ASTM E839-2005 Standard Test Methods for Sheathed Thermocouples and Sheathed Thermocouple Material《铠装热电偶及其材料的标准试验方法》.pdf

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1、Designation: E 839 05Standard Test Methods forSheathed Thermocouples and Sheathed ThermocoupleMaterial1This standard is issued under the fixed designation E 839; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi

2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThermocouples are widely used in industry and they provide reliable service. However, ifthermocouples fail in service, the con

3、sequences can range from negligible to life threatening. Oftena loss of equipment, product, or operating time will result. The user should weigh the potentialconsequences of thermocouple failure when considering what tests should be performed. No tests arerequired by this document except those speci

4、fically ordered by the user. This document lists methodsfor testing sheathed thermocouples and thermocouple material but does not state criteria foracceptance. The acceptance criteria for the particular thermocouple, when subjected to the tests, aregiven in other ASTM standard specifications for tha

5、t thermocouple. Examples from ASTMthermocouple specifications for acceptance criteria are given for many of the tests. These tabulatedvalues are not necessarily those that would be required to meet these tests, but are given here asexamples only.Users should be aware that certain characteristics of

6、thermocouple materials, including the emfversus temperature relationship may change with time in use; consequently, test results andperformance obtained at time of manufacture may not necessarily apply throughout an extendedperiod of use. It should be further noted that due to possible changes in ho

7、mogeneity, attempting torecalibrate used thermocouples is likely to yield irrelevant results, and is not recommended.1. Scope1.1 These are test methods for sheathed thermocouplematerial and assemblies.1.2 The tests are intended to ensure quality control and toevaluate the suitability of sheathed the

8、rmocouple material orassemblies for specific applications. Some alternative testmethods to obtain the same information are given, since in agiven situation an alternative test method may be morepractical. Service conditions are widely variable and so it isunlikely that all the tests described will b

9、e appropriate for agiven thermocouple application. A brief statement is madefollowing each test description to indicate when it might beused.1.3 The tests described herein include test methods tomeasure the following properties of sheathed thermocouplematerial and assemblies.1.3.1 Insulation Propert

10、ies:1.3.1.1 Compactionabsorption method and tensionmethod.1.3.1.2 Thickness.1.3.1.3 Resistanceroom temperature and elevated tem-perature.1.3.2 Sheath Properties:1.3.2.1 Integritywater test (two test methods) and massspectrometer.1.3.2.2 Dimensionslength, diameter, and roundness.1.3.2.3 Wall thicknes

11、s.1.3.2.4 Surfacegross visual, finish, defect detection bydye penetrant, and cold-lap detection by tension test.1.3.2.5 Metallurgical structure.1.3.2.6 Ductilitybend test and tension test.1.3.3 Thermoelement Properties:1.3.3.1 Calibration.1.3.3.2 Homogeneity.1.3.3.3 Drift.1.3.3.4 Thermoelement diame

12、ter, roundness, and surfaceappearance.1.3.3.5 Thermoelement spacing.1.3.3.6 Thermoelement ductility.1.3.3.7 Metallurgical structure.1These test methods are under the jurisdiction of ASTM Committee E20 onTemperature Measurement and is the direct responsibility of Subcommittee E20.04on Thermocouples.C

13、urrent edition approved Nov. 1, 2005. Published December 2005. Originallyapproved in 1989. Last previous edition approved in 1996 as E 839 96 which waswithdrawn in August 2005 and reinstated in November 2005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194

14、28-2959, United States.1.3.4 Thermocouple Assembly Properties:1.3.4.1 Dimensionslength, diameter, and roundness.1.3.4.2 Surfacegross visual, finish, reference end seal,and defect detection by dye penetrant.1.3.4.3 Electricalcontinuity, loop resistance, and connec-tor polarity.1.3.4.4 Radiographic in

15、spection.1.3.4.5 Thermoelement diameter.1.3.4.6 Thermal response time.1.3.4.7 Thermal cycle.2. Referenced Documents2.1 ASTM Standards:2D 2771 Test Methods for Compaction Density of ElectricalGrade Magnesium Oxide3E3 Practice for Preparation of Metallographic SpecimensE94 Guide for Radiographic Exami

16、nationE112 Test Methods for Determining Average Grain SizeE 142 Method for Controlling Quality of RadiographicTesting3E 165 Test Method for Liquid Penetrant ExaminationE 207 Test Method for Thermal EMF Test of Single Ther-moelement Materials By Comparison with a ReferenceThermoelement of Similar EMF

17、-Temperature PropertiesE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 230 Specification and Temperature-Electromotive Force(emf) Tables for Standardized ThermocouplesE 235 Specification for Thermocouples, Sheathed, Type Kand Type N, for Nuclear or for Other High-Reliabil

18、ityApplicationsE 344 Terminology Relating to Thermometry and Hydrom-etryE 585/E 585M Specification for Compacted Mineral-Insulated, Metal-Sheathed, Base Metal ThermocoupleCableE 608/E 608M Specification for Mineral-Insulated, Metal-Sheathed Base Metal ThermocouplesE 780 Test Method for Measuring the

19、 Insulation Resistanceof Sheathed Thermocouple Material at Room TemperatureE 988 Temperature-Electromotive Force (EMF) Tables forTungsten-Rhenium ThermocouplesE 1129/E 1129M Specification for Thermocouple Connec-torsE 1350 Guide for Testing Sheathed Thermocouples Prior to,During, and After Installat

20、ionE 1684 Specification for Miniature Thermocouple Connec-torsE 1751 Guide for Temperature Electromotive Force (emf)Tables for Non-Letter Designated Thermocouple Combi-nationsE 2181/E 2181M Specification for Compacted Mineral-Insulated, Metal-Sheathed, Noble Metal Thermocouplesand Thermocouple Cable

21、2.2 ANSI StandardB 46.1 Surface Texture43. Terminology3.1 DefinitionsThe definitions given in TerminologyE 344 shall apply to these test methods.3.2 Definitions of Terms Specific to This Standard:3.2.1 bulk cable, na single length of thermocouple cable(produced from the same raw material lot) after

22、completion offabrication resulting in sheathed thermocouple material.3.2.2 cable lot, na quantity of finished mineralinsulated,metal-sheathed thermocouple cable manufactured from tubingfrom the same heat, wire from the same spool and heat, andinsulation from the same batch then assembled and process

23、edtogether under controlled production conditions to the requiredfinal outside diameter.3.2.3 cold-lap, nsheath surface defects where the sheathsurface has been galled and torn by a drawing die and the tornsurface smoothed by a subsequent diameter reduction.3.2.4 insulation compaction density, nthe

24、density of acompacted powder is the combined density of the powderparticles and of the voids remaining after the powder compac-tion. Sometimes the insulation compaction density is dividedby the theoretical density of the powder particles to obtain adimensionless fraction of theoretical density as a

25、convenientmethod to express the relative compaction.3.2.5 raw material, ntubing, insulation and wires used inthe fabrication of sheathed thermocouple cable.3.2.6 short range ordering, nthe reversible short-ranged,order-disorder transformation in which the nickel and chro-mium atoms occupy specific (

26、ordered) localized sites in theType EP or Type KP thermoelement alloy crystal structure.3.2.7 thermocouple assembly, nthe cut-to-length, finishedassembly consisting of thermocouple material with thermoele-ments having one end joined in a measuring junction. Theassembly has the sheath closed at the m

27、easuring end and has amoisture seal at the reference junction end of the sheath. Theassembly does not include a reference junction but may includea thermocouple connector, thermocouple extension, or com-pensating wire.4. Summary of Test Methods4.1 Insulation Properties:4.1.1 CompactionThese tests en

28、sure that the insulation iscompacted sufficiently (1) to prevent the insulation fromshifting during use with the possibility of the thermoelementsshorting to each other or to the sheath, and (2) to have goodheat transfer between the sheath and the thermoelements.4.1.2 Insulation ResistanceThe insula

29、tion must be free ofmoisture and contaminants that would compromise thevoltage-temperature relation or shorten the useful life of thesheathed thermocouple. Measurement of insulation resistanceis a useful way to detect the presence of unacceptable levels ofimpurities in the insulation.2For referenced

30、 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 onthe ASTM website.3Withdrawn.4Available from American National Standards Institute (ANSI), 25

31、W. 43rd St.,4th Floor, New York, NY 10036.E8390524.2 Sheath Properties:4.2.1 IntegrityThese tests ensure that (1) the sheath willbe impervious to moisture and gases so the insulation andthermoelements will be protected, (2) surface flaws and cracksthat might develop into sheath leaks are detected, a

32、nd (3) thesheath walls are as thick as specified.4.2.2 DimensionsDetermination of length, diameter, andsheath roundness are often necessary to assure proper dimen-sional fit.4.2.3 Sheath DuctilityThe sheath must be ductile enoughto bend the required amount without breaking or cracking.4.3 Thermoelem

33、ent Properties Service Life:4.3.1 CalibrationThese tests ensure that the temperature-emf relationship corresponds to the standard values bothinitially and after a short time of heating to service tempera-tures.4.3.2 SizeThe thermocouple sheath and thermoelementsizes are related to service life and t

34、he thermoelement spacingis related to possible low insulation resistance or shorting.4.3.3 Thermoelement DuctilityDuctility of the thermoele-ments must be sufficient to allow the assembly to be bentduring assembly or service without significant damage to thethermoelements.4.4 Thermocouple Assembly P

35、ropertiesThe criteria listedabove must apply to both thermocouple assemblies and to bulkcable, and in addition, the following tests are important forthermocouple assemblies.4.4.1 ContinuityThe loop continuity test assures that thethermocouple assembly has a completed circuit.4.4.2 Loop ResistanceThe

36、 loop resistance test can detectshorted or damaged thermoelements.4.4.3 PolarityThe connector polarity test indicateswhether the connector is correctly installed.4.4.4 End SealThe end seal, if faulty, may allow thecontamination of the insulation with moisture or gases.4.4.5 RadiographyRadiographic e

37、xamination of the junc-tion and sheath closure weld can indicate faulty junctions andsheath closures that will lead to early failure. The internaldimensions can also be measured from the radiograph.4.4.6 Response TimeThe thermal response time gives anindication of the quickness with which an install

38、ed thermo-couple will signal a changing temperature under the testconditions.4.4.7 Thermal CycleThe thermal cycle test will offerassurance that the thermocouple will not have early failurebecause of strains imposed from temperature transients.5. Significance and Use5.1 This test method provides a de

39、scription of test methodsused in ASTM specifications that establish certain acceptablelimits for characteristics of thermocouple assemblies andthermocouple cable.5.2 The intended use of these test methods is to define themethods by which the characteristics shall be determined.5.3 The usefulness and

40、 purpose of the included tests aregiven for the category of tests.6. General Requirements6.1 All the inspection operations are to be performed underclean conditions (that is, conditions that will not degrade theinsulation, sheath, or thermoelements), including the use ofsuitable gloves when appropri

41、ate.6.2 During all process steps in which insulation is exposedto ambient atmosphere, the air must be clean, with less than50 % relative humidity, and at a temperature between 20 and26 C (68 and 79 F).6.3 All samples which are tested shall be identified bymaterial code, and shall be traceable to a p

42、roduction run.7. Insulation Properties7.1 Insulation Compaction DensityThe thermal conduc-tivity of the insulation, as well as the ability of the insulation tolock the thermoelements into place, will be affected by theinsulation compaction density.7.1.1 Test Methods D 2771 is a test on representativ

43、especimen to measure the compaction density of electrical grademagnesium oxide. Two methods are used to find the density:Test Method A for water displacement and Test Method B foroil absorption. Both Test Methods A and B require precisionweighing and careful procedure.7.1.2 A direct measurement test

44、 of insulation compactiondensity is applicable if a representative sample can be sec-tioned so the sample ends are perpendicular to the samplelength and the sheath, thermoelements, and insulation form asmooth surface free of burrs. The test procedure is to:7.1.2.1 Weigh the sample section,7.1.2.2 Me

45、asure the sheath diameter and length with amicrometer,7.1.2.3 Separate wires, sheath, and insulation by use of anair abrasive tool (air-driven abrasive particles) to remove theinsulation from the sample,7.1.2.4 Weigh the thermoelements and sheath, and7.1.2.5 Determine the sheath and thermoelements d

46、ensitieseither by experiment or from references.7.1.3 The fraction of the maximum theoretical insulationdensity is determined as follows:A 2 B!/$0.785 C2D 2E/F 1 G/H!#J% (1)where:A = total specimen mass, kg or lb,B = sheath and wires mass, kg or lb,C = sheath diameter, m or in.,D = specimen length,

47、m or in.,E = sheath mass, kg or lb,F = sheath density, kg/m3or lb/in.3,G = wires mass, kg or lb,H = wires density (averaged density if applicable), kg/m3or lb/in.3, andJ = maximum theoretical density of the insulation, kg/m3or lb/in.3.7.2 Insulation Compaction, Tension Test MethodThis is adestructiv

48、e test on representative samples that determines if thethermoelements are locked together with the sheath by thecompacted insulation, but the test does not measure thecompaction density per se. This tension test is the complementof the tests of 7.1 that measure the insulation compactionE839053densit

49、y but does not establish that the thermoelements arelocked to the sheath (since there is no established minimumcompaction density where locking begins). This test can beperformed concurrently with the sheath ductility test (8.5.3).7.2.1 Cut a test specimen about 0.5 m (20 in.) long from oneend of a bulk material length and strip both ends of thespecimen to expose a minimum of 10 mm (0.4 in.) of thethermoelements.7.2.2 Without sealing the exposed insulation, clean thethermoelements (wires) of insulation to provide good electricalcontact and twi