ASTM E145-94(2001)
(Specification)Standard Specification for Gravity-Convection And Forced-Ventilation Ovens
Standard Specification for Gravity-Convection And Forced-Ventilation Ovens
SCOPE
1.1 This specification covers the performance requirements for general-purpose air ovens ordinarily used in testing operations, which have a testing chamber up to 0.6 m3 (25 ft3) in volume. It is applicable to gravity-convection ovens designed to operate over all or part of the temperature range from 20°C above ambient temperature to 200°C and to forced-ventilation ovens designed to operate over all or part of the temperature range from 20°C above ambient temperature to 500°C.
Note 1—Ovens are designed for maximum operating temperatures of about 200°C, 300°C, and 500°C, the thermal insulation and cost of the oven being dependent on the maximum temperature required.
1.2 This specification does not include safety requirements that are essential for ovens used in the presence of combustible vapors or gases.
1.3 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate.
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Designation:E145–94 (Reapproved 2001)
Standard Specification for
Gravity-Convection And Forced-Ventilation Ovens
This standard is issued under the fixed designation E145; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope controllable by an automatic device, and shall be uniform
within the tolerances given inTable 1 for the particular type of
1.1 This specification covers the performance requirements
oven when tested in accordance with Section 4.
for general-purpose air ovens ordinarily used in testing opera-
3 3
3.2 The“timeconstant”isanarbitrarymeasureoftherateat
tions, which have a testing chamber up to 0.6 m (25 ft ) in
which a standard specimen is heated following the procedure
volume. It is applicable to gravity-convection ovens designed
prescribedinSection5.Thevalueofthetimeconstantshallnot
to operate over all or part of the temperature range from 20°C
exceed the maximum value given in Table 1 for the particular
above ambient temperature to 200°C and to forced-ventilation
type of oven.
ovens designed to operate over all or part of the temperature
3.3 The rate of ventilation of the testing chamber shall
range from 20°C above ambient temperature to 500°C.
conform to the requirements specified in Table 1 for the
NOTE 1—Ovens are designed for maximum operating temperatures of
particular type of oven when measured in accordance with the
about 200°C, 300°C, and 500°C, the thermal insulation and cost of the
procedure given in Section 6.
oven being dependent on the maximum temperature required.
TEST METHODS
1.2 This specification does not include safety requirements
thatareessentialforovensusedinthepresenceofcombustible
4. Temperature Uniformity
vapors or gases.
4.1 Placeninecalibratedthermocouples(Note2)madefrom
1.3 The values stated in inch-pound units are to be regarded
iron or copper-constantan wire, approximately 0.5 mm in
as the standard. The metric equivalents of inch-pound units
diameter (No. 24 gage) and having a junction size of not more
may be approximate.
than 2 mm (0.08 in.), in the empty testing chamber with
2. Types
shelves in place and vents open. Locate one thermocouple in
2.1 This specification covers the following four types of air eachoftheeightcornersoftheovenapproximately5cm(2in.)
fromeachwallandplacetheninththermocouplewithin2.5cm
ovens:
2.1.1 Type IA—An oven ventilated by gravity convection (1 in.) of the geometric center of the chamber. A minimum
length of 30 cm (12 in.) of lead wire for each thermocouple
having a uniformity of temperature within 62% of the
differential between oven and ambient temperatures. shall be inside the oven to minimize the conduction of heat
2.1.2 Type IB—An oven ventilated by gravity convection from the thermocouple.
having a uniformity of temperature within 65% of the
NOTE 2—If calibrated thermocouples are not available, nine thermo-
differential between oven and ambient temperatures.
couplesmadefromthesamespoolofwiremaybeusedprovidedtheygive
2.1.3 Type IIA—An oven having forced ventilation and a
thesamevaluefortemperaturewhenplacedadjacenttooneanotherinthe
uniformity of temperature within 61% of the differential testing chamber at the temperature of test.
between oven and ambient temperatures.
4.2 Bring the oven to the specified temperature and allow it
2.1.4 Type IIB—An oven having forced ventilation and a
toreachasteadystate(Note3).Recordthetemperaturesofthe
uniformity of temperature within 62.5% of the differential
nine thermocouples for a period of at least 24 h, and determine
between oven and ambient temperatures.
from the record the maximum deviation of each point from the
desiredtemperatures.Theambientroomtemperatureshallvary
3. Performance Requirements
by not more than a total of 10°C, and the line voltage for
3.1 The temperature within the testing chamber shall be
electrically heated ovens shall vary by not more than a total of
5% during the test.
This specification is under the jurisdiction of ASTM Committee E41 on
NOTE 3—Some ovens may require as much as 24 h to reach a steady
Laboratory Apparatus and is the direct responsibility of Subcommittee E41.01
state. If a steady state does not exist, there is a drift in the temperature
Apparatus.
toward the steady-state condition.
Current edition approved Aug. 15, 1994. Published October 1994. Originally
published as E145–59T. Last previous edition E145–68(1992).
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E145
TABLE 1 Performance Requirements for Oven
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