ASTM D6793-02
(Test Method)Standard Test Method for Determination of Isothermal Secant and Tangent Bulk Modulus
Standard Test Method for Determination of Isothermal Secant and Tangent Bulk Modulus
SCOPE
1.1 This test method covers the determination of isothermal secant and tangent bulk modulus of liquids which are stable and compatible with stainless steel under the conditions of test.
1.2 This test method is designed to be used over the temperature range from -40 to 200°C and from ambient to 68.95 Mpa (10 000 psig).
Note 1—Because of the design of the test apparatus, the upper limit of pressure which can be attained is limited by the bulk modulus of the test fluid. Pressures as high as 68.95 Mpa will not be attained for fluids of relatively low bulk modulus at the test temperature.
1.3 This test method assumes that the user is proficient in the assembly and use of medium pressure (m/p) threaded and coned fittings which are intended for use at pressures up to 137.9 Mpa (20 000 psig).
1.4 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.
Note 2—Because hydraulic pressure in the test system is produced by purely mechanical means, the test method is not subject to the hazards associated with systems which are pressurized pneumatically. Even small leaks will result in immediate drop in pressure to ambient without production of a high pressure liquid stream or mist.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
An American National Standard
Designation:D6793–02
Standard Test Method for
Determination of Isothermal Secant and Tangent Bulk
Modulus
This standard is issued under the fixed designation D6793; 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 3. Terminology
1.1 This test method covers the determination of isothermal 3.1 Definitions:
secant and tangent bulk modulus of liquids which are stable 3.1.1 isothermal secant bulk modulus—theproductoforigi-
andcompatiblewithstainlesssteelundertheconditionsoftest. nal fluid volume and the slope of the secant drawn from the
1.2 This test method is designed to be used over the origin to any specified point on the plot of pressure versus
temperature range from -40 to 200°C and from ambient to volume change divided by volume at constant temperature.
68.95 Mpa (10000 psig). 3.1.2 isothermal tangent bulk modulus—theproductoffluid
volume at any specified pressure and the partial derivative of
NOTE 1—Because of the design of the test apparatus, the upper limit of
fluid pressure with respect to volume at constant temperature.
pressure which can be attained is limited by the bulk modulus of the test
fluid. Pressures as high as 68.95 Mpa will not be attained for fluids of
4. Summary of Test Method
relatively low bulk modulus at the test temperature.
4.1 Determination of Isothermal Secant Bulk Modulus:
1.3 This test method assumes that the user is proficient in
4.1.1 A piston in the form of a medium pressure valve is
the assembly and use of medium pressure (m/p) threaded and
forced into a chamber which is liquid-filled. The pressure
coned fittings which are intended for use at pressures up to
created by the insertion of the piston is measured.
137.9 Mpa (20000 psig).
4.2 A system constant V/DV is determined by use of a
1.4 This standard does not purport to address all of the
standard of known bulk modulus as follows:
safety concerns, if any, associated with its use. It is the
– –
responsibility of the user of this standard to establish appro-
V B B
i i
5 5 (1)
S D
priate safety and health practices and determine the applica-
DV P
~P 2 P !
n o
bility of regulatory limitations prior to use.
where:
NOTE 2—Because hydraulic pressure in the test system is produced by
–
= isothermal secant bulk modulus,
purely mechanical means, the test method is not subject to the hazards B
i
associated with systems which are pressurized pneumatically. Even small
P = pressure at the origin before insertion of the piston,
o
leaks will result in immediate drop in pressure to ambient without
and
production of a high pressure liquid stream or mist.
P = pressure of the system at insertion of piston to
n
Position n.
2. Referenced Documents
NOTE 3—V/DV is thus a constant determined by system volume and
2.1 ASTM Standards:
piston displacement only. It is independent of temperature and when
D235 Specification for Mineral Spirits (Petroleum Spirits)
known, can be used to determine isothermal secant bulk modulus from
(Hydrocarbon Dry Cleaning Solvent)
pressure data obtained for various degrees of piston insertion.
D4057 Practice for Manual Sampling of Petroleum and
3 4.3 Isothermal tangent bulk modulus and sample density, if
Petroleum Products
desired, may be determined from isothermal secant bulk
D4177 Practice for Automatic Sampling of Petroleum and
3 modulusdatadeterminedasafunctionofpressurebyuseofthe
Petroleum Products
4 calculations in Section 12.
E300 Practice for Sampling Industrial Chemicals
5. Significance and Use
5.1 Isothermalsecantbulkmodulus(staticbulkmodulus)is
This test method is under the jurisdiction of ASTM Committee D02 on
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee
a property that measures the compressibility of a liquid. The
D02.11 on Engineering Sciences of High Performance Fluids and Solids.
greater the value, the less the compressibility of the liquid.
Current edition approved April 10, 2002. Published August 2002.
Annual Book of ASTM Standards, Vol 06.04.
Annual Book of ASTM Standards, Vol 05.02.
Annual Book of ASTM Standards, Vol 15.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
D6793–02
5.2 Isothermal secant bulk modulus is employed in the
design of high performance hydraulic fluid and braking sys-
tems. High bulk modulus is desirable in that the response time
of a system is faster when applied pressure more directly
effects the action of the system rather than in the compression
of the working liquid.
5.3 If isothermal secant bulk modulus is known as a
function of pressure, the data may be used to calculate
isothermal tangent bulk modulus and density as a function of
pressure. The data may not, however, be used to determine
isentropic (dynamic) bulk modulus. That property is usually
determined from velocity of sound measurements and differs
from isothermal bulk modulus by the ratio of C /C = g (the
p v
ratio of heat capacity at constant pressure to that at constant
volume for the test specimen.
6. Apparatus
6.1 Theapparatusforthedeterminationofisothermalsecant
bulk modulus is shown schematically in Fig. 1. An oven
capable of maintaining temperature within 60.1°C at the
desiredtesttemperatureisrequired.Allfittingsareoftheconed
andthreadedm/ptypeforuseatworkingpressuresupto137.9
Mpa (20000 psig). Pressure is created in the system by use of
the pressure valve (see 3 in Fig. 1) by which a piston (valve
stem) is inserted into the liquid-filled system by turning
1,2,3…n turns as determined by a scale affixed to the valve
stem to ensure repeatability of turns from the starting point.
Pressure transducers, thermocouples and system fixtures
should be such as to have minimal contribution to system
volume so that the system volume is such as to allow a
maximum pressure increase for any given degree of insertion
of the pressure valve stem.
7. Reagents and Materials
7.1 Cleaning Solvent—MineralspiritsconformingtoSpeci-
fication D235, Type I.
7.2 Other Solvents—Some test specimens may not be
1 = Top valve
soluble in mineral spirits.Asuitable solvent for such materials 2=ATee
will be needed to clean the apparatus after their use. The 3 = Pressure valve
solvent must be compatible with stainless steel and the 4 = Bottom valve
5 = Thermocouple
elastomeric components of the valves in the test apparatus.
6 = Pressure transducer
8. Sampling
7 = Oven
8 = Sample container
8.1 Obtain a representative sample of the test specimen in
accordance with the requirements of Practice D4057, D4177,
NOTE—All fittings are m/p coned and threaded type for use at working
or E300.
pressure up to 20000 psig.
9. Preparation of Apparatus FIG. 1 Apparatus for Determination of Secant Bulk Modulus
9.1 Introduce a portion of mineral spirits into the sample
container (Fig. 1, Item 8).
9.4 Remove the vessel containing excess solvent and with
9.2 OpenValves1and4andslowlydrawthemineralspirits
Valves 1 and 4 open allow the vacuum pump to draw air
through the system by gentle application of vacuum.
through the test system to evaporate the residual solvent. Start
NOTE 4—Always use a trap between the test apparatus and the vacuum
at ambient temperature and raise the oven temperature to
source to prevent introduction of the liquid solvent or the test specimen
100°C while drawing air through the system.
into the vacuum system.
9.5 When the oven temperature reaches 100°C, close Valve
9.3 Replace the sample container with an empty vessel and 4andallowthevacuumpumptoreleasethepressureinthetest
system to complete removal of solvent residues by evapora-
allow excess solvent
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