1、Designation: D3700 16Standard 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 revision.
2、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 forobtaining a representative sample of liquefied petroleum gas(LPG), such as spec
3、ified in ASTM Specification D1835,GPA2140, and comparable international standards. It may also beused for other natural gas liquid (NGL) products that arenormally single phase (for example, NGL mix, field butane,and so forth), defined in other industry specifications orcontractual agreements, and fo
4、r volatile (higher vapor pres-sure) crude oils.NOTE 1Some floating piston cylinders have such tight piston sealsthat the vapor pressure of some high vapor pressure crude oils may not besufficient to allow sampling without a handle to move the piston. Analternative sampling practice for UN Class 3 li
5、quids (under 300 kPa at52 C) is Practice D8009, which utilizes a Manual Piston Cylinder (MPC)sampler.1.2 This practice is not intended for non-specification prod-ucts that contain significant quantities of undissolved gases(N2,CO2), free water or other separated phases, such as raw orunprocessed gas
6、/liquids mixtures and related materials. Thesame equipment can be used for these purposes, but additionalprecautions are generally needed to obtain representativesamples of multi-phase products (see Appendix X1).1.3 This practice includes recommendations for the locationof a sample point in a line o
7、r vessel. It is the responsibility ofthe user to ensure that the sampling point is located so as toobtain a representative sample.1.4 The values stated in SI units are to be regarded asstandard.1.4.1 ExceptionThe values given in parentheses are forinformation only.1.5 This standard does not purport
8、to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices, and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1265
9、Practice for Sampling Liquefied Petroleum (LP)Gases, Manual MethodD1835 Specification for Liquefied Petroleum (LP) GasesD8009 Practice for Manual Piston Cylinder Sampling forVolatile Crude Oils, Condensates, and Liquid PetroleumProducts2.2 GPA Midstream Association Standards:3GPA 2140 Liquefied Petr
10、oleum Gas Specifications and TestMethodsGPA 2174 Obtaining Liquid Hydrocarbon Samples forAnalysis by Gas Chromatography3. Terminology3.1 Definitions:3.1.1 floating piston cylinder (FPC), na high pressuresample container, with a free floating internal piston thateffectively divides the container into
11、 two separate compart-ments.3.1.1.1 DiscussionA floating piston cylinder is used tocollect a sample of liquid under pressure without the formationof a gaseous phase which can result in changes in thecomposition of the liquid sample.3.1.2 maximum fill volume (reduced fill volume), nthevolume of a con
12、tainer occupied by the sample, usually ex-pressed as a percentage of the total capacity.3.1.2.1 DiscussionSome regulatory agencies use the ex-pressions “maximum fill density” and “reduced fill density.”4. Summary of Practice4.1 A liquid petroleum gas (LPG) sample is transferred as aliquid under pres
13、sure from a sample point to a floating pistoncylinder. The floating piston cylinder (FPC) is designed tocollect liquid samples with no vaporization by displacing apiston against a pressurizing fluid (preferably an inert gas). Thepiston serves as a physical barrier between the sample and the1This pra
14、ctice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.H0 on Liquefied Petroleum Gas.Current edition approved Oct. 1, 2016. Published October 2016. Originallyapproved in 1978. Last previous editio
15、n approved in 2014 as D3700 14. DOI:10.1520/D3700-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Availab
16、le from GPA Midstream Association, 6526 E. 60th St., Tulsa, OK74145, www.gpaglobal.org*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1pressurizing fluid, at the sampling
17、 pressure. The position of thepiston at the end of sampling indicates the percent fill of thesample cylinder.4.2 It is the responsibility of the user of this practice tolocate the sample point at a suitable location and orientationwhere the product being sampled is a representative, singlephase, hom
18、ogeneous liquid.5. Significance and Use5.1 This practice allows the collection of a representativesample of LPG that may contain trace volatile dissolvedcomponents such as methane, ethane, and nitrogen. Samplingby Practice D1265 can result in a small, but predictable, loss ofthese lighter components
19、. Practice D1265 is suitable forcollecting samples for routine specification testing, as the smallloss of light components is not significant under SpecificationD1835 specification requirements. Practice D3700 is recom-mended whenever highly accurate determination of light com-ponents is required. F
20、or example, compositions determined onsamples collected according to Practice D3700 may be used toestablish the product value of NGL mixtures (see AppendixX1).6. Interferences6.1 An interference in a sampling procedure is anythingwhich compromises the integrity of the sample.6.2 Incorrect choice of
21、a sample point location can result ina non-representative sample due to solid or liquidcontaminants, two phases, storage tank stratification, and soforth.6.3 Reactivity of steel surfaces can remove or chemicallyalter trace reactive components such as H2S, COS, andmercaptan.6.4 A lubricant used on th
22、e floating piston or other internalwetted parts that is soluble in LPG can contaminate the sample.6.5 Pre-charge (inert) gas can leak into the sample due toworn or damaged piston seals or poor surface finish (see 8.1).6.5.1 Consult the manufacturers guidelines for suitableprocedures to verify a leak
23、-free cylinder, such as pressuretesting each side of the cylinder. It is also possible to analyzethe sample for inert gas, or the inert gas for hydrocarbon, todetect leakage in either direction.6.6 Failure to flush sample lines and dead volumes canresult in contaminants in samples.6.7 Sampling from
24、stratified tanks, dead zones in flowingsystems, or inappropriate time periods in composite samplingsystems can result in non-representative samples.6.8 Any material that can create carryover contaminationfrom one sample to the next has to be removed from thecylinder and the cylinder shall be thoroug
25、hly cleaned. Inaddition to cleaning the interior metal surfaces and cleaning thesoft parts (O-rings, for example), consideration should be givento replacing the soft parts if they might have absorbed anycontamination. Examples of contaminants include glycol,amine, lubricants, sulfur species, solvent
26、s, methanol, etc.7. Apparatus7.1 Floating Piston Cylinder (FPC):7.1.1 Construction, typically fabricated from corrosion re-sistant 316 stainless steel, in accordance with the pressurevessel certification requirements in the jurisdictions in which itis to be used, and through which it will be transpo
27、rted.Protective internal coatings or surface treatments are accept-able provided that they do not adversely affect the freemovement of the piston, or effectiveness of the seals (see Fig.1).7.1.1.1 Users should consult with the manufacturer of thesesample cylinders and sample collection systems any t
28、imeambient or product temperatures, or both, exceed the range of29 C (20 F) to 60 C (140 F). Extreme temperature ef-fects upon metal, O-rings, valve seats, seals, gauges, reliefdevices, sample pump components and other devices andcomponents in the system should be assessed in a hazardsanalysis befor
29、e any sampling takes place.NOTE 2At present, there is no international approval process forpressure cylinders. Cylinders require appropriate approval in each juris-diction in which they are used or transported.7.1.2 Volume of SampleThe minimum volume required isdetermined by the combined volumes req
30、uired by each of thetests to be performed, typically 400 mL (that is, 80 % of a500 mL sample cylinder at 15 C).7.1.2.1 For safe handling of these cylinders under extremesof product or ambient temperatures, or both, the user shallconsider the effects of thermal expansion on the volume ofproduct in th
31、e cylinder. For example, if a product is sampled at40 C (40 F), the user shall plan for the cylinder and sampleto warm considerably during transport and before analysis isperformed in the laboratory. During summer months, thetemperature of the cylinder and product could reasonably beexpected to rise
32、 to as high as 46 C (115 F) in hot environ-ments. A cylinder initially filled cold to 80 % of its capacitywill, upon warming, be over-pressured and the relief device(s)will activate under these conditions. Hydrocarbon releases ofthis type are unexpected and dangerous. In such an extreme,but not unco
33、mmon case, the cylinder should not be filled morethan approximately 60 % of its capacity during the initial fill.Users should review ASTM/API/GPA Midstream volume cor-rection factor calculations, or data from similar samples, orboth, to determine the maximum fill for the product andconditions being
34、sampled, but should always leave at least10 % vapor space after allowing for the worst likely case ofthermal expansion.NOTE 3The appropriate tables for conversion of LPG volume ordensity as a function of temperature are: MNLTP27, Manual on PetroleumMeasurement Standards, Chapter 11Physical Propertie
35、s Data, Section 2,Part 4Temperature Correction for the Volume of NGL and LPG Tables23E, 24E, 53E, 59E, and 60E;2or GPA Midstream Technical PublicationTP-27.37.1.3 Piston Position IndicatorThe FPC shall be equippedwith a piston position indicator such as a magnetic follower,piston rod, or equivalent
36、which indicates the sample volume tocomply with the maximum percent fill (maximum fill volume)allowed for storage and transportation. An outage chamberwith indicating level device may also be used.D3700 1627.1.3.1 Floating piston cylinders that are not equipped witha piston position indicator shall
37、not be used without a proce-dure to allow the operator to verify fill volume immediatelyafter sampling and prior to transport. Consult the authorityhaving jurisdiction for acceptable procedures.7.1.4 The cylinder shall include a mechanism to mix thesample in the sample chamber in case of stratified
38、mixtures orwater haze that can settle after sampling. This mechanism maybe a mechanical mixer/vortex plate on a movable rod, a freelymoving rolling ball or slider, magnetically coupled stirrer, orFIG. 1 Typical Floating Piston Cylinder DesignsD3700 163similar mixing device. It is the responsibility
39、of the user toprovide sufficient mixing with the mechanism used to allow arepresentative sample to be withdrawn.7.2 Lubricants used to lubricate or seal the floating piston,O-ring seals, and other components shall be inert and insolublein LPG.7.2.1 DuPont Krytox (trademarked) AC or AD4,5have beenfou
40、nd to be suitable. DuPont Krytox General Purpose Lubri-cants GPL 107 (viscous oil) and GPL 201 (light grease)4,5have been found to be suitable in floating piston cylinders, andare less costly than the aerospace grades AC andAD of PTFElubricants. These lubricants are insoluble in aliphatic/aromatichy
41、drocarbons, water, caustic, amines, and glycols.7.2.2 Some common grades of silicone based O ringlubricants have been successfully used for LPG due to the lowsolvency of light paraffinic hydrocarbons such as propane andbutanes. However, these lubricants are quickly removed byaromatic hydrocarbons an
42、d crude oils, and are not recom-mended for this service.NOTE 4The use of lubricants that are soluble in hydrocarbon sampleswill result in contamination of the sample and loss of sealing integrity ofthe floating piston.7.3 A safety relief device is required to prevent over-pressure in the event that
43、a cylinder becomes fully liquid filled(hydraulically locked) from either overfilling or liquid thermalexpansion from excessive temperature increase.7.3.1 A rupture disk or a self-resetting pressure relief valveshall be fitted to the cylinder to prevent overpressure fromhydraulic filling due to tempe
44、rature increase. A self-resettingpressure relief valve (“poppet valve”) is preferred.7.3.1.1 DuPont KEL-F4,5has been found to be suitable.7.3.1.2 Polytetrafluoroethylene (PTFE) or other materialsthat are prone to creep under pressure, and metal-to-metalvalve seals are not recommended.7.3.2 Users may
45、 not alter valves or safety relief devices thatare required as part of a cylinder permit or exemption.7.3.2.1 The USA has an exemption system and Canada hasa permitting procedure for non-ASME or DOT cylinders.7.4 Sampling SystemIt is not possible to provide a singleprocedure that will be applicable
46、for all sampling situations.Different procedures and sampling equipment may be requiredfor sampling pipes, storage tanks, rail cars, trucks, and smallerstorage vessels in order to obtain a representative sample (see4.2).7.4.1 Sample equipment and procedures shall be designedand used to obtain repres
47、entative samples of a product, and tomaintain sample integrity for the tests being performed. Atypical sampling system for LPG flowing in a pipe is shown inFig. 2.NOTE 5While not required by this practice, the use of a sample probein a flowing line is recommended. The sample probe should be located
48、onthe top or side of a line, extending into the center third of the flowingstream. Sample points should not be installed on the bottom of a line,unless provisions are made to flush any accumulated debris from thesample point immediately prior to sampling. The sample probe should not4Registered trade
49、marks of E. I. du Pont de Nemours and Company, Wilmington,DE.5The sole source of supply of the apparatus known to the committee at this timeis E. I. du Pont de Nemours and Company, http:/. If you are awareof alternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.FIG. 2 Typical Sampling System with ValvingD3700 164be horizontal; rather it should have enough elevation to be sure
