1、Designation: D3700 12D3700 14Standard 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 (for example, NGLmix, field butane, and so forth),defined in other industry specifications or cont
4、ractual agreements.agreements, and for volatile (higher vapor pressure) crude oils.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
5、 and related materials. The sameequipment can be used for 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
6、 the responsibility of theuser 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 standard. The values given in parentheses are for information only.1.5 This standard does not purport to address all of the safe
7、ty concerns, if any, associated with its use. It is the responsibilityof 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 Liquef
8、ied Petroleum (LP) Gases, Manual MethodD1835 Specification 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
9、 piston cylinder (FPC), na high pressure sample container, with a free floating internal piston that effectivelydivides 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 ph
10、ase which canresult in changes in the composition of the liquid sample.3.1.2 maximum fill volume (reduced fill volume), nthe volume of a container occupied by the sample, usually expressed as apercentage of the total capacity.1 This practice is under the jurisdiction of ASTM Committee D02 on Petrole
11、um Products Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.H0 on Liquefied Petroleum Gas.Current edition approved Nov. 1, 2012May 1, 2014. Published February 2013May 2014. Originally approved in 1978. Last previous edition approved in 20072012 asD3700D3700
12、 12.07. DOI: 10.1520/D3700-12.10.1520/D3700-14.2 For referencedASTM 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 fr
13、om Gas Processors Association (GPA), 6526 E. 60th St., Tulsa, OK 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
14、to adequately depict all changes accurately, ASTM recommends 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 standardCopyrigh
15、t ASTM International, 100 Barr Harbor Drive, PO Box C700, 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 petroleum gas (LPG) sample is transferred as a
16、 liquid under pressure from a sample point to a floating pistoncylinder. The floating piston cylinder (FPC) is designed to collect liquid samples with no vaporization by displacing a pistonagainst a pressurizing fluid (preferably an inert gas). The piston serves as a physical barrier between the sam
17、ple and thepressurizing fluid, at the sampling 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 bei
18、ng sampled is a representative, single phase, 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, ethane, and nitrogen. Sampling by Practice D1265 can result in a smal
19、l, but predictable, loss of these lightercomponents. Practice D1265 is suitable for collecting samples for routine specification testing, as the small loss of lightcomponents is not significant under Specification D1835 specification requirements. Practice D3700 is recommended wheneverhighly accurat
20、e determination of light components is required. For example, compositions determined on samples collectedaccording 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
21、 the integrity of the sample.6.2 Incorrect choice of a sample point location can result in a non-representative sample due to solid or liquid contaminants,two phases, storage tank stratification, and so forth.6.3 Reactivity of steel surfaces can remove or chemically alter trace reactive components s
22、uch 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 manuf
23、acturers guidelines for suitable procedures to verify a leak-free cylinder, such as pressure testing eachside of the cylinder. It is also possible to analyze the sample for inert gas, or the inert gas for hydrocarbon, to detect leakage ineither direction.6.6 Failure to flush sample lines and dead vo
24、lumes can result in contaminants in samples.6.7 Sampling from stratified tanks, dead zones in flowing systems, or inappropriate time periods in composite sampling systemscan result in non-representative samples.6.8 Any material that can create carryover contamination from one sample to the next has
25、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. Examplesof cont
26、aminants 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 jurisdicti
27、ons 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 the manufa
28、cturer of these sample cylinders and sample collection systems any time ambientor product temperatures, or both, exceed the range of 29C (20F) to 60C (140F).29 C (20 F) to 60 C (140 F). Extremetemperature effects upon metal, O-rings, valve seats, seals, gauges, relief devices, sample pump components
29、 and other devices andcomponents in the system should 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 transporte
30、d.7.1.2 Volume of SampleThe minimum volume required is determined by the combined volumes required by each of the teststo be performed, typically 400 mL (that is, 80 % of a 500 mL 500 mL sample cylinder at 15C).15 C).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 40CD3700 142(40F),40 C (40 F), the user shall plan for the cylinder and sample to warm considerably during transport and before analysisis p
32、erformed in the laboratory. During summer months, the temperature of the cylinder and product could reasonably be expectedto rise to as high as 46C (115F)46 C (115 F) in hot environments. A cylinder initially filled cold to 80 % of its capacity will,upon warming, be over-pressured and the relief dev
33、ice(s) will activate under these conditions. Hydrocarbon releases of this typeare unexpected and dangerous. In such an extreme, but not uncommon case, the cylinder should not be filled more thanapproximately 60 % of its capacity during the initial fill. Users should review ASTM/API/GPA volume correc
34、tion factorcalculations, 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 space after allowing for the worst likely case of thermal expansion.NOTE 2The appropriate tables for conversion of LP
35、G volume or density as a function of temperature are: MNLTP27, Manual on PetroleumMeasurement Standards, Chapter 11Physical Properties Data, Section 2, Part 4Temperature Correction for the Volume of NGL and LPG Tables 23E,24E, 53E, 59E, and 60E; 2 or GPA Technical Publication TP-27.3FIG. 1 Typical F
36、loating Piston Cylinder DesignsD3700 1437.1.3 Piston Position IndicatorThe FPC shall be equipped with a piston position indicator such as a magnetic follower, pistonrod, or equivalent which indicates the sample volume to comply with the maximum percent fill (maximum fill volume) allowedfor storage a
37、nd 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 volume immediately after sampling and prior to transpo
38、rt. Consult the authority having jurisdictionfor 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 can settle after sampling. This mechanism may be a mechanical mixer/vortex plate on a movable r
39、od, 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 lubricate or seal the floating piston, O
40、-ring seals, and other components shall be inert and insoluble inLPG.NOTE 3DuPont Krytox AC or AD4 have been found to be suitable.7.2.1 DuPont Krytox (trademarked) AC or AD4,5have been found to be suitable. DuPont Krytox General Purpose LubricantsGPL 107 (viscous oil) and GPL 201 (light grease) 4,5
41、have been found to be suitable in floating piston cylinders, and are less costlythan the aerospace grades AC and AD of PTFE lubricants. These lubricants are insoluble in aliphatic/aromatic hydrocarbons,water, caustic, amines, and glycols.7.2.2 Some common grades of silicone based Oring lubricants ha
42、ve been successfully used for LPG due to the low solvencyof light paraffinic hydrocarbons such as propane and butanes. However, these lubricants are quickly removed by aromatichydrocarbons and crude oils, and are not recommended for this service.NOTE 3The use of lubricants that are soluble in hydroc
43、arbon samples will result in contamination of the sample and loss of sealing integrity of thefloating piston.7.3 A safety relief device is required to prevent over-pressure in the event that a cylinder becomes fully liquid filled(hydraulically locked) from either overfilling or liquid thermal expans
44、ion 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 pressure relief valve (“poppet valve”) is preferred.NOTE 4DuPont KEL-F4 ha
45、s been found to be suitable. Polytetrafluoroethylene (PTFE) or other materials that are prone to creep under pressure, andmetal-to-metal valve seals are not recommended.7.3.1.1 DuPont KEL-F4,5 has been found to be suitable.7.3.1.2 Polytetrafluoroethylene (PTFE) or other materials that are prone to c
46、reep under pressure, and metal-to-metal valve sealsare not recommended.7.3.2 Users may not alter valves or safety relief devices that are required as part of a cylinder permit or exemption.7.3.2.1 The USA has an exemption system and Canada has a permitting procedure for non-ASME or DOT cylinders.7.4
47、 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
48、 (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 shown in Fig. 2.NOTE 4While not required by this practice,
49、the use of a sample probe in a flowing line is recommended. The sample probe should be located on thetop or side of a line, extending into the center third of the flowing stream. Sample points should not be installed on the bottom of a line, unless provisionsare made to flush any accumulated debris from the sample point immediately prior to sampling. The sample probe should not be horizontal; rather itshould have enough elevation to be sure any heavy contaminants that might be encountered, including water, will tend to drain out of
