ASTM E295-82(2000)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E295–82 (Reapproved 2000)
Standard Test Method for
Measured Speed of Oil Diffusion Pumps
This standard is issued under the fixed designation E295; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope inlet,anditsmeanheightshallbe1.5timesthisdiameter(Note
1).Thegasshallbeadmittedthroughatubeprojectingintothe
1.1 This test method covers the determination of the mea-
dome and bent upward so that its exit is located on the axis,
sured speed (volumetric flow rate) of oil diffusion pumps.
facing away from the pump inlet port, and at a distance from
1.2 The values stated in inch-pound units are to be regarded
the pump inlet equal to the dome diameter. The opening to the
as the standard. The metric equivalents of inch-pound units
vacuum gage shall be through a tube radially projecting into
may be approximate.
the test dome. The tubulation center line shall be above the
1.3 This standard does not purport to address all of the
inlet flange, 1 in. (25 mm) or ⁄4 D above the top of the flange,
safety concerns, if any, associated with its use. It is the
whichever is larger (see Fig. 1).
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
NOTE 1—A 10° slope of the dome roof is required only if the dome is
bility of regulatory limitations prior to use. to be used for back-streaming measurements.
5.2 Gage Attachment—The gage connecting line shall be
2. Referenced Documents
less than 6 in. (152 mm) long and at least ⁄4 in. (19 mm) in
2.1 ASTM Standards:
inside diameter; shall contain one right-angle bend upward to
E297 Method for Calibrating Ionization Vacuum Gage
the gage; and shall project ⁄8 in. (3.2 mm) into the test dome.
Tubes
If a McLeod gage is used, it shall be attached in a similar
manner, except that the connecting line, including a mercury
3. Terminology
vapor trap, need not meet the dimensional restrictions above.
3.1 measured speed—the mass flow rate of gas admitted
Theuseofgrease,wax,andrubberinassemblingthegagelines
from a flowmeter divided by the resulting increase in equilib-
should be minimized.
rium static pressure near the inlet of the pump, using the
5.3 Flow-Measuring Devices:
equipment in Fig. 1.
−4
5.3.1 For flows greater than about 5 310 torr L/s (that is,
about25min/atmosphericcm ),anduptoapproximately5torr
4. Summary of Test Method
L/s (that is, about 15 s/100 atmospheric cm ), some type of
4.1 The pump under test is fitted with a test dome of
constant-pressure displacement tube with low-vapor pressure
specified design (Fig. 1). Gas is admitted to the test dome in a
fluid shall be used. These tubes should be provided in a series
specified manner at a measured rate, and the resulting change
of overlapping ranges so that very small through-puts may be
in equilibrium pressure is measured in a specified way.
measured in a reasonably short time and that very large
through-puts may be measured in a time interval long enough
5. Apparatus
to allow precise measurement.
5.1 Test Dome—The test dome (Fig. 1) may be constructed
−4
5.3.2 Flow rates less than about 5 310 torr L/s may be
by any material and by any method acceptable in high-vacuum
determined by a conductance method in which the test gas
practice, and will normally be connected to the pump by the
contained in a reservoir at known pressure is admitted to the
method provided for in the design of the pump. The inside
test dome through a known conductance.
diameter of the test dome shall be equal to that of the pump
5.3.3 For flows greater than 5 torr L/s, special types of
constant-pressure fluid-displacement devices or a series of
variable-area flowmeters (rotameters) of sufficient overlap to
This test method is under the jurisdiction of the ASTM Committee E-21 on
Space Simulation and Applications of Space Technology and is the direct respon-
ensure precise measurement should be used.
sibility of Subcommittee E21.04 on Space Simulation Test Methods.
5.3.4 The timing in all flow measurements shall be made
Current edition approved Sept. 24, 1982. Published November 1982. Originally
with a ⁄10-s stop watch or by some equally precise method.
published as E295–67T. Last previous edition E295–67T.
Discontinued, see 1984 Annual Book of ASTM Standards, Vol 15.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E295
FIG. 1 Test Dome Dimensions
5.4 Leak Control Valve—The leak control valve should that does not exceed the condition for free molecular flow
provide good control of flow and flow changes as reflected in through any part (that is, the mean free path of gas in the
equilibrium pressures through the pressure range of interest. reservoir must be equal to or greater than ten times the largest
linear dimension of the reservoir). Gas introduced into the
6. Test Gas
reservoir must be directed away from the conductance en-
6.1 Air shall normally be used in the measurement of pump
trance.
speeds; and measured speed for air will be considered a basic
8. Calibration and Precision of Vacuum Gages
performance characteristic of a pump.
6.2 Theapparatusandmethodhereindescribedmaybeused 8.1 To cover the full range of pressures at which pump
for measuring pumping speeds for gases other than air as may speeds should be measured requires that at least two types of
be required. vacuum gages be used:
8.1.1 McLeod Gage—For measuring pressures greater than
−3
7. Calibration and Precision of Flow-Measuring Devices
10 torr,aMcLeodgageshallbeused.TheMcLeodgagemay
−5
7.1 Constant-Pressure Displacement Tubes—To cover con- also be used at lower pressures (down to about 10 torr)
veniently the input range suggested in 5.3, displacement tubes provided the gage has an error less than 65% at these lower
of at least three overlapping ranges should be provided. The pressures. Only gages having individually determined gage
displacement tubes should be precision burets of glass tubing constants and individually calculated scales can be depended
selectedforuniformityofboreandhavingaccuratelymeasured upon for this precision. Also, approved procedures must be
inside diameters (accuracy 0.25%, commercially available).
followed, particularly in the lower range of measurable pres-
The instruments should be designed, calibrated, and used in sures.
such a way as to measure the actual quantity of gas transferred
8.1.2 Ionization Gage—For measuring pressures less than
−5
to the test dome in some conveniently measurable time. 10 torr, an untrapped ionization gage of the Bayard-Alpert
Ambient temperature during the measurement shall be 23 6 type shall be used.
3°C. Meters of the constant-pressure displacement type may 8.2 Calibration of vacuum gages used in this test method
take various forms. Two of these are shown in Fig. X1.1 and shall be based on Test Method E297.
discussed in Appendix X2.
9. Procedure
7.2 Conductance Method—This method of measuring input
rate requires a conductance of accurately known dimensions 9.1 The following operating conditions should be noted for
and a reservoir of test gas in which the pressure can be varied subsequent incorporation in the report of speed measurements:
and accurately measured (see Figs. X2.1 and X3.1 andAppen- type and speed of fore-pump system, type and quantity of
dix X3). It requires, in addition, that the dimensions of the diffusion pump fluid, power input to diffusion pump, and
conductance be so chosen as to permit the desired maximum (optionally) cooling water flow rate, inlet temperature, and
−4
through-put (5 310 torr L/s or more) at a reservoir pressure discharge temperature.
E295
9.2 Speed measurements should not be made until the 10. Results
pressure p in the test
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