ASTM E295-1982(2006) Standard Test Method for Measured Speed of Oil Diffusion Pumps《测量油扩散泵速度的试验方法》.pdf
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1、Designation: E 295 82 (Reapproved 2006)Standard Test Method forMeasured Speed of Oil Diffusion Pumps1This standard is issued under the fixed designation E 295; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the mea-sured speed (volumetric flow rate) of oil diffusion pumps.1.2 The values st
3、ated in inch-pound units are to be regardedas the standard. The metric equivalents of inch-pound unitsmay be approximate.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 establish appro-p
4、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 297 Method for Calibrating Ionization Vacuum GageTubes33. Terminology3.1 measured speedthe mass flow rate of gas admittedfrom a flowmeter divided by
5、the resulting increase in equilib-rium static pressure near the inlet of the pump, using theequipment in Fig. 1.4. Summary of Test Method4.1 The pump under test is fitted with a test dome ofspecified design (Fig. 1). Gas is admitted to the test dome in aspecified manner at a measured rate, and the r
6、esulting changein equilibrium pressure is measured in a specified way.5. Apparatus5.1 Test DomeThe test dome (Fig. 1) may be constructedby any material and by any method acceptable in high-vacuumpractice, and will normally be connected to the pump by themethod provided for in the design of the pump.
7、 The insidediameter of the test dome shall be equal to that of the pumpinlet, and its mean height shall be 1.5 times this diameter (Note1). The gas shall be admitted through a tube projecting into thedome and bent upward so that its exit is located on the axis,facing away from the pump inlet port, a
8、nd at a distance fromthe pump inlet equal to the dome diameter. The opening to thevacuum gage shall be through a tube radially projecting intothe test dome. The tubulation center line shall be above theinlet flange, 1 in. (25 mm) or14 D above the top of the flange,whichever is larger (see Fig. 1).NO
9、TE 1A 10 slope of the dome roof is required only if the dome isto be used for back-streaming measurements.5.2 Gage AttachmentThe gage connecting line shall beless than 6 in. (152 mm) long and at least34 in. (19 mm) ininside diameter; shall contain one right-angle bend upward tothe gage; and shall pr
10、oject18 in. (3.2 mm) into the test dome.If a McLeod gage is used, it shall be attached in a similarmanner, except that the connecting line, including a mercuryvapor trap, need not meet the dimensional restrictions above.The use of grease, wax, and rubber in assembling the gage linesshould be minimiz
11、ed.5.3 Flow-Measuring Devices:5.3.1 For flows greater than about 5 3 104torr L/s (that is,about 25 min/atmospheric cm3), and up to approximately 5 torrL/s (that is, about 15 s/100 atmospheric cm3), some type ofconstant-pressure displacement tube with low-vapor pressurefluid shall be used. These tube
12、s should be provided in a seriesof overlapping ranges so that very small through-puts may bemeasured in a reasonably short time and that very largethrough-puts may be measured in a time interval long enoughto allow precise measurement.5.3.2 Flow rates less than about 5 3 104torr L/s may bedetermined
13、 by a conductance method in which the test gascontained in a reservoir at known pressure is admitted to thetest dome through a known conductance.5.3.3 For flows greater than 5 torr L/s, special types ofconstant-pressure fluid-displacement devices or a series ofvariable-area flowmeters (rotameters) o
14、f sufficient overlap toensure precise measurement should be used.5.3.4 The timing in all flow measurements shall be madewith a110-s stop watch or by some equally precise method.1This test method is under the jurisdiction of the ASTM Committee E21 onSpace Simulation and Applications of Space Technolo
15、gy and is the direct respon-sibility of Subcommittee E21.04 on Space Simulation Test Methods.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1967. Last previous edition approved in 2000 as E 295 82 (2000).2For referenced ASTM standards, visit the ASTM website, www
16、.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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
17、tates.5.4 Leak Control ValveThe leak control valve shouldprovide good control of flow and flow changes as reflected inequilibrium pressures through the pressure range of interest.6. Test Gas6.1 Air shall normally be used in the measurement of pumpspeeds; and measured speed for air will be considered
18、 a basicperformance characteristic of a pump.6.2 The apparatus and method herein described may be usedfor measuring pumping speeds for gases other than air as maybe required.7. Calibration and Precision of Flow-Measuring Devices7.1 Constant-Pressure Displacement TubesTo cover con-veniently the input
19、 range suggested in 5.3, displacement tubesof at least three overlapping ranges should be provided. Thedisplacement tubes should be precision burets of glass tubingselected for uniformity of bore and having accurately measuredinside diameters (accuracy 0.25 %, commercially available).The instruments
20、 should be designed, calibrated, and used insuch a way as to measure the actual quantity of gas transferredto the test dome in some conveniently measurable time.Ambient temperature during the measurement shall be 23 63C. Meters of the constant-pressure displacement type maytake various forms. Two of
21、 these are shown in Fig. X1.1 anddiscussed in Appendix X2.7.2 Conductance MethodThis method of measuring inputrate requires a conductance of accurately known dimensionsand a reservoir of test gas in which the pressure can be variedand accurately measured (see Figs. X2.1 and X3.1 and Appen-dix X3). I
22、t requires, in addition, that the dimensions of theconductance be so chosen as to permit the desired maximumthrough-put (5 3 104torr L/s or more) at a reservoir pressurethat does not exceed the condition for free molecular flowthrough any part (that is, the mean free path of gas in thereservoir must
23、 be equal to or greater than ten times the largestlinear dimension of the reservoir). Gas introduced into thereservoir must be directed away from the conductance en-trance.8. Calibration and Precision of Vacuum Gages8.1 To cover the full range of pressures at which pumpspeeds should be measured requ
24、ires that at least two types ofvacuum gages be used:8.1.1 McLeod GageFor measuring pressures greater than103torr, a McLeod gage shall be used. The McLeod gage mayalso be used at lower pressures (down to about 105torr)provided the gage has an error less than 65 % at these lowerpressures. Only gages h
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