1、Designation: D6897 16Standard Test Method forVapor Pressure of Liquefied Petroleum Gases (LPG)(Expansion Method)1This standard is issued under the fixed designation D6897; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. 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 test method covers the use of automatic vaporpressure instruments to determine the vapor pressure of lique-fied
3、 petroleum gas products at a temperature of 37.8 C, vaporto liquid ratio of 0.5:1, and pressures from 200 kPa to 1550 kPaon a sample volume of 3.33 mL.1.2 This test method is applicable to the determination ofvapor pressures of liquefied petroleum gas products at tem-peratures from 37.8 C to 70 C, v
4、apor to liquid ratios of 0.1:1to 4:1, and pressures up to 3500 kPa; however, the precision ofthe test method (see Section 15) has only been determined fora vapor to liquid ratio of 0.5:1, at a temperature of 37.8 C, anda pressure range from 300 kPa to 1500 kPa.NOTE 1This test method is not intended
5、to determine the true vaporpressure of LPG samples, but rather determine and report the vaporpressure of LPG at the 37.8 C temperature and 0.5:1 vapor to liquid ratioas the Test Method D1267 method.NOTE 2This test method is not a true vapor pressure method and willnot measure the full contribution f
6、rom any dissolved gases such asnitrogen or helium if they are present. The contribution of light gases tothe measured vapor pressure is highly dependent on the test temperature,type of gas, and V/L ratio of the test.1.3 The values stated in SI units are to be regarded asstandard.1.3.1 ExceptionNon-S
7、I units are included in parenthesesfor information only.1.4 This standard does not purport 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-bilit
8、y of regulatory limitations prior to use. For specificwarning statements, see Appendix X2.2. Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Petroleum (LP)Gases, Manual MethodD1267 Test Method for Gage Vapor Pressure of LiquefiedPetroleum (LP) Gases (LP-Gas Method)D2892
9、 Test Method for Distillation of Crude Petroleum(15-Theoretical Plate Column)D3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)D6299 Practice for Applying Statistical Quality Assuranceand Control Chartin
10、g Techniques to Evaluate AnalyticalMeasurement System Performance2.2 Energy Institute Standards:3IP 181 Sampling Petroleum Gases3. Terminology3.1 Definitions:3.1.1 liquefied petroleum gases (LPG), nnarrow boilingrange hydrocarbon mixtures, consisting mainly of propane orpropylene, or both (WarningEx
11、tremely flammable. Harmfulif inhaled), butanes and butylenes, or both; in which theconcentration of hydrocarbon compounds with boiling pointgreater than 0 C is less than 5 % by liquid volume, and whosevapor pressure at 37.8 C (100 F) is not greater than 1550 kPa.3.1.2 platinum resistance thermometer
12、, ntemperaturemeasuring device with platinum wire, whose electrical resis-tance changes in relation to temperature.3.1.3 vapor-liquid ratio (V/L), nof a liquid, the ratio of thevapor volume to the liquid volume of specimen, in equilibrium,under specified conditions.1This test method is under the jur
13、isdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.08 on Volatility.Current edition approved July 15, 2016. Published August 2016. Originallyapproved in 2003. Last previous edition approved in 2009 as D6897 09. DOI:1
14、0.1520/D6897-16.2For 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.3Available from Energy Institute, 61 New Cave
15、ndish St., London, WIG 7AR,U.K., http:/www.energyinst.org.uk.*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 States13.2 Definitions of Terms Specific to This Standard:3.2.1 tot
16、al vapor pressure (Ptot),nthe absolute vaporpressure (relative to vacuum) exerted by the specimen at thespecified temperature and vapor-liquid ratio.3.2.2 true vapor pressure, nthe physical property of agiven liquid which specifies the maximum pressure at which avapor phase can coexist with the liqu
17、id phase at a givenequilibrium temperature condition.3.2.3 vapor pressure of LPG, nthe total pressure correctedrelative to normal barometric pressure.3.3 Abbreviations:3.3.1 LPGliquefied petroleum gas3.3.2 V/Lvapor liquid ratio4. Summary of Test Method4.1 Employing a measuring chamber with a built-i
18、n piston,the chamber is rinsed three times with a portion of sample,which is then discarded. A sample of defined volume is drawnfrom a pressurized sampling system into the temperature-controlled chamber at 5 C by moving the piston to the fillingposition.After sealing the chamber, the volume is expan
19、ded bymoving the piston until the final volume produces the desiredvapor to liquid ratio of 0.5:1. The temperature of the measuringchamber is then regulated to the test temperature of interest,such as 37.8 C.4.2 The observed total pressure at equilibrium is correctedrelative to 101.3 kPa and reporte
20、d as the LPG vapor pressure atthe selected test temperature.5. Significance and Use5.1 Information on the vapor pressures of liquefied petro-leum gas is pertinent to selection of properly designed storagevessels, shipping containers, and customer utilization equip-ment to ensure safe handling of the
21、se products.5.2 Determination of the vapor pressure of liquefied petro-leum gas is important for safety reasons to ensure that themaximum operating design pressures of storage, handling, andfuel systems will not be exceeded under normal operatingtemperature conditions.5.3 For liquefied petroleum gas
22、es, vapor pressure can beconsidered a semi-quantitative measure of the amount of themost volatile material present in the product.5.4 This test method uses a small sample volume andexcludes any manual handling of a measuring chamber underhigh pressure.6. Apparatus6.1 Vapor Pressure Apparatus4The typ
23、e of apparatussuitable for this test method employs a small volume, cylin-drically shaped measuring chamber with associated equipmentto control the chamber temperature within the range of 5 C to70 C. The measuring chamber shall contain a movable pistonwith a maximum dead volume of less than 1 % of t
24、he totalvolume at the lowest position to allow sample introduction intothe measuring chamber and expansion to the desired vapor-liquid ratio. A static absolute pressure transducer shall beincorporated in the piston. The measuring chamber shallcontain an inlet/outlet valve combination for sample intr
25、oduc-tion and expulsion. The piston and the valve combination shallbe at the same temperature as the measuring chamber to avoidany condensation or excessive evaporation.6.1.1 The test chamber shall be designed to contain a total of5 mL of liquid and vapor and be capable of maintaining avapor-liquid
26、ratio of 0.5:1 with a maximum deviation of 0.02.NOTE 3The test chamber employed by the instruments used ingenerating the precision and bias statements were constructed of nickel-plated aluminum and stainless steel.NOTE 4Test chambers exceeding a 5 mL capacity can be used, but theprecision and bias s
27、tatements (see Section 15) are not known to apply.6.1.2 Electronic temperature control shall be used to main-tain the measuring chamber at the prescribed temperaturewithin 60.1 C for the duration of the vapor pressure measure-ment.6.1.3 The pressure transducer shall have a range of 0 kPa to3500 kPa
28、with a minimum resolution of 1 kPa. The minimumaccuracy shall be 61 kPa for pressures up to 700 kPa, 62 kPafor pressures up to 1750 kPa, and 64 kPa for pressures up to3500 kPa.6.1.4 A platinum resistance thermometer, or equivalent,shall be used for measuring the temperature of the testchamber. The m
29、inimum temperature range of the measuringdevice shall be from 0 C to 80 C with a resolution of 0.1 Cand a minimum accuracy of 60.1 C.6.2 Vacuum Pump for Calibration , capable of reducing thepressure in the measuring chamber to less than 0.01 kPaabsolute.6.3 McLeod Vacuum Gage or Calibrated Electroni
30、c VacuumMeasuring Device for Calibration, to cover at least the rangefrom 0.01 kPa to 0.67 kPa (0.1 mm to 5 mm Hg). The calibra-tion of the electronic vacuum measuring device shall beregularly verified in accordance with A6.3 of Test MethodD2892.6.4 Pressure Measuring Device for Calibration, capable
31、 ofmeasuring local station pressure with an accuracy and aresolution of 0.1 kPa (1 mm Hg) or better, at the sameelevation relative to sea level as the apparatus in the laboratory.NOTE 5This test method does not give full details of instrumentssuitable for carrying out this test. Details on the insta
32、llation, operation, andmaintenance of each instrument may be found in the manufacturersmanual.7. Reagents and Materials7.1 Purity of ReagentsUse chemicals of at least 99 %purity for quality control checks. Commonly used qualitycontrol check materials are propane, butane, and pentane (seeSection 11).
33、 Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on4The sole source of supply of the apparatus known to the committee at this timeis Grabner Instruments,A-1220 Vienna, Dr. Otto Neurathgasse 1,Austria. If you areaware of alternative suppliers
34、, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee,1which you may attend.D6897 162Analytical Reagents of the American Chemical Society5wheresuch specifications are available. Lower
35、 purities can be used,provided it is first ascertained that the reagent is of sufficientpurity to permit its use without lessening the accuracy of thedetermination.NOTE 6The chemicals in this section are suggested for quality controlprocedures (see Section 11) and are not used for instrument calibra
36、tion.7.2 Cleaning SolventsUse noncorrosive solvents capableof cleaning the measuring chamber, the valves, and the inletand outlet tubes. A commonly used solvent is acetone.(WarningPropane, butane, pentane, and acetone are flam-mable and health hazards.)8. Sampling and Sample Introduction8.1 Samples
37、shall be obtained and stored in accordance withPractice D1265, or IP 181, unless the test samples can be takendirectly from the source of the material to be tested. Use acontainer of not less than 100 mL in size and filled at least70 % with sample up to a maximum fill density as specified inregulati
38、ons, which is typically no more than 80 %. Consult thespecified regulations for more details.8.2 Any method of coupling the vapor pressure apparatus tothe sample source can be employed. Tubing, 3 mm to 7 mm indiameter, of suitable-working pressure, and made of materialcorrosion-resistant to the prod
39、ucts being sampled, is satisfac-tory for this purpose. A flexible transparent polyperfluoro-alkoxyethylene (PFA) tubing greatly facilitates the purging andsampling operations.8.3 Practice D1265 cylinders shall be equilibrated above thesample cell temperature of 5 C to ensure sufficient samplecylinde
40、r pressure to fill the sample cell entirely. Practice D3700cylinders shall be maintained at a pressure above the vaporpressure of the LPG at 5 C (approximately 655 kPa for specialduty propane and approximately 175 kPa for commercialbutanes).9. Preparation of Apparatus9.1 Prepare the instrument for o
41、peration in accordance withthe manufacturers instructions. Since LPG is discharged at theoutlet of the apparatus, connect a tubing to the outlet and leadthe other end of the tubing to a safe exhaust system or a gasrecovery system to protect the environment from LPG.9.2 If contaminated, clean the mea
42、suring chamber with asolvent. Acetone has been used successfully. Cleaning isperformed by drawing the solvent into the chamber by theintegrated piston and expelling the solvent into a wastecontainer.10. Calibration10.1 Pressure Transducer:10.1.1 Check the calibration of the transducer when neededas
43、indicated from the quality control checks performed accord-ing to Section 11. The calibration of the transducer is checkedusing two reference points, zero pressure (that is, 0.1 kPa) andthe ambient barometric pressure.10.1.2 Connect a McLeod gage or a calibrated electronicvacuum-measuring device to
44、the vacuum source in line withthe measuring chamber (Note 7). Apply vacuum to the mea-suring chamber. When the vacuum measuring device registersa pressure less than 0.1 kPa (0.8 mm Hg), adjust the transducercontrol to zero or to the actual reading on the vacuummeasuring device as dictated by the ins
45、trument design ormanufacturers instructions.NOTE 7Refer toAnnexA6.3 of Test Method D2892 for further detailsconcerning the calibration of electronic vacuum measuring devices andproper maintenance of McLeod gages.10.1.3 Open the measuring chamber of the apparatus toatmospheric pressure and observe th
46、e corresponding pressurevalue of the transducer. Ensure that the apparatus is set todisplay the total pressure and not a calculated or correctedvalue. Compare this pressure value with the pressure obtainedfrom a pressure-measuring device (see 6.4), as the pressurereference standard. The pressure-mea
47、suring device shall mea-sure the local station pressure at the same elevation as theapparatus in the laboratory, at the time of pressure comparison.When the instrument is used over the full pressure range, acalibration with a dead-weight tester shall be carried out.(WarningMany aneroid barometers, s
48、uch as those used atweather stations and airports, are pre-corrected to give sealevel readings. These shall not be used for calibration of theapparatus.)10.1.4 Repeat 10.1.2 and 10.1.3 until the zero and baromet-ric pressures read correctly without further adjustments.10.2 Temperature SensorVerify t
49、he calibration of theresistance thermometer or equivalent (see 6.1.4) used tomonitor the measuring chamber temperature when needed asindicated from the quality control checks performed accordingto Section 11 against a temperature sensing device which istraceable to National Institute of Standards and Technology(NIST) or national authorities in the country the equipment isused.11. Quality Control Checks11.1 Use a verification fluid or gas of known vapor pressureas an independent check against the instrument calibration eachday the instrum
