1、Designation: D5423 14 An American National StandardStandard Specification forForced-Convection Laboratory Ovens for Evaluation ofElectrical Insulation1This standard is issued under the fixed designation D5423; the number immediately following the designation indicates the year oforiginal adoption or
2、, 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.1. Scope1.1 This specification covers forced-convection ventilatedelectrically-heated ovens
3、, operating over all or part of thetemperature range from 20C above the ambient temperature to500C, and used for thermal endurance evaluation of electricalinsulating materials.1.2 The specification requirements for Type I ovens arebased on IEC Publication 216-4-1, and are technically identicalto it.
4、 The requirements for Type II ovens are essentiallyidentical to the requirements of Specification D2436. Thisspecification and an associated test method, D5374, havereplaced Specification D2436.1.3 While the ovens covered by this specification areintended primarily for thermal endurance evaluation,
5、they canalso be used wherever their characteristics make them suitablefor other applications.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 and health prac
6、tices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2436 Specification for Forced-Convection Laboratory Ov-ens for Electrical Insulation (Withdrawn 1994)3D5374 Test Methods for Forced-Convection Laboratory Ov-ens for Evaluation of
7、 Electrical Insulation2.2 Other Document:IEC Publication 216-4-1 Guide for the Determination ofThermal Endurance Properties of Electrical InsulatingMaterials, Part 4Aging Ovens, Section1Single-Chamber Ovens43. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 rate of ventilation, n
8、the number of air changes perhour in the oven chamber.3.1.2 set temperature, nthe average of all of the measuredtemperatures within the oven, averaged over the period of anycyclic temperature variation that may occur.3.1.2.1 DiscussionThis is the actual operating temperatureof the oven.3.1.3 tempera
9、ture fluctuation, ntemperature differences atone point in the oven over a period of time.3.1.3.1 DiscussionThis property depends upon the sensi-tivity and type (on/off or proportional) of control used and theheater mass in relation to surface area.3.1.4 temperature gradient, nthe maximum temperature
10、difference at one time between different points in the ovenchamber.3.1.4.1 DiscussionThis property depends on such factorsas uniformity of heater temperature, heater distribution aboutthe oven, and air flow patterns within the oven.3.1.5 temperature variation, ntemperature differenceswith time and l
11、ocation due to the combination of temperaturegradient and temperature fluctuation.3.1.6 thermal lag time, nthe time required for a definedspecimen to reach a specified temperature (or range of tem-perature).3.1.6.1 DiscussionThis property is largely dependentupon the rate of air circulation within t
12、he oven. In IEC 216-4-1,this term is called“ time constant.”3.1.7 time constant, nSee thermal lag time.1This specification is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.17 on Thermal Characteristic
13、s.Current edition approved April 1, 2014. Published May 2014. Originallyapproved in 1993. Last previous edition approved in 2005 as D5423 93 (2004),which was withdrawn in January 2014 and reinstated in April 2014. (1999). DOI:10.1520/D5423-14.2For referenced ASTM standards, visit the ASTM website, w
14、ww.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National
15、Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Classification4.1 Type IOvens with rate of ventilation of 5 to 20 airchanges per hour.4.2 Type IIOvens with ra
16、te of ventilation of 100 to 200 airchanges per hour.5. Test Methods5.1 Determine the properties specified in Section 6 usingTest Methods D5374.6. Performance Requirements6.1 Rate of VentilationThe rate of ventilation at 100C andat the maximum temperature at which the oven is used shall be:6.1.1 For
17、Type I ovens, 5 to 20 air changes per hour,6.1.2 For Type II ovens, 100 to 200 air changes per hour.NOTE 1Past experience in the United States has been to specify 100to 200 air changes per hour, as required for Type II ovens. However,international practice, as defined in IEC Publication 216-4-1, has
18、 been touse the lower rate of ventilation, which is specified for Type I ovens.6.2 Set TemperatureThe set temperature, measured over afive-day test period, shall not vary by more than the valuesgiven in Table 1.6.3 Temperature VariationThe temperature shall not ex-ceed that given in Table 1 for any
19、test temperature.NOTE 2Some test standards may require closer control of temperaturevariation or of set temperature. In such cases, reduction of the variationsspecified in Table 1 is subject to agreement between purchaser andmanufacturer.6.4 Thermal Lag TimeThe thermal lag time, measuredwith the ove
20、n operating at a temperature of 200 6 5C, shallnot exceed 660 s.7. Construction Requirements7.1 The oven shall be soundly constructed of suitablematerials and all electrical and mechanical fittings shall bereadily accessible for inspection, maintenance, and replace-ment purposes.7.2 The interior of
21、the oven shall be constructed of suitablecorrosion-resistant, non-absorbent material, and fabricated soany joints are leak-proof and not subject to corrosion, andhaving interior surfaces that are easy to clean.7.3 The door(s) shall be fitted with hinges and latches toprovide sufficient pressure for
22、an effective seal between theinterior of the oven and the external atmosphere.7.4 The oven shall have provisions for automaticallyswitching off the heaters when the actual oven temperaturesubstantially exceeds the set temperature.7.5 Ports for admitting and exhausting air shall be provided,with fitt
23、ings for attaching conduits for exhaust air. Whenspecified, provisions shall be made for supplying inlet air orother gases from a controlled source.7.6 Dampers for adjusting the rate of ventilation and the aircirculation shall be provided to enable compliance with otherrequirements of this specifica
24、tion.8. Certification8.1 For each oven furnished under this specification, thepurchaser shall be furnished certification that ovens of exactlythe same design have been tested in accordance with thisspecification and Test Methods D5374, and that the require-ments have been met.8.2 Where specified, th
25、e purchaser shall be furnished withresults of tests on the ovens furnished. In such cases, thepositions of the dampers during the tests shall be clearlymarked.9. Product Marking9.1 The following information shall be attached to eachoven furnished under this specification:9.1.1 Name of manufacturer a
26、nd model number of the oven,9.1.2 Purchase order or contract number,9.1.3 Supply voltage, current, and power consumption,9.1.4 Maximum continuous operating temperature,9.1.5 Internal dimensions,9.1.6 External dimensions, and9.1.7 Weight.10. Keywords10.1 forced-convection; ovens; set temperature; tem
27、peraturefluctuation; temperature gradient; thermal endurance evalua-tion; thermal lag time; ventilated; ventilation rateTABLE 1 Temperature RequirementsSet TemperatureRange CTemperature VariationC, maxVariation in SetTemperature, C,max#80 4 280 to #180 5 2.5180 to # 300 6 3300 to # 400 8 4400 to # 5
28、00 10 5D5423 142APPENDIXES(Nonmandatory Information)X1. IN-SERVICE MONITORING BY THE USERX1.1 Regular periodic tests of the oven are necessary inorder to ensure that the oven retains its original characteristicsin service. For ovens in continuous use, these tests should beconducted twice a year. It
29、is good practice to make these testsbefore beginning aging tests at a different temperature.X1.2 These tests are aimed at measuring the set temperatureand temperature variations at the planned aging temperature. Ifpossible, tests should be repeated with the oven loaded withspecimens.X1.3 The values
30、to be determined according to Test Meth-ods D5374 should include at least the following:X1.3.1 The set temperature,X1.3.2 The temperature variation at the set temperature, andX1.3.3 The temperature fluctuation at the center of the ovenchamber over a 24 h period.X1.4 The set temperature measured and
31、reported in X1.3should be recorded as the aging temperature. The temperaturevariation should be within the limits given in Table 1.X2. OVEN LOADINGX2.1 The air circulation within a forced-convection ovenshould be considered when loading specimens into the ovenchamber. Forced-convection ovens are des
32、igned to provideuniform air temperature throughout the test chamber. Thisuniformity of air temperature is achieved by using baffles, ordifferent sizes of holes, or both at the air inlet and outlet to andfrom the chamber.X2.2 The air flow within an oven is almost laminar at the airinlet and outlet an
33、d near the walls of the test chamber. The airis turbulent within the center of the chamber.X2.3 It has been noted that specimens positioned in thelaminar air flow regions age faster than those in the turbulentregion. The reason for this phenomenon is not understood, butit has been observed that the
34、leading edges of flat specimensare a degree or two hotter than the trailing edge. There alsomay be a tendency for plasticizers to be stripped more rapidlyfrom specimens in the laminar flow regions because of higherair velocity across the surface of the specimens.X2.4 For maximum reproducibility of t
35、est results, speci-mens should be placed in the turbulent air flow region. In anempty oven chamber, the turbulent flow region occupies theinner half of the chamber volume. This region decreases withloading, depending on specimen geometry and positioning.Placement of specimens near the inlet or outle
36、t ports should beavoided, because of the laminar air flow.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such pate
37、nt 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 and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited eith
38、er 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 of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair h
39、earing 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 Box 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 ASTM website (www.astm.org/COPYRIGHT/).D5423 143
