ASTM C1057-92(1998)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact
ASTM International (www.astm.org) for the latest information.
e1
Designation: C 1057 – 92 (Reapproved 1998)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Determination of Skin Contact Temperature from Heated
Surfaces Using A Mathematical Model and
Thermesthesiometer
This standard is issued under the fixed designation C 1057; 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.
e NOTE—Keywords were added editorially in July 1998.
1. Scope 3.1.1 acceptable contact time—the limit of time of contact
for the heated surface and the exposed skin. Practice has
1.1 This practice establishes a procedure for evaluating the
suggested limits of 5 s for industrial processes and up to 60 s
skin contact temperature for heated surfaces. Two complimen-
for consumer items.
tary procedures are presented. The first is a purely mathemati-
3.1.2 burns:
cal approximation that can be used during design or for worst
3.1.2.1 first degree burn—the reaction to an exposure where
case evaluation. The second method describes the thermesthe-
the intensity and duration is insufficient to cause complete
siometer, an instrument that analogues the human sensory
necrosis of the epidermal layer. The normal response to this
mechanism and can be used only on operating systems.
level of exposure is dilation of the superficial blood vessels
NOTE 1—Both procedures listed herein are intended for use with Guide
(reddening of the skin).
C 1055. When used in conjunction with that guide, these procedures can
3.1.2.2 second degree burn—the reaction to an exposure
determine the burn hazard potential for a surface.
where the intensity and duration is sufficient to cause complete
1.2 A bibliography of human burn evaluation studies and
necrosis of the epidermis but no significant damage to the
surface hazard measurement is provided in the References at
dermis. The normal response to this exposure is blistering of
the end of Guide C 1055. Thermesthesiometer and mathemati-
the epidermis.
cal modeling references are provided in the References at the
3.1.2.3 third degree burns—the reaction to an exposure
end of this standard (1-5).
where significant dermal necrosis occurs. Significant dermal
1.3 This standard does not purport to address all of the
necrosis has been defined in the literature as a 75 % destruction
safety concerns, if any, associated with its use. It is the
of the dermis thickness. The normal response to this exposure
responsibility of the user of this standard to establish appro-
is open sores that leave permanent scar tissue upon healing.
priate safety and health practices and determine the applica-
3.1.3 skin:
bility of regulatory limitations prior to use.
3.1.3.1 epidermis—the outermost layer of skin cells. This
layer contains no vascular or nerve cells and acts to protect the
2. Referenced Documents
outer skin layers. The thickness of this layer averages 0.08 mm.
2.1 ASTM Standards:
3.1.3.2 dermis—the second layer of skin tissue. This layer
C 680 Practice for Determination of Heat Gain or Loss and
contains blood vessels and nerve endings. The thickness of this
the Surface Temperature of Insulated Pipe and Equipment
layer is about 2 mm.
Systems by Use of a Computer Program
3.1.3.3 necrosis—localized death of living cells. This is a
C 1055 Guide for Heated System Surface Conditions That
clinical term that defines when damage to the skin layer has
Produce Contact Burn Injuries
occurred.
3.1.4 skin contact temperature—the temperature of the skin
3. Terminology
at a depth of 0.08 mm reached after contact with a heated
3.1 Definitions of Terms Specific to This Standard:
surface for a specified time.
3.1.5 thermesthesiometer—an electromechanical device de-
veloped by L. A. Marzetta at National Institute of Standards
This practice is under the jurisdiction of ASTM Committee C-16 on Thermal
and Technology to analogue the touch response of the human
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
skin when it contacts a heated surface. This measurement
Measurement.
Current edition approved Jan. 15, 1992. Published March 1992. Originally
concept holds U.S. Patent No. 3,878,728 dated April 22, 1975,
e1
published as C 1057 – 86. Last previous edition C 1057 – 86 .
and was assigned to the USA as represented by the Department
The boldface numbers in parentheses refer to the list of references at the end of
of Health and Welfare. No known restriction exists to limit the
this practice.
development of units based upon this principle.
Annual Book of ASTM Standards, Vol 04.06.
NOTICE:¬This¬standard¬has¬either¬been¬superceded¬and¬replaced¬by¬a¬new¬version¬or¬discontinued.¬
Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information.¬
C 1057
4. Summary of Practice time, such criteria are developed, extrapolation of the tech-
niques presented here will serve as a basis for cold surface
4.1 This practice provides two procedures for evaluation of
exposure evaluation.
the skin contact temperature from heated surfaces. Either of the
two methods, a mathematical model and a physical measure-
6. Method A—Use of the Mathematical Model
ment, can be used depending upon the availability of the
6.1 This modeling approach is for use when the system is
system (that is, is it built and operating or is it in the design
being designed or, if for some reason, it cannot be operated at
state) and the operating conditions. The first step in using this
design conditions. The model approximates the transient heat
practice is to determine which procedure is to be used. Unless
flow phenomena of the skin contacting a hot surface using the
the system of interest is operating at design “worst case”
equation set described by Dussan (1) and Wu (5). The user is
conditions, such as high system temperatures and high ambient
required to make certain definitions of system geometry and
temperature, the calculational procedure is recommended. On
materials, the system operating conditions, and the allowable
the other hand, if the question is safety at the present
time of exposure. After definition of the input values, the
conditions, the thermesthesiometer provides a quick measure-
equation set yields an estimate of the skin contact temperature
ment with no auxiliary calculations. Sections 4.2 and 4.3
needed for the hazard evaluation. The user must realize that as
outline the two alternative procedures available.
with all mathematical approximations, the estimate is only as
4.2 Calculational Procedure, Method A—First the surface
good as the input data. Where some input parameter is known
temperature of the insulated system is determined by either a
only within some range of values, a sensitivity analysis about
direct measurement, using either thermocouples, thermistors,
that range is recommended.
or infrared noncontact techniques, or by modeling of the
6.2 The first step in estimating the effective skin contact
system using Practice C 680. Once the surface temperature is
temperature is to identify and record the following information
known, the designer uses the equation set to estimate the
describing the system as input for the model:
maximum epidermal contact temperature for the acceptable
6.2.1 System Description—Geometry, location, accessibil-
contact time. This temperature is a function of surface tem-
ity.
perature, time of contact, and composition of both the surface
6.2.2 Present/Design Operating Conditions—Duty cycle,
material and substrate. The designer then refers to Guide
operating temperatures of equipment.
C 1055 to determine the burn hazard potential of the surface.
6.2.3 System/Surface Data (as appropriate)—Substrate (in-
4.3 Thermesthesiometer, Method B—The operator places
sulation) type and thickness, jacket type and thickness, surface
the calibrated sensor probe face firmly against the heated
properties, such as emissivity and condition, shiny, painted,
surface for the acceptable contact time. The device directly
dirty, corroded.
reads the contact temperature from the probe. The maximum
6.2.4 Ambient Conditions, including dry bulb temperature
temperature is used in conjunction with the Guide C 1055 to
and local wind velocity.
determine the burn hazard potential of the surface.
NOTE 2—The design temperatures should be at the worst case (gener-
ally high operating and high ambient) conditions. Care should be used in
5. Significance and Use
the selection of design conditions since the hazard design conditions are
5.1 The procedures in this practice support the determina- different from the heat loss design conditions.
tion of the burn hazard potential for a heated surface. These
6.3 Using Practice C 680 or a compatible program and the
procedures provide an estimate of the maximum skin contact
information gathered in 6.2, calculate the maximum operating
temperature and must be used in conjunction with Guide
surface temperature. This temperature is an input to the model
C 1055 to evaluate the surface hazard potential.
for the contact temperature.
5.2 The two procedures outlined herein are both based upon
6.3.1 Where the system is operating at design conditions,
the same heat transfer principles. Method A uses a mathemati-
direct measurement can be used to determine the surface
cal model to predict the contact temperature, while Method B
temperature. Thermocouples, resistance thermometers, or other
uses a plastic rubber probe having similar heat transfer
means can be used; however, proper application techniques are
characteristics to the human finger to “measure” the contact
required for accurate results. Caution must be observed since
temperature on real systems.
the surface temperature may be high and the surface could
5.3 These procedures serve as an estimate for the skin
constitute a burn hazard.
contact temperatures which might occur for the “average”
6.4 Calculate the expected skin contact temperature versus
individual. Unusual conditions of exposure, incorrect design
time history using the procedure below based upon the hot
assumptions, subject health conditions, or unforeseen operating
surface temperature, time of contact, and system properties.
conditions may negate the validity of the estimations.
The development of the equations below is taken from Dussan
5.4 These procedures are limited to direct contact exposure
(1). A more detailed derivation of the equation set used is
only. Conditions of personal exposure to periods of high included in the papers by Dussan (1) and Wu (5). See Fig. 1.
ambient temperatures, direct flame exposure, or high radiant
6.4.1 Calculate the initial parameter constants, using Eq
fluxes may cause human injury in periods other than deter- 4-11.
mined herein. Evaluation of exposures other than direct contact
6.4.2 The contact temperature for the skin can now be
are beyond the scope of this practice. determined using Eq 1, Eq 2, and Eq 3 together for the system
5.5 Cold Surface Exposure—No consensus criteria exists in question. Note that the solution to this equation is a sum of
for the destruction of skin cells by freezing. If, at some future an infinite series. The solution, however, converges quickly
NOTICE:¬This¬standard¬has¬either¬been¬superceded¬and¬replaced¬by¬a¬new¬version¬or¬discontinued.¬
Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information.¬
C 1057
FIG. 1 Schematic of Heat Transfer Model
(five or six terms) and can be easily handled manually or by a
C 5 specific heat of material i,J/kg·K.
i
small computer.
6.4.3 To obtain the skin contact temperature versus contact
‘ ‘
time history, repeat the calculation at one second intervals for
N N
T 5 T 1 A I erfc ~u ! 1 B I erfc ~u8 ! (1)
( (
c 0 N N
times up to the maximum contact time exposure expected.
N 5 0 N 5 0
6.4.4 The maximum contact temperature used in the analy-
and:
sis of burn hazard (Guide C 1055) is the maximum contact
X / a 1 2·N·l/ a
= =
1 1 2
temperature calculated for the contact period in step 6.4.3.
u 5 (2)
N
2 t
=
6.5 Typical Input Data—Table 1 contains typical values for
the commonly used insulation and jacketing materials. Skin
X / a 1 2· ~N 1 1! · l / a
= =
1 1 2
u8 5 (3)
N
properties are also included. Nonstandard insulations or jacket
2 t
=
material properties may be substituted for the table values in
~P 2 P !·~P 2 P !
2 3 2 1
I 5 (4) the calculation if they are known.
~P 1 P ! · ~P 1 P !
2 3 2 1
NOTE 3—Eq 1-11 work with any system of consistent units.
~T 2 T !·P
i 0 2
A 5 (5)
P 1 P
6.6 Example Calculation—Using the equations listed in 6.4
2 1
and the following input data parameters, the following results
~T 2 T ! · ~P 2 P !·P
i 0 3 2 2
B 5 (6)
P 1 P !· P 1 P !
~ ~
2 3 2 1 TABLE 1 Typical Properties (23°C)
1/2
Specific Conduc-
P 5 ~r ·C ·K ! (7)
1 1 1 1
Density,
Heat, tivity,
1/2 Code Material kg/m ·
P 5 ~r ·C ·K ! (8) J/kg W/m·
2 2 2 2 3
K·10 K
1/2
P 5 ~r ·C ·K ! (9)
3 3 3 3
1 steel 7.80 0.46 45.200
a 5 K /r ·C (10) 2 aluminum 2.70 0.96 154.800
1 1 1 1
3 brass 8.90 0.38 85.400
a 5 K /r · C (11)
2 2 2 2
4 borosilicate glass 2.25 0.84 1.130
5 porcelain 2.20 0.84 1.210
where:
6 concrete 2.47 0.92 2.430
7 brick 1.70 0.84 0.630
T 5 initial tissue temperature, °C,
8 stone 2.30 0.84 0.920
N 5 integral constant, 1 > ‘,
9 plastics 1.28 1.55 0.250
−5
X 5 depth of tissue of interest, normally 8.0 3 10
10 phenolics 1.25 1.38 0.042
m, 11 nylons 1.11 2.09 0.209
12 ABS resins 1.04 1.51 0.170
a 5 thermal diffusivity of layer i,m /s,
i
13 wood 0.66 1.72 0.130
l 5 layer thickness of jacket material, m,
14 paper 0.60 2.81 0.084
−2 −1
P 5 layer thermal inertia; W·m ·K · s,
=
15 human tissue 0.90 4.60 0.544
t 5 time of contact, s, 16 water 1.00 4.19 0.602
17 cork 0.13 2.01 0.042
T 5 initial hot surface temperature, K,
i
18 mineral wool 0.19 1.00 0.059
T 5 contact skin temperature at depth X and at time
c
19 cal silicate 0.24 1.09 0.067
(t) after contact, K,
20 foam glass 0.13 0.76 0.071
erfc(u) 5 complementary error function (a mathematical 21 organic foam 0.05 1.05 0.021
22 glass cloth 0.40 0.63 0.084
function),
23 fiberglas-LD 0.10 1.00 0.046
r 5 density of material i, kg/m ,
i
24 TFE-fluorocarbon 2.15 1.05 0.243
K 5 conductivity of material i, W/m · K, and
25 masonite 1.00 1.67 0.173
i
NOTICE:¬This¬standard¬has¬either¬been¬superceded¬and¬replaced¬by¬a¬new¬version¬or¬discontinued.¬
Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information.¬
C 1057
were obtained for a simulated burn
...