ASTM D6849-02(2012)
(Practice)Standard Practice for Storage and Use of Liquefied Petroleum Gases (LPG) in Sample Cylinders for LPG Test Methods
Standard Practice for Storage and Use of Liquefied Petroleum Gases (LPG) in Sample Cylinders for LPG Test Methods
SIGNIFICANCE AND USE
5.1 LPG samples can change composition during storage and use from preferential vaporization of lighter (lower molecular weight) hydrocarbon components, dissolved inert gases (N2, Ar, He, and so forth) and other dissolved gases/liquids (NH3, CO2, H2S, H2O, etc.). Careful selection of cylinder type, cylinder volume, and use of inert gas for pressurizing cylinders is required to ensure that composition changes are small enough to maintain the integrity of LPG when used as a QC reference material for various LPG test methods.
5.2 Monitoring of ongoing precision and bias on QC materials using control chart techniques in accordance with Practice D6299 can be used to establish the need for calibration or maintenance.
SCOPE
1.1 This practice covers information for the storage and use of LPG samples in standard cylinders of the type used in sampling method, Practice D1265 and floating piston cylinders used in sampling method, Practice D3700.
1.2 This practice is especially applicable when the LPG sample is used as a quality control (QC) reference material for LPG test methods, such as gas chromatography (GC) analysis (Test Method D2163) or vapor pressure (Test Method D6897) that use only a few mL per test, since relatively small portable Department of Transportation (DOT) cylinders (for example, 20 lb common barbecue cylinders) can be used. This practice can be applied to other test methods. However, test methods that require a large amount of sample per test (for example, manual vapor pressure Test Method D1267) will require QC volumes in excess of 1000 L if stored in standard DOT cylinders or American Society of Mechanical Engineers (ASME) vessels.
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Designation:D6849 −02(Reapproved 2012)
Standard Practice for
Storage and Use of Liquefied Petroleum Gases (LPG) in
Sample Cylinders for LPG Test Methods
This standard is issued under the fixed designation D6849; 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 Measurement System Performance
D6897 Test Method for Vapor Pressure of Liquefied Petro-
1.1 This practice covers information for the storage and use
leum Gases (LPG) (Expansion Method)
of LPG samples in standard cylinders of the type used in
sampling method, Practice D1265 and floating piston cylinders
3. Terminology
used in sampling method, Practice D3700.
3.1 Definitions of Terms Specific to This Standard:
1.2 This practice is especially applicable when the LPG
3.1.1 floating piston cylinder (FPC)—a high-pressure
sample is used as a quality control (QC) reference material for
sample container with a free floating internal piston(s) that
LPG test methods, such as gas chromatography (GC) analysis
effectively divides the container into two or more separate
(Test Method D2163) or vapor pressure (Test Method D6897)
compartments. The sample is contained on one side of the
that use only a few mL per test, since relatively small portable
piston (the sample or product side). The chamber on the other
Department of Transportation (DOT) cylinders (for example,
side of the piston (the charge or pre-charge side) is maintained
20 lb common barbecue cylinders) can be used. This practice
at a higher pressure than the vapor pressure of the sample with
can be applied to other test methods. However, test methods
an inert gas. This allows collection of a sample with no loss of
that require a large amount of sample per test (for example,
volatile components and no formation of a gaseous phase that
manual vapor pressure Test Method D1267) will require QC
may alter the composition of the sample. The cylinder is
volumes in excess of 1000 L if stored in standard DOT
equipped with a piston follower or indicating rod or other
cylinders or American Society of Mechanical Engineers
indicating device to show the position of the floating piston.
(ASME) vessels.
3.1.2 standard 80 % fill cylinder—a pressure rated cylinder
2. Referenced Documents
or vessel such as described in Practice D1265, or conforming
to DOT or ASME cylinder standards. These cylinders are not
2.1 ASTM Standards:
equipped with a floating piston, and have both an equilibrium
D1265 Practice for Sampling Liquefied Petroleum (LP)
liquid and vapor phase when used for LPG.
Gases, Manual Method
D1267 Test Method for Gage Vapor Pressure of Liquefied
4. Summary of Practice
Petroleum (LP) Gases (LP-Gas Method)
D2163 Test Method for Analysis of Liquefied Petroleum
4.1 This practice provides information for the design and
(LP) Gases and Propene Concentrates by Gas Chromatog-
operation of LPG sample storage cylinders taking into account
raphy
properties of LPG and types of cylinders in common use for
D3700 Practice for Obtaining LPG Samples Using a Float-
storage of LPG.
ing Piston Cylinder
4.2 This practice provides additional guidelines to Practice
D6299 Practice for Applying Statistical Quality Assurance
D6299 to determine the minimum volume of LPG sample
and Control Charting Techniques to Evaluate Analytical
material required, when used as a QC reference material.
5. Significance and Use
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Products and Lubricants and is the direct responsibility of Subcommittee D02.08 on
5.1 LPG samples can change composition during storage
Volatility.
and use from preferential vaporization of lighter (lower mo-
Current edition approved Nov. 1, 2012. Published November 2012. Originally
lecular weight) hydrocarbon components, dissolved inert gases
approved in 2002. Last previous edition approved in 2007 as D6849–02 (2007).
DOI: 10.1520/D6849-02R12.
(N , Ar, He, and so forth) and other dissolved gases/liquids
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
(NH ,CO ,H S, H O, etc.). Careful selection of cylinder type,
3 2 2 2
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
cylinder volume, and use of inert gas for pressurizing cylinders
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. is required to ensure that composition changes are small
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6849−02 (2012)
enough to maintain the integrity of LPG when used as a QC
reference material for various LPG test methods.
5.2 Monitoring of ongoing precision and bias on QC mate-
rials using control chart techniques in accordance with Practice
D6299 can be used to establish the need for calibration or
maintenance.
6. Reference Materials
6.1 The LPG QC reference material should have a vapor
pressure and composition in the range of the samples regularly
tested by the equipment. This is particularly important for
LPG/natural gas liquid (NGL) mixtures near the critical
temperature, as these liquids have large thermal and pressure
expansion coefficients.
6.2 LPG QC reference materials should be stored in an
environment suitable for long term storage without significant
sample degradation for the test(s) being performed.
NOTE 1—As an example, evidence of a long term shift or bias in the
LPG QC reference material results obtained relative to the established
statistical control limits and average value determined for the test initially,
may indicate that the composition of the LPG QC reference material has
significantly degraded or changed over time. An investigation should be
conducted to determine if the long term stability of the QC reference
material is the cause for the out-of-control situation.
7. Use of Floating Piston Cylinders for LPG Samples
FIG. 1Typical Floating Piston Cylinder (FPC)
7.1 Minimum LPG sample volume can be determined in
accordance with Practice D6299.
matelylinearatlowvaportoliquid(V/L)ratios.Thesechanges
NOTE 2—Estimating the minimum LPG sample volume needed in-
accelerate and become more significant as the remaining
cludes such things as the sample volume needed to conduct the appropri-
ate test(s) and the number of analytical measurements that are expected to
volume of liquid decreases and the cylinder approaches empty.
be made over the intended period of use.
However, if the initial volume is sufficiently large, and the final
7.2 Floating piston cylinders (see Fig. 1) are preferred for
V/L ratio is limited, the change will occur very slowly over
LPG sample materials for tests involving accurate determina- time,andthematerialisstillsuitableasaQC.Intheshortterm,
tion of light gases.
the composition is essentially constant relative to the precision
of the method.
7.3 Excessive inert gas pressure should be avoided for long
8.2.2 In the long run, the control limits can be periodically
term storage of vapor pressure QC or calibrant materials in
adjusted to compensate for any long-term trend, or the charted
floating piston cylinders. Leakage of inert gas past worn or
response can be compensated for the long-term trend using
damaged floating piston seals can cause an increase in dis-
historical data, or equation of state calculations based on
solved gas concentration and vapor pressure of the QC sample
cylinder weight or volume. Consult a statistician for appropri-
material.
ate techniques to develop a prediction model for the long-term
trend.
8. Use of Standard 80 %
...
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