ASTM D6897-16

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Designation: D6897 − 09 D6897 − 16
Standard Test Method for
Vapor Pressure of Liquefied Petroleum Gases (LPG)
(Expansion Method)
This standard is issued under the fixed designation D6897; 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 (´) indicates an editorial change since the last revision or reapproval.
1. 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,37.8 °C, vapor to liquid ratio of 0.5:1, and pressures from 200200 kPa to 1550
kPa 1550 kPa on a sample volume of 3.33 mL.3.33 mL.
1.2 This test method is applicable to the determination of vapor pressures of liquefied petroleum gas products at temperatures
from 37.837.8 °C to 70°C,70 °C, vapor to liquid ratios of 0.1:1 to 4:1, and pressures up to 3500 kPa; 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,37.8 °C, and a pressure range from 300300 kPa to 1500 kPa.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°C37.8 °C temperature and 0.5:1 vapor to liquid ratio as the Test Method D1267 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.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3.1 Exception—Non-SI units are included in parentheses for information only.
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 warning statements, see Appendix X2.
2. Referenced Documents
2.1 ASTM Standards:
D1265 Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
D1267 Test Method for Gage Vapor Pressure of Liquefied Petroleum (LP) Gases (LP-Gas Method)
D2892 Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
D3700 Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
D5191 Test Method for Vapor Pressure of Petroleum Products (Mini Method)
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
2.2 Energy Institute Standards:
IP 181 Sampling Petroleum Gases
3. Terminology
3.1 Definitions:
3.1.1 liquefied petroleum gases (LPG), n—narrow boiling range hydrocarbon mixtures, consisting mainly of propane or
propylene, or both (Warning—WarningExtremely—Extremely flammable. Harmful if inhaled), butanes and butylenes, or both; in
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.08 on Volatility.
Current edition approved April 15, 2009July 15, 2016. Published May 2009 August 2016. Originally approved in 2003. Last previous edition approved in 20032009 as
D6897–03a. DOI: 10.1520/D6897-09. – 09. DOI: 10.1520/D6897-16.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K., http://www.energyinst.org.uk.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6897 − 16
which the concentration of hydrocarbon compounds with boiling point greater than 0°C0 °C is less than 5 % by liquid volume,
and whose vapor pressure at 37.8°C (100°F)37.8 °C (100 °F) is not greater than 1550 kPa.1550 kPa.
3.1.2 platinum resistance thermometer, n—temperature measuring device with platinum wire, whose electrical resistance
changes in relation to temperature.
3.1.3 vapor-liquid ratio (V/L), n—of a liquid, the ratio of the vapor volume to the liquid volume of specimen, in equilibrium,
under specified conditions.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 total vapor pressure (P ) , n—the absolute vapor pressure (relative to vacuum) exerted by the specimen at the specified
tot
temperature and vapor-liquid ratio.
3.2.2 true vapor pressure, n—the physical property of a given liquid which specifies the maximum pressure at which a vapor
phase can coexist with the liquid phase at a given equilibrium temperature condition.
3.2.3 vapor pressure of LPG, n—the total pressure corrected relative to normal barometric pressure.
3.3 Abbreviations:
3.3.1 LPG—liquefied petroleum gas
3.3.2 V/L—vapor liquid ratio
4. Summary of Test Method
4.1 Employing a measuring chamber with a built-in piston, the chamber is rinsed three times with a portion of sample, which
is then discarded. A sample of defined volume is drawn from a pressurized sampling system into the temperature-controlled
chamber at 5°C5 °C by moving the piston to the filling position. After sealing the chamber, the volume is expanded by moving
the piston until the final volume produces the desired vapor to liquid ratio of 0.5:1. The temperature of the measuring chamber is
then regulated to the test temperature of interest, such as 37.8°C.37.8 °C.
4.2 The observed total pressure at equilibrium is corrected relative to 101.3 kPa 101.3 kPa and reported as the LPG vapor
pressure at the selected test temperature.
5. Significance and Use
5.1 Information on the vapor pressures of liquefied petroleum gas is pertinent to selection of properly designed storage vessels,
shipping containers, and customer utilization equipment to ensure safe handling of these products.
5.2 Determination of the vapor pressure of liquefied petroleum gas is important for safety reasons to ensure that the maximum
operating design pressures of storage, handling, and fuel systems will not be exceeded under normal operating temperature
conditions.
5.3 For liquefied petroleum gases, vapor pressure can be considered a semi-quantitative measure of the amount of the most
volatile material present in the product.
5.4 This test method uses a small sample volume and excludes any manual handling of a measuring chamber under high
pressure.
6. Apparatus
6.1 Vapor Pressure Apparatus —The type of apparatus suitable for this test method employs a small volume, cylindrically
shaped measuring chamber with associated equipment to control the chamber temperature within the range of 55 °C to 70°C.70 °C.
The measuring chamber shall contain a movable piston with a maximum dead volume of less than 1 % of the total volume at the
lowest position to allow sample introduction into the measuring chamber and expansion to the desired vapor-liquid ratio. A static
absolute pressure transducer shall be incorporated in the piston. The measuring chamber shall contain an inlet/outlet valve
combination for sample introduction and expulsion. The piston and the valve combination shall be at the same temperature as the
measuring chamber to avoid any condensation or excessive evaporation.
6.1.1 The test chamber shall be designed to contain a total of 5 mL 5 mL of liquid and vapor and be capable of maintaining
a vapor-liquid ratio of 0.5:1 with a maximum deviation of 0.02.
NOTE 3—The test chamber employed by the instruments used in generating the precision and bias statements were constructed of nickel-plated
aluminum and stainless steel.
NOTE 4—Test chambers exceeding a 5 mL 5 mL capacity can be used, but the precision and bias statements (see Section 15) are not known to apply.
6.1.2 Electronic temperature control shall be used to maintain the measuring chamber at the prescribed temperature within
60.1°C60.1 °C for the duration of the vapor pressure measurement.
The sole source of supply of the apparatus known to the committee at this time is Grabner Instruments, A-1220 Vienna, Dr. Otto Neurathgasse 1, Austria. If you are aware
of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend.
D6897 − 16
6.1.3 The pressure transducer shall have a range of 00 kPa to 3500 kPa 3500 kPa with a minimum resolution of 1 kPa. 1 kPa.
The minimum accuracy shall be 61 kPa 61 kPa for pressures up to 700 kPa, 62 kPa 700 kPa, 62 kPa for pressures up to 1750
kPa, and 64 kPa 1750 kPa, and 64 kPa for pressures up to 3500 kPa.3500 kPa.
6.1.4 A platinum resistance thermometer, or equivalent, shall be used for measuring the temperature of the test chamber. The
minimum temperature range of the measuring device shall be from 00 °C to 80°C80 °C with a resolution of 0.1°C0.1 °C and a
minimum accuracy of 60.1°C.60.1 °C.
6.2 Vacuum Pump for Calibration , capable of reducing the pressure in the measuring chamber to less than 0.01 kPa 0.01 kPa
absolute.
6.3 McLeod Vacuum Gage or Calibrated Electronic Vacuum Measuring Device for Calibration, to cover at least the range from
0.01 to 0.67 kPa (0.1 to 5 mm 0.01 kPa to 0.67 kPa (0.1 mm to 5 mm Hg). The calibration of the electronic vacuum measuring
device shall be regularly verified in accordance with A6.3 of Test Method D2892.
6.4 Pressure Measuring Device for Calibration, capable of measuring local station pressure with an accuracy and a resolution
of 0.1 kPa (1 mm 0.1 kPa (1 mm Hg) or better, at the same elevation relative to sea level as the apparatus in the laboratory.
NOTE 5—This test method does not give full details of instruments suitable for carrying out this test. Details on the installation, operation, and
maintenance of each instrument may be found in the manufacturer’s manual.
7. Reagents and Materials
7.1 Purity of Reagents—Use chemicals of at least 99 % purity for quality control checks. Commonly used quality control check
materials are propane, butane, and pentane (see Section 11). Unless otherwise indicated, it is intended that all reagents conform
to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are
available. Lower purities can be used, provided it is first ascertained that the reagent is of sufficient purity to permit its use without
lessening the accuracy of the determination.
NOTE 6—The chemicals in this section are suggested for quality control procedures (see Section 11) and are not used for instrument calibration.
7.2 Cleaning Solvents—Use noncorrosive solvents capable of cleaning the measuring chamber, the valves, and the inlet and
outlet tubes. A commonly used solvent is acetone. (Warning—WarningPropane,—propane, butane, pentane, and acetone are
flammable and health hazards.)
8. Sampling and Sample Introduction
8.1 Samples shall be obtained and stored in accordance with Practice D1265, or IP 181, unless the test samples can be taken
directly from the source of the material to be tested. Use a container of not less than 100 mL 100 mL in size and filled at least 70 %
with sample up to a maximum fill density as specified in regulations, which is typically no more than 80 %. Consult the specified
regulations for more details.
8.2 Any method of coupling the vapor pressure apparatus to the sample source can be employed. Tubing, 33 mm to 7 mm 7 mm
in diameter, of suitable-working pressure, and made of material corrosion-resistant to the products being sampled, is satisfactory
for this purpose. A flexible transparent polyperfluoroalkoxyethylene (PFA) tubing greatly facilitates the purging and sampling
operations.
8.3 Practice D1265 cylinders shall be equilibrated above the sample cell temperature of 5°C5 °C to ensure sufficient sample
cylinder pressure to fill the sample cell entirely. Practice D3700 cylinders shall be maintained at a pressure above the vapor
pressure of the LPG at 5°C5 °C (approximately 655 kPa 655 kPa for special duty propane and approximately 175 kPa 175 kPa for
commercial butanes).
9. Preparation of Apparatus
9.1 Prepare the instrument for operation in accordance with the manufacturer’s instructions. Since LPG is discharged at the
outlet of the apparatus, connect a tubing to the outlet and lead the other end of the tubing to a safe exhaust system or a gas recovery
system to protect the environment from LPG.
9.2
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