ASTM D6377-99
(Test Method)Standard Test Method for Determination of Vapor Pressure of Crude Oil: VPCRx (Expansion Method)
Standard Test Method for Determination of Vapor Pressure of Crude Oil: VPCR<sub>x</sub> (Expansion Method)
SCOPE
1.1 This test method covers the use of automated vapor pressure instruments to determine the vapor pressure of crude oils at temperatures between 5 and 80 °C for vapor-liquid ratios from 4:1 to 0.02:1 (X= 4 to 0.02) and pressures from 7 to 500 kPa (1.0 to 70 psi).
1.2 The values stated in SI units are regarded as standard. The inch-pound units given in parentheses are provided for information only.
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. For specific warning statements, see Note 5.
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An American National Standard
Designation: D 6377 – 99
Standard Test Method for
Determination of Vapor Pressure of Crude Oil: VPCR
x
(Expansion Method)
This standard is issued under the fixed designation D 6377; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 dead crude oil—a term usually employed for crude
oils that, when exposed to normal atmospheric pressure at
1.1 This test method covers the use of automated vapor
room temperature, will not result in actual boiling of the
pressure instruments to determine the vapor pressure of crude
sample.
oils at temperatures between 5 and 80°C for vapor-liquid ratios
3.1.1.1 Discussion—Sampling and handling of dead crude
from 4:1 to 0.02:1 (X=4to 0.02) and pressures from 7 to 500
oils can usually be done without problems in normal sample
kPa (1.0 to 70 psi).
containers, such as cans and so forth. The use of pressure
1.2 The values stated in SI units are regarded as standard.
cylinders for (sub)sampling and sample storage is a necessary
The inch-pound units given in parentheses are provided for
and mandatory requirement in this test method for live crude
information only.
oils and, to prevent the loss of volatile material and preserve
1.3 This standard does not purport to address all of the
precision, is strongly recommended for dead crude oils as well.
safety concerns, if any, associated with its use. It is the
3.1.2 live crude oil—a term usually employed for crude oils
responsibility of the user of this standard to establish appro-
contained in pressurized systems that, when brought to normal
priate safety and health practices and determine the applica-
atmospheric pressure at room temperature, will result in actual
bility of regulatory limitations prior to use. For specific
boiling of the sample.
warning statements, see Note 5.
3.1.2.1 Discussion—Sampling and handling of samples of
2. Referenced Documents
live crude oils will necessitate the use of pressure cylinders and
preclude the use of normal sample containers, such as cans and
2.1 ASTM Standards:
so forth.
D 323 Test Method for Vapor Pressure of Petroleum Prod-
3.1.3 REID vapor pressure equivalent (RVPE)— a value
ucts (REID Method)
calculated by a correlation equation (see 14.3) from VPCR ,
D 1160 Test Method for Distillation of Petroleum Products 4
which is related to the value obtained on the sample by Test
at Reduced Pressure
Method D 323.
D 3700 Practice for Containing Hydrocarbon Fluid Samples
3.1.4 vapor-liquid ratio (V/L), n—the ratio of the vapor
Using a Floating Piston Cylinder
volume to the liquid specimen volume.
D 4057 Practice for Manual Sampling of Petroleum and
3.1.4.1 Discussion—The total measuring chamber volume
Petroleum Products
is the sum of the vapor volume and the liquid specimen
D 4177 Practice for Automatic Sampling of Petroleum and
volume.
Petroleum Products
3.1.5 vapor pressure of crude oil (VPCR , n—the pressure
D 5191 Test Method for Vapor Pressure of Petroleum Prod- x)
exerted in an evacuated chamber at a vapor-liquid ratio of X:1
ucts (Mini Method)
by conditioned or unconditioned crude oil, which may contain
D 5853 Test Method for Pour Point of Crude Oils
gas, air or water, or a combination thereof, where X may vary
3. Terminology
from 4 to 0.02.
3.1 Definitions of Terms Specific to This Standard:
4. Summary of Test Method
4.1 Employing a measuring chamber with a built-in piston,
This test method is under the jurisdiction of ASTM Committee D-2 on
a sample of known volume is drawn from a pressurized
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
sampling system (floating piston cylinder) into the temperature
D02.08 on Volatility.
controlled chamber at 20°C or higher. After sealing the
Current edition approved Jan. 10, 1999. Published March 1999.
Annual Book of ASTM Standards, Vol 05.01. chamber, the volume is expanded by moving the piston until
Annual Book of ASTM Standards, Vol 05.02.
Annual Book of ASTM Standards, Vol 05.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6377–99
Measuring chambers exceedinga5mL capacity and having a different
the final volume produces the desired V/L value. The tempera-
design can be used, but the precision and bias statements (see Section 14)
ture of the measuring chamber is then regulated to the
are not known to apply.
measuring temperature.
6.1.2 The pressure transducer shall have a minimum opera-
4.2 After temperature and pressure equilibrium, the mea-
sured pressure is recorded as the VPCR of the sample. The test tional range from 0 to 500 kPa (0 to 72.5 psi) with a minimum
x
resolution of 0.1 kPa (0.01 psi) and a minimum accuracy of
specimen shall be mixed during the measuring procedure by
shaking the measuring chamber to achieve pressure equilib- 60.5 kPa (60.07 psi). The pressure measurement system shall
include associated electronics and readout devices to display
rium in a reasonable time between 5 and 30 min.
4.3 For results related to Test Method D 323, the final the resulting pressure reading.
6.1.3 Electronic temperature control shall be used to main-
volume of the measuring chamber shall be five times the test
specimen volume and the measuring temperature shall be tain the measuring chamber at the prescribed temperature
within 60.1°C for the duration of the test.
37.8°C.
6.1.4 A platinum resistance thermometer shall be used for
5. Significance and Use
measuring the temperature of the measuring chamber. The
minimum temperature range of the measuring device shall be
5.1 Vapor pressure of crude oil at various V/Ls is an
from 0 to 100°C with a resolution of 0.1°C and an accuracy of
important physical property for shipping and storage.
60.1°C.
5.2 Vapor pressure of crude oil is important to crude oil
6.1.5 The vapor pressure apparatus shall have provisions for
producers and refiners for general handling and initial refinery
rinsing the measuring chamber with the next sample to be
treatment.
tested or with a solvent of low vapor pressure.
NOTE 1—A V/L of 0.02:1 (X = 0.02) mimics closely the situation of an
6.1.6 The vapor pressure apparatus shall have provisions for
oil tanker.
shaking the sample during the measuring procedure with a
5.3 To prevent losses of high volatile compounds, the
minimum frequency of 1.5 cycles per second.
sample is always maintained at a pressure at least 100 kPa
6.2 Vacuum Pump for Calibration, capable of reducing the
(14.5 psi) higher than the vapor pressure.
pressure in the measuring chamber to less than 0.01 kPa (0.001
5.4 The vapor pressure determined by this test method at a
psi) absolute.
V/L of 4:1 (VPCR ) of crude oil at 37.8°C can be related to the
6.3 McLeod Vacuum Gage or Calibrated Electronic Vacuum
vapor pressure value determined on the same material when
Measuring Device for Calibration, to cover at least the range
tested by Test Method D 323 (see Appendix X1).
from 0.01 to 0.67 kPa (0 to 5 mm Hg). The calibration of the
5.5 Chilling and air saturation of the sample prior to the
electronic measuring device shall be regularly verified in
vapor pressure measurement is not required.
accordance with Annex A1 of Test Method D 1160.
5.6 This test method allows the determination of VPCR
x
6.4 Pressure Measuring Device for Calibration, capable of
samples having pour points above 0°C.
measuring local station pressure with an accuracy and a
resolution of 0.1 kPa (1 mm Hg) or better, at the same elevation
6. Apparatus
relative to sea level as the apparatus in the laboratory.
6.1 The apparatus suitable for this test method employs a
NOTE 3—This test method does not give full details of instruments
small volume, cylindrically shaped measuring chamber with
suitable for carrying out this test. Details on the installation, operation, and
associated equipment to control the chamber temperature
maintenance of each instrument may be found in the manufacturer’s
within the range from 5 to 80°C. The measuring chamber shall
manual.
contain a movable piston with a minimum dead volume of less
7. Reagents and Materials
than 1 % of the total volume at the lowest position to allow
sample introduction into the measuring chamber and expansion
7.1 Purity of Reagents—Use chemicals of at least 99 %
to the desired V/L. A static pressure transducer shall be
purity for quality control checks (see Section 11). Unless
incorporated in the piston. The measuring chamber shall
otherwise indicated, it is intended that all reagents conform to
contain an inlet/outlet valve combination for sample introduc-
the specifications of the Committee on Analytical Reagents of
tion and expulsion. The piston and the valve combination shall
the American Chemical Society where such specifications are
be at the same temperature as the measuring chamber to avoid
available. Other grades may be used, provided it is first
any condensation or excessive evaporation.
ascertained that the reagent is of sufficient high purity to permit
6.1.1 The measuring chamber shall be designed to have a
its use without lessening the accuracy of the determination.
total volume of 5 to 15 mL and shall be capable of maintaining
NOTE 4—The chemicals in this section are suggested for cleaning and
a V/L of 4:1 to 0.02:1. The accuracy of the adjusted V/L shall
quality control procedures (see Section 11) and are not used for instrument
be within 0.01.
calibration.
NOTE 2—The measuring chambers employed by the instruments used
in generating the precision and bias statements were constructed of nickel
plated aluminum and stainless steel with a total volume of 5 mL. Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Vapor pressure apparatus meeting these requirements are available from and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
Grabner Instruments, A-1220 Vienna, Dr. Neurathgasse 1, Austria. MD.
D6377–99
2,2-Dimethylbutane (Warning–See Note 5)
second inlet. Close the rinsing valve, and let the piston move
2,3-Dimethylbutane (Warning–See Note 5)
slowly until at least 200 mL of sample has entered the cylinder.
Toluene (Warning–See Note 5)
Close the inlet valve, and apply the back pressure immediately.
Pentane (Warning–See Note 5)
Check the filling of the cylinder to be at least 200 mL.
Methanol (Warning–See Note 5)
8.2.2 If the sample is taken from a nonpressurized source
Acetone (Warning–See Note 5)
like a storage tank, oil tanker, drum, or other small container,
NOTE 5—Warning: 2,2-dimethylbutane, 2,3-dimethylbutane, toluene,
pentane, methanol, and acetone are flammable and a health hazard. obtain the sample in accordance with Practice D 4057 and fill
the sample into an open floating piston cylinder at ambient
7.2 Cleaning Solvents—Use suitable solvents capable of
pressure. Close the floating piston cylinder, and apply the
cleaning the measuring chamber, the valves, and the inlet and
back-pressure immediately after the cylinder is filled with the
outlet tubes. Two commonly used solvents are toluene and
sample. Turn the cylinder in a vertical position so that the inlet
acetone.
is on top, and open the inlet valve of the cylinder until the
crude oil emerges at the inlet to discharge the captured air.
8. Sampling and Sample Introduction
Close the valve, and check the filling of the cylinder to be at
8.1 General Requirements:
least 200 mL.
8.1.1 The extreme sensitivity of vapor pressure measure-
8.3 Sample Transfer— Transfer the sample from the cylin-
ments to losses through evaporation and the resulting changes
der into the measuring cell at room temperature but at least 5°C
in composition requires the utmost precaution and the most
above the pour point (as determined by Test Method D 5853)
meticulous care in the drawing and handling of samples.
of the sample. Apply a back-pressure that is higher than the
Sampling of live crude oil shall be performed in accordance
vapor pressure of the sample at the introduction temperature
with Practice D 3700. Sampling in accordance with Practice
plus a minimum of 100 kPa (15 psi) for the piston movement.
D 4057 shall only be used for dead crude oil and if Practice
The applied back-pressure shall not exceed the maximum limit
D 3700 is impractical.
of the pressure transducer used in the vapor pressure apparatus.
NOTE 6—Sampling in accordance with Practice D 4177 may also be
9. Preparation of Apparatus
used instead of Practice D 4057.
9.1 Prepare the instrument for operation in accordance with
8.1.2 A floating piston cylinder with a minimum sample
the manufacturer’s instructions.
volume of 200 mL shall be used if the overall volume of the
9.2 Rinse the measuring chamber, if necessary, with a
test specimen required for the vapor pressure determination,
solvent. Toluene has a low vapor pressure and can be used
including the rinsing procedure, is not larger than 20 mL.
successfully. Rinsing is performed by drawing the solvent into
Larger floating piston cylinders can be used. The minimum
the chamber by the piston and expelling the solvent into the
piston back-pressure shall be higher than the sample vapor
waste container.
pressure at the introduction temperature of the measuring
9.3 To avoid contamination of the test specimen with the
chamber plus 100 kPa (15 psi) for the shifting of the piston.
previous sample or the solvent, rinse the measuring chamber a
The maximum back-pressure shall not exceed the maximum
minimum of three times wit the sample to be tested. Fill the
measurement pressure of the apparatus pressure transducer.
measuring chamber with sample to at least half the total
Compressed air, or any other compressed gas, can be used as
volume of the chamber for each rinse. This rinsing procedure
the back-pressuring agent. The floating piston cylinder shall
shall always be carried out immediately before the measuring
have provisions for mechanical stirring of the sample and a
procedure (see 12.4).
second valve at the inlet for rinsing.
NOTE 7—The present precision statement was derived using samples in
10. Calibration
250–mL floating piston cylinders.
10.1 Pressure Transducer:
8.1.3 Do not unnecessarily expose the samples to tempera-
10.1.1 Check the transducer calibration on a monthly basis
tures exceeding 30°C during s
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