1、Designation: D3700 07D3700 12Standard Practice forObtaining LPG Samples Using a Floating Piston Cylinder1This standard is issued under the fixed designation D3700; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers the equipment and procedures for obtaining a representative sample of specification liquefied petroleum
3、gas (LPG), such as specified in ASTM Specification D1835, GPA 2140, and comparable international standards. It may also beused for other natural gas liquid (NGL) products that are normally single phase (NGL (for example, NGL mix, field butane, andso forth), defined in other industry specifications o
4、r contractual agreements.1.2 This practice is not intended for non-specification products that contain significant quantities of undissolved gases (N2,CO2), free water or other separated phases, such as raw or unprocessed gas/liquids mixtures and related materials. The sameequipment can be used for
5、these purposes, but additional precautions are generally needed to obtain representative samples ofmulti-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 theuser to ensure that the sampling
6、 point is located so as to obtain a representative sample.1.4 The values stated in SI units are to be regarded as standard. The values given 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 re
7、sponsibilityof the user of this standard to establish appropriate safety and health practices, and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Petroleum (LP) Gases, Manual MethodD1835 Specification
8、 for Liquefied Petroleum (LP) Gases2.2 GPA Standards:3GPA 2174 Obtaining Liquid Hydrocarbon Samples for Analysis by Gas ChromatographyGPA 2140 Liquefied Petroleum Gas Specifications and Test Methods3. Terminology3.1 Definitions:3.1.1 floating piston cylinder (FPC)(FPC), na high pressure sample conta
9、iner, with a free floating internal piston thateffectively divides the container into two separate compartments.3.1.1.1 DiscussionA floating piston cylinder is used to collect a sample of liquid under pressure without the formation of a gaseous phase which canresult in changes in the composition of
10、the liquid sample.3.1.2 maximum fill densityvolume (reduced fill density)volume), nthe volume of a container occupied by the sample, usuallyexpressed as a percentage of the total capacity.1 This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants and is the
11、direct responsibility of Subcommittee D02.H0 onLiquefied Petroleum Gas.Current edition approved Feb. 15, 2007Nov. 1, 2012. Published March 2007February 2013. Originally approved in 1978. Last previous edition approved in 20012007 asD370001.07. DOI: 10.1520/D3700-07.10.1520/D3700-12.2 For referencedA
12、STM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from Gas Processors Association (GPA), 6526 E. 60th St., Tulsa, OK
13、 74145.74145, www.gpaglobal.orgThis document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommen
14、ds that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
15、West Conshohocken, PA 19428-2959. United States13.1.2.1 DiscussionSome regulatory agencies use the expressions “maximum fill density” and “reduced fill density.”4. Summary of Practice4.1 A liquid LPG petroleum gas (LPG) sample is transferred as a liquid under pressure from a sample point to a floati
16、ng pistoncylinder. The floating piston cylinder (FPC) is designed to collect liquid samples with no vaporization by displacing a pistonagainst a pressurizing fluid (usually(preferably an inert gas). The piston serves as a physical barrier between the sample and thepressurizing fluid, at the sampling
17、 pressure. The position of the piston at the end of sampling indicates the percent fill of the samplecylinder.4.2 It is the responsibility of the user of this practice to locate the sample point at a suitable location and orientation where theproduct being sampled is a representative, single phase,
18、homogeneous liquid.5. Significance and Use5.1 This practice allows the collection of a representative sample of LPG that may contain trace volatile dissolved componentssuch as methane, nitrogen,ethane, and ethane.nitrogen. Sampling by Practice D1265 maycan result in a small, but predictable, lossof
19、these lighter components. Practice D1265 is suitable for collecting samples for routine specification testing, as the small lossof light components is not significant under Specification D1835 specification requirements. Practice D3700 is recommendedwhenever highly accurate determination of light co
20、mponents is required. For example, compositioncompositions determined onsamples collected according to Practice D3700 may be used to establish the product value of NGL mixtures (see Appendix X1).6. Interferences6.1 An interference in a sampling procedure is anything which compromises the integrity o
21、f the sample.6.2 Sample Incorrect choice of a sample point location can give result in a non-representative sample due to solid or liquidcontaminants, two phases, storage tank stratification, and so forth.6.3 Reactivity of steel surfaces can remove or chemically alter trace reactive components such
22、as H2S, COS, and mercaptan.6.4 A lubricant used on the floating piston or other internal wetted parts that is soluble in LPG can contaminate the sample.6.5 Pre-charge (inert) gas can leak into the sample due to worn or damaged piston seals or poor surface finish (see 8.1).6.5.1 Consult the manufactu
23、rers guidelines for suitable procedureprocedures to verify a leak-free cylinder, such as pressuretesting each side of the cylinder. It is also possible to analyze the sample for inert gas, or the inert gas for hydrocarbon, to detectleakage in either direction.6.6 Failure to flush sample lines and de
24、ad volumes can result in contaminants in samples.6.7 Sampling from stratified tanks, dead zones in flowing systems, or inappropriate time periods in composite sampling systemswillcan result in non-representative samples.6.8 Any material that can create carryover contamination from one sample to the
25、next has to be removed from the cylinder andthe cylinder shall be thoroughly cleaned. In addition to cleaning the interior metal surfaces and cleaning the soft parts (O-rings,for example), consideration should be given to replacing the soft parts if they might have absorbed any contamination. Exampl
26、esof contaminants include glycol, amine, lubricants, sulfur species, solvents, methanol, etc.7. Apparatus7.1 Floating Piston Cylinder (FPC):7.1.1 Construction, typically fabricated from corrosion resistant 316 stainless steel, in accordance with the pressure vesselcertification requirements in the j
27、urisdictions in which it is to be used, and through which it will be transported. Protective internalcoatings or surface treatments are acceptable provided that they do not adversely affect the free movement of the piston, oreffectiveness of the seals (see Fig. 1).7.1.1.1 Users should consult with t
28、he manufacturer of these sample cylinders and sample collection systems any time ambientor product temperatures, or both, exceed the range of 29C (20F) to 60C (140F). Extreme temperature effects upon metal,O-rings, valve seats, seals, gauges, relief devices, sample pump components and other devices
29、and components in the systemshould be assessed in a hazards analysis before any sampling takes place.NOTE 1At present, there is no international approval process for pressure cylinders. Cylinders require appropriate approval in each jurisdiction inwhich they are used or transported.7.1.2 Volume of S
30、ample, Sampleas required by the The minimum volume required is determined by the combined volumesrequired by each of the tests to be performed, typically 400 mL (that is, 80 % 80 % of a 500 mL sample cylinder at 15C).7.1.2.1 For safe handling of these cylinders under extremes of product or ambient t
31、emperatures, or both, the user shall considerthe effects of thermal expansion on the volume of product in the cylinder. For example, if a product is sampled at 40C (40F),D3700 122the user shall plan for the cylinder and sample to warm considerably during transport and before analysis is performed in
32、 thelaboratory. During summer months, the temperature of the cylinder and product could reasonably be expected to rise to as highas 46C (115F) in hot environments.Acylinder initially filled cold to 80 % of its capacity will, upon warming, be over-pressuredand the relief device(s) will activate under
33、 these conditions. Hydrocarbon releases of this type are unexpected and dangerous. Insuch an extreme, but not uncommon case, the cylinder should not be filled more than approximately 60 % of its capacity duringthe initial fill. Users should review ASTM/API/GPA volume correction factor calculations,
34、or data from similar samples, or both,to determine the maximum fill for the product and conditions being sampled, but should always leave at least 10 % vapor spaceafter allowing for the worst likely case of thermal expansion.NOTE 2For safe handling of these cylinders under extremes of product or amb
35、ient temperatures, or both, the user must consider the effects of thermalexpansion on the volume of product in the cylinder. For example, if a very cold product is sampled, 40C (40F) for example, the cylinder should beexpected to warm considerably before analysis is performed during transport and in
36、 the laboratory. During summer months, the temperature of thecylinder and product could reasonably be expected to rise to as high as 46C (115F) in hot environments.Acylinder initially filled to 80 % of its capacityFIG. 1 Typical Floating Piston CylindersCylinder DesignsD3700 123will be over-pressure
37、d and the relief device(s) will activate under these conditions. Releases of this type are unexpected and dangerous. In such anextreme, but not uncommon case, the cylinder should not be filled more than approximately 60 % during the initial fill. Users should reviewASTM/GPAvolume correction factor c
38、alculations, or data, or both, to determine the maximum fill for the product being sampled, but should always leave at least10 % vapor space afterThe appropriate tables for conversion of LPG volume or density as a function of temperature are: MNLTP27, Manual on PetroleumMeasurement Standards, Chapte
39、r 11Physical Properties Data, Section 2, Part 4Temperature Correction for the Volume of NGL and LPG Tables 23E,24E, 53E, 59E, and 60E; 2 allowing for the worst likely or GPA Technical Publication TP-27.case3 of thermal expansion.NOTE 3It is recommended that users work with the manufacturer of these
40、sample cylinders and sample collection systems any time ambient orproduct temperatures, or both, exceed the range of 29C (20F) to 60C (140F). The consideration of extreme temperatures shall consider effects onmetal, O-rings, valve seats, seals, gauges, relief devices, sample pump components and othe
41、r devices and components in the system.7.1.3 Piston Position IndicatorThe FPC shall be equipped with a piston position indicator such as a magnetic follower, pistonrod, or equivalent which can be used to indicate indicates the sample volume to comply with the maximum percent fill (maximumfill densit
42、y)volume) allowed for storage and transportation. An outage chamber with indicating level device may also be used.7.1.3.1 Floating piston cylinders that are not equipped with a piston position indicator shall not be used without a procedure toallow the operator to verify fill densityvolume immediate
43、ly after sampling and prior to transport. Consult the authority havingjurisdiction for acceptable procedures.7.1.4 The cylinder shall include a mechanism to mix the sample in the sample chamber in case of stratified mixtures or waterhaze that maycan settle after sampling.This mechanism may be a mech
44、anical mixer/vortex plate on a movable rod, a freely movingrolling ball or slider, magnetically coupled stirrer, or similar mixing device. It is the responsibility of the user to provide sufficientmixing with the mechanism used to allow a representative sample to be withdrawn.7.2 Lubricants used to
45、lubricate or seal the floating piston, O ring O-ring seals, and other components shall be inert to andinsoluble in LPG.NOTE 3DuPont Krytox AC or AD4 have been found to be suitable.7.3 A safety relief device is required to prevent over-pressure in the event that a cylinder becomes fully liquid filled
46、(hydraulically locked) from either overfilling or liquid thermal expansion from excessive temperature increase.7.3.1 Arupture disk or a self-resetting pressure relief valve shall be fitted to the cylinder to prevent overpressure from hydraulicfilling due to temperature increase. A self-resetting pre
47、ssure relief valve (“poppet valve”) is preferred.NOTE 4DuPont KEL-F,KEL-F4 or similar materials have has been found to be suitable. Polytetrafluoroethylene (PTFE) or other materials that areprone to creep under pressure, and metal-to-metal valve seals are not recommended.7.3.2 Users may not alter va
48、lves or safety relief devices that are required as part of a cylinder permit or exemption. (The USAhas an exemption system and Canada has a permitting procedure for non-ASME or DOT cylinders.)7.3.2.1 The USA has an exemption system and Canada has a permitting procedure for non-ASME or DOT cylinders.
49、7.4 Sampling SystemIt is not possible to provide a single procedure that will be applicable for all sampling situations.Different procedures and sampling equipment may be required for sampling pipes, storage tanks, rail cars, trucks, and smallerstorage vessels in order to obtain a representative sample (see 4.2).7.4.1 Sample equipment and procedures shall be designed and used to obtain representative samples of a product, and tomaintain sample integrity for the tests being performed. A typical sampling system for LPG flowing in a pipe is
