Copyright ASTM Standard Specication for Gravity-Convection And Forced-Ventilation Ovens1 This standard is issued under the xed designation E ; 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. Scope 1. It is applicable to gravity-convection ovens designed to operate over all or part of the temperature range from 20C above ambient temperature to C and to forced-ventilation ovens designed to operate over all or part of the temperature range from 20C above ambient temperature to C.
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A number in parentheses indicates the year of last reapproval. This standard has been approved for use by agencies of the U. Department of Defense. The metric equivalents of inch-pound unitsmay be approximate. Performance Requirements3. The value of the time constant shall notexceed the maximum value given in Table 1 for the particulartype of oven. Temperature Uniformity4.
Locate one thermocouple ineach of the eight corners of the oven approximately 5 cm 2 in. A minimumlength of 30 cm 12 in. NOTE 2—If calibrated thermocouples are not available, nine thermo-couples made from the same spool of wire may be used provided they givethe same value for temperature when placed adjacent to one another in thetesting chamber at the temperature of test.
Record the temperatures of thenine thermocouples for a period of at least 24 h, and determinefrom the record the maximum deviation of each point from thedesired temperatures. Current edition approved Dec. Published December Originallyapproved in Last previous edition approved in as E — 94 DOI: If a steady state does not exist, there is a drift in the temperaturetoward the steady-state condition.
Time Constant5. Prepare a standard specimen consisting of a smoothbrass cylinder 9. Suspend the specimen vertically within 25mm 1 in. Place the free junction of the differential thermo-couple in the air space of the chamber at least 75 mm 3 in. Then close the door and eitherrecord or measure the temperature differential every 10 s.
Rate of Ventilation Note 4 6. Connect a watt-hour meter, with the smallest division readingin 0. NOTE 4—This method is only applicable to electrically heated ovens.
Methods are being developed by the committee for determining the rate ofventilation of ovens that are not electrically heated and for determining theuniformity of air-flow within the testing chamber. NOTE 5—In forced-ventilation ovens, the space around the motor shaftwhere it enters the oven must be closed, but the fan speed must not beaffected by the closure. The ambient room temperature measured at a pointapproximately2m 6ft from the oven, approximately levelwith its base and at least 0.
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