API Designation: Manual of Petroleum Measurement Standards (MPMS), Chapter 9.1
Designation: D1298 – 12b
Designation: 160/99
Standard Test Method for
Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method 1 This standard is issued under the fixed designation D1298; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (ϵ) indicates an editorial change since the last revision or reapproval.
1. Sco Scope* pe*
1.5 Annex A1 contains A1 contains a procedure for verifying or certifying the equipment for this test method. 1.6 1. 6 Th Thee va valu lues es st state ated d in SI un units its are to be re rega gard rded ed as standar stan dard. d. The valu values es giv given en in par parent enthes heses es are pro provid vided ed for information only. standard d doe doess not purport purport to add addre ress ss all of the 1.7 This standar safet sa fetyy co conc ncern erns, s, if an anyy, as asso socia ciated ted wi with th its us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.1 Thi Thiss test met method hod cov covers ers the lab labora orator tory y det determ ermina ination tion using usin g a gl glas asss hy hydr drom omete eterr in co conj njun unct ctio ion n wi with th a ser series ies of calculations, of the density, relative density, or API gravity of crude petroleum, petroleum products, or mixtures of petroleum and nonpetroleum products normally handled as liquids, and having a Reid vapor pressure of 101.325 kPa (14.696 psi) or less. les s. Val alue uess ar aree de deter termin mined ed at ex exist istin ing g tem tempe pera ratu ture ress an and d corrected to 15°C or 60°F by means of a series of calculations and international standard tables. 1.2 The ini initial tial hyd hydrom romete eterr rea readin dings gs obt obtain ained ed are unc uncor or-rected rect ed hyd hydrom rometer eter rea readin dings gs and not den density sity mea measur sureme ements nts.. Readings are measured on a hydrometer at either the reference temperature or at another convenient temperature, and readings are corrected for the meniscus effect, the thermal glass expansion effect, alternate calibration temperature effects and to the reference temperature by means of the Petroleum Measurement Tables; values obtained at other than the reference temperature being hydrometer readings and not density measurements. 1.3 Readings determined as density, relative density, density, or API gravity gravit y can be converted to equivalent equivalent values in the other units or alternate reference temperatures by means of Interconversion Proce Procedures dures (API MPMS Chapter Chapter 11 11.5) .5),, or Adjunct Adjunct to D1250 Guide D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1), or both, or tables, as applicable. 1.4 The initial hydrometer hydrometer readings readings determined determined in the laboratory shall be recorded before performing any calculations. The calculations required in Section Section 10 10 shall be applied to the initial hydrometer hydrometer readin reading g with observations observations and resul results ts reported as required by Section 11 11 prior prior to use in a subsequent calculation calculat ion procedure (ticket calcula calculation, tion, meter factor calculation, or base prover volume determination).
2. Referenc Referenced ed Documents 2.1 ASTM Standards: 2 D1250 Guide for Use of the Petroleum Measurement Tables D4057 Practi Practice ce for Man Manual ual Sam Sampli pling ng of Pet Petrol roleum eum and Petroleum Products (API MPMS Chapter Chapter 8.1) D4177 Practice for Automatic Sampling of Petroleum and Petroleum Petro leum Produ Products cts (API MPMS Chapter Chapter 8.2) D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products (API MPMS Chapter Chapter 8.3) E1 Specification for ASTM Liquid-in-Glass Thermometers E100 Specification for ASTM Hydrometers Standards:3 2.2 API Standards: MPMS Chapter Chapter 8.1 Manual Manual Sam Samplin pling g of Petr Petrole oleum um and Petroleum Petrole um Produ Products cts (ASTM Practice D4057 Practice D4057)) MPMS Chapter Chapter 8.2 Autom Automatic atic Sampling of Petroleum and Petroleum Petrole um Produ Products cts (ASTM Practice D4177 Practice D4177)) Chapter 8.3 8.3 Mixing and Handling of Liquid Liquid Samples MPMS Chapter of Pet Petrol roleum eum and Petr Petrole oleum um Pro Produc ducts ts (AS (ASTM TM Pra Practic cticee D5854)) D5854 Chapter 11. 11.1 1 Temper Temperature ature and Pressu Pressure re Volume MPMS Chapter Correction Factors for Generalized Crude Oils, Refined Products and Lubricating Oils (Adjunct to ASTM D1250 ASTM D1250))
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Thiss tes Thi testt met method hod is und under er the juri jurisdi sdicti ction on of AST ASTM M Com Commit mittee tee D02 on Petroleum Products and Lubricants and the API Committee on Petroleum Measurement, and is the direct responsibility of Subcommittee D02.02 D02.02 /COMQ, /COMQ, the joint ASTM-API Committee on Hydrocarbon Measurement for Custody Transfer (Joint ASTM-API). Current Curre nt editio edition n appro approved ved June 1, 2012. Publi Published shed October 2012. Origin Originally ally approved in 1953. Last previous edition approved in 2012 as D1298–12a. DOI: 10.1520/D1298-12B.
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For refere referenced nced ASTM stand standards, ards, visit the ASTM webs website, ite, www www.ast .astm.org m.org,, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 3 Published as Manual of Petroleum Measurement Standards. Available from the American Petroleum Institute (API), 1220 L St., NW, Washington, DC 20005.
*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.
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D1298 – 12b 11.5 5 Density/Weight/Volume Density/Weight/Volume Intraconver MPMS Chapter 11. sion Standards:4 2.3 Energy Institute Standards: IP 389 Deter Determina mination tion of wax app appeara earance nce temp temperat erature ure (WA (W AT) of middle distillate fuels by dif different ferential ial therma thermall analysis (DTA) or differential scanning calorimetry (DSC) IP Stand Standard ard Methods Book, Book, Appen Appendix dix A, Specifications Specifications – IP Standard Thermometers Standards:5 2.4 ISO Standards: ISO 649-1 Laboratory glassware – Density hydrometers for general purpose – Part 1: Specification 2.5 ASTM Adjuncts: Adjunct to D1250 to D1250 Guide Guide for Petroleum Measurement Tables (API MPMS Chapter Chapter 11.1)6
only hyd only hydrom rometer eter rea readin dings gs and not den density sity,, rel relativ ativee den densit sity y (specific gravity), or API gravity at that other temperature. pour point , n—lo 3.1.6 pour —lowes westt tem temper peratu ature re at whi which ch a tes testt portion portio n of crude petro petroleum leum or petro petroleum leum product will contin continue ue to flow when it is cooled under specified conditions. 3.1.7 relative density (specific gravity), n—the ratio of the mass of a given volume of liquid at a specific temperature to the mass of an equal volume of pure water at the same or differen dif ferentt temper temperature. ature. Both refer reference ence temper temperatures atures shall be explicitly explic itly stated. 3.1.7.1 Discussion—Co —Commo mmon n ref refere erence nce temp tempera eratur tures es include 60/60°F, 60/60°F, 20/20 20/20°C, °C, 20/4° 20/4°C. C. The histor historic ic depre deprecated cated term specific gravity may still be found. 3.1.8 wax appearance temperature (WAT), n—temperature at wh whic ich h wa waxy xy so soli lids ds fo form rm wh when en a cr crud udee pe petr trol oleu eum m or petroleum product is cooled under specified conditions.
3. Terminology 3.1 Definitions of Terms Specific to This Standard: 3.1.1 API gravity, n —a special function of relative density (specific gravity) 60/60°F, represented by: °API 5 [141.5 / ~relative density 60/60 °F!# 2 131.5
4. Summa Summary ry of Test Method 4.1 The sample is brought brought to a specifi specified ed temperature temperature and a test portion is transferred to a hydrometer cylinder that has been bee n bro brough ughtt to app approx roximat imately ely the sam samee temp tempera eratur ture. e. The approp app ropria riate te hyd hydrom rometer eter and the thermo rmomete meter, r, als also o at a sim similar ilar temperature, are lowered into the test portion and allowed to settle. sett le. Aft After er temp tempera eratur turee equ equilib ilibriu rium m has bee been n rea reache ched, d, the hydr hy drom omete eterr sc scale ale is re read ad,, an and d th thee tem tempe pera ratu ture re of th thee te test st portion is taken. The observed hydrometer reading is corrected for the men meniscu iscuss ef effec fect, t, the the therma rmall glas glasss exp expans ansion ion ef effec fect, t, alternate calibration temperature effects and then reduced to the refere ref erence nce temp temperat erature ure by mea means ns of the vol volume ume cor correc rectio tion n factors or tables as applicable by use of the appropriate Adjunct to D1250 Guide Guide for Petr Petrole oleum um Mea Measur suremen ementt Table abless (AP (APII MPMS Chapte Chapterr 11 11.1) .1) and obs observ erved ed tem temper peratu ature re fro from m the thermometer. 4.2 If necessary, necessary, the hydrometer hydrometer cylinder and its conten contents ts are placed in a constant temperature bath to avoid excessive temperature variation during the test.
(1)
3.1.1.1 Discussion—No statement of refer reference ence temperature is required, as 60°F is included in the definition. 3.1.2 cloud point , n—temperature at which a cloud of wax crystals first appears in a liquid when it is cooled under specific conditions. 3.1.3 density, n —the mass of liquid per unit volume at 15°C and 101.325 kPa with the standard unit of measurement being kilograms per cubic metre. 3.1.3.1 Discussion—Other reference temperatures, such as 20°C, may be used for some products or in some locations. Less pre prefer ferred red uni units ts of mea measur suremen ementt (fo (forr exa exampl mple, e, kg/ kg/L L or g/mL) are still in use. 3.1.4 hydrometer reading, n—the point on the hydrometer scale at which the surface of the liquid cuts the scale. 3.1.4.1 Discussion—In pra practic cticee for tra transp nsparen arentt flui fluids ds thi thiss can be readily determined by aligning the surface of the liquid on both sides of the hydrometer and reading the Hydrometer scale where these surface readings cut the scale (Hydrometer Reading – Observed). For nontransparent fluids the point at which the liquid surface cuts the Hydrometer scale cannot be determined directly and requires a correction (Meniscus Correction). The value represented by the point (Meniscus Reading) at which the liquid sample rises above the main surface of the liquid subtracted from the value represented by where the main surface of the liquid cuts the Hydrometer scale is the amount of the correction or Meniscus correction. This meniscus cor correct rection ion is doc docume umente nted d and then subtracte subtracted d fro from m the valu va luee re repr pres esen ented ted by th thee Me Meni nisc scus us Rea Readi ding ng to yi yield eld th thee Hydrometer Hydro meter Readin Reading g corre corrected cted for the Menisc Meniscus us (Hydr (Hydrometer ometer Reading – Observed, Meniscus Corrected). 3.1.5 observed values, n—values observed at temperatures other than the specified reference temperature. These values are 4
5. Signi Significanc ficancee and Use 5.1 Accur Accurate ate determination determination of the density, density, relativ relativee densit density y (specific gravity), or API gravity of petroleum and its products is ne nece cess ssar ary y fo forr th thee co conv nver ersio sion n of me measu asure red d vo volu lume mess to volumes volum es or masses, or both, at the standa standard rd reference temperatures of 15°C or 60°F during custody transfer. 5.2 This pro proced cedure ure is mos mostt sui suitabl tablee for determini determining ng the density, relative density (specific gravity), or API gravity of low viscosity transparent liquids. This procedure can also be used use d for viscous viscous liqu liquids ids by allo allowin wing g suf suffficie icient nt time for the hydrometer to reach temperature equilibrium, and for opaque liquids by employing a suitable meniscus correction. Additionally for both transparent and opaque fluids the readings shall be corrected for the thermal glass expansion effect and alternate calibration temperature effects before correcting to the reference temperature. 5.3 When used in connection connection with bulk oil measu measurements rements,, volume vol ume cor correct rection ion err errors ors are min minimi imized zed by obs observ erving ing the hydrometer reading at a temperature close to that of the bulk oil temperature.
Available from Energy Institute, 61 New Cavendish St., London, W1M 8AR,
UK. 5
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036. 6 Availa vailable ble from ASTM Inter Internatio national nal Head Headquart quarters. ers. Orde Orderr Adju Adjunct nct No. ADJD1250.. Original adjunct produced in 1983. ADJD1250
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D1298 – 12b TABLE TAB LE 2 Recommended Thermometers
5.4 Density Density,, rel relativ ativee den density sity,, or API gra gravit vity y is a fac factor tor governing the quality and pricing of crude petroleum. However, this property of petroleum is an uncertain indication of its quality unless correlated with other properties. 5.5 Density is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and combustion.
6.1 Hydrometers, of gla glass, ss, gra gradua duated ted in uni units ts of den density sity,, relativ rela tivee den density sity,, or API gra gravity vity as req requir uired, ed, con confor formin ming g to Specification E100 or or ISO ISO 649-1, 649-1, and the requirements given in Table in Table 1. 1. 6.1.1 The user should ascertain ascertain that the instruments instruments used for this procedure conform to the requirements set out above with respec res pectt to mate materia rials, ls, dim dimens ension ions, s, and sca scale le err errors ors.. In cas cases es where the instrument is provided with a calibration certificate issued by a recognized standardizing body, the instrument is classed clas sed as cer certifie tified d and the app approp ropria riate te cor correc rection tionss for the meniscus effect, the thermal glass expansion effect, and alternative calibration temperature effects shall be applied to the observed readings prior to corrections. Instruments that satisfy the requirements of this test method, but are not provided with a recognized calibration certificate, are classed as uncertified. 6.2 Thermometers, having range, graduation intervals and maximum permitted scale error shown in Table in Table 2 and 2 and conforming to Specification E Specification E1 1 or IP Appendix A. 6.2.1 Altern Alternate ate measuring devices devices or system systemss may be used, provided that the total uncertainty of the calibrated system is no greater than that specified in 6.2 6.2.. The stated repeatability and reproducibility values are not applicable if alternate fluids are used in the liquid-in-glass thermometers. 6.3 Hydrometer Cylinder , clear glass, or plastic (see 6.3.1 (see 6.3.1). ). The inside diameter of the cylinder shall be at least 25 mm greater than the outside diameter of the hydrometer and the height shall be such that the appropriate hydrometer floats in the sample test portion with at least 25 mm clearance between the bottom of the hydrometer and the bottom of the cylinder. 6.3.1 Hydro Hydrometer meter cylinders cylinders constr constructed ucted of plastic materials materials shall be resistant to discoloration or attack by oil samples and shall not affect the material being tested. They shall not become opaque under prolonged exposure to sunlight. 6.4 Constant-Temperature Bath, if required, of dimensions such that it can accommodate the hydrometer cylinder with the testt po tes port rtio ion n fu fully lly im immer mersed sed be belo low w th thee tes testt po porti rtion on liq liqui uid d surface, and a temperature control system capable of maintain-
Total Density, kg/m3 at 15 15°C °C
Relative Relati ve densit density, y, 60/60° 60/60°F F
Relative Relati ve dens density ity,, 60/ 60/60° 60°F F API Gravity A
ScaleA
0.2 0.5 1.0 0.0002 0.0005 0.001 0.0005 0.0 005 0 .1
Scale Error
°C °C °F
−1 - +38 −20 - +102 −5 - +215
0 .1 0. 2 0 .5
6 0.1 6 0.15 6 0.25
7.1 Unless Unless oth otherw erwise ise spe specifie cified, d, sam sample pless of non non-vo -volati latile le petr pe trol oleu eum m an and d pe petr trol oleu eum m pr prod oduc ucts ts sh shal alll be tak taken en by th thee MPMS procedures described in Practice D4057 D4057 (API (API Chapter 8.1) and D4177 D4177 (API (API MPMS Chapter 8.2). 7.2 Sample Sampless of volati volatile le crude petroleum petroleum or petroleum prodproductss are pre uct prefer ferabl ably y tak taken en by Pra Practic cticee D4177 (API MPMS Chapter 8.2), using a variable volume (floating piston) sample receiver to minimize any loss of light components which may affect the accuracy of the density measurement. In the absence of this facility, extreme care shall be taken to minimize these loss lo sses es,, in inclu cludi ding ng th thee tr tran ansf sfer er of th thee sa samp mple le to a ch chill illed ed container contai ner immedia immediately tely after sampli sampling. ng. Sample Mixin Mixing g—M 7.3 Sample —May ay be ne nece cess ssar ary y to ob obtai tain n a te test st portio por tion n rep repres resent entativ ativee of the bulk samp sample le to be test tested, ed, but precau pre caution tionss sha shall ll be tak taken en to mai maintai ntain n the integrity integrity of the sample during this operation. Mixing of volatile crude petroleum or petroleum products containing water or sediments, or both bo th,, or th thee he heat atin ing g of wa waxy xy vo volat latile ile cr crud udee pe petr trol oleu eum m or petroleum petro leum products may result in the loss of light components. components. The fol follow lowing ing sub subsec section tionss (7.3.1 to 7.3.4) 7.3.4) wi will ll gi give ve so some me guidance on sample integrity maintenance. 7.3.1 Volatile Crud Crudee Petr Petroleum oleum and Petr Petroleum oleum Pro Products ducts Having an RVP Greater than 50 kPa—Mix the sample in its original closed container in order to minimize the loss of light components. NOTE 1—Mixing volatile samples in open containers will lead to loss of light com light compon ponent entss and con conseq sequen uently tly af affec fectt the val value ue of the den densit sity y obtained.
7.3.2 Waxy —Iff th thee pe petr trol oleu eum m ha hass an Waxy Crud Crudee Petr Petroleum oleum—I expecte exp ected d pou pourr poi point nt abo above ve 10° 10°C, C, or a clo cloud ud poi point nt or WAT WAT above 15°C, warm the sample to a temperature that is sufficient for ensuring the material is fluid enough to provide adequate mixing mix ing with without out exc excess essive ively ly hea heating ting the mate materia riall tha thatt wou would ld otherw oth erwise ise com compro promis misee the int integr egrity ity of the samp sample. le. Sam Sample pless heated to 9°C above its pour point, or 3°C above its cloud point or WAT have been found to be suitable temperatures to warm samples prior to mixing. Whenever possible, mix the sample in its original closed container in order to minimize the loss of light components. 7.3.3 Waxy Distillate—Warm the sample to a temperature that is sufficient for ensuring the material is fluid enough to provid pro videe ade adequa quate te mix mixing ing with without out exc excessi essivel vely y hea heating ting the material that would otherwise compromise the integrity of the sample. Samples heated to 3°C above its cloud point or WAT have been found to be suitable temperatures to warm samples prior to mixing.
Meniscus
Each IntervalA ErrorA Correction Unit
600 60 0 - 110 100 0 20 600 - 1100 50 600 - 1100 50 0.600 - 1.100 0.020 0.600 - 1.100 0.050 0.600 - 1.100 0.050 0.650 0.6 50 - 1.1 1.100 00 0.0 0.050 50 −1 - +101 12
Graduation Interval
7. Sampl Sampling ing
TABLE TABL E 1 Recommended Hydrometers Range
Range
ing the bath temperature within 0.25°C of the test temperature throughout the duration of the test. 6.5 Stirring Rod , optional, of glass or plastic, approximately 400 mm in length.
6. Appar Apparatus atus
Units
Sc a l e
6 0.2 +0.3 6 0.3 +0.7 6 0.6 +1.4 6 0.0002 +0.0003 6 0.0003 +0.0007 6 0.0006 +0.0014 60.0005 +0.00 +0.0007 07 6 0. 1 -0.1
Interval and Error relate to Scale.
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D1298 – 12b 7.3.4 Resid —Hea eatt th thee sa samp mple le to th thee te test st Residual ual Fue Fuell Oil Oilss—H temperature prior to mixing (see 9.1.1 and and Note Note 4). 4). 7.4 Addit Additional ional information information on the mixing and handl handling ing of liquid samples will be found in Practice D5854 (API MPMS Chapter 8.3).
the temperature of the surrounding medium does not change more mo re th than an 2° 2°C C du durin ring g th thee ti time me tak taken en to co comp mplet letee th thee tes test. t. When the temperature of the test portion differs by more than 2°C from ambient, use a consta constant nt temperature temperature bath to maintain an even temperature throughout the test duration. 9.2.6 9.2 .6 Ins Insert ert the app approp ropria riate te the thermo rmomete meterr or tem temper peratu ature re measurement device and stir the test portion with a stirring rod, using usi ng a com combin binatio ation n of ver vertica ticall and rot rotatio ational nal mot motion ionss to ensuree unifo ensur uniform rm temper temperature ature and densit density y throu throughou ghoutt the hydrometer cylinder. Record the temperature of the sample to the nearest 0.1°C and remove the thermometer/temperature measuring device and stirring rod from the hydrometer cylinder.
8. Apparatus Verification Verification or Certification Certification 8.1 Hydro Hydromet meters ers and the thermo rmomete meters rs sha shall ll be ver verified ified in accordance with the procedures in Annex in Annex A1. A1 . 9. Pro Procedu cedure re 9.1 Temperature of Test : 9.1.1 Bring the sample sample to the test temperature temperature which shall shall be such that the sample is sufficiently fluid but not so high as to cause the loss of light components, nor so low as to result in the appearance of waxy solids in the test portion.
NOTE 6—If a liquid liquid-in-g -in-glass lass thermometer thermometer is used, this is comm commonly only used as the stirring rod.
9.2.7 Lower the appropriate appropriate hydrometer hydrometer into the liquid and release when in a position of equilibrium, taking care to avoid wetting the stem above the level at which it floats freely. For low vis viscos cosity ity tran transpa sparen rentt or tra transl nsluce ucent nt liq liquid uidss obs observ ervee the menisc men iscus us sha shape pe whe when n the hyd hydrom rometer eter is pre presse ssed d bel below ow the point of equilibrium about 1 to 2 mm and allowed to return to equilib equ ilibriu rium. m. If the men meniscu iscuss cha change nges, s, clea clean n the hyd hydrom rometer eter stem and repeat until the meniscus shape remains constant. 9.2.8 For opaque viscous viscous liquids, allow the hydrometer hydrometer to settle slowly into the liquid. 9.2.9 9.2 .9 For low vis viscos cosity ity tran transpa sparen rentt or tran translu slucen centt liq liquid uidss depres dep resss the hyd hydrom rometer eter abo about ut two sca scale le div divisio isions ns int into o the liqui liq uid, d, an and d th then en re rele lease ase it, imp impar artin ting g a sli sligh ghtt sp spin in to th thee hydrometer on release to assist in bringing it to rest floating freely from the walls of the hydrometer cylinder. Ensure that the remainder remainder of the hydromet hydrometer er stem stem,, whi which ch is abo above ve the liquid level, is not wetted as liquid on the stem affects the reading obtained. 9.2.10 9.2.1 0 Allow suff sufficient time for the hydrometer hydrometer to come to rest, and for all air bubb bubbles les to come to the surface. surface. Remove any air bubbles before taking a reading (see 9.2.12 9.2.12). ). 9.2.11 9.2.1 1 If the hydrometer hydrometer cylinder is made of plastic, dissipatee any static pat static cha charg rges es by wiping wiping the outside outside with a dam damp p cloth. ( Static charges often build up on plastic cylinders and may prevent the hydrometer from floating freely.) 9.2.12 9.2.1 2 When the hydrometer hydrometer has come to rest floating floating freely away from the walls of the cylinder, read the hydrometer scale readin rea ding g to the nearest nearest one one-fif -fifth th or one one-te -tenth nth of a ful fulll sca scale le division depending upon the number of subdivisions (that is, 5 or 10, respectively) that exist between a full scale division in accordance with 9.2.12.1 with 9.2.12.1 or or 9.2.12.2 9.2.12.2.. 9.2.12 9.2 .12.1 .1 For tran transpa sparen rentt liq liquid uids, s, rec record ord the hyd hydrom rometer eter read re adin ing g as th thee po poin intt on th thee hy hydr drom omet eter er sc scale ale at wh whic ich h th thee principal surface of the liquid cuts the scale by placing the eye slightly below the level of the liquid and slowly raising it until the surface, first seen as a distorted ellipse, appears to become a straight line cutting the hydrometer scale (see Fig. (see Fig. 1) 1). 9.2.12.2 9.2.1 2.2 For opaque liquids record the hydr hydrometer ometer reading at the point on the hydrometer scale to which the sample rises above abo ve its main surface, surface, by obs observ erving ing with the eye sli slight ghtly ly above the plane of the surface of the liquid (see Fig. 2). 2). This reading readin g requi requires res a meniscu meniscuss corre correction. ction. This correction can be determined by one of two methods: 1) observe the height above the main surface of the liquid to which the sample rises on the
NOTE 2—The density, relative density or API gravity determined by by the hydrometer is most accurate at or near the reference temperature. NOTE 3—The volume and densi density ty,, the relative density, density, and the API correc cor rectio tions ns in the vol volume ume cor correc rectio tion n tab tables les are bas based ed on the ave averag ragee expansions of a number of typical materials. Since the same coefficients were used in compiling each set of tables, corrections made over the same temperature temper ature interv interval al minim minimize ize errors arising from possible dif differenc ferences es between betw een the coe coefffici icient ent of the mat materi erial al und under er tes testt and the sta standa ndard rd coefficients. This effect becomes more important as temperatures diverge from the reference temperature. NOTE 4—The hydrometer reading is obtained at a temperature appropriate to the physico-chemical characteristics of the material under test. This temperature is preferably close to the reference temperature, or when the value is used in conjunction with bulk oil measurements, within 3°C of the bulk temperature (see 5.3 (see 5.3)).
9.1.2 For crude petroleu 9.1.2 petroleum, m, bri bring ng the sample close to the reference temperature or, if wax is present, to 9°C above its expected pour point or 3°C above its expected cloud point or WAT, whichever is higher. NOTE 5—For crude petroleum an indication of the WAT can be found using IP 389, using IP 389, with the modification of using 50 µL 6 5 µL of sample. The precision of WAT for crude petroleum using this technique has not been determined.
9.2 Density Measurement : 9.2.1 9.2 .1 Brin Bring g the hyd hydrom rometer eter cyl cylind inder er and ther thermom mometer eter to within approximately 5°C of the test temperature. 9.2.2 9. 2.2 Tran Transfe sferr th thee sa sampl mplee to th thee cle clean, an, tem tempe perat ratur ureestabilized hydrometer cylinder without splashing, to avoid the formati for mation on of air bub bubble bles, s, and min minimiz imizee eva evapor poratio ation n of the lower low er bo boili iling ng con consti stitue tuents nts of mor moree vo volat latile ile sam sample ples. s. (Warning— Extrem remely ely flammab flam mable. le. V apors apo rs may cause cau se flash flas h Warning—Ext fire!) 9.2.3 Transfer highly volatile samples by siphoning or water displacement. (Warning— (Warning—Do Do not siphon by mouth as it could result in ingestion of sample!) 9.2.3.1 9.2.3 .1 Samples containing containing alcoho alcoholl or other water-soluble water-soluble materials should be placed into the cylinder by siphoning. 9.2. 9. 2.4 4 Remove Remove an any y air bu bubb bbles les fo form rmed ed af after ter th they ey ha have ve collected on the surface of the test portion, by touching them with a piece of clean filter paper or other suitable means before inserting the hydrometer. 9.2.5 9.2 .5 Place the cylinder cylinder con contain taining ing the tes testt por portion tion in a vertical position in a location free from air currents and where 4
D1298 – 12b
FIG. 2 Hydro Hydrometer meter Scale Readin Reading g for Opaqu Opaque e Fluid Fluids s
FIG. 1 Hydro Hydrometer meter Scale Readin Reading g for Transparent Transparent Liquids
hydrometer scale when the hydrometer in question is immersed in a transparent liquid having a surface tension similar to that of a sample under test; 2) uses the nominal values shown in Table 1. 1. Document this value as the Meniscus correction.
10.2 Record the observed observed hydrometer hydrometer scale readings to the 3 nearestt 0.1 kg/m in den neares density sity,, 0.0 0.0001 001 g/m g/mL, L, kg/ kg/L L or rel relativ ativee density, or 0.1° API for transparent liquids. 10.2.1 10. 2.1 For opa opaque que sam samples ples,, app apply ly the rel releva evant nt men menisc iscus us correction corre ction given in Table Table 1 or determin determinee it as ind indicat icated ed in 9.2.12.2 to the obs observ erved ed hyd hydrom rometer eter rea readin ding g (9.2.12.2 9.2.12.2)) as hydrometers are calibrated to be read at the principal surface of the liquid. 10.3 Apply any hydrometer hydrometer correction correction identified in a calibration bra tion certificat certificatee to the obs observ erved ed rea readin ding g and record the corrected hydrometer scale reading to the nearest 0.1 kg/m 3 in density, 0.0001 g/mL, kg/L or relative density, or 0.1 °API. 10.4 Appli Application cation of the glass thermal expansion expansion correction correction depend dep endss upo upon n wha whatt ver versio sion n of Adjunct Adjunct to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter Chapter 11.1) will be used to calculate the base density. (a) The 1980 version of the Adjunct to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter Chapter 11.1) has the hydrometer glass thermal expansion correction included. Inputt into the VCF software requires the Hydr Inpu Hydrometer ometer Reading – Obs Observ erved ed or Hyd Hydrom rometer eter Read Reading ing – Obs Observ erved, ed, Men Menisc iscus us 3 Corrected Corre cted in API, R.D., or kg/m units from 9.2.12.2 from 9.2.12.2,, observed temperature of the sample, and the built-in hydrometer glass thermal correction switch set to on (0) or off (1). It will return API or R.D. @ 60°F or kg/m 3@ 15°C.
NOTE 7—W 7—When hen tes testin ting g opa opaque que liq liquid uidss usi using ng a met metal al hyd hydrom rometer eter cylinder, accurate readings of the hydrometer scale can only be ensured if the liquid surface is within 5 mm of the top of the cylinder.
9.2.13 Imm 9.2.13 Immedi ediatel ately y afte afterr rec record ording ing the hyd hydrom rometer eter scal scalee reading, carefully lift the hydrometer out of the liquid, insert the thermometer or temperature measurement device and stir the tes testt por portio tion n ver vertica tically lly with the stir stirrin ring g rod rod.. Reco Record rd the tempera temp eratur turee of the test portion portion to the nearest nearest 0.1 0.1°C. °C. If thi thiss temperature differs from the previous reading ( 9.2.6 9.2.6)) by more than 0.05°C, repeat the hydrometer observations and thermometer observations until the temperature becomes stable within 0.05°C. If a stable temperature cannot be obtained, place the hydrometer cylinder in a constant temperature bath and repeat the procedure from 9.1 9.1.. 9.2.14 9.2.1 4 If the test temperature temperature is highe higherr than 38°C, allow all hydrometers of the lead shot-in-wax type to drain and cool in a vertical position. 10. Calc Calculati ulation on 10.1 App 10.1 Apply ly any rel releva evant nt the thermo rmomete meterr cor correc rectio tions ns to the temperature reading observed in 9.2.6 and 9.2.13 and record the average of those two temperatures to the nearest 0.1 °C. 5
D1298 – 12b (b) The 2004 version of the Adjunct to D1250 Guide for Petroleum Petrole um Measu Measurement rement Tables (API MPMS Chapter 11 11.1) .1) doess not inc doe includ ludee the hyd hydrom romete eterr glas glasss the therma rmall exp expans ansion ion correction, so that correction must be made before entering the software. Depending on the specific end use of the calculation results, the final value may be left rounded or unrounded. The following steps are required to implement 10.4 10.4b: b: Step 1. Convert the corrected hydrometer scale reading to density in kg/m3 if necessary, using either Eq 2 or Eq 3. Scale Units API gravity
Measurement Tables (API MPMS Chapter 11.1–2004), which will return a calculated density in kg/m3 units at the selected base temperature. NOTE 10—Pressure will have to be atmospheric gauge, 0 psig, 101.325 kPa or 0 bar as the Adjunct to D1250 D1250 Guide Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1) values are only valid at atmospheric pressure.
c. Fu Futu ture re ve vers rsio ions ns of th thee Ad Adju junc nctt to D1250 Guide Guide for Petroleum Measur Petroleum Measurement ement Tables (API MPMS Chapter 11 11.1) .1) code will be corrected so that it can accept any combination of input units and return any combination of output units. When available, availab le, the Adjun Adjunct ct to D1250 to D1250 Guide Guide for Petroleum Measurement Tables (API MPMS Chapter Chapter 11.1) code can be accessed directly from Step 3 and return API @ 60 °F, R.D. @ 60 °F, °F, and kg/m3 at any selected base temperature.
Conversion
Density ~kg / m3! 5 ~141.5 * 999.016 ! / ~131.5 1 ° API ! Scale Units Relative density
(2)
Conversion
Density ~kg / m3! 5 R. D D. * 999.016
(3)
Leave the result unrounded. Step 2. Calculate the hydrometer thermal glass expansion correc cor rectio tion n fac factor tor usi using ng the app approp ropria riate te equ equatio ation n bel below ow (t is observed temperature). Correction for a Base Temperature (Tb) of 60°F: HYC 5 1.0 – [0.00001278 ~t – – 60!# – [0.0000000062 ~t – – 60!2#
(4)
Correction for a Base Temperature (Tb) of 15°C: HYC 5 1.0 – [0.000023 ~t – – 15!# – [0.00000002 ~t – – 15!2#
(5)
Correction for a Base Temperature (Tb) of 20°C: HYC 5 1.0 – [0.000023 ~t – – 20!# – [0.00000002 ~t – – 20!2#
(6)
Leave the result un-rounded. Step 3. Multiply the density in kg/m3 from Step 1 by the proper HYC from Step 2 to obtain the glass thermal expansion corrected hydrometer density reading. kg / m3 HYC 5 kg / m3 * HYC
S am p l e : Observed Temperature: Observ Obs erved ed Hyd Hydrom romete eterr Rea Readin ding: g: Observed Pressure: Base Temperature: S te p 1 : S te p 2 : S te p 3 : S te p 5 .1 : S te p 5 .2
Example 2: Example Crude Oil 2 5 . 0 °C 858.29 858 .29 kg/ kg/m m3 0 b ar 15°C 8 5 8 .2 9 0 0 0 0 0 0 0 ... 0 .9 9 9 7 6 8 0 0 0 . .. 8 5 8 .0 9 0 8 7 6 7 2 0 ... 8 6 5 . 2 0 7 4 7 0 0 8 2 . .. 865.21 kg/m3
Example Exampl e 3: S am p l e : Crude Oil Observed Temperature: 7 7 . 0 °F Observed Hydrometer Reading (R.D.):0.859138 Observed Pressure 0 ps i g Base Temp: 6 0 °F S te p 1 : 8 5 8 .2 9 2 6 0 8 2 0 8 ... S te p 2 : 0 .9 9 9 7 8 0 9 4 8 . .. S te p 3 : 8 5 8 .1 0 4 5 9 7 6 6 7 ... S te p 4 a : 0 .8 5 8 9 4 9 8 0 4 . .. S te p 4 b 0 . 8 6 5 6 7 8 4 5 1 . .. S te p 4 c 0 . 8 6 5 7 .. .
Convertt the densit densities ies calculated calculated in Ste Step p 3 tha thatt Step 4a. Conver Step star st arte ted d as AP APII Gr Grav avit ity y or Re Rela lati tive ve De Dens nsit ity y (R (RD) D) to RD (Relative Density). NOTE 8—The current current C source code compiled dll and Excel Add-i Add-in n has 3 an omission and cannot use a kg/m call with degree F. (8)
Step 4b. Input 4b. Input R.D. and degree F into section 11.1.6.2 of the Adjunctt to D1250–04 Adjunc D1250–04 Gui Guide de for Pet Petrol roleum eum Mea Measur sureme ement nt Tables (API MPMS Chapter Chapter 11.1–2004), which returns R.D. @ 60 °F.
2, Eq 3 4, E q 5 , E q 6 7 8 9 unrounded 9 rounded
no conversion necessary Eq 4 Eq 7 unrounded rounded
Eq 2, E q 3 E q 4, E q 5 , E q 6 Eq 7 Eq 8 unrounded rounded
10.5 If the hydrometer hydrometer has been calibrated calibrated at a temper temperature ature other than the reference temperature, use the equation below to correct the hydrometer scale reading: ρr
NOTE 9—Pressure will have to be atmospheric gauge, or 0 psig as the Adjunct Adjun ct to to D1250 D1250 Guide Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1) values are only valid at atmospheric pressure.
5
ρt –6
1 – [23 3 10
~t – r! – 2 3 10–8 ~t – r!2#
(10)
where: ρr = hydr hydrometer ometer reading reading at at the reference reference temperatur temperature, e, r °C, and hydrom romete eterr rea readin ding g on the hyd hydrom rometer eter scale whose whose ρt = hyd reference temperature is t °C.
Step 4c. Convert the calculated R.D. value @ 60°F to a calculated API Gravity @ 60 °F using Eq 9, if the original input was in API units. API Gravity 5 ~141.5 / R.D.! – 131.5
Example 1: Example Crude Oil 7 7 °F 33.2 33. 2 API Gra Gravit vity y 60°F 8 5 8 .2 9 2 4 3 4 7 2 9 8 . ..E q 0 .9 9 9 7 8 0 9 4 8 . .. Eq 8 5 8 .1 0 4 4 2 4 2 2 7 E q 0 .8 5 8 9 4 9 6 3 1 . .. Eq 0 .8 6 5 6 7 8 2 7 9 . .. 3 1 . 9 5 5 6 4 3 3 1 2 ... E q 3 2 . 0 °A P I Eq
(7)
If the temperature was in degrees Celsius, skip to Step 5.
R. D D. 5 kg / m3 HYC /999.016
S am p l e : Observed Temperature: Observ Obs erved ed Hyd Hydrom romete eterr Rea Readin ding: g: Base Temperature: S te p 1 : S te p 2 : S te p 3 : S te p 4 a : S te p 4 b : S te p 4 c 1 : S te p 4 c 2 :
(9)
11. Repo Report rt
calculated in Step 3 in kg/m3 HYC, Step 5. Input 5. Input the density calculated degr de gree ee C, ba base se te temp mper erat atur uree (1 (15° 5°C C or 20 20°C °C)) in into to Se Secti ction on 11.1. 11 .1.7.2 7.2 of the Adjunct Adjunct to D1250–04 D1250–04 Gui Guide de for Petr Petrole oleum um
11.1 Report the final value as density, density, in kilograms per cubic metre, at the reference temperature, to the nearest 0.1 kg/m3. 6
D1298 – 12b TABLE 3 Precisi Precision on Values
11.2 Report the final value as densit 11.2 density y, in kilogr kilograms ams per litre or gra grams ms per millilitre millilitre at the reference reference temperatur temperature, e, to the nearest 0.0001. 11. 1.3 3 Rep Repor ortt th thee fin final al va valu luee as re rela lativ tivee de dens nsity ity,, wi with th no dimensions, at the two reference temperatures, to the nearest 0.0001. 11.4 11 .4 Report the final final value as API gravity gravity to the nearest 0.1° 0.1° API. 11.5 11 .5 The reporting reporting values have no precis precision ion or bias deter deter-mination. It is up to the user to determine whether this test method provides results of sufficient accuracy for the intended purpose. 11.6 Certified hydrometers from a recognized standardizing body, such as NIST, report the output density as ‘Density in Vacuo.’
Product: Transparent Low-viscosity Liquids Parameter Density Rela Re lati tive ve De Dens nsit ity y API Gravity
Temperature Range, °C (°F) – 2 t o 2 4 .5 (29 to 76) –2 to 24 24.5 .5 (29 to 76) (42 to 78)
Repeatability
Reproducibility
kg/m3 kg/L or g/mL NONE
0.5 0.0005 0 .0 0 0 5
1.2 0.0012 0 .0 0 1 2
°A P I
0 .1
0 .3
Repeatability
Reproducibility
kg/m3 kg/L or g/mL NONE
0.6 0.0006 0 .0 0 0 6
1.5 0.0015 0 .0 0 1 5
°A P I
0 .2
0 .5
Units
Product: Opaque Liquids Parameter Density Rela Re lati tive ve De Dens nsit ity y
12. Pre Precisi cision on and Bias
API Gravity
12.1 Precision—The precision of the test method as determined by statisti statistical cal examination of interla interlaborat boratory ory results is as follows: 12.1.1 Repeatability—The difference between two test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test method, exceed the values in Table in Table 3 only 3 only in 1 case in 20. 12.1.2 Reproducibility—The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in 1 case in 20. 12.1.3 The repeatability and reproducibility values provided in Table 3 are not based on any interlaboratory round robin results res ults.. The They y sho should uld be con consid sidere ered d his histor torical ical num number bers, s, the
Temperature Range, °C (°F) – 2 t o 2 4 .5 (29 to 76) –2 to 24 24.5 .5 (29 to 76) (42 to 78)
Units
source of which can not be verified by either source either ASTM or API and have been in this document prior to the current slate of blended crude oils, RFG gasoline’s and reformulated distillates. These values do not apply to the current calculation procedures and it is up to the user to determine whether this test method provides results of sufficient accuracy for the intended purpose. 12.2 Bias—Bias for this test method has not been determine mi ned. d. Ho Howe weve verr, th ther eree sh shou ould ld be no bi bias as fr from om ab abso solu lute te measur mea sureme ements nts,, if the cali calibra bratio tion n of the hyd hydrom rometer eter and the thermometer thermo meter is traceab traceable le to Inter Internation national al Standa Standards, rds, such as supplied by the National Institute of Standards and Technology. 13. Keyw Keywords ords 13.1 13. 1 API gra gravit vity; y; cru crude de pet petrol roleum eum;; den density sity;; hyd hydrom rometer eter;; Petroleum Measurement Tables; petroleum products; relative density; densit y; specifi specificc gravi gravity ty
ANNEX (Mandatory Information) A1. APPARA APPARATUS TUS
A1.1 Apparatus Verification Verification and Certification Certification
A1.1.2 Thermometers, shall be verified at intervals of no moree than six mon mor months ths for con confor forman mance ce wit with h spe specifi cificati cations ons.. Either comparison with a referenced temperature measurement system traceable to an international standard, or a determination of ice point, is suitable.
A1.1.1 Hydrometers, sha shall ll eith either er be cer certifie tified d or ver verified ified.. Veri erifica fication tion shall be eith either er by com compar pariso ison n with a cer certifie tified d hydrometer (see 6.1.1) 6.1.1) or by the use of a certified reference material (CRM) specific to the reference temperature used. A1.1.1 A1. 1.1.1 .1 The hyd hydrom rometer eter scal scalee sha shall ll be cor correc rectly tly loc located ated within the hydrometer stem by reference to the datum mark. If the scale has moved, reject the hydrometer.
7
D1298 – 12b SUMMARY OF CHANGES Subcommittee D02.02 has identified the location of selected changes to this standard since the last issue (D1298–12a) that may impact the use of this standard. (Approved June 1, 2012) (1) Add Added ed 3.1.4 3.1.4.. Subcommittee D02.02 has identified the location of selected changes to this standard since the last issue (D1298–12) that may impact the use of this standard. (Approved May 15, 2012) (1) Rev Revised ised 9.2.12.2 9.2.12.2..
(2) Revised Section Section 10 10..
Subcommittee D02.02 has identified the location of selected changes to this standard since the last issue (D1298–99(2005)) that may impact the use of this standard. (Approved April 1, 2012) (1) Add Added ed 10.4 10.4 to to represent the thermal glass correction now required in this standard.
(2) Made clarifications clarifications and corrections corrections in Section Sectionss 9 9,, 11 11,, a and nd 12.. 12
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