ASTM D287-22

Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer/Method)

SIGNIFICANCE AND USE
5.1 Accurate determination of the gravity of petroleum and its products is necessary for the conversion of measured volumes to volumes at the standard temperature of 60 °F (15.56 °C).  
5.2 This procedure is most suitable for determining the API gravity of low viscosity transparent liquids. This test method can also be used for viscous liquids by allowing sufficient 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 before correcting to the reference temperature.  
5.3 When used in connection with bulk oil measurements, volume correction errors are minimized by observing the hydrometer reading at a temperature as close to reference temperature as feasible.  
5.4 Gravity is a factor governing the quality of crude oils. However, the gravity of a petroleum product is an uncertain indication of its quality. Correlated with other properties, gravity can be used to give approximate hydrocarbon composition and heat of combustion.  
5.5 Gravity is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and combustion.
SCOPE
1.1 This test method covers the determination by means of a glass hydrometer in conjunction with a series of calculations of the API gravity of crude petroleum and petroleum products normally handled as liquids and having a Reid vapor pressure (Test Method D323) of 14.696 psi (101.325 kPa) or less. Values are determined at existing temperatures and corrected to values at 60 °F (15.56 °C), or converted to values at 60 °F, by means of 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 Lubricating Oils (API MPMS Chapter 11.1). These tables are not applicable to nonhydrocarbons or essentially pure hydrocarbons such as the aromatics.  
1.2 The initial values obtained are uncorrected hydrometer readings and not density measurements. Values 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 The initial hydrometer readings determined shall be recorded before performing any calculations. Then the calculations required in Section 9 shall be performed and documented before using the final result in a subsequent calculation procedure (measurement ticket calculation, meter factor calculation, or base prover volume determination).  
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statement, see 8.5.  
1.6 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.

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 75.080 - Petroleum products in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.02 - Hydrocarbon Measurement for Custody Transfer (Joint ASTM-API)

Relations

• Refers: ASTM E344-23 - Terminology Relating to Thermometry and Hydrometry
• Effective Date: 01-Dec-2023
• Refers: ASTM D6822-23 - Standard Test Method for Density, Relative Density, and API Gravity of Crude Petroleum and Liquid Petroleum Products by Thermohydrometer Method
• Effective Date: 01-Dec-2023
• Refers: ASTM E344-19 - Terminology Relating to Thermometry and Hydrometry
• Effective Date: 01-Sep-2019
• Refers: ASTM E100-19 - Standard Specification for ASTM Hydrometers
• Effective Date: 01-May-2019
• Refers: ASTM E126-19 - Standard Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
• Effective Date: 01-May-2019
• Refers: ASTM E2877-12(2019) - Standard Guide for Digital Contact Thermometers
• Effective Date: 01-May-2019
• Refers: ASTM D1250-19e1 - 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 Lubricating Oils: API MPMS Chapter 11.1
• Effective Date: 01-May-2019
• Refers: ASTM D8164-18a - Standard Guide for Digital Contact Thermometers for Petroleum Products, Liquid Fuels, and Lubricant Testing
• Effective Date: 01-Jul-2018
• Refers: ASTM E344-18 - Terminology Relating to Thermometry and Hydrometry
• Effective Date: 01-Apr-2018
• Refers: ASTM D8164-18 - Standard Guide for Digital Contact Thermometers for Petroleum Products, Liquid Fuels, and Lubricant Testing
• Effective Date: 01-Apr-2018
• Refers: ASTM D7962-16 - Standard Practice for Determination of Minimum Immersion Depth and Assessment of Temperature Sensor Measurement Drift
• Effective Date: 01-Dec-2016
• Refers: ASTM E344-16 - Terminology Relating to Thermometry and Hydrometry
• Effective Date: 01-Nov-2016
• Refers: ASTM E100-15a - Standard Specification for ASTM Hydrometers
• Effective Date: 01-Dec-2015
• Refers: ASTM D7962-15a - Standard Practice for Determination of Minimum Immersion Depth and Assessment of Temperature Sensor Measurement Drift
• Effective Date: 01-Dec-2015
• Refers: ASTM E100-15 - Standard Specification for ASTM Hydrometers
• Effective Date: 01-Aug-2015

Overview

ASTM D287-22 is the established standard test method for determining the API gravity of crude petroleum and petroleum products using a hydrometer. Developed by ASTM International, this method is essential for accurately converting measured petroleum volumes to the standard reference temperature of 60 °F (15.56 °C). API gravity is a key indicator in the petroleum industry, influencing storage, handling, and processing decisions for both crude and refined products.

This test method applies to petroleum liquids with a Reid vapor pressure of 14.696 psi (101.325 kPa) or less, and is suitable for low-viscosity transparent liquids as well as more viscous or opaque ones with additional procedural adjustments. API gravity measurement is routinely used in refining, transportation, and quality control across the global oil and gas sector.

Key Topics

• API Gravity Measurement: API gravity is a calculated value used to express the density of petroleum liquids relative to water, making it easier to compare oils and fuels.
• Hydrometer Method: A glass hydrometer calibrated in API units is floated in a sample, and the scale is read at the liquid’s surface or correctly corrected meniscus.
• Temperature Correction: Data is corrected to the reference temperature (60 °F/15.56 °C) using standardized volume correction tables to ensure compatibility between different sample conditions.
• Sample Suitability: The method is most accurate for low-viscosity, transparent samples but can be adapted for viscous or opaque oils with proper meniscus and thermal expansion corrections.
• Volume Correction Factors: The standard refers to the API MPMS Chapter 11.1 tables (or the ASTM D1250 Guide) for temperature and pressure corrections, ensuring precise petroleum measurements.
• Quality Implications: API gravity gives a general indication of hydrocarbon composition and heat of combustion, but should be correlated with other properties for product specification.
• Operational Relevance: Proper API gravity measurement directly impacts logistical operations like custody transfer, blending, and regulatory reporting.

Applications

• Bulk Storage and Custody Transfer: API gravity is used to convert observed volumes of crude oil or refined products to a standard volume at 60 °F, minimizing volume correction errors and facilitating accurate transactions.
• Product Quality Control: Automotive, aviation, and marine fuel quality assessments often specify API gravity limits, as this property impacts combustion performance and storage behavior.
• Oil Blending and Processing: Refineries and transport terminals rely on API gravity data to blend components for targeted product specifications and to optimize refinery yields.
• Regulatory Compliance: Many contractual and regulatory frameworks mandate API gravity reporting at standardized conditions for fair trade and reporting accuracy.

Related Standards

Several other standards are referenced alongside ASTM D287-22 for petroleum measurement accuracy and equipment compliance:

• ASTM D323 - Test Method for Vapor Pressure of Petroleum Products (Reid Method)
• ASTM D1250 - Guide for Temperature and Pressure Volume Correction Factors (API MPMS Chapter 11.1)
• ASTM D1298 - Density, Relative Density, or API Gravity of Crude Petroleum by Hydrometer Method
• ASTM D6822 - Thermohydrometer Method for Density and API Gravity
• ASTM E100 - Specification for ASTM Hydrometers
• ASTM E1 / E2251 - Specifications for ASTM Liquid-in-Glass Thermometers

Collaboration with standards such as API MPMS Chapter 9.1 and 11.1, and Energy Institute (IP) specifications, ensures this method integrates seamlessly within international petroleum measurement systems.

By implementing ASTM D287-22, organizations ensure reliable, standardized API gravity results, supporting efficient operations and upholding quality in the global petroleum supply chain.

Standards Content (Sample)

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.
Designation: D287 − 22
Standard Test Method for
API Gravity of Crude Petroleum and Petroleum Products
(Hydrometer/Method)
This standard is issued under the fixed designation D287; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* conversions to SI units that are provided for information only
and are not considered standard.
1.1 This test method covers the determination by means of
1.5 This standard does not purport to address all of the
a glass hydrometer in conjunction with a series of calculations
safety concerns, if any, associated with its use. It is the
of theAPI gravity of crude petroleum and petroleum products
responsibility of the user of this standard to establish appro-
normally handled as liquids and having a Reid vapor pressure
priate safety, health, and environmental practices and deter-
(Test Method D323) of 14.696 psi (101.325kPa) or less.
mine the applicability of regulatory limitations prior to use.
Valuesaredeterminedatexistingtemperaturesandcorrectedto
For specific warning statement, see 8.5.
values at 60°F (15.56°C), or converted to values at 60°F, by
1.6 This international standard was developed in accor-
means ofAdjunct to D1250 Standard Guide for the Use of the
dance with internationally recognized principles on standard-
Joint API and ASTM Adjunct for Temperature and Pressure
ization established in the Decision on Principles for the
Volume Correction Factors for Generalized Crude Oils, Re-
Development of International Standards, Guides and Recom-
fined Products, and Lubricating Oils (API MPMS Chapter
mendations issued by the World Trade Organization Technical
11.1). These tables are not applicable to nonhydrocarbons or
Barriers to Trade (TBT) Committee.
essentially pure hydrocarbons such as the aromatics.
2. Referenced Documents
1.2 The initial values obtained are uncorrected hydrometer
readings and not density measurements. Values are measured
2.1 ASTM Standards:
on a hydrometer at either the reference temperature or at
D323TestMethodforVaporPressureofPetroleumProducts
another convenient temperature, and readings are corrected for
(Reid Method)
the meniscus effect, the thermal glass expansion effect, alter-
D1250Guide for the Use of the Joint API and ASTM
nate calibration temperature effects and to the reference tem-
Adjunct for Temperature and Pressure Volume Correction
peraturebymeansofthepetroleummeasurementtables;values
FactorsforGeneralizedCrudeOils,RefinedProducts,and
obtainedatotherthanthereferencetemperaturebeinghydrom-
Lubricating Oils: API MPMS Chapter 11.1
eter readings and not density measurements.
D1298Test Method for Density, Relative Density, or API
Gravity of Crude Petroleum and Liquid Petroleum Prod-
1.3 The initial hydrometer readings determined shall be
ucts by Hydrometer Method
recorded before performing any calculations. Then the calcu-
D6822Test Method for Density, Relative Density, and API
lations required in Section 9 shall be performed and docu-
Gravity of Crude Petroleum and Liquid Petroleum Prod-
mentedbeforeusingthefinalresultinasubsequentcalculation
ucts by Thermohydrometer Method
procedure (measurement ticket calculation, meter factor
D7962Practice for Determination of Minimum Immersion
calculation, or base prover volume determination).
Depth and Assessment of Temperature Sensor Measure-
1.4 The values stated in inch-pound units are to be regarded
ment Drift
as standard. The values given in parentheses are mathematical
D8164Guide for Digital Contact Thermometers for Petro-
leum Products, Liquid Fuels, and Lubricant Testing
E1Specification for ASTM Liquid-in-Glass Thermometers
This test method is under the jurisdiction of ASTM Committee D02 on
E77Test Method for Inspection and Verification of Ther-
Petroleum Products, Liquid Fuels, and Lubricants and the API Committee on
mometers
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). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2022. Published February 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1928. Last previous edition approved in 2019 as D287–12b (2019). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D0287-22. the ASTM website.
*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
D287 − 22
E100Specification for ASTM Hydrometers 3.1.3 observed values, n—values observed at temperatures
E126Test Method for Inspection, Calibration, and Verifica- otherthanthespecifiedreferencetemperature;thesevaluesare
tion of ASTM Hydrometers only hydrometer readings and not density, relative density, or
E344Terminology Relating to Thermometry and Hydrom- API gravity at those other temperatures.
etry
3.1.4 specific gravity, n—historical term, no longer used,
E2251Specification for Liquid-in-Glass ASTM Thermom-
which has been replaced by relative density.
eters with Low-Hazard Precision Liquids
3.2 Acronyms:
E2877Guide for Digital Contact Thermometers
3.2.1 PRT—platinum resistance temperature device
2.2 API Standards:
3.2.1.1 Discussion—While there may be other types of
MPMS Chapter 9.1Test Method for Density, Relative
RTDs available, for Custody Transfer operations in conjunc-
Density, or API Gravity of Crude Petroleum and Liquid
tion with other standards organizations Platinum RTDs have
Petroleum Products by Hydrometer Method (ASTM Test
been standardized on for their accuracy and discrimination.
Method D1298)
MPMSChapter 9.3 Test Method for Density, Relative
4. Summary of Test Method
Density, andAPI Gravity of Crude Petroleum and Liquid
4.1 This test method is based on the principle that the
Petroleum Products by Thermohydrometer Method
gravity of a liquid varies directly with the depth of immersion
(ASTM Test Method D6822)
of a body floating in it. The floating body, which is graduated
MPMS Chapter 11.1Temperature and PressureVolume Cor-
by API gravity units in this test method, is called an API
rection Factors for Generalized Crude Oils, Refined
hydrometer.
Products,andLubricatingOils(AdjuncttoASTMD1250)
4.2 TheAPI gravity is read by observing the freely floating
2.3 ASTM Adjuncts:
ASTM hydrometer (calibrated forAPI gravity) and noting the
Adjunct to D1250 Standard Guide for the Use of the Joint
graduationnearesttotheapparentintersectionofthehorizontal
API and ASTM Adjunct for Temperature and Pressure
plane surface of the liquid with the vertical scale of the
Volume Correction Factors for Generalized Crude Oils,
hydrometer, after temperature equilibrium has been reached.
RefinedProducts,andLubricatingOils:API MPMSChap-
4 The temperature of the sample shall be read from a separate
ter 11.1)
accurate ASTM thermometer placed in the sample, which
meets either Specifications E1 or E2251 requirements or
3. Terminology
ASTM Digital Contact Thermometers, which meet Guide
3.1 Definitions:
E2877requirements.Thetemperaturedeterminationdevice,be
3.1.1 API gravity, n—a special function of relative density
it the bulb of a ASTM Thermometer (Specifications E1 or
60/60°F (15.56/15.56°C), represented by:
E2251) or a sensor of a Digital Contact Thermometer (Guide
°API 5 141.5/ relativedensity60/60 °F 2131.5 (1)
@ ~ !# E2877) shall be placed at the same elevation (within the stated
tolerances) as the hydrometer bulb.
No statement of reference temperature is required, since
60°F is included in the definition. NOTE 1—Through various testings that Subcommittee D02.02 (Joint
ASTM/API Subcommittee) measurement committee and others have
3.1.2 hydrometer reading, n—the point on the hydrometer
conducted, it has been determined that temperature stratifications do exist
scale at which the surface of the liquid cuts the scale.
verticallyfromtoptobottomofahydrocarboncontaineraswellasacross
3.1.2.1 Discussion—In practice for transparent fluids this
the diameter of the container. Therefore, as temperature affects the
viscosity as well as the fluid density, the buoyancy of the hydrometer
can be readily determined by aligning the surface of the liquid
floatingintheliquidisthereforeaffected,clarifyingprocedureshavebeen
on both sides of the hydrometer and reading the Hydrometer
added to the Procedure section.
scale where these surface readings cut the scale (Hydrometer
4.3 The observed hydrometer reading is corrected for the
Reading – Observed). For nontransparent fluids the point at
meniscus effect, the thermal glass expansion effect on the
which the liquid surface cuts the Hydrometer scale cannot be
hydrometer, alternate calibration temperature effects and re-
determined directly and requires a correction (Meniscus Cor-
duced to the reference temperature by means of the petroleum
rection). The value represented by the point (Meniscus Read-
measurement tables. If necessary, the hydrometer cylinder and
ing) at which the liquid sample rises above the main surface of
its contents are placed in a constant temperature bath to avoid
the liquid subtracted from the value represented by where the
excessive temperature variation during the test.
main surface of the liquid cuts the Hydrometer scale is the
amount of the correction or Meniscus correction. This menis-
5. Significance and Use
cus correction is documented and then subtracted from the
5.1 Accurate determination of the gravity of petroleum and
value represented by the Meniscus Reading to yield the
its products is necessary for the conversion of measured
Hydrometer Reading corrected for the Meniscus (Hydrometer
volumes to volumes at the standard temperature of 60°F
Reading – Observed, Meniscus Corrected).
(15.56°C).
5.2 This procedure is most suitable for determining theAPI
Available from American Petroleum Institute (API), 200 Massachusetts Ave.
gravity of low viscosity transparent liquids. This test method
NW, Suite 1100, Washington, DC 20001, http://www.api.org.
can also be used for viscous liquids by allowing sufficient time
Available from ASTM International Headquarters. Order Adjunct No.
ADJD1250-A1A2-E-PDF. Original adjunct produced in 1983. for the hydrometer to reach temperature equilibrium, and for
D287 − 22
TABLE 2 Available Hydrometers Scaled, Degrees API (Low
opaque liquids by employing a suitable meniscus correction.
Hazardous Liquid Type)
Additionally for both transparent and opaque fluids the read-
ASTM
ings shall be corrected for the thermal glass expansion effect Scale
API Range,
Hydrometer Type Each Unit
deg
before correcting to the reference temperature.
Division Error
Designation
52HL thermo –1 to 11 12 0.1 0.1
5.3 When used in connection with bulk oil measurements,
52HL thermo 9 to 21 12 0.1 0.1
volume correction errors are minimized by observing the
53HL thermo 19 to 31 12 0.1 0.1
54HL thermo 29 to 41 12 0.1 0.1
hydrometer reading at a temperature as close to reference
55HL thermo 39 to 51 12 0.1 0.1
temperature as feasible.
56HL thermo 49 to 61 12 0.1 0.1
57HL thermo 59 to 71 12 0.1 0.1
5.4 Gravity is a factor governing the quality of crude oils.
58HL thermo 69 to 81 12 0.1 0.1
However, the gravity of a petroleum product is an uncertain
59HL thermo 79 to 91 12 0.1 0.1
indication of its quality. Correlated with other properties,
60HL thermo 89 to 101 12 0.1 0.1
gravity can be used to give approximate hydrocarbon compo-
sition and heat of combustion.
5.5 Gravityisanimportantqualityindicatorforautomotive,
liquid-in-glass thermometers. The stated repeatability and re-
aviation and marine fuels, where it affects storage, handling
producibility values are not applicable if alternate fluids are
and combustion.
used in the liquid-in-glass thermometers.
6.2.3 Digital Temperature Sensors—Digital Contact Ther-
6. Apparatus
mometers of the PRT style shall meet the requirements of
6.1 Hydrometers, of glass, graduated in degrees API as
Guide E2877 and may be used instead of glass thermometers
listed in Table 1 and conforming to Specification E100 or as
with the following exceptions:
listed in Table 2 and conforming to Specification E2251.
6.2.3.1 Thermocouples shall not be used.
6.1.1 Theusershouldascertainthattheinstrumentsusedfor
6.2.3.2 Thermistors shall not be used.
this method conform to the requirements set out above with
6.3 Hydrometer Cylinder, transparent material (see 6.3.2).
respect to materials, dimensions, and scale errors. In cases
The inside diameter of the cylinder shall be at least 0.25in.
where the instrument is provided with a calibration certificate
(6.35mm)greater(seeAinFig.1)thantheoutsidediameterof
traceable to a NMI (National Metrology Institute), the instru-
the hydrometer body and the temperature measuring device
ment is classed as certified and the appropriate corrections for
plus the separation interval specified in Fig. 1 and the height
the meniscus effect, the thermal glass expansion effect, and
shall be such that the appropriate hydrometer floats in the test
alternative calibration temperature effects shall be applied to
portion with at least 1 in. (25mm) clearance between the
the observed readings prior to corrections. Instruments that
bottomofthehydrometerandthebottomofthecylinder,under
satisfy the requirements of this test method, but are not
all densities and temperatures. Ensure that the hydrometer
provided with a recognized calibration certificate, are classed
cylinder is cleaned after each use to ensure that no contami-
as uncertified.
nants remain.
6.2 Temperature Determination:
6.3.1 When using separate hydrometer (or thermohydrom-
6.2.1 Thermometers (Glass), having a range from −5°F to
eter) and temperature measuring devices, care shall be exer-
+215°F and conforming to the requirements for Thermometer
cised to ensure that neither interfere with each other and that
12F as prescribed in Specification E1.
they are not affected by external temperature effects. The
minimum separation distances as shown in Fig. 1 shall be
NOTE2—TheASTMGravityThermometer12Fhas0.5°Fsubdivisions
and allowable 60.25°F scale error and is suitable for use in determining
required. These separation distances are a function of the
temperature of bulk crude oil volumes, such as lease production tanks.
diameters of the measuring devices and the minimum distance
Additional thermometers conform to Specification E1 standard or Speci-
from the sides of the measuring chamber to minimize external
fication E2251 standard having a narrower range than the 12F or S12F
thermal effects.
Thermometers may also be used, if they have similar performance
characteristics.
where:
6.2.2 Alternate liquid measuring device (Thermometer
A = minimum separation interval specified in 6.3 between
S12F) conforming to the requirements prescribed in Specifi-
the inside diameter of hydrometer cylinder and the sum
cation E2251 may be used, provided that the total uncertainty
of the OD of the hydrometer body plus the OD of
of the calibrated system is no greater than when using
temperature measuring device plus the minimum sepa-
ration interval between devices of 0.25in. (6.35mm),
see Fig. 1, and
TABLE 1 Available Hydrometers Scaled, Degrees API
B = minimum separation interval between measuring de-
API Range, deg Scale
vices of 0.5in. (12.7mm).
Designation Type
Series Total Each Unit Division Error
6.3.2 Hydrometer cylinders constructed of transparent ma-
1H to 10H long plain −1 to 101 12 0.1 0.1
21H to 40H short plain 0 to 101 6 0.1 0.2 terials shall be resistant to discoloration or attack by the
41H to 45 H thermo 15 to 51 8 0.1 0.1
petroleum or petroleum product samples and shall not affect
51H to 60H thermo −1 to 101 12 0.1 0.1
the material being tested.They shall not become opaque under
71H to 74H thermo −1 to 41 12 0.1 0.1
prolonged exposure to sunlight. If the opacity prevents the
D287 − 22
FIG. 1 Separation Intervals (minimum requirements) between Devices and Hydrometer Cylinder
observation of both devices then the hydrometer cylinder shall sample physical properties to ensure that the devices can
be replaced before continuing with the test. function properly. For example, with highly volatile samples
6.3.3 The minimum separation intervals specified is to being measured in an open container the light ends may
preventanycapillaryactionbetweendevicesandtoensurethat evaporate while the devices are reaching temperature equilib-
external temperature effects are minimized on the values rium.Thisisafunctionofambienttemperatureaswellasfluid
determined for density and temperature. temperature and composition. Conversely, if the fluid is too
viscous (thick) the hydrometer may not float freely, which is a
7. Temperature of Test (Limiting Conditions of Test)
requirement for a buoyance device.
7.1 The gravity determined by the hydrometer method is
most accurate at or near the standard temperature of 60°F 8. Procedure
(15.56°C).Usethisoranyothertemperaturebetween0°Fand
8.1 For referee testing, use the long plain form of hydrom-
195°F (–18°C and + 90°C) for the test, so far as it is
eter (1H to 10H). For field testing, the thermohydrometer
consistent with the type of sample and necessary limiting
method inTest Method D6822 (API MPMS Chapter 9.3) is the
conditions shown in Table 3.
preferred method. However, if the user desires to use a
7.2 The purpose of Table 3 is to clarify what actions are liquid-in-glass thermometer with low-hazard glass precision
required to ensure that the sample does not change its physical fluid as specified in Specification E2251 or a Digital Contact
makeup during the testing period or modifications to the Thermometer as specified in Guide E2877 and 6.2.3, the user
TABLE 3 Limiting Conditions and Testing Temperatures
Initial Boiling Point
Sample Type Gravity Limits Other Limits Test Temperature
Limits
Highly volatile lighter than 70° API Cool to 35 °F (2 °C) or lower in original closed
container.
Moderately volatile heavier than 70° API below 250 °F (120 °C) Cool to 65 °F (18 °C) or lower in original closed
container.
Moderately volatile and viscous heavier than 70° API below 250 °F (120 °C) Viscosity too high at Heat to minimum temperature for sufficient
65 °F (18 °C) fluidity.
Nonvolatile heavier than 70° API above 250 °F (120 °C) Any temperature between 0 °F and 195 °F
(−18 °C and 90 °C) as convenient.
Mixtures of nonpetroleum products or 60 °F ± 0.25 °F (15.56 °C ± 0.1 °C)
essentially pure hydrocarbons
D287 − 22
can use Test Method D6822 (API MPMS Chapter 9.3) with a bubblestocometothesurface.Thisisparticularlynecessaryin
modified procedure as detailed in 8.11 of this test method. the case of the more viscous samples.
8.1.1 As shown in Table 1 and Table 2, the user has access
8.7 Lowerthetemperaturemeasuringdeviceslowlyintothe
to hydrometers covering various ranges of API gravity. The
sample, in close proximity to the hydrometer installed in 8.6
user should select a hydrometer which results in the liquid
making sure that neither touch, nor come in contact with the
interface cutting the hydrometer stem in the center third of the
side walls of the sample cylinder. Refer to Fig. 2a and Fig. 2b
range. The hydrometer should not be used when the liquid
and Fig. 3a and Fig. 3b. The temperature measuring device
interfacecutsthescaleinthebottomtwoAPIgravityvaluesor
may also be used to cautiously and slowly stir the sample
at the top two API gravity values.
instead of the hydrometer, to minimize stratification.
8.1.2 When using digital temperature devices the user shall
8.7.1 Thehydrometerisabuoyancydevice,itsperformance
utilize only intrinsically rated temperature devices that con-
or where it floats is dependent on the temperature of the fluid
form to the appropriate standard.
around the point of buoyancy.Therefore, it is essential that the
sampletemperaturebetakenasclosetothispointofbuoyancy.
NOTE 3—In practice whether in a lab or field environment this test
In practice with opaque samples this point can be difficult to
method is used in a potentially hazardous environment (that is, explosive)
determine. However, it can be estimated from knowing the
and as these devices are electrically powered which could possibly
produce a spark, potentially resulting in an explosion/fire.All companies lengths of the various instruments and then estimating their
generally have Engineering and Operating standards that refer to NFPA
relative positions.
(National Fire Protection Association) and NEC (National Electrical
8.8 When the hydrometer has come to rest, floating freely,
Code) codes that detail the requirements for the use of electrical devices
in classified areas. These company requirements should take precedence.
and the temperature of the sample is constant to within 0.2°F
(0.1°C), read and record the hydrometer reading to the nearest
8.2 Prior to lowering the selected hydrometer and/or tem-
scale division. The correct reading is that point on the
perature determination instrument into the sample perform the
hydrometer scale at which the surface of the liquid cuts the
Equipment Validation enumerated in Annex A1.
scale. Determine this point by placing the eye slightly below
8.3 Verify that the selected density and/or temperature
the level of the liquid and slowly raising it until the surface,
determination instruments conform to the requirements of
first seen as a distorted ellipse, appears to become a straight
Annex A2.
line cutting the hydrometer scale. See Fig. 4.
8.4 Adjustthetemperatureofthesampleinaccordancewith
8.9 To make a reading with nontransparent liquids, observe
Table 3. For field testing, test temperatures other than those
the point on the hydrometer scale to which the sample rises
listedinTable3maybeused.Thehydrometercylindershallbe
aboveitsmainsurface,placingtheeyeslightlyabovetheplane
approximatelythesametemperatureasthesampletobetested.
surface of the liquid. This reading requires a correction.
Determine this correction (meniscus correction) for the par-
8.5 Transfer the sample into the clean hydrometer cylinder
ticular hydrometer in use by observing the height above the
without splashing, so as to avoid the formation of air bubbles
and to reduce to a minimum the evaporation of the lower
boiling constituents of the more volatile samples. (Warning—
Samples may be extremely flammable.Vapors may cause flash
fire.) For the more volatile samples, transfer to the hydrometer
cylinder by siphoning. (Do not start the siphon by mouth.)
Remove any air bubbles formed, after they have collected on
the surface of the sample, by touching them with a piece of
clean filter paper or other suitable means before inserting the
hydrometer. For field testing, the gravity measurement is
directly made in the sampling core thief or hydrometer
cylinder. Place the cylinder containing the sample in a vertical
position in a location free from air currents. Take precautions
to prevent the temperature of the sample from changing
appreciably during the time necessary to complete the test.
Duringthisperiod,thetemperatureofthesurroundingmedium
where:
should not change more than 5°F (3°C).
A = separation interval specified in 6.3 and Fig. 1,
8.6 Lower the hydrometer gently into the sample and, when
B = separation interval specified in 6.3 and Fig. 1, and
ithassettled,depressitabouttwoscaledivisionsintotheliquid
C = relative vertical alignment between the density and
andthenreleaseit;keeptherestofthestemdry,asunnecessary
temperature measuring devices (the bottom of the sens-
liquid on the stem changes the effective weight of the
ing portion of the temperature measuring device should
instrument, and so affects the reading obtained. With samples
be within 60.5in. (612.5mm) and not more than
of low viscosity, a slight spin imparted to the instrument on
61.0in.(625mm)ofthebottomofthedensitysensor).
releasingassistsinbringingittorest,floatingfreelyawayfrom
the walls of the hydrometer cylinder.Allow sufficient time for
FIG. 2 a Hydrometer and Liquid-in-Glass Thermometer Placement
the hydrometer to become completely stationary and for all air (Typical)
D287 − 22
where:
where:
A = separation interval specified in 6.3 and Fig. 1,
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and
C = relative vertical alignment between the density and
temperature measuring devices (the bottom of the sens-
temperature measuring devices (the bottom of the sens-
ing portion of the temperature measuring device should
ing portion of the temperature measuring device should
be within 60.5in. (612.5mm) and not more than
be within 60.5in. (612.5mm) and not more than
61.0in.(625mm)ofthebottomofthedensitysensor).
61.0in.(625mm)ofthebottomofthedensitysensor).
FIG. 2 b Thermohydrometer and Liquid-in-Glass Thermometer
FIG. 3 b Thermohydrometer and Digital Contact Thermometer
Placement (Typical) (continued)
Placement (Typical) (continued)
where:
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and
temperature measuring devices (the bottom of the sens-
ing portion of the temperature measuring device should
be within 60.5in. (612.5mm) and not more than
61.0in.(625mm)ofthebottomofthedensitysensor).
FIG. 3 a Hydrometer and Digital Contact Thermometer (Typical)
FIG. 4 Hydrometer Scale Reading for Transparent Liquids
(Typical)
main surface of the liquid to which the sample rises on the
hydrometerscalewhenthehydrometerinquestionisimmersed 8.9.2 When gravity readings have been observed on opaque
in a transpare
...

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.
Designation: D287 − 12b (Reapproved 2019) D287 − 22
Standard Test Method for
API Gravity of Crude Petroleum and Petroleum Products
(Hydrometer Method)(Hydrometer/Method)
This standard is issued under the fixed designation D287; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers the determination by means of a glass hydrometer in conjunction with a series of calculations of the
API gravity of crude petroleum and petroleum products normally handled as liquids and having a Reid vapor pressure (Test Method
D323) of 101.325 kPa (14.696 psi) 14.696 psi (101.325 kPa) or less. GravitiesValues are determined at existing temperatures and
corrected to values at 60 °F (15.56 °C), or converted to values at 60 °F, by means of Adjunct to D1250 Guide for Petroleum
Measurement Tables 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 Lubricating Oils (API MPMS Chapter 11.1). These tables
are not applicable to nonhydrocarbons or essentially pure hydrocarbons such as the aromatics.
1.2 The initial values obtained are uncorrected hydrometer readings and not density measurements. Values 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
volume correction tables.the petroleum measurement tables; values obtained at other than the reference temperature being
hydrometer readings and not density measurements.
1.3 The initial hydrometer readings determined shall be recorded before performing any calculations. Then the calculations
required in Section 9 shall be performed and documented before using the final result in a subsequent calculation procedure
(measurement ticket calculation, meter factor calculation, or base prover volume determination).
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warning statement, see 8.38.5.
1.6 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.
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).
Current edition approved Dec. 1, 2019Dec. 1, 2022. Published December 2019February 2023. Originally approved in 1928. Last previous edition approved in 20122019
as D287–12b. –12b (2019). DOI: 10.1520/D0287-12BR19.10.1520/D0287-22.
*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
D287 − 22
2. Referenced Documents
2.1 ASTM Standards:
D323 Test Method for Vapor Pressure of Petroleum Products (Reid Method)
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
D6822 Test Method for Density, Relative Density, and API Gravity of Crude Petroleum and Liquid Petroleum Products by
Thermohydrometer Method
D7962 Practice for Determination of Minimum Immersion Depth and Assessment of Temperature Sensor Measurement Drift
D8164 Guide for Digital Contact Thermometers for Petroleum Products, Liquid Fuels, and Lubricant Testing
E1 Specification for ASTM Liquid-in-Glass Thermometers
E77 Test Method for Inspection and Verification of Thermometers
E100 Specification for ASTM Hydrometers
E126 Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers
E344 Terminology Relating to Thermometry and Hydrometry
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
E2877 Guide for Digital Contact Thermometers
2.2 EI Standards:
Specifications for IP Standard Thermometers
IP Specifications for Petroleum Hydrometers
2.2 API Standards:
MPMS Chapter 9.1 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum
Products by Hydrometer Method (ASTM Test Method D1298)
MPMSChapter 9.3 Test Method for Density, Relative Density, and API Gravity of Crude Petroleum and Liquid Petroleum
Products by Thermohydrometer Method (ASTM Test Method D6822)
MPMS Chapter 11.1 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and
Lubricating Oils (Adjunct to ASTM D1250)
2.3 ASTM Adjuncts:
Adjunct to D1250 Guide for Petroleum Measurement Tables (API 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
Lubricating Oils: API MPMS Chapter 11.1)
3. Terminology
3.1 Definitions:
3.1.1 API gravity, n—a special function of relative density 60/60 °F (15.56/15.56 °C), represented by:
°API 5 141.5/ relative density 60/60°F 2 131.5 (1)
@ ~ !#
°API 5 141.5/ relative density 60/60 °F 2 131.5 (1)
@ ~ !#
No statement of reference temperature is required, since 60 °F is included in the definition.
3.1.2 hydrometer reading, n—the point on the hydrometer scale at which the surface of the liquid cuts the scale.
3.1.2.1 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).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K., http://www.energyinst.org.
Available from American Petroleum Institute (API), 1220 L. St., NW, 200 Massachusetts Ave. NW, Suite 1100, Washington, DC 20005-4070,20001, http://www.api.org.
Available from ASTM International Headquarters. Order Adjunct No. ADJD1250ADJD1250-A1A2-E-PDF. Original adjunct produced in 1983.
D287 − 22
3.1.3 observed values, n—values observed at temperatures other than the specified reference temperature; these values are only
hydrometer readings and not density, relative density, or API gravity at those other temperatures.
3.1.4 specific gravity, n—historical term, no longer used, which has been replaced by relative density.
3.2 Acronyms:
3.2.1 PRT—platinum resistance temperature device
3.2.1.1 Discussion—
While there may be other types of RTDs available, for Custody Transfer operations in conjunction with other standards
organizations Platinum RTDs have been standardized on for their accuracy and discrimination.
4. Summary of Test Method
4.1 This test method is based on the principle that the gravity of a liquid varies directly with the depth of immersion of a body
floating in it. The floating body, which is graduated by API gravity units in this test method, is called an API hydrometer.
4.2 The API gravity is read by observing the freely floating API hydrometerASTM hydrometer (calibrated for API gravity) 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 temperature of the sample is shall be read from a separate
accurate ASTM thermometer placed in the sample.sample, which meets either Specifications E1 or E2251 requirements or ASTM
Digital Contact Thermometers, which meet Guide E2877 requirements. The temperature determination device, be it the bulb of
a ASTM Thermometer (Specifications E1 or E2251) or a sensor of a Digital Contact Thermometer (Guide E2877) shall be placed
at the same elevation (within the stated tolerances) as the hydrometer bulb.
NOTE 1—Through various testings that Subcommittee D02.02 (Joint ASTM/API Subcommittee) measurement committee and others have conducted, it
has been determined that temperature stratifications do exist vertically from top to bottom of a hydrocarbon container as well as across the diameter of
the container. Therefore, as temperature affects the viscosity as well as the fluid density, the buoyancy of the hydrometer floating in the liquid is therefore
affected, clarifying procedures have been added to the Procedure section.
4.3 The observed hydrometer reading is corrected for the meniscus effect, the thermal glass expansion effect, effect on the
hydrometer, alternate calibration temperature effects and reduced to the reference temperature by means of the volume
correctionpetroleum measurement tables. If necessary, the hydrometer cylinder and its contents are placed in a constant
temperature bath to avoid excessive temperature variation during the test.
5. Significance and Use
5.1 Accurate determination of the gravity of petroleum and its products is necessary for the conversion of measured volumes to
volumes at the standard temperature of 60 °F (15.56 °C).
5.2 This procedure is most suitable for determining the API gravity of low viscosity transparent liquids. This test method can also
be used for viscous liquids by allowing sufficient 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 before correcting to the reference temperature.
5.3 When used in connection with bulk oil measurements, volume correction errors are minimized by observing the hydrometer
reading at a temperature as close to reference temperature as feasible.
5.4 Gravity is a factor governing the quality of crude oils. However, the gravity of a petroleum product is an uncertain indication
of its quality. Correlated with other properties, gravity can be used to give approximate hydrocarbon composition and heat of
combustion.
5.5 Gravity is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and
combustion.
D287 − 22
6. Apparatus
6.1 Hydrometers, of glass, graduated in degrees API as listed in Table 1 and conforming to Specification E100 or as listed in Table
2 and conforming to Specification E2251.
6.1.1 The user should ascertain that the instruments used for this method 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, traceable to a NMI (National Metrology Institute), the instrument is classed as certified 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. 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, Temperature Determination: having a range from −5 °F to +215 °F and conforming to the requirements for
Thermometer 12F as prescribed in Specification E1 or Thermometer 64F of the Specification for IP Standard Thermometers.
6.2.1 Thermometers (Glass), having a range from −5 °F to +215 °F and conforming to the requirements for Thermometer 12F as
prescribed in Specification E1.
NOTE 2—The ASTM Gravity Thermometer 12F has 0.5 °F subdivisions and allowable 60.25 °F scale error and is suitable for use in determining
temperature of bulk crude oil volumes, such as lease production tanks. Additional thermometers conform to Specification E1 standard or Specification
E2251 standard having a narrower range than the 12F or S12F Thermometers may also be used, if they have similar performance characteristics.
6.2.2 Alternate measuring devices or systems liquid measuring device (Thermometer S12F) conforming to the requirements
prescribed in Specification E2251 may be used, provided that the total uncertainty of the calibrated system is no greater than when
using liquid-in-glass thermometers. The stated repeatability and reproducibility values are not applicable if alternate fluids are used
in the liquid-in-glass thermometers.
NOTE 1—The ASTM Gravity Thermometer 12F has 0.5 °F subdivisions and allowable 60.25 °F scale error.
6.2.3 Digital Temperature Sensors—Digital Contact Thermometers of the PRT style shall meet the requirements of Guide E2877
and may be used instead of glass thermometers with the following exceptions:
6.2.3.1 Thermocouples shall not be used.
6.2.3.2 Thermistors shall not be used.
6.3 Hydrometer Cylinder, clear glass, plastic, or metal transparent material (see 6.3.16.3.2). The inside diameter of the cylinder
shall be at least 25 mm greater 0.25 in. (6.35 mm) greater (see A in Fig. 1) than the outside diameter of the hydrometer and the
body and the temperature measuring device plus the separation interval specified in Fig. 1 and the height shall be such that the
appropriate hydrometer floats in the test portion with at least 25 mm 1 in. (25 mm) clearance between the bottom of the hydrometer
and the bottom of the cylinder.cylinder, under all densities and temperatures. Ensure that the hydrometer cylinder is cleaned after
each use to ensure that no contaminants remain.
6.3.1 When using separate hydrometer (or thermohydrometer) and temperature measuring devices, care shall be exercised to
ensure that neither interfere with each other and that they are not affected by external temperature effects. The minimum separation
TABLE 1 Available Hydrometers Scaled, Degrees API
API Range, deg Scale
Designation Type
Series Total Each Unit Division Error
1H to 10H long plain −1 to 101 12 0.1 0.1
21H to 40H short plain 0 to 101 6 0.1 0.2
41H to 45 H thermo 15 to 51 8 0.1 0.1
51H to 60H thermo −1 to 101 12 0.1 0.1
71H to 74H thermo −1 to 41 12 0.1 0.1
A
thermo 15 to 51 8
A
Eight-degree range thermohydrometers are available.
D287 − 22
TABLE 2 Available Hydrometers Scaled, Degrees API (Low
Hazardous Liquid Type)
ASTM
Scale
API Range,
Hydrometer Type Each Unit
deg
Division Error
Designation
52HL thermo –1 to 11 12 0.1 0.1
52HL thermo 9 to 21 12 0.1 0.1
53HL thermo 19 to 31 12 0.1 0.1
54HL thermo 29 to 41 12 0.1 0.1
55HL thermo 39 to 51 12 0.1 0.1
56HL thermo 49 to 61 12 0.1 0.1
57HL thermo 59 to 71 12 0.1 0.1
58HL thermo 69 to 81 12 0.1 0.1
59HL thermo 79 to 91 12 0.1 0.1
60HL thermo 89 to 101 12 0.1 0.1
distances as shown in Fig. 1 shall be required. These separation distances are a function of the diameters of the measuring devices
and the minimum distance from the sides of the measuring chamber to minimize external thermal effects.
where:
A = minimum separation interval specified in 6.3 between the inside diameter of hydrometer cylinder and the sum of the OD
of the hydrometer body plus the OD of temperature measuring device plus the minimum separation interval between devices
of 0.25 in. (6.35 mm), see Fig. 1, and
B = minimum separation interval between measuring devices of 0.5 in. (12.7 mm).
6.3.2 Hydrometer cylinders constructed of plastictransparent materials shall be resistant to discoloration or attack by oil the
petroleum or petroleum product samples and shall not affect the material being tested. They shall not become opaque under
prolonged exposure to sunlight. If the opacity prevents the observation of both devices then the hydrometer cylinder shall be
replaced before continuing with the test.
6.3.3 The minimum separation intervals specified is to prevent any capillary action between devices and to ensure that external
temperature effects are minimized on the values determined for density and temperature.
7. Temperature of Test (Limiting Conditions of Test)
7.1 The gravity determined by the hydrometer method is most accurate at or near the standard temperature of 60 °F (15.56 °C).
Use this or any other temperature between 0 °F and 195 °F (–18 °C and + 90 °C) for the test, so far as it is consistent with the type
of sample and necessary limiting conditions shown in Table 23.
7.2 The purpose of Table 3 is to clarify what actions are required to ensure that the sample does not change its physical makeup
during the testing period or modifications to the sample physical properties to ensure that the devices can function properly. For
example, with highly volatile samples being measured in an open container the light ends may evaporate while the devices are
reaching temperature equilibrium. This is a function of ambient temperature as well as fluid temperature and composition.
Conversely, if the fluid is too viscous (thick) the hydrometer may not float freely, which is a requirement for a buoyance device.
8. Procedure
8.1 For referee testing, use the long plain form of hydrometer (1H to 10H). For field testing, use the thermohydrometer method
in Test Method D6822 (API MPMS Chapter 9.3) is the preferred method. However, if the user desires to use a liquid-in-glass
thermometer with low-hazard glass precision fluid as specified in Specification E2251 or a Digital Contact Thermometer as
specified in Guide E2877 and 6.2.3, the user can use Test Method D6822 (API MPMS Chapter 9.3).9.3) with a modified procedure
as detailed in 8.11 of this test method.
8.1.1 As shown in Table 1 and Table 2, the user has access to hydrometers covering various ranges of API gravity. The user should
select a hydrometer which results in the liquid interface cutting the hydrometer stem in the center third of the range. The
hydrometer should not be used when the liquid interface cuts the scale in the bottom two API gravity values or at the top two API
gravity values.
D287 − 22
FIG. 1 Separation Intervals (minimum requirements) between Devices and Hydrometer Cylinder
TABLE 23 Limiting Conditions and Testing Temperatures
Initial Boiling Point
Sample Type Gravity Limits Other Limits Test Temperature
Limits
Highly volatile lighter than 70° API Cool to 35 °F (2 °C) or lower in original closed
container.
Moderately volatile heavier than 70° API below 250 °F (120 °C) Cool to 65 °F (18 °C) or lower in original closed
container.
Moderately volatile and viscous heavier than 70° API below 250 °F (120 °C) Viscosity too high at Heat to minimum temperature for sufficient
65 °F (18 °C) fluidity.
Nonvolatile heavier than 70° API above 250 °F (120 °C) Any temperature between 0 °F and 195 °F
(−18 °C and 90 °C) as convenient.
Mixtures of nonpetroleum products or 60 °F ± 0.25 °F (15.56 °C ± 0.1 °C)
essentially pure hydrocarbons
8.1.2 When using digital temperature devices the user shall utilize only intrinsically rated temperature devices that conform to the
appropriate standard.
NOTE 3—In practice whether in a lab or field environment this test method is used in a potentially hazardous environment (that is, explosive) and as these
devices are electrically powered which could possibly produce a spark, potentially resulting in an explosion/fire. All companies generally have
Engineering and Operating standards that refer to NFPA (National Fire Protection Association) and NEC (National Electrical Code) codes that detail the
requirements for the use of electrical devices in classified areas. These company requirements should take precedence.
8.2 Prior to lowering the selected hydrometer and/or temperature determination instrument into the sample perform the Equipment
Validation enumerated in Annex A1.
8.3 Verify that the selected density and/or temperature determination instruments conform to the requirements of Annex A2.
8.4 Adjust the temperature of the sample in accordance with Table 23. For field testing, test temperatures other than those listed
in Table 23 may be used. The hydrometer cylinder shall be approximately the same temperature as the sample to be tested.
D287 − 22
8.5 Transfer the sample into the clean hydrometer cylinder without splashing, so as to avoid the formation of air bubbles and to
reduce to a minimum the evaporation of the lower boiling constituents of the more volatile samples. (Warning—Extremely
Samples may be extremely flammable. Vapors may cause flash fire.) For the more volatile samples, transfer to the hydrometer
cylinder by siphoning. (Do not start the siphon by mouth.) Use a rubber aspirator bulb. Remove any air bubbles formed, after they
have collected on the surface of the sample, by touching them with a piece of clean filter paper or other suitable means before
inserting the hydrometer. For field testing, make the gravity measurement is directly made in the sampling thief. core thief or
hydrometer cylinder. Place the cylinder containing the sample in a vertical position in a location free from air currents. Take
precautions to prevent the temperature of the sample from changing appreciably during the time necessary to complete the test.
During this period, the temperature of the surrounding medium should not change more than 5 °F (2 °C).(3 °C).
8.6 Lower the hydrometer gently into the sample and, when it has settled, depress it about two scale divisions into the liquid and
then release it; keep the rest of the stem dry, as unnecessary liquid on the stem changes the effective weight of the instrument, and
so affects the reading obtained. With samples of low viscosity, a slight spin imparted to the instrument on releasing assists in
bringing it to rest, floating freely away from the walls of the hydrometer cylinder. Allow sufficient time for the hydrometer to
become completely stationary and for all air bubbles to come to the surface. This is particularly necessary in the case of the more
viscous samples.
8.7 Lower the temperature measuring device slowly into the sample, in close proximity to the hydrometer installed in 8.6 making
sure that neither touch, nor come in contact with the side walls of the sample cylinder. Refer to Fig. 2a and Fig. 2b and Fig. 3a
and Fig. 3b. The temperature measuring device may also be used to cautiously and slowly stir the sample instead of the hydrometer,
to minimize stratification.
8.7.1 The hydrometer is a buoyancy device, its performance or where it floats is dependent on the temperature of the fluid around
the point of buoyancy. Therefore, it is essential that the sample temperature be taken as close to this point of buoyancy. In practice
with opaque samples this point can be difficult to determine. However, it can be estimated from knowing the lengths of the various
instruments and then estimating their relative positions.
8.8 When the hydrometer has come to rest, floating freely, and the temperature of the sample is constant to within 0.2 °F (0.1 °C),
read and record the hydrometer reading to the nearest scale division. The correct reading is that point on the hydrometer scale at
where:
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and temperature measuring devices (the bottom of the sensing portion of the
temperature measuring device should be within 60.5 in. (612.5 mm) and not more than 61.0 in. (625 mm) of the bottom
of the density sensor).
FIG. 2 a Hydrometer and Liquid-in-Glass Thermometer Placement (Typical)
D287 − 22
where:
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and temperature measuring devices (the bottom of the sensing portion of the
temperature measuring device should be within 60.5 in. (612.5 mm) and not more than 61.0 in. (625 mm) of the bottom
of the density sensor).
FIG. 2 b Thermohydrometer and Liquid-in-Glass Thermometer Placement (Typical) (continued)
where:
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and temperature measuring devices (the bottom of the sensing portion of the
temperature measuring device should be within 60.5 in. (612.5 mm) and not more than 61.0 in. (625 mm) of the bottom
of the density sensor).
FIG. 3 a Hydrometer and Digital Contact Thermometer (Typical)
which the surface of the liquid cuts the scale. Determine this point 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. 4.
8.9 To make a reading with nontransparent liquids, observe the point on the hydrometer scale to which the sample rises above its
main surface, placing the eye slightly above the plane surface of the liquid. This reading requires a correction. Determine this
correction (meniscus correction) for the particular hydrometer in use by observing the height above the main surface of the liquid
D287 − 22
where:
A = separation interval specified in 6.3 and Fig. 1,
B = separation interval specified in 6.3 and Fig. 1, and
C = relative vertical alignment between the density and temperature measuring devices (the bottom of the sensing portion of the
temperature measuring device should be within 60.5 in. (612.5 mm) and not more than 61.0 in. (625 mm) of the bottom
of the density sensor).
FIG. 3 b Thermohydrometer and Digital Contact Thermometer Placement (Typical) (continued)
FIG. 4 Hydrometer Scale Reading for Transparent Liquids
(Typical)
to which the sample rises on the 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. See Fig. 5.
8.9.1 Record the observed hydrometer scale readings to the nearest 0.1° AP
...