ASTM D6897-03
(Test Method)Standard Test Method for Vapor Pressure of Liquefied Petroleum Gases (LPG) (Expansion Method)
Standard Test Method for Vapor Pressure of Liquefied Petroleum Gases (LPG) (Expansion Method)
SCOPE
1.1 This test method covers the use of automatic vapor pressure instruments to determine the vapor pressure of liquefied petroleum gas products at a temperature of 37.8°C, vapor to liquid ratio of 0.5:1, and pressures from 200 to 1550 kPa on a sample volume of 3.33 mL.
1.2 This test method is applicable to the determination of vapor pressures of liquefied petroleum gas products at temperatures from 37.8 to 70°C, vapor to liquid ratios of 0.1:1 to 4:1, and pressures up to 3500 kPa; however, the precision of the test method (see Section 15) has only been determined for a vapor to liquid ratio of 0.5:1, at a temperature of 37.8°C, and a pressure range from 300 to 1500 kPa.
Note 1—This test method is not intended to determine the true vapor pressure of LPG samples, but rather determine and report the vapor pressure of LPG at the 37.8°C temperature and 0.5:1 vapor to liquid ratio as the Test Method D 1267 method.
Note 2—This test method is not a true vapor pressure method and will not measure the full contribution from any dissolved gases such as nitrogen or helium if they are present. The contribution of light gases to the measured vapor pressure is highly dependent on the test temperature, type of gas, and V/L ratio of the test. A task group has been formed to determine or quantify the effect that the contribution of light gases have on the measured vapor pressure of LPG sample types as a function of the test temperature, type of gas, and V/L ratio of the test.
1.3 The values stated in SI units are to be regarded as standard.
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. For specific hazard statements, see Appendix X2.
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An American National Standard
Designation: D 6897 – 03
Standard Test Method for
Vapor Pressure of Liquefied Petroleum Gases (LPG)
(Expansion Method)
This standard is issued under the fixed designation D 6897; 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 D 1265 Practice for Sampling Liquefied Petroleum (LP)
Gases (Manual Method)
1.1 This test method covers the use of automatic vapor
D 1267 Test Method for Gage Vapor Pressure of Liquefied
pressure instruments to determine the vapor pressure of lique-
Petroleum (LP) Gases (LP-Gas Method)
fied petroleum gas products at a temperature of 37.8°C, vapor
D 3700 Practice for Obtaining LPG Samples Using a Float-
to liquid ratio of 0.5:1, and pressures from 200 to 1550 kPa on
ing Piston Cylinder
a sample volume of 3.33 mL.
D 5191 Test Method for Vapor Pressure of Petroleum Prod-
1.2 This test method is applicable to the determination of
ucts (Mini Method)
vapor pressures of liquefied petroleum gas products at tem-
D 6299 Practice for Applying Statistical Quality Assurance
peratures from 37.8 to 70°C, vapor to liquid ratios of 0.1:1 to
Techniques to Evaluate Analytical Measurement System
4:1, and pressures up to 3500 kPa; however, the precision of
Performance
the test method (see Section 15) has only been determined for
2.2 IP Standards:
a vapor to liquid ratio of 0.5:1, at a temperature of 37.8°C, and
IP 181 Sampling Petroleum Gases
a pressure range from 300 to 1500 kPa.
NOTE 1—This test method is not intended to determine the true vapor 3. Terminology
pressure of LPG samples, but rather determine and report the vapor
3.1 Definitions:
pressure of LPG at the 37.8°C temperature and 0.5:1 vapor to liquid ratio
3.1.1 liquefied petroleum gases (LPG), n—narrow boiling
as the Test Method D 1267 method.
range hydrocarbon mixtures, consisting mainly of propane or
NOTE 2—This test method is not a true vapor pressure method and will
propylene, or both (Warning—Extremely flammable. Harmful
not measure the full contribution from any dissolved gases such as
nitrogen or helium if they are present. The contribution of light gases to
if inhaled), butanes and butylenes, or both; in which the
the measured vapor pressure is highly dependent on the test temperature,
concentration of hydrocarbon compounds with boiling point
type of gas, and V/L ratio of the test. A task group has been formed to
greater than 0°C is less than 5 % by liquid volume, and whose
determine or quantify the effect that the contribution of light gases have on
vapor pressure at 37.8°C (100°F) is not greater than 1550 kPa.
the measured vapor pressure of LPG sample types as a function of the test
3.2 Definitions of Terms Specific to This Standard:
temperature, type of gas, and V/L ratio of the test.
3.2.1 total pressure (P ), n—the absolute pressure (relative
tot
1.3 The values stated in SI units are to be regarded as
to vacuum) exerted by the specimen at the specified tempera-
standard.
ture and vapor-liquid ratio.
1.4 This standard does not purport to address all of the
3.2.2 true vapor pressure, n—the physical property of a
safety concerns, if any, associated with its use. It is the
given liquid which specifies the maximum pressure at which a
responsibility of the user of this standard to establish appro-
vapor phase can coexist with the liquid phase at a given
priate safety and health practices and determine the applica-
equilibrium temperature condition.
bility of regulatory limitations prior to use. For specific hazard
3.2.3 vapor pressure of LPG, n—the total pressure corrected
statements, see Appendix X2.
relative to normal barometric pressure.
3.2.4 vapor to liquid ratio, n—the ratio of the volume of the
2. Referenced Documents
vapor in equilibrium to the fill volume of liquid.
2.1 ASTM Standards:
D 1160 Test Method for Distillation of Petroleum Products
4. Summary of Test Method
at Reduced Pressure
4.1 Employing a measuring chamber with a built-in piston,
the chamber is rinsed three times with a portion of sample,
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee Annual Book of ASTM Standards, Vol 05.02.
D02.08 on Volatility. Annual Book of ASTM Standards, Vol 05.03.
Current edition approved March 10, 2003. Published May 2003. Available from Institute of Petroleum (IP), 61 New Cavendish St., London,
Annual Book of ASTM Standards, Vol 05.01. WIG 7AR, U.K.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6897–03
which is then discarded. A sample of defined volume is drawn 6.1.2 Electronic temperature control shall be used to main-
from a pressurized sampling system into the temperature- tain the measuring chamber at the prescribed temperature
controlled chamber at 5°C by moving the piston to the filling within 60.1°C for the duration of the vapor pressure measure-
position. After sealing the chamber, the volume is expanded by ment.
moving the piston until the final volume produces the desired
6.1.3 The pressure transducer shall have a range of 0 to
vapor to liquid ratio of 0.5:1. The temperature of the measuring
3500 kPa with a minimum resolution of 1 kPa. The minimum
chamber is then regulated to the test temperature of interest,
accuracy shall be 61 kPa for pressures up to 700 kPa, 62 kPa
such as 37.8°C.
for pressures up to 1750 kPa and 64 kPa for pressures up to
4.2 The observed total pressure at equilibrium is corrected
3500 kPa.
relative to 101.3 kPa and reported as the LPG vapor pressure at
6.1.4 A platinum resistance thermometer or equivalent shall
the selected test temperature.
be used for measuring the temperature of the test chamber. The
minimum temperature range of the measuring device shall be
5. Significance and Use
from 0 to 80°C with a resolution of 0.1°C and a minimum
5.1 Information on the vapor pressures of liquefied petro-
accuracy of 60.1°C.
leum gas is pertinent to selection of properly designed storage
6.2 Vacuum Pump for Calibration, capable of reducing the
vessels, shipping containers, and customer utilization equip-
pressure in the measuring chamber to less than 0.01 kPa
ment to ensure safe handling of these products.
absolute.
5.2 Determination of the vapor pressure of liquefied petro-
6.3 McLeod Vacuum Gage or Calibrated Electronic Vacuum
leum gas is important for safety reasons to ensure that the
Measuring Device for Calibration, to cover at least the range
maximum operating design pressures of storage, handling, and
of 0.01 to 0.67 kPa. The calibration of the electronic measuring
fuel systems will not be exceeded under normal operating
device shall be regularly verified in accordance with Annex A
temperature conditions.
of Test Method D 1160.
5.3 For liquefied petroleum gases, vapor pressure can be
6.4 Pressure Measuring Device for Calibration, capable of
considered a semi-quantitative measure of the amount of the
measuring local station pressure with an accuracy and a
most volatile material present in the product.
resolution of 0.1 kPa (1 mm Hg) or better, at the same elevation
5.4 This test method uses a small sample volume and
relative to sea level as the apparatus in the laboratory.
excludes any manual handling of a measuring chamber under
high pressure.
NOTE 5—This test method does not give full details of instruments
suitable for carrying out this test. Details on the installation, operation and
6. Apparatus
maintenance of each instrument may be found in the manufacturer’s
6 manual.
6.1 Vapor Pressure Apparatus —The type of apparatus
suitable for this test method employs a small volume, cylin-
7. Reagents and Materials
drically shaped measuring chamber with associated equipment
7.1 Purity of Reagents—Use chemicals of at least 99 %
to control the chamber temperature within the range of 5 to
purity for quality control checks. Commonly used quality
70°C. The measuring chamber shall contain a movable piston
control check materials are propane, butane, and pentane (see
with a maximum dead volume of less than 1 % of the total
Section 11). Unless otherwise indicated, it is intended that all
volume at the lowest position, to allow sample introduction
reagents conform to the specifications of the Committee on
into the measuring chamber and expansion to the desired
Analytical Reagents of the American Chemical Society where
vapor-liquid ratio. A static absolute pressure transducer shall be
such specifications are available. Lower purities can be used,
incorporated in the piston. The measuring chamber shall
provided it is first ascertained that the reagent is of sufficient
contain an inlet/outlet valve combination for sample introduc-
purity to permit its use without lessening the accuracy of the
tion and expulsion. The piston and the valve combination shall
determination.
be at the same temperature as the measuring chamber to avoid
any condensation or excessive evaporation.
NOTE 6—The chemicals in this section are suggested for quality control
6.1.1 The test chamber shall be designed to contain a total of
procedures (see Section 11) and are not used for instrument calibration.
5 mL of liquid and vapor and be capable of maintaining a
7.2 Cleaning Solvents—Use noncorrosive solvents capable
vapor-liquid ratio of 0.5:1 with a maximum deviation of 0.02.
of cleaning the measuring chamber, the valves, and the inlet
NOTE 3—The test chamber employed by the instruments used in
and outlet tubes. A commonly used solvent is acetone.
generating the precision and bias statements were constructed of nickel-
(Warning—propane, butane, pentane, and acetone are flam-
plated aluminum and stainless steel.
mable and health hazards.)
NOTE 4—Test chambers exceedinga5mL capacity can be used, but the
precision and bias statements (see Section 15) are not known to apply.
Reagent Chemicals, American Chemical Society Specifications, American
The sole source of supply of the apparatus known to the committee at this time Chemical Society, Washington, DC. For suggestions on the testing of reagents not
is Grabner Instruments, A-1220 Vienna, Dr. Otto Neurathgasse 1, Austria. If you are listed by the American Chemical Society, see Annual Standards for Laboratory
aware of alternative suppliers, please provide this information to ASTM Interna- Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
tional Headquarters. Your comments will receive careful consideration at a meeting and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
of the responsible technical committee , which you may attend. MD.
D6897–03
8. Sampling and Sample Introduction When the instrument is used over the full pressure range, a
calibration with a dead weight balance shall be carried out.
8.1 Samples shall be obtained and stored in accordance with
(Warning—Many aneroid barometers, such as those used at
Practice D 1265, or IP 181, unless the test samples can be taken
weather stations and airports, are pre-corrected to give sea
directly from the source of the material to be tested. Use a
level readings. These shall not be used for calibration of the
container of not less than 100 mL in size filled at least 70 %
apparatus.)
with sample up to a maximum fill density as specified in
10.1.4 Repeat 10.1.2 and 10.1.3 until the zero and baromet-
regulations, which is typically no more than 80 %. Consult the
ric pressures read correctly without further adjustments.
specified regulations for more details.
10.2 Temperature Sensor—Verify the calibration of the
8.2 Any method of coupling the vapor pressure apparatus to
resistance thermometer or equivalent (see 6.1.4) used to
the sample source can be employed. Tubing, 3 to 7 mm in
monitor the measuring chamber temperature when needed as
diameter, of suitable-working pressure, and made of material
indicated from the quality control checks performed according
corrosion-resistant to the products being sampled, is satisfac-
to Section 11 against a temperature sensing device which is
tory for this purpose. A flexible transparent polyperfluoro-
traceable to National Institute of Standards and Technology
alkoxyethylene (PFA) tubing greatly facilitates the purging and
(NIST) or national authorities in the country the equipment is
sampling operations.
used.
8.3 Practice D 1265 cylinders shall be equilibrated above
the sample cell temperature of 5°C to ensure sufficient sample
11. Quality Control Checks
cylinder pressure to entirely fill the sample cell. Practice
11.1 Use a verification fluid or gas of known vapor pressure
D 3700 cylinders shall be maintained at a pressure above the
as an independent check against the instrument calibration each
vapor pressure of the LPG at 5°C (approximately 655 kPa for
day the instrument is in use. For pure compounds, multiple test
special duty propane and approximately 175 kPa for commer-
specimens may be taken from the same container over time.
cial butanes).
11.2 A possible pure gas for verification of the instrument
and its corresponding vapor pressure at 37.8°C and a vapor to
9. Preparation of Apparatus
liquid ratio of 0.5:1 is:
9.1 Prepare the instrument for operation in accordance with
the manufacturer’s instructions. Since LPG is discharged at the Propane VP ~37.8°C! 5 1301 kPa
tot
outlet of the apparatus, connect a tubing to the outlet and lead
11.2.1 If the observed total pressure differs from the refer-
the other end of the tubing to a safe exhaust system or a gas
ence value by more than 7.0 kPa, then check the instrument
recovery system to protect the environment from LPG.
calibration (see Section 10).
9.2 If contaminated, clean the measuring chamber with a
11.3 A second possible pure gas for verification of the
solvent. Acetone has been used successfully. Cleaning is
instrument and its corresponding vapor pressure at 37.8 °C and
performed by drawing the solvent into the chamber by the
a vapor to liquid ratio of 0.5:1 is:
integrated piston and expelling the solvent into a waste
Butane VP ~37.8°C! 5 356.5 kPa
container.
tot
11.3.1 If the observed total pressure differs from the refer-
10. Calibration
ence value by more than 6.0 kPa, then check the instrument
calibration (see Section 10).
10.1 Pressure Transducer:
11.4 If a liquid is used to check the performance of the test,
10.1.1 Check the calibration of the transducer when needed
cool and air saturate the liquid according to the corresponding
as indicated from the quality control checks
...
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