1、Designation: D5423 14Standard 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, in the case of revision, the
2、 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, operating over all or part o
3、f 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. The requirements for Type II
4、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, they canalso be used wherever
5、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 practices and determine the applic
6、a-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Documents2.1 ASTM Standards:2D2436 Specification for Forced-Convection Laboratory Ov-ens for Electrical Insulation (Withdrawn 1994)3D5374 Test Methods for Forced-Convection Laboratory Ov-ens for Evaluation of Electrical Insulation2.2 Othe
7、r 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, nthe number of air changes perh
8、our 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 temperature fluctuation, ntemperature
9、 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 temperaturedifference at one time between
10、 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 location due to the combination
11、 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 the oven. In IEC 216-4-1,this t
12、erm 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 Characteristics.Current edition approved Apr
13、il 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, www.astm.org, orcontact ASTM Cu
14、stomer 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 Standards Institute (ANSI), 25
15、 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 rate of ventilation of 100 to 20
16、0 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 Type I ovens, 5 to 20 air chan
17、ges 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 been touse the lower rate of
18、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 test temperature.NOTE 2Some te
19、st 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 oven operating at a temperature o
20、f 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 the oven shall be constructed
21、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 an effective seal between thei
22、nterior 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 fittings for attaching conduits fo
23、r 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 specification.8. Certification8.1 For e
24、ach 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, the purchaser shall be furnished
25、 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 and model number of the oven,9.
26、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; temperaturefluctuation; temperatu
27、re 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 # 500 10 5D5423 142APPENDIXES(Non
28、mandatory 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 is good practice to make these
29、 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 to be determined according to
30、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 reported in X1.3should be reco
31、rded 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 designed to provideuniform air te
32、mperature 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 and near the walls of the test c
33、hamber. 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 leading edges of flat specimen
34、sare 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 test results, speci-mens should
35、 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 outlet ports should beavoided, beca
36、use 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 patent rights, and the riskof infr
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