ASTM C1113-99

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Designation: C 1113 – 99
Standard Test Method for
Thermal Conductivity of Refractories by Hot Wire (Platinum
Resistance Thermometer Technique)
This standard is issued under the fixed designation C 1113; 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 2.2 ISO Standard:
DIS*8894-2 Refractory Materials - Determination of Ther-
1.1 This test method covers the determination of thermal
mal Conductivity up to 1250°C of Dense and Insulating
conductivity of non-carbonacious, dielectric refractories.
Refractory Products According to the Hot Wire Parallel
1.2 Applicable refractories include refractory brick, refrac-
Method
tory castables, plastic refractories, ramming mixes, powdered
materials, granular materials, and refractory fibers.
3. Terminology
1.3 Thermal conductivity k-values can be determined from
3.1 Symbols:
room temperature to 1500°C (2732°F), or the maximum
3.1.1 R —hot wire resistance at any temperature, ohms.
T
service limit of the refractory, or to the temperature at which
3.1.2 R —hot wire resistance at 0°C (32°F) (from an ice
the refractory is no longer dielectric.
bath), ohms.
1.4 This test method is applicable to refractories with
3.1.3 L—hot wire length, cm.
k-values less than 15 W/m·K (100 Btu·in./h·ft ·°F).
3.1.4 T—sample test temperature, °C.
1.5 In general it is difficult to make accurate measurements
3.1.5 V—average voltage drop across hot wire, volts.
of anisotropic materials, particularly those containing fibers,
3.1.6 V —average voltage drop across standard resistor,
s
and the use of this test method for such materials should be
volts.
agreed between the parties concerned.
3.1.7 R —average resistance of standard resistor, ohms.
s
1.6 The values stated in SI units are to be regarded as
3.1.8 I—average current through hot wire (V /R ), amperes.
s s
standard.
3.1.9 Q—average power input to hot wire (I*V*100/L)
1.7 This standard does not purport to address the safety
during test, watts/m.
concerns, if any, associated with it’s use. It is the responsibility
3.1.10 t—time, min.
of the user of this standard to establish appropriate safety and
3.1.11 B—slope of linear region in R vs. ln(t) plot.
T
health practices and determine the applicability of regulatory
3.1.12 k—thermal conductivity, W/m·K.
limitations prior to use.
3.1.13 a, b, c—coefficients of a second degree polynomial
2. Referenced Documents equation relating hot wire resistance and temperature.
3.1.14 V, I, and Q are preferably measured in the linear
2.1 ASTM Standards:
region of the R versus ln(t) plot for maximum data accuracy.
T
C 134 Test Methods for Size and Bulk Density of Refrac-
tory Brick and Insulating Firebrick
4. Summary of Test Method
C 201 Test Methods for Thermal Conductivity of Refracto-
2 4.1 A constant electrical current is applied to a pure plati-
ries
2 num wire placed between two brick. The rate at which the wire
C 865 Practice for Firing Refractory Concrete Specimens
heats is dependent upon how rapidly heat flows from the wire
E 691 Practice for Conducting an Interlaboratory Test Pro-
3 into the constant temperature mass of the refractory brick. The
gram to Determine the Precision of Test Methods
rate of temperature increase of the platinum wire is accurately
determined by measuring its increase in resistance in the same
This test method is under the jurisdiction of ASTM Committee C-8 on way a platinum resistance thermometer is used. A Fourier
Refractories and is the direct responsibility of Subcommittee C08.02 on Thermal
and Thermochemical Properties.
Current edition approved March 10, 1999. Published July 1999. Originally
E1
published as C 1113–90. Last previous edition C 1113–90 (1997) .
2 4
Annual Book of ASTM Standards, Vol 15.01. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 14.02. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1113
equation is used to calculate the k-value based on the rate of 1°C (1.8°F) precision such that the temperature variation with
temperature increase of the wire and power input. time is minimized. Temperature stability measurements are not
required by this test method because small temperature varia-
5. Significance and Use
tions with time are difficult to measure and dependent on
5.1 The k-values determined at one or more temperatures thermocouple placement (in air, a protection tube, or in the
can be used for ranking products in relative order of their
sample). However, if sample temperature measurements are
thermal conductivities. averaged during a 30 minute period after furnace equilibration
5.2 Estimates of heat flow, interface temperatures, and cold
(prior to a hot wire test), the maximum-minimum difference
face temperatures of single, and multi-component linings can should preferably be less than 1°C (1.8°F). In addition, if a
be calculated using k-values obtained over a wide temperature
linear regression analysis is done on the average temperature
range. vs. time data, the rate of temperature change should preferably
5.3 The k-values determined are “at temperature” measure-
be less than 0.05°C (0.09°F)/min. Four holes with alumina
ments rather than “mean temperature” measurements. Thus, a protection tubes shall be provided in the kiln wall for the
wide range of temperatures can be measured, and the results
platinum voltage and current leads. These holes should be
are not averaged over the large thermal gradient inherent in widely spaced to minimize electrical conductivity at elevated
water-cooled calorimeters. temperatures.
5.4 The k-values measured are the combination of the
6.1.2 Thermocouple, to measure sample temperature.
k-values for the width and thickness of the sample, as the heat
6.1.3 Programmable Power Supply, capable of constant
flow from the hot wire is in both of those directions. The
current control in the range from 0 to 10 A (0 to 50 V). During
water-cooled calorimeter measures k-value in one direction,
a 10-min test period, stability should be 6 0.002 A. Size the
through the sample thickness.
power supply according to the anticipated wire harnesses
5.5 The test method used should be specified when report-
diameter and type of materials to be tested. A high (5–10 A)
ing k-values, as the results obtained may vary with the type of
ampere supply is suggested for large diameter wire and/or
test method that is used. Data obtained by the hot wire method
testing of high conductivity materials. However, lower ampere
are typically 10 to 30 % higher than data obtained by the water
supplies will giver better current control for low currents used
calorimeter method given in Test Method C 201.
for low conductivity materials or with a smaller diameter wire
harness.
6. Apparatus
6.1.4 Shunt, with a resistance of 0.1 V rated at 15 A.
6.1 A block diagram of a suggested test apparatus is shown
6.1.5 Programmable Scanner, capable of directing several
in Fig. 1. Details of the equipment are as follows:
different voltage inputs to the digital voltmeter. It is also used
6.1.1 Furnace, with a heating chamber capable of support-
to activate a relay to turn on and off the test circuit.
ing two 228-mm (9-in.) straight brick. The furnace temperature
6.1.6 Relay, with a current rating of 25 A at 24 V.
may be controlled with a set point controller adjusted manually
6.1.7 Programmable Digital Voltmeter, with auto ranging,
between test temperatures, with a programmable controller, or
auto calibration, and 6 ⁄2 digit resolution.
with the computer. If a programmable controller is used, and
6.1.8 Computer, capable of controlling the operation of the
the hot wire power is applied by computer, the furnace
power supply, scanner, and digital voltmeter. It must also be
temperature program must be synchronized with the computer
able to collect and analyze the test results. Commercially
program used to collect the test data. The furnace temperature
available data acquisition (with an IEEE device and sequential
should be accurate to 6 5°C (9°F) and controlled to within a 6
file numbering capability) and analysis (spreadsheet with
macro capability) software is acceptable; custom software is
not necessary.
Morrow, G.D., “Improved Hot Wire Thermal Conductivity Technique”, Bull.
Amer. Ceram. Soc., 58(7), 1979, pp. 687–90.
6.1.9 Printer/Plotter, capable of documenting the raw data
and various calculated values. The plotter function is used to
plot the resistance versus ln (time) relationship. This is used to
visually determine if a linear relationship was obtained and the
location of the linear region.
6.2 Reusable Test Harness, consisting of a straight section at
least 30-cm (11.8-in.) long with two perpendicular voltage
leads about 15-cm (5.9-in.) apart near the center per Fig. 2. To
avoid thermocouple effect voltage errors, use pure platinum
wire for the test harness, and for the entire length of voltage
leads. Platinum alloy wire may be used only for current leads
from outside the furnace to the test harness section itself. The
platinum voltage lead wires may be taken to an insulated
terminal box on the side of the furnace for connection to lower
temperature lead wires, or run all the way back to the digital
voltmeter terminals. The main part of the harness wire shall be
FIG. 1 Diagram of Apparatus between 0.330 and 0.508-mm (0.013 and 0.020-in.) diameter.
C 1113
shall be placed together with the steps touching each other to
check for any noticable rock or movement between the two
bricks; no visible movement is acceptable. Rock is most often
caused by the use of a grinding wheel which has a high spot in
the center, causing a smaller step depth close to the step than
across the rest of the mating surface. Dressing the wheel so that
it is flat or that the side which forms the step edge is high will
normally provide acceptable results. After the step height and
mating surfaces are acceptable, voltage lead grooves shall be
cut across the high part of the step in one of the samples. To
accommodate the weld beads at the junctions of the main wire
and voltage leads, it is permissible to chip out small cavities in
the brick at these locations using a hammer and center punch.
7.2.2 Refractory Castables—Refractory castables speci-
mens can be cut into brick shapes and prepared as in 7.2.1 or
a special castable mold with the 0.8-mm (0.032 in.) step can be
used to form the brick shapes. Two thin grooves must be cut for
the perpendicular voltage leads in one of the brick. The hot
wire harness can also be cast in place for a single usage.
7.2.3 Plastic Refractories and Ramming Mixes—
Immediately after forming, press the hot wire harness between
two 228-mm (9-in.) straight bricks. Pressure should be applied
during drying to keep the brick in very close contact.
7.2.4 Low-Strength Materials—Use a sharp knife to scribe
FIG. 2 Hot Wire Sample Setup
grooves into one of the brick into which the hot wire harness
will be pressed.
The voltage leads may be the same size as the main harness
7.2.5 Compressible Refractory Fiber Blankets—Fabricate a
wire, although it is recommended that they be 0.330-mm weighted cover to compress and hold the samples to the desired
(0.013-in.) or smaller such that their area is less than half that
thickness (and bulk density) during testing. A cover and side
of the main wire. The current leads up to the main harness shall spacers are required.
be at least the same size as the main harness wire. The main
7.2.6 Powdered or Granular Materials—A refractory con-
harness may be fabricated by butt welding voltage leads to a
tainer must be fabricated to contain powdered or granular
solid main wire using a micro torch or arc percussion welder,
materials. The container may be of two parts each the size of
or by arc welding the wires into a bead. If beads are made by
a 228-mm (9-in) straight brick. The lower part will have four
arc welding, keep the bead size as small as possible, and
sides and a bottom. The upper part will have four sides only.
carefully straighten out the bead to form a tee joint with the
Alternatively, a container of one part only may be used. The
voltage lead perpendicular to the main wire.
one-part container will have the volume of two 228-mm (9-in)
brick. Record the weight and interior volume for use in
7. Sampling and Specimen Preparation
calculating the apparent bulk density of the test material.
7.1 The test specimens consist of two 228-mm (9-in.)
straight brick or equivalent. Select these specimens for unifor-
8. Calibration
mity of structure and bulk density. Bulk density should be
8.1 Depending on the data analysis calculation method
determined in accordance with Test Method C 134.
used, it may be necessary to determine the resistance of each
7.2 The hot wire harness is positioned near the center of the
test harness at 0°C (32°F) (R ). This can be done experimen-
o
two brick shaped specimens and in intimate contact with both
tally by placing the harness in a plastic tray with a slurry of
either by using samples with a step diamond ground into the
crushed ice, and measuring the resistance using the same
mating surface, by forming the sample around the harness, or
4-wire method which is used for elevated temperature resis-
by deformation of soft samples. See Fig. 2 for a schematic of
tance measurements. An alternate method is to measure the
how the steps provide intimate lateral contact with both halves
resistance of the harness at room temperature and calculate an
of the sample assembly.
R value from R /R 5(a+b*T+c*T ) where the equation coef-
o T o
7.2.1 Refractory Brick—The steps cut in the brick shall
ficients are obtained from prior tests of the wire lot. Wire
have a maximum depth of 0.8-mm (0.032-in.), although lesser
harness calibration at 0°C (32°F) is not required if the wire
depths can be used for wires smaller than the 0.508-mm
resistance vs. temperature measurement method is used.
(0.020-in.) maximum wire size. To insure that samples do not
rock, the average depth of both steps shall be within 0.1-mm
9. Setup Procedure
(0.004-in.) of each other. In addition, the mating surfaces shall
be flat to less than 0.1-mm (0.004-in.) as determined by the 9.1 Measure the hot wire length, L, to the nearest 0.025-cm
following procedure. After the steps are ground, the bricks (0.01-in.). This distance is measured between the voltage leads.
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