equipment
that results in a temperature rise above that of its surroundings.
including a heater and temperature control system, supplemen-
2.1.2 spontaneous heating temperature or self-heating tem-
tary electronic bath temperature controller, high-temperature
perature, n—the lowest temperature at which spontaneous or
limit switch, motor stirrer, multichannel recorder, thermo-
self heating occurs under the specified test conditions. This
couples, and controlled air supply.
temperature refers to a much earlier stage of reaction than that
5.1.1 Test Chamber—A double-walled insulated container,
associated with the autoignition temperature of the material.
capable of holding an oil bath at temperatures ranging to
3. Summary of Test Method 250°C, an immersed sample well, and provision for admission
of air at bath temperature to the sample well, will satisfy the
3.1 A small quantity of the test material held within a
needs of this test. A hood is recommended to facilitate removal
loosely packed inert material is heated in a thermostatically
of noxious products of combustion.
controlled chamber and the sample temperature is monitored to
5.1.1.1 The recommended test chamber should be con-
determine the temperature rise due to exothermic reaction.
structed of double-walled stainless steel sheeting or other
Bath temperature, sample quantity, and particle size of solids
suitable metal. An 8-in. (203-mm) diameter stainless steel
are varied to obtain the relative self-heating temperature of the
beaker can be used as the inner container and a 9-in. (229-mm)
material.
diameter stainless steel beaker can serve as the outer wall with
4. Significance and Use
the bottom cut away to conform in height to the inner container
and to expose the bottom of the inner container to the heating
4.1 This test method is applicable to solid and liquid
surface. The annular space between the inner and outer wall is
materials and provides a means of accelerating the tendency of
filled with insulating material and assures an integral tight-
a material toward spontaneous heating which may eventually
fitting unit.
lead to a fire.
5.1.1.2 A 12-ft (3.66-m) coil of ⁄4-in. (6.35-mm) copper
4.2 Tests at temperatures covering the range expected in
tubing is attached to the bottom of the test sample well by
manufacturing processes or material usage can be of consid-
metal fittings to provide a supply of heated air to the test
erable value in determining safe operating conditions.
sample. The well and coil are immersed in heat-transfer oil
having a flash point well above the maximum operating
temperature of the bath. The sample well in the test chamber is
This test method is under the jurisdiction of ASTM Committee E-27 on Hazard
supported by the coil and the chamber cover.
Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on
Flammability and Ignitability of Chemicals.
5.1.1.3 The test sample well is constructed of a 6-in. (152
Current edition approved May 25, 1990. Published July 1990. Originally
mm) length of 3-in. (76-mm) diameter stainless steel pipe of
published as E 771 – 81. Last previous edition E 771 – 81.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 771
FIG. 1 Spontaneous Heating Apparatus
approximately 0.035-in. (0.88-mm) thickness with a welded 5.1.3.1 Bath heating proceeds at a rate consistent with the
bottom perforated and fitted to admit air from the coil. The capabilities of the hot plate and prevents excessive loss of
fittings are constructed so that the air is admitted centrally exothermic sample heat.
about ⁄2 in. (12.7 mm) above the bottom of the well. 5.1.4 The high-temperature limit switch opens the supple-
5.1.1.4 The cover of the annular space containing the oil mentary circuit when the maximum safe bath temperature is
bath support a temperature limit switch and has feed-through reached.
facilities for air admission, thermocouples to measure the bath 5.1.5 Both the sample and bath have controlling thermo-
temperature, and a stirrer rod. An 8-in. (203-mm) stainless steel couples fed into the supplementary circuit and recording
beaker cover may be used for this purpose. The cover of the thermocouples fed into the multichannel recorder. Chromel-
test sample holder has feed through facilities for thermocouples Alumel 20 gage, Type K thermocouples are suggested for this
measuring the sample temperature. purpose.
5.1.2 Controllable Hot Plate, having a minimum surface 5.2 Suitable Circuit Diagram, as provided in Fig. 2.
2 2
area of 81 in. (523 cm ) is used to heat the bath.
6. Materials
5.1.2.1 A separate power source from the supplementary
controller is wired to the hot plate bypassing the thermostatted
6.1 The heat-transfer medium shall be any suitable oil with
potentiometer.
a flash point well in excess of the maximum operating
5.1.3
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