ASTM C1113-99(2004)
(Test Method)Standard Test Method for Thermal Conductivity of Refractories by Hot Wire (Platinum Resistance Thermometer Technique)
Standard Test Method for Thermal Conductivity of Refractories by Hot Wire (Platinum Resistance Thermometer Technique)
SIGNIFICANCE AND USE
The k-values determined at one or more temperatures can be used for ranking products in relative order of their thermal conductivities.
Estimates of heat flow, interface temperatures, and cold face temperatures of single, and multi-component linings can be calculated using k-values obtained over a wide temperature range.
The k-values determined are “at temperature” measurements rather than “mean temperature” measurements. Thus, a wide range of temperatures can be measured, and the results are not averaged over the large thermal gradient inherent in water-cooled calorimeters.
The k-values measured are the combination of the k-values for the width and thickness of the sample, as the heat flow from the hot wire is in both of those directions. The water-cooled calorimeter measures k-value in one direction, through the sample thickness.
The test method used should be specified when reporting k-values, as the results obtained may vary with the type of test method that is used. Data obtained by the hot wire method are typically 10 to 30 % higher than data obtained by the water calorimeter method given in Test Method C 201.
SCOPE
1.1 This test method covers the determination of thermal conductivity of non-carbonacious, dielectric refractories.
1.2 Applicable refractories include refractory brick, refractory castables, plastic refractories, ramming mixes, powdered materials, granular materials, and refractory fibers.
1.3 Thermal conductivity k-values can be determined from room temperature to 1500°C (2732°F), or the maximum service limit of the refractory, or to the temperature at which the refractory is no longer dielectric.
1.4 This test method is applicable to refractories with k-values less than 15 W/mK (100 Btuin./hft 2F).
1.5 In general it is difficult to make accurate measurements of anisotropic materials, particularly those containing fibers, and the use of this test method for such materials should be agreed between the parties concerned.
1.6 The values stated in SI units are to be regarded as standard.
This standard does not purport to address the safety concerns, if any, associated with it's 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:C1113–99 (Reapproved 2004)
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 E 691 Practice for Conducting an Interlaboratory Test Pro-
gram to Determine the Precision of Test Methods
1.1 This test method covers the determination of thermal
2.2 ISO Standard:
conductivity of non-carbonacious, dielectric refractories.
DIS*8894-2 Refractory Materials - Determination of Ther-
1.2 Applicable refractories include refractory brick, refrac-
mal Conductivity up to 1250°C of Dense and Insulating
tory castables, plastic refractories, ramming mixes, powdered
Refractory Products According to the Hot Wire Parallel
materials, granular materials, and refractory fibers.
Method
1.3 Thermal conductivity k-values can be determined from
room temperature to 1500°C (2732°F), or the maximum
3. Terminology
service limit of the refractory, or to the temperature at which
3.1 Symbols:
the refractory is no longer dielectric.
3.1.1 R —hot wire resistance at any temperature, ohms.
T
1.4 This test method is applicable to refractories with
3.1.2 R —hot wire resistance at 0°C (32°F) (from an ice
k-values less than 15 W/m·K (100 Btu·in./h·ft ·°F).
bath), ohms.
1.5 In general it is difficult to make accurate measurements
3.1.3 L—hot wire length, cm.
of anisotropic materials, particularly those containing fibers,
3.1.4 T—sample test temperature, °C.
and the use of this test method for such materials should be
3.1.5 V—average voltage drop across hot wire, volts.
agreed between the parties concerned.
3.1.6 V —average voltage drop across standard resistor,
s
1.6 The values stated in SI units are to be regarded as
volts.
standard.
3.1.7 R —average resistance of standard resistor, ohms.
s
1.7 This standard does not purport to address the safety
3.1.8 I—average current through hot wire (V /R ), amperes.
s s
concerns, if any, associated with it’s use. It is the responsibility
3.1.9 Q—average power input to hot wire (I*V*100/L)
of the user of this standard to establish appropriate safety and
during test, watts/m.
health practices and determine the applicability of regulatory
3.1.10 t—time, min.
limitations prior to use.
3.1.11 B—slope of linear region in R vs. ln(t) plot.
T
2. Referenced Documents 3.1.12 k—thermal conductivity, W/m·K.
2 3.1.13 a, b, c—coefficients of a second degree polynomial
2.1 ASTM Standards:
equation relating hot wire resistance and temperature.
C 134 Test Methods for Size and Bulk Density of Refrac-
3.1.14 V, I, and Q are preferably measured in the linear
tory Brick and Insulating Firebrick
region of the R versus ln(t) plot for maximum data accuracy.
T
C 201 Test Methods for Thermal Conductivity of Refracto-
ries
4. Summary of Test Method
C 865 Practice for Firing Refractory Concrete Specimens
4.1 A constant electrical current is applied to a pure plati-
num wire placed between two brick.The rate at which the wire
heats is dependent upon how rapidly heat flows from the wire
This test method is under the jurisdiction of ASTM Committee C08 on
into the constant temperature mass of the refractory brick. The
Refractories and is the direct responsibility of Subcommittee C08.02 on Thermal
rate of temperature increase of the platinum wire is accurately
and Thermochemical Properties.
determined by measuring its increase in resistance in the same
Current edition approved Sept. 1, 2004. Published October 2004. Originally
approved in 1990. Last previous edition approved in 1999 as C 1113–99.
way a platinum resistance thermometer is used. A Fourier
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 Available from American National Standards Institute, 11 W. 42nd St., 13th
the ASTM website. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1113–99 (2004)
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 10A(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 Ablock 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.
ingtwo228-mm(9-in.)straightbrick.Thefurnacetemperature
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
shouldbeaccurateto 65°C(9°F)andcontrolledtowithina 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,consistingofastraightsectionat
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.
C1113–99 (2004)
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
acrosstherestofthematingsurface.Dressingthewheelsothat
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
usedtoformthebrickshapes.Twothingroovesmustbecutfor
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 weightedcovertocompressandholdthesamplestothedesired
(0.013-in.) or smaller such that their area is less than half that
thickness (and bulk density) during testing. A cover and side
ofthemainwire.Thecurrentleadsuptothemainharnessshall 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 =(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,
...
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