ASTM D720-91(2004)
(Test Method)Standard Test Method for Free-Swelling Index of Coal
Standard Test Method for Free-Swelling Index of Coal
SCOPE
1.1 This test method is a small-scale test for obtaining information regarding the free-swelling properties of a coal. The results may be used as an indication of the caking characteristic of the coal when burned as a fuel. This test is not recommended as a method for the determination of expansion of coals in coke ovens.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.
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Designation: D 720 – 91 (Reapproved 2004)
Standard Test Method for
Free-Swelling Index of Coal
This standard is issued under the fixed designation D 720; 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 be the same as those obtained when using the gas heating
2 method. The apparatus common to both electric and gas
1.1 This test method is a small-scale test for obtaining
methods shall consist of the following:
information regarding the free-swelling properties of a coal.
4.1.1 Crucible, translucent silica, low-form, with a flat,
The results may be used as an indication of the caking
close-fitting silica ring-handle lid and an extra pierced lid for
characteristic of the coal when burned as a fuel.This test is not
use in determining the crucible temperature, conforming to the
recommended as a method for the determination of expansion
following requirements:
of coals in coke ovens.
Weight, g 11.0 to 12.75
1.2 The values stated in SI units are to be regarded as the
External height, mm 26 6 0.5
standard. The values given in parentheses are for information
External diameter at top, mm 41 6 0.75
only.
Internal diameter at base, min, mm 11
Capacity (approximate), cm 17
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1.2 Sight Tube, as shown in Fig. 1, for viewing the coke
responsibility of the user of this standard to establish appro-
buttons so that the effect of parallax will be eliminated. Make
priate safety and health practices and determine the applica-
the tube of any rigid and preferably opaque material and
bility of regulatory limitations prior to use.
support vertically on a ring stand.
4.1.3 Thermocouple and Potentiometer.
2. Referenced Documents
4.1.4 Weight, 500 g.
2.1 ASTM Standards:
4.2 The electric apparatus shall consist of the following:
D 2013 Practice of Preparing Coal Samples for Analysis
4.2.1 Furnace, consisting of a base, a heating element, and
a chimney. The unit is shown in Fig. 2.
3. Significance and Use
4.2.1.1 Chimney—Fig. 2 shows the chimney design. Make
3.1 This test method, in addition to indicating the caking
the unit from firebrick and coat with firebrick bonding mortar.
properties of a coal when burned as a fuel, can be used to give
Maintain the chimney under compression by a sheet-metal
a broad indication of the degree of oxidation of a coal.
envelope (Fig. 2) to prevent cracking. Make the envelope in
four pieces, each piece covering a corner. The pieces shall
4. Apparatus
overlap at the center of the flat faces and be held together by
4.1 This test method can be made with either electric or gas
bolts and springs. Place two layers of asbestos paper between
heating. When using electric heating, the results obtained must
the chimney brick and the envelope. Cut two grooves in the
upper inside chimney walls to accommodate the crucible
support. In cases in which the furnace is located in a drafty
This test method is under the jurisdiction of ASTM Committee D05 on Coal
area, it is advisable to shield the chimney to prevent large
and Coke and is the direct responsibility of Subcommittee D05.15 on Metallurgical
Properties of Coal and Coke.
fluctuations in furnace temperature.
Current edition approved April 1, 2004. Published May 2004. Originally
4.2.2 Crucible Support—A convenient crucible support
approved in 1943. Last previous edition approved in 1999 as D 720 – 91 (1999).
2 consists of a cradle support made from nickel-chromium wire
This test method is an adaptation of the Crucible Swelling Test for Coal of the
suspended from a metal ring. The height of the support inside
British Standards Institution. For information concerning the experimental work on
which this adaptation is based, see paper by Ostborg, H. N., Limbacker, H. R., and
the furnace can be adjusted by loosening the two screws that
Sherman, R.A., “An Experimental Investigation of the British Standard Method for
hold the wire legs of the support in place.
the Crucible Swelling Test for Coal,” Proceedings,Am. Soc. Testing Mats., Vol 42,
4.2.3 Electric Controls, consisting of a rheostat, an a-c
1042, p. 851. See also a paper by Selvig, W.A., and Ode, W. H., “An Investigation
of a Laboratory Test for Determination of the Free-Swelling Index of Coal,” U.S. ammeter, and two timers. These components shall conform to
Bureau of Mines Report of Investigation 4238, Revision of R. I. 3989, 1948.
the following specifications:
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.
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D 720 – 91 (2004)
Measure the temperature at the inside base of the crucible with
a thermocouple and a potentiometer. The unprotected junction
of the thermocouple must be in contact with the inside base of
thecrucible.Attheendof1 ⁄2min,thetemperatureshouldread
800 6 10°C (1472 6 18°F).Adjust the variable transformer as
necessary to provide this temperature.
5.1.3 A temperature of 820 6 5°C (1508 6 9°F) must be
attained at the end of 2 ⁄2 min. The second timer shall be used
here. The control unit rheostat must be properly adjusted to
reduce the heating rate at the end of 2 ⁄2 min. If the rheostat is
set initially so that at the end of 1 ⁄2 min the ammeter reading
is reduced by 0.6 or 0.7A, the specified temperature at the end
of 2 ⁄2 min should be attained. Several trials will no doubt be
1 1
necessary before the proper temperatures at 1 ⁄2 and 2 ⁄2 min
are reached; however, the information given above provides a
general guide for calibration. The silica crucible and cover
must be at room temperature before each calibration run.
FIG. 1 Sight Tube
5.1.4 After each calibration attempt or sample run, switch
the timer to the HOLD position, and allow about 1 min for the
Ammeter a-c, 0 to 10-A range
furnace to reach equilibrium.
Rheostat 100 W, 10 V
5.2 Gas Burner:
Variable transformer 7.4 A, 120 V
5.2.1 With the burner assembly arranged as shown in Fig. 3,
Timer mechanical, 0–5 min minimum span, with a hold
position, and electrical contact closed during
and with an empty crucible in position, light the burner about
timing cycle
15 min before making a determination to allow the draft shield
4.2.3.1 One timer shall actuate the rheostat, at a predeter-
to rise to an equilibrium temperature.
mined setting, after 1 ⁄2 min of operation. Preset the rheostat to
5.2.2 After placing a crucible in position adjust the flow of
reduce the rate of heating of the furnace so that a temperature
gas and the relative positions of the burner and the draft shield
of 820 6 5°C (1508 6 9°F) is achieved at the end of 2 ⁄2 min.
so that the temperature of the inner surface of the bottom of the
A variable transformer is desirable for establishing the input
crucible reaches 800 6 10°C (1472 6 18°F) in 1 ⁄2 min and
voltage to the furnace.
820 6 5°C (1508 6 9°F) in 2 ⁄2 min. These desired tempera-
4.3 The gas apparatus shall consist of the following:
tures may usually be obtained by setting the draft shield so that
4.3.1 Burner Assembly—A gas burner with a grid of exter-
the bottom of the crucible is approximately 10 mm (0.4 in.)
nal diameter, 30 to 42 mm (1.18 to 1.65 in.), a draft shield, and
above the burner grid, and then adjusting the gas flame.
a triangular crucible support as shown in Fig. 3. Make the draft
Determine the crucible temperature by means of a thermo-
shield, conforming to the dimensions shown in Fig. 3 from the
couple and a potentiometer. Insert the thermocouple through
asbestos-cement pipe, and at the top it shall have three slots, 25
the pierced crucible lid so that the unprotected junction of the
mm (1 in.) in depth, in which the wires of the crucible support
thermocouple is in contact with the base of the crucible.
rest. Support the draft shield on a ring stand, so that the
6. Preparation of Sample
distance between the base of the c
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