ASTM_E_145_-_19.pdf

Designation:E14519Standard Specification forGravity-Convection and Forced-Ventilation Ovens1This standard is issued under the fixed designation E145;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This specification covers the performance requirementsfor general-purpose air ovens ordinarily used in testingoperations,which have a testing chamber up to 0.6 m3(25 ft3)in volume.It is applicable to gravity-convection ovens de-signed to operate over all or part of the temperature range from20 C above ambient temperature to 200 C and to forced-ventilation ovens designed to operate over all or part of thetemperature range from 20 C above ambient temperature to500 C.NOTE1Ovens are designed for maximum operating temperatures ofabout 200 C,300 C,and 500 C,the thermal insulation and cost of theoven being dependent on the maximum temperature required.1.2 This specification does not include safety requirementsthat are essential for ovens used in the presence of combustiblevapors or gases.1.3 The values stated in SI units are to be regarded asstandard.The values given in parentheses after SI units areprovided for information only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Types2.1 This specification covers the following four types of airovens:2.1.1 Type IAan oven ventilated by gravity convectionhaving a uniformity of temperature within 62%of thedifferential between oven and ambient temperatures.2.1.2 Type IBan oven ventilated by gravity convectionhaving a uniformity of temperature within 65%of thedifferential between oven and ambient temperatures.2.1.3 Type IIAan oven having forced ventilation and auniformity of temperature within 61%of the differentialbetween oven and ambient temperatures.2.1.4 Type IIBan oven having forced ventilation and auniformity of temperature within 62.5%of the differentialbetween oven and ambient temperatures.3.Performance Requirements3.1 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 4.3.2 The“time constant”is an arbitrary measure of the rate atwhich a standard specimen is heated following the procedureprescribed in Section 5.The value of the time constant shall notexceed the maximum value given in Table 1 for the particulartype of oven.3.3 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 theprocedure given in Section 6.TEST METHODS4.Temperature Uniformity4.1 Place nine calibrated thermocouples(Note 2)made fromiron or copper-constantan wire,approximately 0.5 mm indiameter(No.24 gauge)and having a junction size of not morethan 2 mm(0.08 in.),in the empty testing chamber withshelves in place and vents open.Locate one thermocouple ineach of the eight corners of the oven approximately 5 cm(2 in.)from each wall and place the ninth thermocouple within 2.5 cm(1 in.)of the geometric center of the chamber.A minimumlength of 30 cm(12 in.)of lead wire for each thermocoupleshall be inside the oven to minimize the conduction of heatfrom the thermocouple.1This specification is under the jurisdiction of ASTM Committee E41 onLaboratory Apparatus and is the direct responsibility of Subcommittee E41.06 onLaboratory Instruments and Equipment.Current edition approved March 1,2019.Published March 2019.Originallyapproved in 1959.Last previous edition approved in 2011 as E145 94(2011).DOI:10.1520/E0145-19.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 NOTE2If calibrated thermocouples are not available,nine thermo-couples made from the same