1、Designation: E 1652 03Standard Specification forMagnesium Oxide and Aluminum Oxide Powder andCrushable Insulators Used in the Manufacture of Metal-Sheathed Platinum Resistance Thermometers, Base MetalThermocouples, and Noble Metal Thermocouples1This standard is issued under the fixed designation E 1
2、652; 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 (e) indicates an editorial change since the last revision or reappr
3、oval.1. Scope1.1 This specification covers the requirements for magne-sium oxide (MgO) and aluminum oxide (Al2O3) powders andcrushable insulators used to manufacture metal-sheathed plati-num resistance thermometers (PRTs), noble metal thermo-couples, base metal thermocouples, and their respective ca
4、bles.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 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 establis
5、h appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 329 Test Method for Apparent Density of Metal Powdersand Related Compounds Using the Scott Volumeter2C 573 Methods for Chemical Analysis of F
6、ireclay andHigh-Alumina Refractories3C 574 Method for Chemical Analysis of Magnesite andDolomite Refractories4C 809 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade AluminumOxide and Aluminum Oxide-Boron Carbide CompositePellets5C 832 Test Method for Measur
7、ing the Thermal Expansionand Creep of Refractories Under Load6D 2766 Test Method for Specific Heat of Liquids andSolids7D 2858 Test Method for Thermal Conductivity of ElectricalGrade Magnesium Oxide8E 228 Test Method for Linear Thermal Expansion of SolidMaterials with a Vitreous Silica Dilatometer9E
8、 235 Specification for Thermocouples, Sheathed, Type K,for Nuclear or for Other High-Reliability Applications10E 344 Terminology Relating to Thermometry and Hydrom-etry10E 585/E 585M Specification for Compacted Mineral-Insulated, Metal-Sheathed, Base Metal ThermocoupleCable10E 1137 Specification for
9、 Industrial Platinum ResistanceThermometers10E 1225 Test Method for Thermal Conductivity of Solids byMeans of the Guarded-Comparative-Longitudinal HeatFlow Technique9E 2181/E 2181M Specification for Compacted Mineral-Insulated, Metal-Sheathed, Noble Metal Thermocouplesand Thermocouple Cable103. Term
10、inology3.1 The definitions given in Terminology E 344 shall applyto this specification.4. Significance and Use4.1 Magnesium oxide and aluminum oxide are used toelectrically isolate and mechanically support the thermoele-ments of a thermocouple (see Specifications E 235, E 585/E 585M, and E 2181/E 21
11、81M) and the connecting wires of aPRT (see Specification E 1137) within a metal sheath. The1This specification is under the jurisdiction of ASTM Committee E20 onTemperature Measurement and is the direct responsibility of Subcommittee E20.04on Thermocouples.Current edition approved May 10, 2003. Publ
12、ished June 2003. Originallyapproved in 1995. Last previous edition approved in 2000 as E 1652 00.2Annual Book of ASTM Standards, Vol 02.05.3Discontinued. See 1994 Annual Book of ASTM Standards, Vol 03.05.4Discontinued. See 1992 Annual Book of ASTM Standards, Vol 03.06.5Annual Book of ASTM Standards,
13、 Vol 12.01.6Annual Book of ASTM Standards, Vol 15.01.7Annual Book of ASTM Standards, Vol 05.01.8Annual Book of ASTM Standards, Vol 10.02.9Annual Book of ASTM Standards, Vol 14.02.10Annual Book of ASTM Standards, Vol 14.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho
14、hocken, PA 19428-2959, United States.metal sheath is typically reduced in diameter to compact theoxide powder or crushable oxide insulators around the thermo-elements or wires.4.2 In order to be suitable for this purpose, the materialsshall meet certain criteria for purity and for mechanical anddime
15、nsional characteristics. Material that does not meet thepurity criteria may cause premature failure of the sensor.4.3 Use of this specification for the procurement of powderand crushable insulators will help to ensure that the productobtained is suitable for the intended purpose.4.4 Useful informati
16、on about alumina and magnesia is givenin the appendixes.5. Ordering Information5.1 The purchaser shall specify the following when order-ing:5.1.1 Materialfrom 5.1.1.1 through 5.1.1.5 below:5.1.1.1 Al2O3Type 1 per Table 1.5.1.1.2 Al2O3Type 2 per Table 1 and SupplementaryRequirement S1.5.1.1.3 MgO Typ
17、e 1 per Table 1.5.1.1.4 MgO Type 2 per Table 1 and Supplementary Re-quirement S1.5.1.1.5 MgO Type 3 per Supplementary Requirement S2.5.1.2 Insulator Outside Diameter.5.1.3 Hole Diameter.5.1.4 Number of Holes.5.1.5 Hole Pattern.5.1.6 Length.5.1.7 Particle Size (if supplied as powder).5.1.8 Minimum In
18、side Diameter of Tubing, into whichinsulators will be inserted.5.2 Consult the insulator manufacturer for limitations ofrelationships between outside diameter, hole diameters, holepatterns, and length.6. Chemical Requirements6.1 The final product shall be chemically analyzed usingappropriate methods
19、 listed in 9.1. Major impurities shall notexceed the limits indicated in Table 1 unless permitted bysupplementary requirements. Any detected impurity with aconcentration greater than 0.001 % (mass) shall be reported tothe purchaser.7. Physical Properties7.1 DensityThe density of crushable magnesium
20、oxideand aluminum oxide insulators typically ranges from 2060kg/m3(0.074 lbm/in.3) to 3060 kg/m3(0.111 lbm/in.3).Specific density requirements, as well as the test method to beused to determine density, shall be negotiated between thepurchaser and manufacturer. See Appendix X3 for suggestedtest meth
21、ods.7.2 Modulus of RuptureIn the past, a breaking force testhas been used that is based on a relative modulus of rupture andis related to crushability. However, with variations in modulusfrom 21 to 83 MPa (3000 to 12 000 lb/in.2) influenced byinsulator configuration, number of holes, and cross-secti
22、onaldimensions, specific modulus requirements cannot be listed foreach configuration. The modulus of rupture is best used for lotto lot comparison of a given insulator size and configuration.See Appendix X4 for a suggested test method.8. Dimensional Requirements8.1 Outside diameter and hole diameter
23、 tolerances for insu-lators shall be as specified in Table 2 and Table 3, respectively,unless otherwise agreed to between purchaser and manufac-turer.8.2 Wall and web thicknesses (see Fig. 1) shall be equalwithin outside diameter tolerance as specified in Table 2 unlessotherwise agreed to between pu
24、rchaser and manufacturer.8.3 Camber shall not exceed 0.3 % of the length. Insulatorshall be capable of passing through a rigid straight tube longerthan the insulator and with an inside diameter as specified in5.1.8.8.4 Helical twist of holes shall not exceed 2 per cm (5 perin.) of length.8.5 Length
25、shall be as specified in 5.1.6 with a toleranceof +6/0.00 mm ( +0.25/0.00 in.).8.6 The ends of each insulator should be cut square and notbe chipped.9. Test Methods9.1 Chemical Composition:9.1.1 Wet chemical analysis, or fusion calorimetric analysis,or both, can be used for quantitative determinatio
26、n of silicondioxide (SiO2), iron oxide (Fe2O3), and zirconium oxideTABLE 1 Impurity LimitsAAluminum Oxide (Al2O3) 99.65 %(mass) minMagnesium Oxide (MgO) 99.40 %(mass) minImpurityConcentration,% (mass)ImpurityConcentration,% (mass)Fe2O30.04 maxBCaO 0.35 maxCSiO20.08 maxDAl2O30.15 maxCCaO 0.08 max Fe2
27、O30.04 maxB,CMgO 0.08 max SiO20.13 maxC,DZrO20.08 max C 0.02 maxNa2O 0.06 max S 0.005 maxC 0.01 max B 0.0035 maxS 0.005 max Cd 0.001 maxCd 0.001 max B + Cd 0.004 maxB 0.001 maxAThe total compositional analysis should equal 100 %.BThe presence of Fe2O3can adversely affect the electrical resistivity o
28、f theseinsulators. Moreover, changes in the thermometric properties of platinum and itsalloys that are exposed to Fe2O3concentrations above 0.04 % become morepronounced when exposed to the higher service temperatures, for example, above650 C (1200 F), for prolonged periods. However, at lower service
29、 temperatures,purchaser may choose to allow Fe2O3concentrations of up to 0.1 % in Al2O3or0.15 % in MgO. See Supplemental Requirement S1.CSee Supplemental Requirement S2 for base-metal thermocouple applications.DThe presence of SiO2can, at elevated temperatures, lead to changes in theelectrical resis
30、tivity, thermoelectric characteristics, and mechanical properties ofplatinum and its alloys.TABLE 2 Outside Diameter (O.D.) ToleranceNominal Insulator O.D. O.D. Tolerance0.25 to 1.48 mm (0.010 to 0.058 in.) 60.05 mm (60.002 in.)1.49 to 6.33 mm (0.059 to 0.249 in.) 60.08 mm (60.003 in.)6.34 to 9.51 m
31、m (0.250 to 0.374 in.) 60.10 mm (60.004 in.)9.52 to 12.70 mm (0.375 to 0.500 in.) 60.15 mm (60.006 in.)12.71 mm (0.501 in.) and larger 61.6 %E1652032(ZrO2) with gravimetric determination for SiO2and Fe2O3.The SiO2filtrate can be used for further calcium oxide (CaO)determination.9.1.2 Test Method C 8
32、09 can be used for quantitativeanalysis of elemential impurities.9.1.3 Methods C 573 can be used for quantitative analysisof Fe2O3, SiO2, CaO, MgO, and sodium monoxide (Na2O) inAl2O3.9.1.4 Method C 574 can be used for quantitative analysis ofCaO, Al2O3,Fe2O3, and SiO2in MgO.9.1.5 Any method used for
33、 quantitative determinationshould have a detection sensitivity of at least 0.001 % (mass).9.2 Density (Powder)Test Method B 329 can be used fordetermining the density of Al2O3and MgO powders.9.3 Appendix X5 lists other optional test methods.10. Handling and Storage Precautions10.1 Powders and crusha
34、ble insulators shall be shipped andstored in containers that prevent contamination and breakage.Powders and crushable insulators should be stored in a sealedcontainer to prevent contamination by moisture absorption.(See Appendix X2.)11. Keywords11.1 aluminum oxide; crushable; insulator; magnesium ox
35、-ide; mineral-insulated, metal-sheathed cable; platinum resis-tance thermometer; thermocouple, base metal; thermocouple,noble metalSUPPLEMENTARY REQUIREMENTSThe following supplementary requirement shall apply only when specified by the purchaser in theinquiry, contract, or order.S1. Iron Oxide (Fe2O
36、3) ConcentrationS1.1 Insulators used in service at temperatures 650 C(1200 F) and below shall conform to the chemical require-ments of 6.1 except that the impurity Fe2O3may have amaximum concentration of 0.10 % for Al2O3or 0.15 % forMgO. These oxide compositions shall be designated Al2O3Type 2 and M
37、gO Type 2, respectively.S2. Insulators for Base Metal ThermocouplesS2.1 Calcium oxide, aluminum oxide, and silicon oxide areno more likely than is magnesium oxide to react deleteriouslywith the thermoelement alloys of base metal thermocouples attemperatures that are recommended for the operation of
38、thosethermoelement alloys. Therefore, optionally, for base metalthermocouples only, MgO insulators shall conform to thechemical requirements of 6.1 and Table S2.1 instead of Table1. This oxide composition shall be designated MgO Type 3.TABLE 3 Hole Diameter ToleranceNominal Insulator Hole Diameter H
39、ole Diameter Tolerance0.18 to 0.26 mm (0.007 to 0.010 in.) 60.038 mm (60.0015 in.)0.27 to 1.51 mm (0.011 to 0.059 in.) 60.05 mm (60.002 in.)1.52 to 2.52 mm (0.060 to 0.099 in.) 60.08 mm (60.003 in.)2.53 to 3.79 mm (0.100 to 0.149 in.) 604 %3.80 mm (0.150 in.) and larger 605 %FIG. 1 Wall and Web Thic
40、knessesTABLE S2.1 Impurity LimitsAMagnesium Oxide (MgO) 97.00 % (mass) minImpurity Concentration, % (mass)CaO 0.80 maxAl2O31.00 maxFe2O30.08 maxSiO21.20 maxFe 0.02 maxC 0.02 maxS 0.005 maxB 0.0025 maxCd 0.001 maxB + Cd 0.003 maxMgO + CaO + Al2O3+ SiO299.50 minAThe total compositional analysis should
41、 equal 100 %.E1652033APPENDIXES(Nonmandatory Information)X1. MATERIALS AND MANUFACTUREX1.1 Alumina (Al2O3)X1.1.1 Sources:X1.1.1.1 Bauxite is the principal source of alumina. Gibb-site, Al(OH)3, is the most stable phase. Boehmite, AlO(OH),also occurs in nature. High grade bauxite is low in iron andsi
42、lica content. The major use of purified alumina is in theproduction of aluminum metal.X1.1.1.2 Depending upon the application, the economics,and the purity of the bauxite, the purification process could bewet alkaline, wet acid, alkaline furnace, carbothermic furnace,or electrolytic processes.X1.1.1
43、.3 The wet alkaline processes are most economical.Gibbsite bauxite is easier to dissolve. It is digested in sodiumhydroxide (NaOH) solution at about 150 C (302 F) at 345kPa (50 lb/in.2). Boehmitic bauxite, AlO(OH), is more difficultto dissolve. It requires a higher concentration of NaOHsolution, a p
44、ressure of 1930 to 4826 kPa (280 to 700 lb/in.2),and a temperature of about 238 C (545 F).X1.1.1.4 When digested, the slurry is cooled to about100 C (212 F) by releasing pressure to atmospheric, and theundissolved “mud” is sedimented or filtered off. When cooledto about 50 C (122 F) and seeded with
45、alumina-trihydrate,precipitation occurs. The precipitated trihydrate is washed andthen calcinated. The trihydrate dehydrates slowly. At atmo-spheric pressures, the dehydration process involves two steps.X1.1.1.5 The trihydrate dehydrates first to a compositionclose to boehmite (Al2O3H2O). Even at 20
46、0 C (392 F) therate of dehydration is very slow. Dehydration is found to beessentially complete at 400 C (752 F) in an oven at belowatmospheric pressure or at 500 C (932 F) at atmosphericpressure. In a study, the heating at 538 C (1000 F) for 7 h stillshowed 0.1 moles of H2O per mole Al2O3, that is,
47、 about 2 %.Differential thermal analysis (DTA) studies show endothermiceffects at 225, 300, and 550 C (437, 572, and 1022 F,respectively). The peak at 550 C (1022 F) represents thedehydration of boehmite.X1.1.1.6 Activated alumina is a desiccant and, when acti-vated in vacuum, is more easily rehydra
48、ted. Alumina activatedin vacuum at 180 to 200 C (356 to 392 F) and then heated inair at about 350 to 450 C (662 to 842 F) does not rehydrateas easily. No rehydration was found with alpha alumina of lowsurface area. To achieve low surface area the alumina should beheated to at least 1700 C (3092 F).
49、Alumina is sintered atabout 1700 to 2000 C (3092 to 3632 F). It melts around2050 C (3722 F).X1.1.2 Typical Crystal Properties:X1.1.2.1 Coeffcient of Thermal Expansion6 to 9 3 106/K (3.3 to 5 3 106/F) between 20 and 1000 C (68 and1832 F).X1.1.2.2 Crystal Shape Hexagonal.X1.1.2.3 Maximum Theoretical Density3.98 3 103kg/m3(0.144 lbm/in.3).X1.1.2.4 Dielectric Strength5600 kV/m (142 000 V/in.).X1.1.2.5 Hardness (MOHS)9.X1.1.2.6 Softening Temperature1750 C (3182 F).X1.1.2.7 Melting Temperature2050 C (3722 F).X1.1.2.8 Molecular Weigh
