1、Designation: D 6897 03aAn American National StandardStandard Test Method forVapor Pressure of Liquefied Petroleum Gases (LPG)(Expansion Method)1This standard is issued under the fixed designation D 6897; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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
3、 the vapor pressure of lique-fied petroleum gas products at a temperature of 37.8C, vaporto liquid ratio of 0.5:1, and pressures from 200 to 1550 kPa ona 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-pera
4、tures from 37.8 to 70C, vapor to liquid ratios of 0.1:1 to4:1, 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 37.8C, anda pressure range from 300 to 1500 kPa.NOTE 1This test met
5、hod is not intended to determine the true vaporpressure of LPG samples, but rather determine and report the vaporpressure of LPG at the 37.8C temperature and 0.5:1 vapor to liquid ratioas the Test Method D 1267 method.NOTE 2This test method is not a true vapor pressure method and willnot measure the
6、 full contribution from 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. A task group has been formed todetermine or quantify the effect
7、 that the contribution of light gases have onthe measured vapor pressure of LPG sample types as a function of the testtemperature, type of gas, and V/L ratio of the test.1.3 The values stated in SI units are to be regarded asstandard.1.4 This standard does not purport to address all of thesafety con
8、cerns, 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. For specificwarning statements, see Appendix X2.2. Referenced Documents2.1 ASTM
9、Standards:2D 1265 Practice for Sampling Liquefied Petroleum (LP)Gases (Manual Method)D 1267 Test Method for Gage Vapor Pressure of LiquefiedPetroleum (LP) Gases (LP-Gas Method)D 2892 Test Method for Distillation of Crude Petroleum(15-Theoretical Plate Column)D 3700 Practice for Obtaining LPG Samples
10、 Using a Float-ing Piston CylinderD 5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)D 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance2.2 Energy Institute Standards:3IP 181 Sampling Petroleum Gases3. Termi
11、nology3.1 Definitions:3.1.1 liquefied petroleum gases (LPG), nnarrow boilingrange hydrocarbon mixtures, consisting mainly of propane orpropylene, or both (WarningExtremely flammable. Harmfulif inhaled), butanes and butylenes, or both; in which theconcentration of hydrocarbon compounds with boiling p
12、ointgreater than 0C is less than 5 % by liquid volume, and whosevapor pressure at 37.8C (100F) is not greater than 1550 kPa.3.2 Definitions of Terms Specific to This Standard:3.2.1 total pressure (Ptot), nthe absolute pressure (relativeto vacuum) exerted by the specimen at the specified tempera-ture
13、 and vapor-liquid ratio.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.08 on Volatility.Current edition approved Dec. 1, 2003. Published January 2004. Originallyapproved in 2003. Last previous
14、edition approved in 2003 as D 689703.2For 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 I
15、nstitute, 61 New Cavendish St., London, WIG 7AR,U.K.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2 true vapor pressure, nthe physical property of agiven liquid
16、which specifies the maximum pressure at which avapor phase can coexist with the liquid phase at a givenequilibrium temperature condition.3.2.3 vapor pressure of LPG, nthe total pressure correctedrelative to normal barometric pressure.3.2.4 vapor to liquid ratio, nthe ratio of the volume of thevapor
17、in equilibrium to the fill volume of liquid.4. Summary of Test Method4.1 Employing a measuring chamber with a built-in 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
18、-controlled chamber at 5C by moving the piston to the fillingposition.After sealing the chamber, the volume is expanded 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
19、interest,such as 37.8C.4.2 The observed total pressure at equilibrium is correctedrelative to 101.3 kPa and reported 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 proper
20、ly designed storagevessels, shipping containers, and customer utilization equip-ment to ensure safe handling of these 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
21、, andfuel systems will not be exceeded under normal operatingtemperature conditions.5.3 For liquefied petroleum gases, 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 andexcl
22、udes any manual handling of a measuring chamber underhigh pressure.6. Apparatus6.1 Vapor Pressure Apparatus4The type 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
23、of 5 to70C. The measuring chamber shall contain a movable pistonwith a maximum dead volume of less than 1 % of the 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 be
24、incorporated in the piston. The measuring chamber shallcontain an inlet/outlet valve combination for sample introduc-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 cham
25、ber shall be designed to contain a total of5 mL of liquid and vapor and be capable of maintaining avapor-liquid 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 alu
26、minum and stainless steel.NOTE 4Test chambers exceedinga5mLcapacity can be used, but theprecision and bias statements (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 60.1C for the durati
27、on of the vapor pressure measure-ment.6.1.3 The pressure transducer shall have a range of 0 to3500 kPa 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 resi
28、stance thermometer, or equivalent,shall be used for measuring the temperature of the testchamber. The minimum temperature range of the measuringdevice shall be from 0 to 80C with a resolution of 0.1C anda minimum accuracy of 60.1C.6.2 Vacuum Pump for Calibration, capable of reducing thepressure in t
29、he measuring chamber to less than 0.01 kPaabsolute.6.3 McLeod Vacuum Gage or Calibrated Electronic VacuumMeasuring Device for Calibration, to cover at least the rangefrom 0.01 to 0.67 kPa (0.1 to 5 mm Hg). The calibration of theelectronic vacuum measuring device shall be regularly verifiedin accorda
30、nce with A6.3 of Test Method D 2892.6.4 Pressure Measuring Device for Calibration, capable ofmeasuring local station pressure with an accuracy and aresolution of 0.1 kPa (1 mm Hg) or better, at the same elevationrelative to sea level as the apparatus in the laboratory.NOTE 5This test method does not
31、 give full details of instrumentssuitable for carrying out this test. Details on the installation, 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. Comm
32、only used qualitycontrol check materials are propane, butane, and pentane (seeSection 11). Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society5wheresuch specifications are available. Lower p
33、urities can be used,4The 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, please provide this information to ASTM Interna-tional Headquarters. Your comments will
34、receive careful consideration at a meetingof the responsible technical committee1, which you may attend.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see A
35、nalar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 6897 03a2provided it is first ascertained that the reagent is of sufficientpurity to permit its use without les
36、sening the accuracy of thedetermination.NOTE 6The chemicals in this section are suggested for quality controlprocedures (see Section 11) and are not used for instrument calibration.7.2 Cleaning SolventsUse noncorrosive solvents capableof cleaning the measuring chamber, the valves, and the inletand o
37、utlet 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 shall be obtained and stored in accordance withPractice D 1265,orIP 181, unless the test samples can be takendirectly from t
38、he 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 inregulations, which is typically no more than 80 %. Consult thespecified regulations for more details.8.2 Any method of coupling the v
39、apor pressure apparatus tothe sample source can be employed. Tubing, 3 to 7 mm indiameter, of suitable-working pressure, and made of materialcorrosion-resistant to the products being sampled, is satisfac-tory for this purpose. A flexible transparent polyperfluoro-alkoxyethylene (PFA) tubing greatly
40、facilitates the purging andsampling operations.8.3 Practice D 1265 cylinders shall be equilibrated abovethe sample cell temperature of 5C to ensure sufficient samplecylinder pressure to fill the sample cell entirely. PracticeD 3700 cylinders shall be maintained at a pressure above thevapor pressure
41、of the LPG at 5C (approximately 655 kPa forspecial duty propane and approximately 175 kPa for commer-cial butanes).9. Preparation of Apparatus9.1 Prepare the instrument for operation in accordance withthe manufacturers instructions. Since LPG is discharged at theoutlet of the apparatus, connect a tu
42、bing 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 measuring chamber with asolvent. Acetone has been used successfully. Cleaning isperformed by drawing the solvent into the chamber
43、 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 indicated from the quality control checks performed accord-ing to Section 11. The calibration of the transducer is checkedusin
44、g two reference points, zero pressure (that is, 0.1 kPa)and the ambient barometric pressure.10.1.2 Connect a McLeod gage or a calibrated electronicvacuum-measuring device to the vacuum source in line withthe measuring chamber (Note 7). Apply vacuum to the mea-suring chamber. When the vacuum measurin
45、g 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 instrument design ormanufacturers instructions.NOTE 7Refer to Annex A6.3 of Test Method D 2892 for furtherdetails concerning the
46、calibration of electronic vacuum measuring devicesand proper maintenance of McLeod gages.10.1.3 Open the measuring chamber of the apparatus toatmospheric pressure and observe the corresponding pressurevalue of the transducer. Ensure that the apparatus is set todisplay the total pressure and not a ca
47、lculated or correctedvalue. Compare this pressure value with the pressure obtainedfrom a pressure-measuring device (see 6.4), as the pressurereference standard. The pressure-measuring device shall mea-sure the local station pressure at the same elevation as theapparatus in the laboratory, at the tim
48、e of pressure comparison.When the instrument is used over the full pressure range, acalibration with a dead weight balance shall be carried out.(WarningMany aneroid barometers, such as those used atweather stations and airports, are pre-corrected to give sealevel readings. These shall not be used fo
49、r 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 the 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 isu
