ASTM E295-82(2006)
(Test Method)Standard Test Method for Measured Speed of Oil Diffusion Pumps
Standard Test Method for Measured Speed of Oil Diffusion Pumps
ABSTRACT
This test method establishes the apparatus required, calibration and precision of the devices to be used, and the standard procedures for determining the measured speed, or volumetric flow rate, of oil diffusion pumps. This method shall make use of test dome, gage attachment or connecting line, flow-measuring devices, and leak control valve. The pump under test shall be fitted with a test dome of specified design. Gas is then admitted to the test dome in a specified manner at a measured rate, and the resulting change in equilibrium pressure is measured in the specified way.
SCOPE
1.1 This test method covers the determination of the measured speed (volumetric flow rate) of oil diffusion pumps.
1.2 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E295 − 82(Reapproved 2006)
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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope practice, and will normally be connected to the pump by the
method provided for in the design of the pump. The inside
1.1 This test method covers the determination of the mea-
diameter of the test dome shall be equal to that of the pump
sured speed (volumetric flow rate) of oil diffusion pumps.
inlet,anditsmeanheightshallbe1.5timesthisdiameter(Note
1.2 The values stated in inch-pound units are to be regarded
1).Thegasshallbeadmittedthroughatubeprojectingintothe
as the standard. The metric equivalents of inch-pound units
dome and bent upward so that its exit is located on the axis,
may be approximate.
facing away from the pump inlet port, and at a distance from
1.3 This standard does not purport to address all of the the pump inlet equal to the dome diameter. The opening to the
safety concerns, if any, associated with its use. It is the
vacuum gage shall be through a tube radially projecting into
responsibility of the user of this standard to establish appro- the test dome. The tubulation center line shall be above the
priate safety and health practices and determine the applica-
inlet flange, 1 in. (25 mm) or ⁄4 D above the top of the flange,
bility of regulatory limitations prior to use. whichever is larger (see Fig. 1).
NOTE 1—A10° slope of the dome roof is required only if the dome is
2. Referenced Documents
to be used for back-streaming measurements.
2.1 ASTM Standards:
5.2 Gage Attachment—The gage connecting line shall be
E297Test Method for Calibrating Ionization Vacuum Gage
3 less than 6 in. (152 mm) long and at least ⁄4 in. (19 mm) in
Tubes (Withdrawn 1983)
inside diameter; shall contain one right-angle bend upward to
the gage; and shall project ⁄8 in. (3.2 mm) into the test dome.
3. Terminology
If a McLeod gage is used, it shall be attached in a similar
3.1 measured speed—the mass flow rate of gas admitted
manner, except that the connecting line, including a mercury
from a flowmeter divided by the resulting increase in equilib-
vapor trap, need not meet the dimensional restrictions above.
rium static pressure near the inlet of the pump, using the
Theuseofgrease,wax,andrubberinassemblingthegagelines
equipment in Fig. 1.
should be minimized.
4. Summary of Test Method
5.3 Flow-Measuring Devices:
−4
5.3.1 For flows greater than about 5×10 torr L/s (that is,
4.1 The pump under test is fitted with a test dome of
specified design (Fig. 1). Gas is admitted to the test dome in a about25min/atmosphericcm ),anduptoapproximately5torr
L/s (that is, about 15 s/100 atmospheric cm ), some type of
specified manner at a measured rate, and the resulting change
in equilibrium pressure is measured in a specified way. constant-pressure displacement tube with low-vapor pressure
fluid shall be used. These tubes should be provided in a series
5. Apparatus
of overlapping ranges so that very small through-puts may be
measured in a reasonably short time and that very large
5.1 Test Dome—The test dome (Fig. 1) may be constructed
through-puts may be measured in a time interval long enough
byanymaterialandbyanymethodacceptableinhigh-vacuum
to allow precise measurement.
−4
5.3.2 Flow rates less than about 5×10 torr L/s may be
This test method is under the jurisdiction of the ASTM Committee E21 on
determined by a conductance method in which the test gas
Space Simulation and Applications of Space Technology and is the direct respon-
contained in a reservoir at known pressure is admitted to the
sibility of Subcommittee E21.04 on Space Simulation Test Methods.
Current edition approved April 1, 2006. Published April 2006. Originally
test dome through a known conductance.
approved in 1967. Last previous edition approved in 2000 as E295–82 (2000).
5.3.3 For flows greater than 5 torr L/s, special types of
DOI: 10.1520/E0295-82R06.
2 constant-pressure fluid-displacement devices or a series of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
variable-area flowmeters (rotameters) of sufficient overlap to
Standards volume information, refer to the standard’s Document Summary page on
ensure precise measurement should be used.
the ASTM website.
5.3.4 The timing in all flow measurements shall be made
The last approved version of this historical standard is referenced on
www.astm.org. with a ⁄10-s stop watch or by some equally precise method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E295 − 82 (2006)
FIG. 1 Test Dome Dimensions
−4
5.4 Leak Control Valve—The leak control valve should through-put (5×10 torr L/s or more) at a reservoir pressure
provide good control of flow and flow changes as reflected in that does not exceed the condition for free molecular flow
equilibrium pressures through the pressure range of interest. through any part (that is, the mean free path of gas in the
reservoir must be equal to or greater than ten times the largest
6. Test Gas
linear dimension of the reservoir). Gas introduced into the
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
performance characteristic of a pump.
8. Calibration and Precision of Vacuum Gages
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:
7. Calibration and Precision of Flow-Measuring Devices
8.1.1 McLeod Gage—For measuring pressures greater than
−3
10 torr,aMcLeodgageshallbeused.TheMcLeodgagemay
7.1 Constant-Pressure Displacement Tubes—To cover con-
−5
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
to the test dome in some conveniently measurable time.
−5
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
take various forms. Two of these are shown in Fig. X1.1 and
8.2 Calibration of vacuum gages used in this test method
discussed in Appendix X2.
shall be based on Test Method E297.
7.2 Conductance Method—This method of measuring input
9. Procedure
rate requires a conductance of accurately known dimensions
and a reservoir of test gas in which the pressure can be varied 9.1 The following operating conditions should be noted for
and accurately measured (see Figs. X2.1 and X3.1 and Appen- subsequent incorporation in the report of speed measurements:
dix X3). It requires, in addition, that the dimensions of the type and speed of fore-pump system, type and quantity of
conductance be so chosen as to permit the desired maximum diffusion pump fluid, power input to diffusion pump, and
E295 − 82 (2006)
(optionally) cooling water flow rate, inlet temperature, and 10. Results
discharge temperature.
10.
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