1、Designation: D7969 15Standard Specification forGravity Convection and Forced Ventilation Ovens1This standard is issued under the fixed designation D7969; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the performance requirementsfor general purpose air ovens ordinarily used in testingoperations, which have a
3、testing chamber up to 0.6 m3(25 ft3)in volume.1.2 It is applicable to gravity convection ovens designed tooperate over all or part of the temperature range from 20Cabove ambient room temperature to 200C.1.3 It is applicable to forced ventilation ovens designed tooperate over all or part of the tempe
4、rature range from 20Cabove ambient room temperature to 500C.1.4 This specification does not include safety requirementsthat are essential for ovens used in the presence of combustiblematerials.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are fo
5、r referenceonly and may be approximate.1.5.1 The SI base unit of the expression of temperature isKelvin (K), the unit of measure used in this specification isCelsius (C) and has been derived mathematically.1.6 Calibration ovens to this standard are necessary toassure their operative performance unde
6、r typical conditions ofuse and shall be performed periodically, either according to themanufacturers recommendations, the quality requirements ofthe end user, their customers, or suppliers.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
7、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E145 Specification for Gravity-Convection and Forced-Ventilation Ovens3. Terminolog
8、y3.1 Definitions:3.1.1 ambient room temperaturea temperature asrecorded, typically but not necessarily, close to room tempera-ture.3.1.2 room temperaturea temperature in the range from 20to 30C (68 to 86F).3.1.3 standard laboratory atmospherean atmosphere hav-ing a temperature of 23 6 2C (73.4 6 3.6
9、F) and a relativehumidity of 50 6 10 % RH (40 to 60 % RH) shall be thestandard laboratory atmosphere.3.1.4 standard laboratory temperaturea temperature of 236 2C (73.4 6 3.6F) shall be the standard laboratorytemperature.4. Oven Types4.1 This specification covers the following four types of airovens:
10、4.1.1 Type IAGCAn oven ventilated by gravity convectionhaving a uniformity of temperature within 62 % of thedifferential between oven and ambient temperatures.4.1.2 Type IBGCAn oven ventilated by gravity convectionhaving a uniformity of temperature within 65 % of thedifferential between oven and amb
11、ient temperatures.4.1.3 Type IIAFVAn oven having forced ventilation and auniformity of temperature within 61 % of the differentialbetween oven and ambient temperatures.4.1.4 Type IIBFVAn oven having forced ventilation and auniformity of temperature within 62.5 % of the differentialbetween oven and a
12、mbient temperatures.5. Performance Requirements5.1 The temperature within the testing chamber shall becontrollable by an automatic device, and shall be uniformwithin the tolerances given in Table 1 for the particular type ofoven when tested in accordance with Section 6.5.1.1 Conformance to temperatu
13、re uniformity (Section 6)isa requirement.5.2 The time constant measurement is nonmandatory and isfound in Appendix X1 of this specification.1This specification is under the jurisdiction ofASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.15 on Degradation Tests.Current
14、 edition approved July 1, 2015. Published September 2015. DOI:10.1520/D7969-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page o
15、nthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.3 The rate of ventilation of the testing chamber shallconform to the requirements specified in Table 1 for theparticular type of oven when measured in accordance with
16、 theprocedure given in Section 7.5.3.1 Conformance to the rate of ventilation (Section 7)isarequirement.TEST PROCEDURES6. Temperature Uniformity6.1 Place nine calibrated thermocouples approximately 0.5mm in diameter (No. 24 gauge) and having a junction size ofnot more than 2 mm (0.08 in.), in a clea
17、n, properly maintained,empty testing chamber with any shelves or commonly usedappurtenances in place and all vents fully open.6.1.1 Locate one thermocouple in each of the eight cornersof the oven approximately 50 mm (2 in.) from each wall.6.1.2 Place the ninth thermocouple within 25 mm (1 in.) ofthe
18、 geometric center of the chamber.6.1.3 Aminimum length of 300 mm (12 in.) of lead wire foreach thermocouple shall be inside the oven to minimize theconduction of heat from the thermocouple.6.2 The ambient room temperature shall not vary during theduration of the test by more than a total of 10C as m
19、easuredby a tenth thermocouple placed externally no less than2m(78in.) from the oven and not in contact with materials known toradiate heat or be thermally conductive, preferably suspendedat the approximate midpoint height of the oven.6.3 Bring the oven to the specified temperature and allow itto re
20、ach a steady state.6.3.1 It may require as much as 24 hours to reach a steadystate, that is no more than the deviation from the specifiedtemperature differential as indicated in Table 1 for a period ofno less than three hours prior to assessment.6.3.2 If a steady state is not achieved, a drift in th
21、etemperature toward the steady-state condition should exist andbe within 3C of the desired testing temperature (set point) atthe time of assessment.6.4 Record the temperatures of the ten thermocouples for aperiod of no less than three hours at intervals of no greater than15 minutes, and determine, f
22、rom the record, the maximumdeviation of each point from the desired temperatures.6.5 Report the results of the recorded observations fromeach of the ten thermocouples including the time period forwhich they were obtained.7. Rate of Ventilation7.1 Position a calibrated, digital, vane anemometer, capa
23、bleof accounting for the diameter of the vane opening diameterand calculating the volume of air flow, securely to the ovensair exhaust port so that all air exhausted from the oven passesthrough the vane area and does not circumvent it.7.1.1 In instances where positioning the anemometer is notpossibl
24、e due to encumbrances of exhaust hoods, permanentlymounted vents, etc., the procedure in E145, Part 5, should befollowed and reported accordingly.7.2 Heat the oven to a temperature of 20 6 2C above theambient room temperature and, while at this temperature,record the airflow through the vane anemome
25、ter for period ofat least 30 minutes.7.2.1 Calculate the number of changes per hour consideringthe volume of the chamber, the air flow recorded by the vaneanemometer, and the time during which the air flow wasrecorded and report the result as demonstrated in Eq 1.7.3 The ambient room temperature sha
26、ll be measured asdescribed in 6.2 for the duration of the test.7.4 Calculate the number of changes per hour of the air inthe test chamber from the following equation:N 5SevD360 (1)where:N = number of air changes per hours,v = volume of the testing chamber (ft3or m3), ande = exhaust air flow measured
27、 by a vane anemometer perminute (cfm or cmm).NOTE 1It is important, when performing the above calculation, thatthe units of measure are in agreement, for example, ft3and cubic foot perminute (cfm); m3and cubic metres per minute (cmm).8. Keywords8.1 forced-ventilation; gravity-convection; ovensTABLE
28、1 Performance Requirements for OvensCharacteristic Type IAGC Type IBGC Type IIAFV Type IIBFVDeviation from specified temperature of test throughout testingchamber during 3 h period for the following differentials betweenambient and test temperatures:#50C | maximum percent of differential 1.0 2.5 0.5
29、 1.2550C | maximum percent of differential 2.0 5.0 1.0 2.5Rate of ventilation testing chamber, air changes per hour:Minimum 10 10 50 50Maximum 200 200D7969 152APPENDIXES(Nonmandatory Information)X1. TIME CONSTANTX1.1 The “time constant” is an arbitrary measure of the rateat which a standard specimen
30、 is heated following the procedureprescribed below. The value of the time constant should notexceed the maximum value given in Table X1.1 for theparticular type of oven.X1.1.1 Conformance to the time constant is not arequirement, but may be valuable in assessing the ovensperformance in routine servi
31、ce. It should be studied when otherparameters are questioned.TABLE X1.1 Time Constant Performance Requirements for OvensNOTE 1Time constant only, other values for reference only, refer to Table 1 in this specification.Characteristic Type IAGC Type IBGC Type IIAFV Type IIBFVDeviation from specified t
32、emperature of test throughout testing chamberduring 3 h period for the following differentials between ambient and testtemperatures:#50C | maximum percent of differential 1.0 2.5 0.5 1.2550C | maximum percent of differential 2.0 5.0 1.0 2.5Time constant, maximum seconds 600 720 480 660Rate of ventil
33、ation of testing chamber, air changes per hour:Minimum 10 10 50 50Maximum 200 200D7969 153X2. PROCEDUREX2.1 Heat the oven to within 10C of the maximumoperating temperature for which it is designed and allow it tostabilize for at least 1 h.X2.2 Alternatively, heat the oven to within 10C of theoperati
34、ng temperature for which it is typically used and allowit to stabilize for at least 1 h.X2.3 Prepare a standard specimen consisting of a smoothbrass cylinder 9.5 6 0.1 mm (0.375 6 0.005 in.) in diameterand 57 6 1 mm (2.25 6 0.05 in.) in length, and solder onejunction of a differential thermocouple t
35、o it.X2.4 Open the door of the oven for 1 min while the standardspecimen and differential thermocouple are being suspended inthe testing chamber. Suspend the specimen vertically within 25mm (1 in.) of the geometric center of the chamber by means ofa cord of fine wire (0.3 mm maximum diameter, No. 30
36、 gauge).X2.5 Place the free junction of the differential thermocouplein the air space of the chamber at least 75 mm (3 in.) removedfrom the specimen.X2.6 Close the door and either record or measure thetemperature differential every 10 s.X2.7 Determine the time in seconds required for the teme-pratur
37、e difference to decrease to one tenth of the original ormaximum value (for example, from 120 to 12C) and considerthis to be the time constant of the oven and report accordingly.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item ment
38、ionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee
39、and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting
40、 of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO B
41、ox C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 154
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