ASTM D6822-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D6822 − 12b (Reapproved 2017) D6822 − 23
Manual of Petroleum Measurement Standards (MPMS), Chapter 9.3
Standard Test Method for
Density, Relative Density, and API Gravity of Crude
Petroleum and Liquid Petroleum Products by
Thermohydrometer Method
This standard is issued under the fixed designation D6822; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorially corrected adjunct information in March 2023.
1. Scope Scope*
1.1 This test method covers the determination, using a glass thermohydrometer in conjunction with a series 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 pressures of 101.325 kPa (14.696 psi) or less. Values are determined
at existing temperatures and corrected to 15 °C or 60 °F by means of a series of calculations and international standard tables.
1.2 The initial thermohydrometer readings obtained are uncorrected hydrometer readings and not density measurements. Readings
are measured on a thermohydrometer 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 calculations and Adjunct to D1250 Guide for Use of the Petroleum Measurement Tables (API MPMS
Chapter 11.1).
1.3 Readings determined as density, relative density, or API gravity can be converted to equivalent values in the other units or
alternate reference temperatures by means of Interconversion Procedures (API MPMS Chapter 11.5) or Adjunct to D1250 Guide
for Use of the Petroleum Measurement Tables (API MPMS Chapter 11.1), or both, or tables as applicable.
1.4 The initial thermohydrometer reading shall be recorded before performing any calculations. The calculations required in
Section 9 shall be applied to the initial thermohydrometer reading with observations and results reported as required by Section
11 prior to use in a subsequent calculation procedure (measurement ticket calculation, meter factor calculation, or base prover
volume determination).
1.5 Annex A1 contains a procedure for verifying or certifying the equipment of this test method.
1.6 The values stated in SI units are to be regarded as standard.
1.6.1 Exception—The values given in parentheses are for information only.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and the API Committee on Petroleum
Measurement, and is the direct responsibility of Subcommittee D02.02 /COMQ, the joint ASTM-API Committee on Hydrocarbon Measurement for Custody Transfer (Joint
ASTM-API). This test method has been approved by the sponsoring committees and accepted by the Cooperating Societies in accordance with established procedures.
Current edition approved July 15, 2017Dec. 1, 2023. Published July 2012January 2024. Originally approved in 2002. Last previous edition approved in 20122017 as
ɛ1
D6822 – 12b.D6822 – 12b (2017) . DOI: 10.1520/D6822-12BR17E01.10.1520/D6822-23.
*A Summary of Changes section appears at the end of this standard
© Jointly copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, USA and the American Petroleum Institute (API), 1220 L Street NW, Washington DC 20005, USA
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1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1250 Guide for the Use of the Joint API and ASTM Adjunct for Temperature and Pressure Volume Correction Factors for
Generalized Crude Oils, Refined Products, and Lubricating Oils: API MPMS Chapter 11.1
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
E100 Specification for ASTM Hydrometers
2.2 API Standards:
MPMS Chapter 1 Terms and Definitions Database
MPMS Chapter 8.1 Practice for Manual Sampling of Petroleum and Petroleum Products (ASTM Practice D4057)
MPMS Chapter 8.2 Practice for Automatic Sampling of Petroleum and Petroleum Products (ASTM Practice D4177)
MPMSChapter 8.3 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products (ASTM Practice
D5854)
MPMS Chapter 9.1 Hydrometer Test Method for Density, Relative Density or API Gravity of Crude Petroleum and Liquid
Petroleum Products (ASTM Test Method D1298)
MPMS Chapter 11.1 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and
Lubricating Oils (Adjunct to ASTM D1250)
MPMS Chapter 11.5 Density/Weight/Volume Intraconversion
2.3 ASTM Adjuncts:
Adjunct to D1250 Standard Guide for the Use of the Joint API and ASTM Adjunct for Temperature and Pressure Volume
Correction Factors for Generalized Crude Oils, Refined Products, and Lubricant Oils: API MPMS Chapter 11.1, Addenda 1
and 2
3. Terminology
3.1 Definitions:
3.1.1 For terms and definitions used in this test method, refer to Terminology D4175 and API MPMS Ch 1 Terms and Definitions
Database.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 API gravity (°API), n—a special function of relative density 60/60 °F, represented by:
°API 5 141.5/ relative density 60/60°F 2 131.5 (1)
@ ~ !#
3.2.1.1 Discussion—
No statement of reference temperature is required, as 60 °F is included in the definition.
3.2.2 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 (kg/m ).
3.2.2.1 Discussion—
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Petroleum Institute (API), 1220 L. St., NW, Washington, DC 20005-4070, www.api.org.
Available from ASTM International Headquarters. Order Adjunct No. ADJD1250-A1A2-E-PDF. Original adjunct produced in 1983.
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Other reference temperatures, such as 20 °C, may be used for some products or in some locations. Less preferred units of
measurement, for example, kg/L or g/mL, are still in use.
3.2.3 hydrometer reading, n—the point on the hydrometer scale at which the surface of the liquid cuts the scale.
3.2.3.1 Discussion—
In practice for transparent fluids this 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 correction is documented and then subtracted from the value
represented by the Meniscus Reading to yield the Hydrometer Reading corrected for the Meniscus (Hydrometer Reading –
Observed, Meniscus Corrected).
3.2.4 observed values, n—hydrometer readings observed at a temperature other than the defined reference temperature.
3.2.4.1 Discussion—
These values are only hydrometer readings and not density, relative density, or API gravity at the temperature.
3.2.5 relative density, 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 different temperature. Both reference temperatures shall be explicitly stated.
3.2.5.1 Discussion—
Common reference temperatures include 15/15 °C, 60 ⁄60 °F, 20/20 °C, and 20/4 °C. The historic term specific gravity may still
be found.
3.2.6 thermohydrometer, n—a glass hydrometer with a self-contained thermometer.
4. Summary of Test Method
4.1 The density or API gravity, after temperature equilibrium has been reached, is read by observing the freely floating
thermohydrometer and noting the graduation nearest to the apparent intersection of the horizontal plane surface of the liquid with
the vertical scale of the hydrometer after temperature equilibrium has been reached. The observed thermohydrometer reading is
reduced to the reference temperature value by means of the Petroleum Measurement Tables (the appropriate adjunct to Adjunct
to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1) and observed temperature from the enclosed
thermometer.
5. Significance and Use
5.1 Density and API gravity are used in custody transfer quantity calculations and to satisfy transportation, storage, and regulatory
requirements. Accurate determination of density or API gravity of crude petroleum and liquid petroleum products is necessary for
the conversion of measured volumes to volumes at the standard temperatures of 15 °C or 60 °F.
5.2 Density and API gravity are also factors that indicate the quality of crude petroleum. Crude petroleum prices are frequently
posted against values in kg/m or in degrees API. However, this property of petroleum is an uncertain indication of its quality
unless correlated with other properties.
5.3 Field of Application—Because the thermohydrometer incorporates both the hydrometer and thermometer in one device, it is
more applicable in field operations for determining density or API gravity of crude petroleum and other liquid petroleum products.
The procedure is convenient for gathering main trunk pipelines and other field applications where limited laboratory facilities are
available. The thermohydrometer method may have limitations in some petroleum density determinations. When this is the case,
other methods such as Test Method D1298 (API MPMS Chapter 9.1) may be used.
5.4 This procedure is suitable for determining the density, relative density, or API gravity of low viscosity, transparent or opaque
liquids, or both. This procedure, when used for opaque liquids, requires the use of a meniscus correction (see 9.2). 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. This procedure can also be used for viscous liquids by allowing
sufficient time for the thermohydrometer to reach temperature equilibrium.
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6. Apparatus
6.1 Glass Thermohydrometers, as specified in Specification E100 (shown in Fig. 1), and graduated in:
6.1.1 Kilograms/cubic metre (kg/m ) and degrees Celsius for density hydrometers, as shown in Table 1.
6.1.2 Degrees API (°API) and degrees Fahrenheit for hydrometers measuring in API Gravity, as shown in Table 2.
6.1.3 The user should ascertain that the instruments used for this procedure conform to the requirements set out above with respect
to materials, dimensions, and scale errors. In cases where the instrument is provided with a calibration certificate issued by a
recognized standardizing body, the instrument is classed as certified and the appropriate corrections for the meniscus effect, the
FIG. 1 Typical Thermohydrometer Designs
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TABLE 1 Density Thermohydrometers
ASTM Hydrometer No. Density, Range, kg/m
300H 600 to 650
301H 650 to 700
302H 700 to 750
303H 750 to 800
304H 800 to 850
305H 850 to 900
306H 900 to 950
307H 950 to 1000
308H 1000 to 1050
309H 1050 to 1100
345H 775 to 825
Hydrometer
Total length, mm 374 to 387
Body diameter, mm 18 to 25
Stem diameter, mm, min 4.0
Hydrometer Scale
Standard temperature, °C 15
Subdivisions, kg/m 0.5
Short intermediate lines at, kg/m 1
Long intermediate lines at, kg/m 5
Main (numbered) lines at, kg/m 10
Scale error at any point not to 0.5
exceed, kg/m
Length of nominal scale, mm 125 to 145
Scale extension beyond nominal 2.5
range limits, kg/m
Thermometer Scale
Range, °C
Designation L −20 to +65
Designation M 0 to +85
Designation H +20 to +105
Immersion total
Subdivisions, °C 1.0
Intermediate lines at, °C 5
Main (numbered) lines at, °C 10
Scale error at any point not to 1.0
exceed, °C
Scale length, mm 80 to 100
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 and the appropriate corrections for the meniscus effect, the thermal glass expansion effect, and
alternative calibration temperature effects shall be applied to the observed readings prior to corrections.
6.2 Hydrometer Cylinders, clear glass, plastic, or metal. For convenience of pouring, the cylinder may have a pouring lip. The
inside diameter shall be at least 25 mm (1 in.) greater than the outside diameter of the thermohydrometer used. The height of the
cylinder shall be such that the bottom of the thermohydrometer clears the bottom of the cylinder by at least 25 mm (1 in.) when
suspended in the sample test portion.
6.2.1 For field testing, a sample thief of suitable dimensions may be more convenient than a hydrometer cylinder. The liquid level
shall be level with the top of the thief.
6.3 Temperature Bath, to control temperature close to the bulk hydrocarbon temperature or to control temperature close to the
reference temperature of 15 °C or 60 °F.
7. Sampling, Test Specimens, and Test Units
7.1 Unless otherwise specified, samples of non-volatile petroleum and petroleum products shall be taken by the procedures
described in Practices D4057 (API MPMS Chapter 8.1) and D4177 (API MPMS Chapter 8.2).
7.2 Samples of volatile crude petroleum or petroleum products are preferably taken by Practice 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 losses, including the
transfer of the sample to a chilled container immediately after sampling.
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TABLE 2 API Gravity Thermohydrometers
NOTE 1—For petroleum products and other liquids of similar surface tensions (33 dynes/cm or less).
Thermometer Scale in Body Thermometer Scale in Stem
ASTM Hydrometer Nominal API Gravity ASTM Hydrometer Nominal API Gravity
No. Range, degrees No. Range, degrees
41H-66 15 to 23 71H-62 −1 to +11
42H-66 22 to 30 72H-62 9 to 21
43H-66 29 to 37 73H-62 19 to 31
44H-66 36 to 44 74H-62 29 to 41
45H-66 43 to 51
51H-62 −1 to +11
52H-62 9 to 21
53H-62 19 to 31
54H-62 29 to 41
55H-62 39 to 51
56H-62 49 to 61
57H-62 59 to 71
58H-62 69 to 81
59H-62 79 to 91
60H-62 89 to 101
255H-04 37 to 49
258H-04 64 to 76
Hydrometer
Thermometer Scale Thermometer Scale
in Body in Stem
Total length, mm 374 to 387 374 to 387
Body diameter, mm 18 to 25 23 to 27
Stem diameter, mm, min 4.0 6.0
Total Length, mm (thermometer scale) for 255H and 258H 110 to 140
Hydrometer Scale
Standard temperature, °F 60
Subdivisions, °API 0.1
Intermediate lines at, °API 0.5
Main (numbered) lines at, °API 1.0
Scale error at any point not to exceed, °API 0.1
Length of nominal scale, mm 125 to 145
Thermometer Scale
Thermometer Scale Thermometer Scale
in Body in Stem
A
Range, °F
Designation L 0 to 150
Designation M 30 to 180 30 to 220
Designation H 60 to 220
Designation H (for Aviation Fuels only) 0 to 100
Immersion Total Total
Subdivisions, °F 2 2
Intermediate lines at, °F 10 10
Main (numbered) lines at, °F 20 20
Scale error at any point not to exceed, °F 1 1
Scale length, mm 80 to 110 105 to 145
A
Indication of the thermometer range is made by the use of the listed designation used as a suffix to the ASTM hydrometer number. For example, 54HL is an instrument
with an API gravity range of 29 to 41°API and a thermometer range of 0 °F to 150 °F. An instrument with the same gravity range but a thermometer range of 60 °F to 220 °F
would be designated 54HH. The number 57HM would identify an instrument with an API gravity range of 59 to 71°API and a thermometer range of 30 °F to 180 °F.
7.3 Sample Mixing—May be necessary to obtain a test portion representative of the bulk sample to be tested, but precautions shall
be taken to maintain the integrity of the sample during this operation. Mixing of volatile crude petroleum or petroleum products
containing water or sediments, or both, or the heating of waxy volatile crude petroleum or petroleum products may result in the
loss of light components. The following sections (7.3.1 – 7.3.4) will give some guidance on sample integrity maintenance.
7.3.1 Volatile Crude Petroleum and Petroleum Products Having an RVP Greater than 50 kPa—Mix the sample in its original
closed container in order to minimize the loss of light components.
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NOTE 1—Mixing volatile samples in open containers will lead to loss of light components and consequently affect the value of the density obtained.
7.3.2 Waxy Crude Petroleum—If the petroleum has an expected pour point above 10 °C, or a cloud point or WAT above 15 °C,
warm the sample to a temperature that is sufficient for ensuring the material is fluid enough to provide adequate mixing without
excessively heating the material that would otherwise compromise the integrity of the sample. Samples 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 provide
adequate mixing without excessively heating 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.
7.3.4 Residual Fuel Oils—Heat the sample to the test temperature prior to mixing (see 9.1.1 and Note 3).
7.4 Additional information on the mixing and handling of liquid samples will be found in Practice D5854 (API MPMS Chapter
8.3).
8. Apparatus Verification or Certification
8.1 Hydrometers and thermometers shall be verified in accordance with the procedures in Annex A1.
9. Procedure
9.1 Effect of Test Temperature:
9.1.1 The density or API gravity determined by the thermohydrometer method is most accurate at or near the reference
temperature of 15 °C or 60 °F. Other temperatures within the range of the enclosed thermometer may be used, if consistent with
the type of sample and the necessary limiting conditions shown in Table 3.
9.1.2 Bring the sample to the test temperature which shall be such that the sample is sufficiently fluid but not as high as to cause
the loss of light components, or so low as to result in the appearance of wax in the test portion.
NOTE 2—The volume and density, the relative density, and the API corrections in the volume correction procedures are based on the average expansions
of a number of typical materials. Since the same coefficients were used in compiling each set of tables, corrections made over the sam
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