1、Designation: D 6378 07e1An American National StandardStandard Test Method forDetermination of Vapor Pressure (VPX) of PetroleumProducts, Hydrocarbons, and Hydrocarbon-OxygenateMixtures (Triple Expansion Method)1This standard is issued under the fixed designation D 6378; the number immediately follow
2、ing the designation indicates the year oforiginal adoption or, in the 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.e1NOTERemoved apparatus sole
3、source of supply footnote editorially in September 2007.1. Scope*1.1 This test method covers the use of automated vaporpressure instruments to determine the vapor pressure exerted invacuum by volatile, liquid petroleum products, hydrocarbons,and hydrocarbon-oxygenate mixtures. This test method issui
4、table for testing samples with boiling points above 0C(32F) that exert a vapor pressure between 7 and 150 kPa (1.0and 21psi) at 37.8C (100F) at a vapor-to-liquid ratio of 4:1.The liquid sample volume size required for analysis is depen-dent upon the vapor-to-liquid ratio chosen (see Note 1) and them
5、easuring chamber volume capacity of the instrument (see6.1.1 and Note 3).NOTE 1The test method is suitable for the determination of the vaporpressure of volatile, liquid petroleum products at temperatures from 0 to100C at vapor to liquid ratios of 4:1 to 1:1 (X = 4 to 1) and pressures upto 500 kPa (
6、70 psi), but the precision statement (see Section 16) may notbe applicable.1.2 The vapor pressure (VPX) determined by this testmethod at a vapor-liquid ratio of 4:1 (X = 4) of gasoline andgasolineoxygenate blends at 37.8C can be correlated to thedry vapor pressure equivalent (DVPE) value determined
7、byTest Method D 5191 (see 16.2).1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.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 o
8、f 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 7.2-7.8.2. Referenced Documents2.1 ASTM Standards:2D 323 Test Method for Vapor Pressure of Petroleum Prod-ucts (Reid Meth
9、od)D 2892 Test Method for Distillation of Crude Petroleum(15-Theoretical Plate Column)D 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 4953 Test Method for Vapor Pressure of Gasoline andGasoline-Oxygenate
10、 Blends (Dry Method)D 5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)D 5842 Practice for Sampling and Handling of Fuels forVolatility MeasurementD 5854 Practice for Mixing and Handling of LiquidSamples of Petroleum and Petroleum ProductsD 6299 Practice for Applying Statistic
11、al Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformanceD 6708 Practice for Statistical Assessment and Improve-ment of Expected Agreement Between Two Test Methodsthat Purport to Measure the Same Property of a Material3. Terminology3.1 Definitions of Terms Specific to This
12、Standard:3.1.1 dry vapor pressure equivalent (DVPE)a value cal-culated by a correlation equation from the total pressure (TestMethod D 5191), which is equivalent to the value obtained onthe sample by Test Method D 4953, Procedure A.1This test method is under the jurisdiction of ASTM Committee D02 on
13、Petroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.08 on Volatility.Current edition approved May 1, 2007. Published July 2007. Originally approvedin 1999. Last previous edition approved in 2006 as D 637806.2For referenced ASTM standards, visit the ASTM website, www
14、.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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive,
15、PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2 partial pressure from dissolved air (PPA), nthepressure exerted in vacuum from dissolved air that escapesfrom the liquid phase into the vapor phase.3.1.3 Reid vapor pressure equivalent (RVPE)a value cal-culated by a correlation equat
16、ion from the TPX, which isequivalent to the value obtained on the same by Test MethodD 323.3.1.4 total pressure (TPX), nthe pressure exerted invacuum by air- and gas-containing petroleum products, com-ponents and feedstocks, and other liquids, in the absence ofundissolved water at a vapor-liquid rat
17、io of X:1.3.1.5 vapor pressure (VPX), nthe total pressure minus thePPA in the liquid at a vapor-liquid ratio of X:1.VPX5 TPX2 PPA (1)3.2 Abbreviations:3.2.1 DVPEdry vapor pressure equivalent3.2.2 PPApartial pressure from dissolved air3.2.3 RVPEReid vapor pressure equivalent3.2.4 TPXtotal pressure3.2
18、.5 VPXvapor pressure4. Summary of Test Method4.1 Employing a measuring chamber with a built-in piston,a sample of known volume is drawn into the temperaturecontrolled chamber at 20C or higher. After sealing thechamber, the temperature of the chamber is increased to aspecified value simultaneously wi
19、th the first expansion. Twofurther expansions are performed to a final volume of (X+1)times that of the test specimen. After each expansion, the TPXis determined. The PPAand the solubility of air in the specimenare calculated from the three resulting pressures. The (VPX)iscalculated by subtracting t
20、he PPA in the liquid from TPX.NOTE 2For liquids containing very low levels of high vapor pressurecontaminants, which behave like a gas, this test method of determinationof the PPA and gases may lead to wrong results since the partial pressureof the contaminants will be included in the PPA. This effe
21、ct is shown whenthe value of the PPA and gases exceeds the average maximum limit of7 kPa (1 psi).5. Significance and Use5.1 Vapor pressure is a very important physical property ofvolatile liquids for shipping and storage.5.2 The vapor pressure of gasoline and gasoline-oxygenateblends is regulated by
22、 various government agencies.5.3 Specifications for volatile petroleum products generallyinclude vapor pressure limits to ensure products of suitablevolatility performance.5.4 In this test method, an air saturation procedure prior tothe measurement is not required, thus eliminating losses ofhigh vol
23、atile compounds during this step. This test method isfaster and minimizes potential errors from improper air satu-ration. This test method permits VPXdeterminations in thefield.5.5 This test method can be applied in online applications inwhich an air saturation procedure prior to the measurementcann
24、ot be performed.6. Apparatus6.1 The apparatus suitable for this test method employs asmall volume, cylindrically shaped measuring chamber withassociated equipment to control the chamber temperaturewithin the range from 0 to 100C. The measuring chambershall contain a movable piston with a maximum dea
25、d volumeof less than 1 % of the total volume at the lowest position toallow sample introduction into the measuring chamber andexpansion to the desired vapor-liquid ratio. A static pressuretransducer shall be incorporated in the piston. The measuringchamber shall contain an inlet/outlet valve combina
26、tion forsample introduction and expulsion. The piston and the valvecombination shall be at the same temperature as the measuringchamber to avoid any condensation or excessive evaporation.6.1.1 The measuring chamber shall be designed to containbetween 5 and 15 mL of liquid and vapor and be capable of
27、maintaining a vapor-liquid ratio of 4:1 to 1:1. The accuracy ofthe adjusted vapor-liquid ratio shall be within 0.05.NOTE 3The measuring chamber employed by the instruments used ingenerating the precision and bias statements were constructed of nickelplated aluminum and stainless steel with a total v
28、olume of 5 mL.Measuring chambers exceeding a 5-mL capacity can be used, but theprecision and bias statements (see Section 16) are not known to apply.6.1.2 The pressure transducer shall have a minimum opera-tional range from 0 to 200 kPa (0 to 29 psi) with a minimumresolution of 0.1 kPa (0.01 psi) an
29、d a minimum accuracy of60.2 kPa (60.03 psi). The pressure measurement system shallinclude associated electronics and readout devices to displaythe resulting pressure reading.6.1.3 Electronic temperature control shall be used to main-tain the measuring chamber at the prescribed temperaturewithin 60.1
30、C for the duration of the vapor pressure measure-ment.6.1.4 A platinum resistance thermometer shall be used formeasuring the temperature of the measuring chamber. Theminimum temperature range of the measuring device shall befrom 0 to 100C with a resolution of 0.1C and an accuracy of60.1C.6.1.5 The v
31、apor pressure apparatus shall have provisions forrinsing the measuring chamber with a solvent of low vaporpressure or with the next sample to be tested.6.2 Vacuum Pump for Calibration, capable of reducing thepressure in the measuring chamber to less than 0.01 kPa(0.001 psi) absolute.6.3 McLeod Vacuu
32、m 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 accordance with Annex A6.3 on Vacuum Sensors in TestMethod D 2892.6.4 Pres
33、sure 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 sameelevation relative to sea level as the apparatus in the laboratory.NOTE 4This test method does not give full details of instrumentssuitable f
34、or carrying out this test. Details on the installation, operation, andmaintenance of each instrument may be found in the manufacturersmanual.D637807e127. Reagents and Materials7.1 Purity of ReagentsUse chemicals of at least 99 %purity for verification of instrument performance (see Section11). Unles
35、s otherwise indicated, it is intended that all reagentsconform to the specifications of the Committee of AnalyticalReagents of the American Chemical Society3where suchspecifications are available. Lower purities can be used,provided it is first ascertained that the reagent is of sufficientpurity to
36、permit its use without lessening the accuracy of thedetermination.7.1.1 The chemicals in 7.3, 7.4, and 7.7 are suggested forverification of instrument performance (see Section 11), basedon the reference fuels analyzed in the 2003 interlaboratorystudy (ILS)4(see Table 1 and Note 12). Such reference f
37、uelsare not to be used for instrument calibration. Table 1 identifiesthe accepted reference value (ARV) and uncertainty limits, aswell as the acceptable testing range for each of the referencefuels listed.NOTE 5Verification fluids reported by 12 of the D 6378 data setparticipants in the 2003 ILS4inc
38、luded the following (with number of datasets identified in parentheses): 2,2-dimethylbutane (11), and 2,3-dimethylbutane (1).7.2 Cyclopentane,(WarningCyclopentane is flammableand a health hazard).7.3 2,2-Dimethylbutane,(Warning2,2-dimethylbutane isflammable and a health hazard).7.4 2,3-Dimethylbutan
39、e,(Warning2,3-dimethylbutane isflammable and a health hazard).7.5 Methanol,(WarningMethanol is flammable and ahealth hazard).7.6 2-Methylpentane,(Warning2-methylpentane is flam-mable and a health hazard).7.7 Pentane,(WarningPentane is flammable and a healthhazard).7.8 Toluene,(WarningToluene is flam
40、mable and a healthhazard).8. Sampling and Sample Introduction8.1 General Requirements:8.1.1 The extreme sensitivity of vapor pressure measure-ments to losses through evaporation and the resulting changesin composition is such as to require the utmost precaution andthe most meticulous care in the dra
41、wing and handling ofsamples.8.1.2 Obtain a sample and test specimen in accordance withPractice D 4057, D 4177, D 5842,orD 5854 when appropriate,except do not use the Sampling by Water Displacement sectionfor fuels containing oxygenates. Use either a 250-mL or 1-L(1-qt) sized container filled between
42、 70 and 80 % with sample.See Note 6 on effect of sample size on testing precision.NOTE 6The current precision statements were derived from the 2003ILS4using samples in 250-mL and 1-L (1-qt) clear glass containers.However, samples in containers of other sizes as prescribed in PracticeD 4057 may be us
43、ed, with the same filling requirement, but the precisioncan be affected. The differences in precision results obtained from 250-mLand 1-L containers were found to be statistically significant, in addition tohaving a statistically observable bias being detected between 250-mL and1-L containers. See T
44、ables 2 and 3, as well as Figs. 1 and 2 for morespecific details on precision differences as a function of VP4(37.8 C) andcontainer size, as well as 16.2.3 for specific details on the relative biasbetween 250-mL and 1-L containers. In general, numerically betterrepeatability values were determined a
45、t VP4(37.8 C) values 100 kPa, such as pentane, the precision appears toworsen with diminishing liquid volume in the bottle. It is recommendedthat if pentane is used, that the % capacity in the container be $50 %.11.2 Values obtained within the acceptable testing rangeintervals in Table 1 indicate th
46、at the instrument is performingat the level deemed acceptable by this standard. If valuesoutside the acceptable testing range intervals are obtained,verify the quality of the pure compound(s) and re-check thecalibration of the instrument (see Section 10).NOTE 12A reference fluid consisting of a 44.0
47、/56.0 (m/m) blend ofpentane/toluene was included in the 2003 ILS,4but results indicated thatthe data was not normally distributed.12. Quality Control Checks12.1 After having verified that the instrument is performingproperly, use a quality control (QC) sample that is representa-tive of the fuel(s) r
48、outinely tested by the laboratory to confirmthat the instrument is in statistical control following theguidelines given in D 6299.12.2 Record the VP4(37.8C) value and compare this to thedecision criteria for statistical control. If the result is found tobe outside the decision criteria for statistic
49、al control, initiate aninvestigation for root causes.12.3 Store the QC sample in an environment suitable forlong term storage without sample degradation. See AppendixX4 for guidelines and suggestions for preparing, storing, andisolating QC samples for use in the test.13. Procedure13.1 Set the sample introduction temperature of the measur-ing chamber between 20 and 37.8C.D637807e1613.2 Set the vapor-liquid ratio to the desired value X:1 (fortest results related to Test Method D 5191, set the vapor-liquidratio to 4:1).13.3 Connect an aliquot of
