ASTM D3700-94
(Practice)Standard Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
Standard Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
SCOPE
1.1 This practice covers the equipment and procedures for obtaining a representative sample of specification liquefied petroleum gas (LPG), such as specified in Specification D 1835, GPA 2140, and comparable international standards. It may also be used for other natural gas liquid (NGL) products that are normally single phase (NGL mix, field butane, and so forth), defined in other industry specifications or contractual agreements.
1.2 This practice is not intended for non-specification products that contain significant quantities of undissolved gases (N 2, CO2), free water or other separated phases, such as raw or unprocessed gas/liquids mixtures and related materials. The same equipment can be used for these purposes, but additional precautions are generally needed to obtain representative samples of multi-phase products (see Appendix X1).
1.3 This practice includes recommendations for the location of a sample point in a line or vessel. It is the responsibility of the user to ensure that the sampling point is located so as to obtain a representative sample.
1.4 The values stated in SI units are to be regarded as the standard. The values provided in parentheses are for information only.
1.5 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.
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Designation: D 3700 – 94 An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Containing Hydrocarbon Fluid Samples Using a Floating
1
Piston Cylinder
This standard is issued under the fixed designation D 3700; 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 3.2 Particular emphasis should be given to the necessity of
obtaining accurate, representative samples for analysis since
1.1 This practice describes equipment and a procedure for
those analyses, regardless of the care and accuracy of the
obtaining a representative sample of a homogeneous hydrocar-
laboratory test, can be useless if the samples are not valid.
bon fluid and the subsequent preparation of that sample for
laboratory analysis.
4. Apparatus
1.2 It is not possible, nor is it the intent of this practice, to
4.1 Container, shown in Fig. 1 as Cylinder X, constructed of
provide a procedure that will be applicable for all sampling
metal tubing, honed, and polished on the inside surface. The
situations. It is strongly recommended that the samples be
cylinder is closed with threaded end caps to provide access to
obtained under the supervision of a person knowledgeable in
remove and service the moving piston. The end caps are drilled
the phase behavior of hydrocarbon systems and experienced in
and tapped for valves. The cylinder is designed to exceed the
all sampling operations.
maximum pressure anticipated during sampling and to be
1.3 This practice does not include recommendations for the
resistant to materials being sampled, the pressurizing fluid, the
location of the sampling point in a line or vessel, although the
cleaning solvents, and the expected corrodents. The volume of
importance of the proper sampling location cannot be over-
the cylinder will depend on the amount of sample needed for
emphasized.
the laboratory analysis.
1.4 This standard does not purport to address all of the
4.1.1 The cylinder contains a moving piston. The piston is
safety concerns, if any, associated with its use. It is the
equipped with O-rings, TFE-fluorocarbon rings, or other de-
responsibility of the user of this standard to establish appro-
vices to affect a leak-free seal between the sample and the
priate safety and health practices and determine the applica-
pressurizing fluid, and to allow for the free movement of the
bility of regulatory limitations prior to use.For specific hazard
piston within the cylinder. The use of guide rings is recom-
statements, see 5.1 and Annex A2.
mended to ensure smooth piston travel. The piston and sealing
device must be resistant to the sample, the pressurizing fluid,
2. Summary of Practice
the cleaning solvents, and expected corrodents.
2.1 A hydrocarbon fluid sample is transferred under pres-
4.1.2 All valves and safety devices must meet the appropri-
sure from a source to a moving piston cylinder. The piston-type
ate material and pressure specifications.
cylinder is designed to collect fluid samples by displacing a
4.2 Displacement Container—This container, Fig. 1, Cylin-
pressurizing fluid (usually an inert gas) at sampling pressure.
der Y, shall be fabricated from metal tubing, be designed to
The piston serves as a barrier between the sample and the inert
meet the same pressure requirements as the piston cylinder, and
gas which maintains the integrity of the sample by preventing
have a volume of no more than 80 % of the pressurizing
the selective absorption of sample components in the pressur-
volume of the piston cylinder (80 % of piston cylinder volume
izing fluid as is possible in conventional displacement tech-
minus the volume of the piston).
niques. The method provides for a 20 % inert gas volume for
4.3 Transfer Lines, Valves, and Gages—The transfer system
safe storage and transport of the sample.
shall be designed to exceed the maximum anticipated pressure
3. Significance and Use
and be resistant to all expected corrodents. The transfer lines
1
should have a minimum diameter of 6.35 mm ( ⁄4in.) and be as
3.1 The objective of any sampling operation is to secure, in
short as is practical, see Fig. 1. The use of filters and dryers is
a suitable container, an adequate portion of hydrocarbon fluid
discouraged.
under pressure having the same composition as the stream
being sampled.
5. Hazards
5.1 Safety Precautions:
1
This practice is under the jurisdiction of ASTM Committee D-2 on Petroleum
5.1.1 Warning—Sampling hydrocarbon fluids can be haz-
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