ASTM D287-22 Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (HydrometerMethod)

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)1

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* 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
a glass hydrometer in conjunction with a series of calculations 1.5 This standard does not purport to address all of the
of the API gravity of crude petroleum and petroleum products safety concerns, if any, associated with its use. It is the
normally handled as liquids and having a Reid vapor pressure responsibility of the user of this standard to establish appro-
(Test Method D323) of 14.696 psi (101.325 kPa) or less. priate safety, health, and environmental practices and deter-
Values are determined at existing temperatures and corrected to mine the applicability of regulatory limitations prior to use.
values at 60 °F (15.56 °C), or converted to values at 60 °F, by For specific warning statement, see 8.5.
means of Adjunct to D1250 Standard Guide for the Use of the
Joint API and ASTM Adjunct for Temperature and Pressure 1.6 This international standard was developed in accor-
Volume Correction Factors for Generalized Crude Oils, Re- dance with internationally recognized principles on standard-
fined Products, and Lubricating Oils (API MPMS Chapter ization established in the Decision on Principles for the
11.1). These tables are not applicable to nonhydrocarbons or Development of International Standards, Guides and Recom-
essentially pure hydrocarbons such as the aromatics. mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.

1.2 The initial values obtained are uncorrected hydrometer
readings and not density measurements. Values are measured 2. Referenced Documents
on a hydrometer at either the reference temperature or at
another convenient temperature, and readings are corrected for 2.1 ASTM Standards:2
the meniscus effect, the thermal glass expansion effect, alter- D323 Test Method for Vapor Pressure of Petroleum Products
nate calibration temperature effects and to the reference tem-
perature by means of the petroleum measurement tables; values (Reid Method)
obtained at other than the reference temperature being hydrom- D1250 Guide for the Use of the Joint API and ASTM
eter readings and not density measurements.
Adjunct for Temperature and Pressure Volume Correction
1.3 The initial hydrometer readings determined shall be Factors for Generalized Crude Oils, Refined Products, and
recorded before performing any calculations. Then the calcu- Lubricating Oils: API MPMS Chapter 11.1
lations required in Section 9 shall be performed and docu- D1298 Test Method for Density, Relative Density, or API
mented before using the final result in a subsequent calculation Gravity of Crude Petroleum and Liquid Petroleum Prod-
procedure (measurement ticket calculation, meter factor ucts by Hydrometer Method
calculation, or base prover volume determination). D6822 Test Method for Density, Relative Density, and API
Gravity of Crude Petroleum and Liquid Petroleum Prod-
1.4 The values stated in inch-pound units are to be regarded ucts by Thermohydrometer Method
as standard. The values given in parentheses are mathematical D7962 Practice for Determination of Minimum Immersion
Depth and Assessment of Temperature Sensor Measure-
1 This test method is under the jurisdiction of ASTM Committee D02 on ment Drift
Petroleum Products, Liquid Fuels, and Lubricants and the API Committee on D8164 Guide for Digital Contact Thermometers for Petro-
Petroleum Measurement, and is the direct responsibility of Subcommittee D02.02 leum Products, Liquid Fuels, and Lubricant Testing
/COMQ, the joint ASTM-API Committee on Hydrocarbon Measurement for E1 Specification for ASTM Liquid-in-Glass Thermometers
Custody Transfer (Joint ASTM-API). E77 Test Method for Inspection and Verification of Ther-
mometers
Current edition approved Dec. 1, 2022. Published February 2023. Originally
approved in 1928. Last previous edition approved in 2019 as D287–12b (2019). 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/D0287-22. contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on

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

1

D287 − 22

E100 Specification for ASTM Hydrometers 3.1.3 observed values, n—values observed at temperatures
E126 Test Method for Inspection, Calibration, and Verifica- other than the specified reference temperature; these values are
only hydrometer readings and not density, relative density, or
tion of ASTM Hydrometers API gravity at those other temperatures.
E344 Terminology Relating to Thermometry and Hydrom-
3.1.4 specific gravity, n—historical term, no longer used,
etry which has been replaced by relative density.
E2251 Specification for Liquid-in-Glass ASTM Thermom-
3.2 Acronyms:
eters with Low-Hazard Precision Liquids 3.2.1 PRT—platinum resistance temperature device
E2877 Guide for Digital Contact Thermometers 3.2.1.1 Discussion—While there may be other types of
2.2 API Standards:3 RTDs available, for Custody Transfer operations in conjunc-
MPMS Chapter 9.1 Test Method for Density, Relative tion with other standards organizations Platinum RTDs have
been standardized on for their accuracy and discrimination.
Density, or API Gravity of Crude Petroleum and Liquid
Petroleum Products by Hydrometer Method (ASTM Test 4. Summary of Test Method
Method D1298)
MPMSChapter 9.3 Test Method for Density, Relative 4.1 This test method is based on the principle that the
Density, and API Gravity of Crude Petroleum and Liquid gravity of a liquid varies directly with the depth of immersion
Petroleum Products by Thermohydrometer Method of a body floating in it. The floating body, which is graduated

(ASTM Test Method D6822) by API gravity units in this test method, is called an API
MPMS Chapter 11.1 Temperature and Pressure Volume Cor- hydrometer.
rection Factors for Generalized Crude Oils, Refined
Products, and Lubricating Oils (Adjunct to ASTM D1250) 4.2 The API gravity is read by observing the freely floating
ASTM hydrometer (calibrated for API gravity) and noting the
2.3 ASTM Adjuncts: graduation nearest to the apparent intersection of the horizontal
Adjunct to D1250 Standard Guide for the Use of the Joint plane surface of the liquid with the vertical scale of the
hydrometer, after temperature equilibrium has been reached.
API and ASTM Adjunct for Temperature and Pressure The temperature of the sample shall be read from a separate
Volume Correction Factors for Generalized Crude Oils, accurate ASTM thermometer placed in the sample, which
Refined Products, and Lubricating Oils: API MPMS Chap- meets either Specifications E1 or E2251 requirements or
ter 11.1)4 ASTM Digital Contact Thermometers, which meet Guide
E2877 requirements. The temperature determination device, be
3. Terminology it the bulb of a ASTM Thermometer (Specifications E1 or
E2251) or a sensor of a Digital Contact Thermometer (Guide
3.1 Definitions: E2877) shall be placed at the same elevation (within the stated
3.1.1 API gravity, n—a special function of relative density tolerances) as the hydrometer bulb.
60/60 °F (15.56/15.56 °C), represented by:
NOTE 1—Through various testings that Subcommittee D02.02 (Joint
°API 5 @141.5/~relative density 60/60 °F!# 2 131.5 (1) ASTM/API Subcommittee) measurement committee and others have
conducted, it has been determined that temperature stratifications do exist
No statement of reference temperature is required, since vertically from top to bottom of a hydrocarbon container as well as across
60 °F is included in the definition. the diameter of the container. Therefore, as temperature affects the
viscosity as well as the fluid density, the buoyancy of the hydrometer
3.1.2 hydrometer reading, n—the point on the hydrometer floating in the liquid is therefore affected, clarifying procedures have been
scale at which the surface of the liquid cuts the scale. added to the Procedure section.

3.1.2.1 Discussion—In practice for transparent fluids this 4.3 The observed hydrometer reading is corrected for the
can be readily determined by aligning the surface of the liquid meniscus effect, the thermal glass expansion effect on the
on both sides of the hydrometer and reading the Hydrometer hydrometer, alternate calibration temperature effects and re-

scale where these surface readings cut the scale (Hydrometer duced to the reference temperature by means of the petroleum
Reading – Observed). For nontransparent fluids the point at measurement tables. If necessary, the hydrometer cylinder and
which the liquid surface cuts the Hydrometer scale cannot be its contents are placed in a constant temperature bath to avoid
determined directly and requires a correction (Meniscus Cor- excessive temperature variation during the test.
rection). The value represented by the point (Meniscus Read-
ing) at which the liquid sample rises above the main surface of 5. Significance and Use
the liquid subtracted from the value represented by where the
main surface of the liquid cuts the Hydrometer scale is the 5.1 Accurate determination of the gravity of petroleum and
amount of the correction or Meniscus correction. This menis- its products is necessary for the conversion of measured
cus correction is documented and then subtracted from the volumes to volumes at the standard temperature of 60 °F
value represented by the Meniscus Reading to yield the (15.56 °C).
Hydrometer Reading corrected for the Meniscus (Hydrometer
Reading – Observed, Meniscus Corrected). 5.2 This procedure is most suitable for determining the API
gravity of low viscosity transparent liquids. This test method
3 Available from American Petroleum Institute (API), 200 Massachusetts Ave. can also be used for viscous liquids by allowing sufficient time
NW, Suite 1100, Washington, DC 20001, . for the hydrometer to reach temperature equilibrium, and for

4 Available from ASTM International Headquarters. Order Adjunct No.
ADJD1250-A1A2-E-PDF. Original adjunct produced in 1983.

2

D287 − 22

opaque liquids by employing a suitable meniscus correction. TABLE 2 Available Hydrometers Scaled, Degrees API (Low
Additionally for both transparent and opaque fluids the read- Hazardous Liquid Type)
ings shall be corrected for the thermal glass expansion effect
before correcting to the reference temperature. ASTM Type API Range, Each Unit Scale
Hydrometer deg
5.3 When used in connection with bulk oil measurements, Designation thermo 12 Division Error

volume correction errors are minimized by observing the thermo –1 to 11 12
hydrometer reading at a temperature as close to reference 52HL thermo 9 to 21 12 0.1 0.1
temperature as feasible. 52HL thermo 19 to 31 12 0.1 0.1
53HL thermo 29 to 41 12 0.1 0.1
5.4 Gravity is a factor governing the quality of crude oils. 54HL thermo 39 to 51 12 0.1 0.1
However, the gravity of a petroleum product is an uncertain 55HL thermo 49 to 61 12 0.1 0.1
indication of its quality. Correlated with other properties, 56HL thermo 59 to 71 12 0.1 0.1
gravity can be used to give approximate hydrocarbon compo- 57HL thermo 69 to 81 12 0.1 0.1
sition and heat of combustion. 58HL thermo 79 to 91 12 0.1 0.1
59HL 89 to 101 0.1 0.1
5.5 Gravity is an important quality indicator for automotive, 60HL 0.1 0.1
aviation and marine fuels, where it affects storage, handling
and combustion. liquid-in-glass thermometers. The stated repeatability and re-
producibility values are not applicable if alternate fluids are
6. Apparatus used in the liquid-in-glass thermometers.

6.1 Hydrometers, of glass, graduated in degrees API as 6.2.3 Digital Temperature Sensors—Digital Contact Ther-
listed in Table 1 and conforming to Specification E100 or as mometers of the PRT style shall meet the requirements of
listed in Table 2 and conforming to Specification E2251. Guide E2877 and may be used instead of glass thermometers
with the following exceptions:
6.1.1 The user should ascertain that the instruments used for
this method conform to the requirements set out above with 6.2.3.1 Thermocouples shall not be used.
respect to materials, dimensions, and scale errors. In cases 6.2.3.2 Thermistors shall not be used.
where the instrument is provided with a calibration certificate
traceable to a NMI (National Metrology Institute), the instru- 6.3 Hydrometer Cylinder, transparent material (see 6.3.2).
ment is classed as certified and the appropriate corrections for The inside diameter of the cylinder shall be at least 0.25 in.
the meniscus effect, the thermal glass expansion effect, and (6.35 mm) greater (see A in Fig. 1) than the outside diameter of
alternative calibration temperature effects shall be applied to the hydrometer body and the temperature measuring device
the observed readings prior to corrections. Instruments that plus the separation interval specified in Fig. 1 and the height
satisfy the requirements of this test method, but are not shall be such that the appropriate hydrometer floats in the test

provided with a recognized calibration certificate, are classed portion with at least 1 in. (25 mm) clearance between the
as uncertified. bottom of the hydrometer and the bottom of the cylinder, under
all densities and temperatures. Ensure that the hydrometer
6.2 Temperature Determination: cylinder is cleaned after each use to ensure that no contami-
6.2.1 Thermometers (Glass), having a range from −5 °F to nants remain.
+215 °F and conforming to the requirements for Thermometer
12F as prescribed in Specification E1. 6.3.1 When using separate hydrometer (or thermohydrom-
eter) and temperature measuring devices, care shall be exer-
NOTE 2—The ASTM Gravity Thermometer 12F has 0.5 °F subdivisions cised to ensure that neither interfere with each other and that
and allowable 60.25 °F scale error and is suitable for use in determining they are not affected by external temperature effects. The
temperature of bulk crude oil volumes, such as lease production tanks. minimum separation distances as shown in Fig. 1 shall be
Additional thermometers conform to Specification E1 standard or Speci- required. These separation distances are a function of the
fication E2251 standard having a narrower range than the 12F or S12F diameters of the measuring devices and the minimum distance
Thermometers may also be used, if they have similar performance from the sides of the measuring chamber to minimize external
characteristics. thermal effects.

6.2.2 Alternate liquid measuring device (Thermometer where:
S12F) conforming to the requirements prescribed in Specifi-
cation E2251 may be used, provided that the total uncertainty A = minimum separation interval specified in 6.3 between
of the calibrated system is no greater than when using the inside diameter of hydrometer cylinder and the sum
of the OD of the hydrometer body plus the OD of
TABLE 1 Available Hydrometers Scaled, Degrees API temperature measuring device plus the minimum sepa-
ration interval between devices of 0.25 in. (6.35 mm),
Designation Type API Range, deg Scale see Fig. 1, and
Series Total Each Unit Division Error
B = minimum separation interval between measuring de-
1H to 10H long plain −1 to 101 12 0.1 0.1 vices of 0.5 in. (12.7 mm).
21H to 40H short plain 0 to 101
41H to 45 H thermo 6 0.1 0.2 6.3.2 Hydrometer cylinders constructed of transparent ma-
51H to 60H thermo 15 to 51 terials shall be resistant to discoloration or attack by the

71H to 74H thermo −1 to 101 8 0.1 0.1 petroleum or petroleum product samples and shall not affect
−1 to 41 the material being tested. They shall not become opaque under
12 0.1 0.1 prolonged exposure to sunlight. If the opacity prevents the

12 0.1 0.1

3

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
being measured in an open container the light ends may
6.3.3 The minimum separation intervals specified is to evaporate while the devices are reaching temperature equilib-
prevent any capillary action between devices and to ensure that rium. This is a function of ambient temperature as well as fluid
external temperature effects are minimized on the values temperature and composition. Conversely, if the fluid is too
determined for density and temperature. viscous (thick) the hydrometer may not float freely, which is a
requirement for a buoyance device.
7. Temperature of Test (Limiting Conditions of Test)
8. Procedure
7.1 The gravity determined by the hydrometer method is
most accurate at or near the standard temperature of 60 °F 8.1 For referee testing, use the long plain form of hydrom-
(15.56 °C). Use this or any other temperature between 0 °F and eter (1H to 10H). For field testing, the thermohydrometer
195 °F (–18 °C and + 90 °C) for the test, so far as it is method in Test Method D6822 (API MPMS Chapter 9.3) is the
consistent with the type of sample and necessary limiting preferred method. However, if the user desires to use a
conditions shown in Table 3. liquid-in-glass thermometer with low-hazard glass precision
fluid as specified in Specification E2251 or a Digital Contact
7.2 The purpose of Table 3 is to clarify what actions are Thermometer as specified in Guide E2877 and 6.2.3, the user

required to ensure that the sample does not change its physical
makeup during the testing period or modifications to the

TABLE 3 Limiting Conditions and Testing Temperatures

Sample Type Gravity Limits Initial Boiling Point Other Limits Test Temperature
Highly volatile Limits
Moderately volatile
Moderately volatile and viscous lighter than 70° API below 250 °F (120 °C) Viscosity too high at Cool to 35 °F (2 °C) or lower in original closed
heavier than 70° API below 250 °F (120 °C) 65 °F (18 °C) container.
Nonvolatile heavier than 70° API above 250 °F (120 °C)
Mixtures of nonpetroleum products or heavier than 70° API Cool to 65 °F (18 °C) or lower in original closed
container.
essentially pure hydrocarbons
Heat to minimum temperature for sufficient
fluidity.

Any temperature between 0 °F and 195 °F
(−18 °C and 90 °C) as convenient.
60 °F ± 0.25 °F (15.56 °C ± 0.1 °C)

4

D287 − 22

can use Test Method D6822 (API MPMS Chapter 9.3) with a bubbles to come to the surface. This is particularly necessary in
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 Lower the temperature measuring device slowly into the
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
interface cuts the scale in the bottom two API gravity values or 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 The hydrometer is a buoyancy device, its performance
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
sample temperature be taken as close to this point of buoyancy.
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 lengths of the various instruments and then estimating their
produce a spark, potentially resulting in an explosion/fire. All companies relative positions.
generally have Engineering and Operating standards that refer to NFPA
(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 and the temperature of the sample is constant to within 0.2 °F
in classified areas. These company requirements should take precedence. (0.1 °C), read and record the hydrometer reading to the nearest
scale division. The correct reading is that point on the
8.2 Prior to lowering the selected hydrometer and/or tem- hydrometer scale at which the surface of the liquid cuts the
perature determination instrument into the sample perform the scale. Determine this point by placing the eye slightly below
Equipment Validation enumerated in Annex A1. the level of the liquid and slowly raising it until the surface,
first seen as a distorted ellipse, appears to become a straight
8.3 Verify that the selected density and/or temperature line cutting the hydrometer scale. See Fig. 4.
determination instruments conform to the requirements of
Annex A2. 8.9 To make a reading with nontransparent liquids, observe
the point on the hydrometer scale to which the sample rises
8.4 Adjust the temperature of the sample in accordance with above its main surface, placing the eye slightly above the plane
Table 3. For field testing, test temperatures other than those surface of the liquid. This reading requires a correction.
listed in Table 3 may be used. The hydrometer cylinder shall be Determine this correction (meniscus correction) for the par-

approximately the same temperature as the sample to be tested. ticular hydrometer in use by observing the height above the

8.5 Transfer the sample into the clean hydrometer cylinder where:
without splashing, so as to avoid the formation of air bubbles A = separation interval specified in 6.3 and Fig. 1,
and to reduce to a minimum the evaporation of the lower B = separation interval specified in 6.3 and Fig. 1, and
boiling constituents of the more volatile samples. (Warning— C = relative vertical alignment between the density and
Samples may be extremely flammable. Vapors may cause flash
fire.) For the more volatile samples, transfer to the hydrometer temperature measuring devices (the bottom of the sens-
cylinder by siphoning. (Do not start the siphon by mouth.) ing portion of the temperature measuring device should
Remove any air bubbles formed, after they have collected on be within 60.5 in. (612.5 mm) and not more than
the surface of the sample, by touching them with a piece of 61.0 in. (625 mm) of the bottom of the density sensor).
clean filter paper or other suitable means before inserting the
hydrometer. For field testing, the gravity measurement is FIG. 2 a Hydrometer and Liquid-in-Glass Thermometer Placement
directly made in the sampling core thief or hydrometer (Typical)
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 (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

5

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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 60.5 in. (612.5 mm) and not more than be within 60.5 in. (612.5 mm) and not more than
61.0 in. (625 mm) of the bottom of the density sensor). 61.0 in. (625 mm) of the bottom of the density sensor).

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 60.5 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)

main surface of the liquid to which the sample rises on the FIG. 4 Hydrometer Scale Reading for Transparent Liquids
hydrometer scale when the hydrometer in question is immersed (Typical)
in a transparent liquid having a surface tension similar to that
of a sample under test. See Fig. 5. 8.9.2 When gravity readings have been observed on opaque
liquids using the procedure given in 8.9, subtract the meniscus
8.9.1 Record the observed hydrometer scale readings to the correction from the hydrometer reading observed and record
nearest 0.1° API for transparent liquids. the meniscus corrected hydrometer scale reading to the nearest
0.1° API.

6

D287 − 22

9. Calculation

9.1 Apply any relevant thermometer corrections to the
temperature reading observed in 8.10 and record the average of
those two temperatures to the nearest 1 °F.

FIG. 5 Hydrometer Scale Reading for Opaque Fluids (Typical) 9.2 Application of the glass thermal expansion correction
depends upon what edition of Adjunct to D1250 Standard
NOTE 4—The meniscus correction for a particular hydrometer in use is Guide for the Use of the Joint API and ASTM Adjunct for
determined by observing the maximum height above the principal surface Temperature and Pressure Volume Correction Factors for
of the liquid to which liquid rises on the hydrometer scale when the Generalized Crude Oils, Refined Products, and Lubricating
hydrometer in question is immersed in a transparent liquid having a Oils (API MPMS Chapter 11.1) will be used to calculate the
surface tension similar to that of the sample under test. base density.

8.10 Observe the temperature of the sample immediately 9.2.1 The 1980 version of the Adjunct to D1250 Guide for
before and after the observation of the gravity, the liquid in the Petroleum Measurement Tables (API MPMS Chapter 11.1) has
cylinder being thoroughly but cautiously stirred with the the hydrometer glass thermal expansion correction included.

thermometer (Note 5), and the whole of the temperature thread Input into the Adjunct to D1250 Standard Guide for the Use of
being immersed. Should these temperature readings differ by the Joint API and ASTM Adjunct for Temperature and Pressure
more than 1 °F (0.5 °C), repeat the temperature and gravity Volume Correction Factors for Generalized Crude Oils, Re-
observations when the temperature of the sample has become fined Products, and Lubricating Oils (API MPMS Chapter
more stable. Record the mean of the thermometer reading 11.1) software (see API MPMS Ch. 11.1.1.3 paragraphs 5 and
before and after the final hydrometer reading, to the nearest 6) requires the Hydrometer Reading – Observed or Hydrometer
1 °F, as the temperature of the test. Reading – Observed, Meniscus Corrected in API units from
8.9.1 or 8.9.2, observed temperature of the sample, and the
8.11 When using a separate temperature measuring device built-in hydrometer glass thermal correction switch set to “on”
such as a liquid-in-glass thermometer; a liquid-in-glass ther- (0) or “off” (1). It will return API @ 60 °F.
mometer with low-hazard precision liquid or a digital contact
thermometer they shall be placed in the sample measurement 9.2.2 The 2004 version of the Adjunct to D1250 Guide for
cylinder as shown in Fig. 2a and Fig. 2b as well as Fig. 3a and Petroleum Measurement Tables (API MPMS Chapter 11.1)
Fig. 3b. does not include the hydrometer glass thermal expansion
correction, so that correction must be made before entering the
NOTE 5—When only thermohydrometers are used, stir the sample by Adjunct to D1250 Standard Guide for the Use of the Joint API
carefully moving the thermohydrometer in a side to side motion, without and ASTM Adjunct for Temperature and Pressure Volume
immersing the thermohydrometer any lower into sample. It is satisfactory Correction Factors for Generalized Crude Oils, Refined
in this case to read the thermometer scale of the thermohydrometer after Products, and Lubricating Oils (API MPMS Chapter 11.1)
the hydrometer reading has been observed. Read the thermometer to the software. Depending on the specific end use of the calculation
nearest 1 °F (0.5 °C). If using a separate device to measure temperature, results, the final value may be left rounded or unrounded. See
use the temperature measuring device to stir the sample and read 9.3.
according to 8.10.
9.3 The following steps are required to implement 9.2.2:

Step 1. Convert the meniscus corrected hydrometer scale
reading to density in kg/m3 using Eq 2.

Hydrometer Scale Conversion to Density
Reading Units

For API gravity:

density ~kg / m3! 5 ~141.5*999.016!/~131.51API! (2)

Leave the result unrounded.
Step 2. Calculate the hydrometer thermal glass expansion
correction factor (HYC) using the appropriate equation below
(t is observed temperature).

Correction for a Base Temperature (Tb) of 60 °F:

HYC 5 1.0 2 @0.00001278 ~τ 2 60!# 2 @0.0000000062 ~τ 2 60!2#

(3)

Leave the result unrounded.

Step 3. Multiply the hydrometer reading in kg/m3 from Step
1 by HYC from Step 2 to obtain the glass expansion corrected
hydrometer reading.

kg/m3HYC 5 kg/m3*HYC (4)

7

D287 − 22

Step 4a. Convert the hydrometer reading in density (kg/ 10.2 Report the final value as API gravity, at the reference
m HYC 3 ) from Step 3 to a R.D. (relative density) hydrometer temperature (nearest whole degree °F), to the nearest 0.1° API.

reading.
10.3 The reporting values have no precision or bias deter-
NOTE 6—The current C source code, compiled dll and Excel Add-in has mination. It is up to the user to determine whether this test
an omission and cannot use a kg/m3 call with degree F. method provides results of sufficient accuracy for the intended
purpose.
R.D. 5 kg/m HYC 3 /999.016 (5)
10.4 If the hydrometer readings are being used as an input to
Step 4b. Input R.D. and degree F into section 11.1.6.2 of the a calculation process intended to return a volume correction
Adjunct to D1250-04 Guide for Petroleum Measurement factor for use in ticket or meter proving calculations, stop the
Tables (API MPMS Chapter 11.1-2004) which returns R.D. @ calculation process identified above at Step 3 (if the density
60 °F. value is desired at flowing conditions) or Step 4 (if the density
value is desired at base density conditions) and input the results
NOTE 7—Pressure will have to be atmospheric gauge, or 0 psig as the into the calculation process.
Adjunct to D1250 Standard Guide for the Use of the Joint API and ASTM
Adjunct for Temperature and Pressure Volume Correction Factors for 10.5 Certified hydrometers traceable to a NMI (National
Generalized Crude Oils, Refined Products, and Lubricating Oils (API Metrology Institute), report the output density as ‘Density in
MPMS Chapter 11.1) values are only valid at atmospheric pressure. Vacuo’.

Step 4c. Convert the calculated R.D. value @ 60 °F to a 11. Precision and Bias
calculated API Gravity @ 60 °F using Eq 6.
11.1 The precision of this test method as obtained by
API Gravity 5 ~141.5/R.D.! 2 131.5 (6) statistical examination of interlaboratory test results is as
follows:
9.4 Future versions of the Adjunct to D1250 Standard Guide
for the Use of the Joint API and ASTM Adjunct for Tempera- 11.1.1 Repeatability—The difference between successive
ture and Pressure Volume Correction Factors for Generalized test results obtained by the same operator with the same
Crude Oils, Refined Products, and Lubricating Oils (API apparatus under constant operating conditions on identical test
MPMS Chapter 11.1) code will be corrected so that it can material, would in the long run, in the normal and correct
accept any combination of input units and return any combi- operation of the test method, exceed 0.2° API only in one case
nation of output units. When available, the Adjunct to D1250 in twenty.

Standard Guide for the Use of the Joint API and ASTM
Adjunct for Temperature and Pressure Volume Correction 11.1.2 Reproducibility—The difference between two single
Factors for Generalized Crude Oils, Refined Products, and and independent results, obtained by different operators, work-
Lubricating Oils (API MPMS Chapter 11.1) code can be ing in different laboratories on identical test material, would in
accessed directly from Step 3 and return API Gravity @ 60 °F, the long run, in the normal and correct operation of the test
R.D. @ 60 °F, and kg/m3 at any selected base temperature. method, exceed 0.5° API only in one case in twenty.

Sample: Example 1 (Eq 2) NOTE 8—The precision for this test method was not obtained in
Observed Temperature: Crude Oil (Eq 3) accordance with RR:D02-1007.
Observed Hydrometer Reading: 77 °F (Eq 4)
Observed Pressure: 33.2 API Gravity (Eq 5) NOTE 9—The precision for this test method only applies to measure-
Base Temperature: 0 psig ments made with a liquid-in-glass thermometer.
Step 1: 60 °F (Eq 6)
Step 2: 858.292434730... (Eq 6) NOTE 10—This precision statement applies only to measurements made
Step 3: 0.999780948... at temperatures differing from 60 °F (15.56 °C) by less than 18 °F (10 °C).
Step 4a: 858.104424227...
Step 4b: 0.858949631... 11.2 Bias—Bias for this test method has not been deter-
Step 4c.1: 0.865678279... mined.
Step 4c.2: 31.955643312... unrounded
32.0 °API rounded 12. Keywords

10. Report 12.1 API gravity; crude petroleum; digital contact thermom-
eter; hydrometer; thermohydrometer; thermometer
10.1 Report the corrected hydrometer reading as degrees
API (°API) or as API Gravity.

8

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ANNEXES

(Mandatory Information)
A1. PERFORMANCE CHECK EQUIPMENT VALIDATION AS TO FIT FOR USE AT TIME OF TEST

A1.1 Immediately prior to determining test values the den- (e) The paper scale within the thermohydrometer stem
sity and temperature measuring instruments being used for the shall contain an information label that documents the ASTM
test shall be verified that they are “Fit for Use at Time of Test” hydrometer designation, units of density, and a serial number.
as delineated by the following procedures. The specific proce-
dures the user shall use will be dependent on the specific test (f) The thermohydrometer shall contain a scale slippage
instruments being used for that test. indicator and shall be positioned at the proper position relative
to the scale. This is typically the whole unit value graduation
A1.2 These verifications shall be performed on each test mark for the upper range the instrument is designed for.
instrument immediately prior to each test being performed.
(3) If any of the items in A1.4.1.2(2) do not meet the
A1.3 Each test instrument shall be in a clean condition prior defined criteria, the instrument shall no longer be used and
to the equipment validation so that each component of the Test shall be replaced.
Instrument can be validated.
A1.4.2 Temperature Instruments:
A1.4 Equipment Validation Procedures
A1.4.2.1 Liquid-in-Glass Type Instruments:
A1.4.1 Density Instruments: (1) Ensure that the liquid-in-glass temperature instrument

A1.4.1.1 Hydrometers: scale range selected for the analytical test covers the expected
(1) Ensure that the hydrometer scale range selected for the temperature reading.

analytical test covers the expected density reading. (2) Inspect the liquid-in-glass temperature instrument to
(2) Inspect the hydrometer and ensure that it meets the ensure it meets the following requirements:

following requirements: (a) The temperature instrument glass shall contain no
(a) The hydrometer glass shall contain no cracks, fissures, cracks, fissures, deep scratches, rough areas, or other obvious

damage.
deep scratches, rough areas, or other obvious damage.
(b) The ballast at the bottom of the hydrometer shall (b) The temperature glass instrument shall contain per-
manent markings that document the ASTM temperature instru-
contain no loose components. ment designation and the instrument’s serial number.
(c) The ballast at the bottom of the hydrometer shall be
(c) The liquid column is continuous from the fluid reser-
firmly affixed to glass envelope of the test instrument. voir to the indicated temperature.
(d) The paper scale within the hydrometer stem shall be
(d) Ensure that the temperature scale and its graduation
straight and without twist. markings are intact on the instrument.
(e) The paper scale within the hydrometer stem shall
(3) If any of the items in A1.4.2.1(2) do not meet the
contain an information label that documents the ASTM hy- defined criteria, the instrument shall no longer be used and
drometer designation, units of density, and a serial number. shall be replaced, with the exception of item A1.4.2.1(2)(c).

(f) The hydrometer shall contain a scale slippage indica- (4) If the liquid column is non-continuous, the temperature
tor and shall be positioned at the proper position relative to the instrument shall be placed in a liquid bath and the temperature
scale. This is typically the whole unit value graduation mark of the bath increased until it causes the liquid column to expand
for the upper range the instrument is designed for. into the upper expansion area. After this occurs, remove the
temperature instrument from the liquid bath and cool the
(3) If any of the items in A1.4.1.1(2) do not meet the instrument down to ambient temperature. Reverify that the
defined criteria, the instrument shall no longer be used and liquid column is now continuous.
shall be replaced.
(5) If the liquid column is now continuous verify that the
A1.4.1.2 Thermohydrometers: instrument still indicates the correct temperature in accordance
(1) Ensure that the thermohydrometer scale range selected wiAnnex A2th . If the column is non-continuous the instrument
shall not be used, perform the procedure in A1.4.2.1(4) again
for the analytical test covers the expected density reading. to try to re-unite the column and then re-verify per A1.4.2.1(5).
(2) Inspect the thermohydrometer and ensure that it meets

A1.4.2.2 Digital Contact Thermometer:
the following requirements: (1) Inspect the Digital Contact Thermometer to ensure it
(a) The thermohydrometer glass shall contain no cracks,
meets the following requirements:
fissures, deep scratches, rough areas, or other obvious damage. (a) The temperature instrument sensor shall be a PRT
(b) The ballast at the bottom of the thermohydrometer
style meeting the requirements of Guide E2877.
shall contain no loose components (b) The temperature instrument shall meet the require-
(c) The ballast at the bottom of the thermohydrometer
ments of 6.2.3 of this test method.
shall be firmly affixed to glass envelope of the test instrument. (c) Inspect the temperature instrument and ensure that all
(d) The paper scale within the thermohydrometer stem
components meet all mechanical and electrical requirements.
shall be straight and without twist.

9

D287 − 22

(d) Perform an operational performance check in accor- (d) Verify that the display(s) are legible.
dance with the manufacturer’s requirements: (e) Verify that when turned on the temperature reading is
indicating a change and the change is indicating in the correct
(1) Note—For digital contact thermometers being used direction:
multiple times in a short period of time, such as determining (1) The comparison device for the operational perfor-
the temperature reading of multiple samples in a laboratory mance check could be a liquid-in-glass thermometer; a pocket
over a very short interval (an hour or less) this step may be dial thermometer; an ambient air reading from a local source or
skipped once it is performed once. other suitable source.
(2) This check is intended to verify that the instrument is
(2) However, if an interval of 60 min or more is experi- working properly and not that it is measuring temperature
enced between analytical tests then this performance check is accurately.

required prior to any further testing. (e) Verify that the temperature instrument shall have been
calibrated in accordance with Annex A3.
(3) Operational Performance Check: (2) The digital contact thermometer shall be calibrated in
(a) Verify that the device is in good working order. accordance with Annex A3 if any of the requirements in
(b) Verify that there is no mechanical damage to the A1.4.2.2 are not met prior to any use.
instrument case body, temperature sensor, or the connecting
wiring.
(c) Verify that the battery voltage is in the manufacturer’s
recommended operating range.

A2. PERFORMANCE VERIFICATION OF DENSITY AND TEMPERATURE MEASURING INSTRUMENTS

A2.1 All density and temperature measuring instruments A2.3.1.1 Test Method E126 shall be used as the reference
shall be verified on a periodic schedule, which depends on the standard (for the calibration of the Primary Verification De-
frequency of use. vice) for the verification of density instruments.

A2.2 Verification Process—Verification is a process A2.3.1.2 Density instruments shall be verified at two test
whereby the working instrument is compared to another similar points (approximately lower half and upper half on the
device with a higher accuracy (lower uncertainty). This device hydrometer scale) on the density scale. Test points shall be
is typically referred to as a “Primary Verification Device or chosen to bracket the range of use.
Master Device”.
A2.3.1.3 For routine verification work, one may use a
A2.2.1 The Primary Verification Device shall have been standard hydrometer as specified in Section 6 of Test Method
calibrated using standards traceable to a NMI (National Me- E126 and a reference fluid with similar surface tension and
trology Institute) and calibrated in accordance with the appro- density of the liquids the hydrometer is intended to be used, see
priate sections of Test Method E126. Table 2 in Test Method E126 for guidance.

NOTE A2.1—In the United States, the NMI is the National Institute of A2.3.2 Temperature Instruments:
Standards and Technology (NIST) and in Canada it is Measurement A2.3.2.1 Test Method E77 shall be used as the reference
Canada. Many companies which supply hydrometers, thermometers to the standard for the verification of temperature instruments.

industry have the capability to provide equipment with NMI traceability.
(1) Secondary standard thermometers as specified in 5.5 of
A2.2.2 The calibration of the Primary Verification Device Test Method E77 are more suitable for routine work.
shall be performed on an annual basis.
(2) Alternatively the user may also use a primary standard
A2.2.3 Verifications shall be performed using a liquid bath thermometer as specified in 5.4 of Test Method E77.
both for density and temperature instruments.
A2.3.2.2 Temperature instruments shall be verified at two or
A2.2.3.1 A Primary Verification Device used with a test/dry more test points on the temperature scale. Test points shall be
block may be substituted for a liquid bath for temperature chosen to bracket the range of use.
instruments, provided that it facilitates the ability to determine
the temperature readings of both the Primary Verification A2.4 Frequency of Verification:
Device and the working instrument without moving the instru-
ments within the test block. A2.4.1 Density Instruments:
A2.4.1.1 Hydrometers and thermohydrometers should be
A2.3 Verification Test Points: verified monthly (at a minimum they shall be verified quar-
terly) for frequently used instruments (used four or more times
A2.3.1 Density Instruments: in a seven day period).
A2.4.1.2 Hydrometers and thermohydrometers should be
verified bi-monthly (at a minimum they shall be verified every

10

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four months) for infrequently used instruments (used three A2.4.2 Temperature Instruments:
times or less in a seven day period).
A2.4.2.1 Temperature instruments shall be verified monthly
A2.4.1.3 The preferred method is a comparison in a liquid (at a minimum; weekly verifications would be optimal) for
bath, using a fluid with a similar surface tension and density for frequently used instruments (used four or more times in a seven

which the hydrometer is intended to be used. See Test Method day period).
E126 for guidance.
A2.4.2.2 Temperature instruments shall be verified bi-
A2.4.1.4 The verification test is a comparison of the stan- monthly (at a minimum: every four months) for infrequently
dard hydrometer reading (which has been calibrated in accor- used instruments (used three times or less in a seven day
dance with Test Method E126 guidelines) to the reading of the period).
working hydrometer within one (1) scale division (0.1°API).

A3. CERTIFICATION CALIBRATION OF DENSITY AND TEMPERATURE MEASURING INSTRUMENTS

A3.1 All density and temperature measuring instruments A3.2.1.1 Test Method E126 shall be used as the reference
shall be calibrated on a periodic schedule, which depends on standard guide for the calibration of density instruments.
the frequency of use.
A3.2.1.2 Density instruments shall be calibrated at three test
A3.1.1 Calibration Process—Calibration is a process points (approximately low, medium, and high on the hydrom-
whereby the primary verification device (may also be called eter scale) on the density scale. Test points shall be chosen to
master device) is subjected to a set of operations that establish, bracket the range of use.
under specified conditions, the relationship between the values
indicated by a measuring device and the corresponding known A3.2.2 Temperature Instruments:
values indicated when using a suitable measuring standard, A3.2.2.1 Test Method E77 shall be used as the reference
traceable to a NMI, which is then applied to adjust the values standard guide for the calibration of temperature liquid-in-glass
determined by the measuring device. instruments.
A3.2.2.2 Guide E2877 and Test Method E77 shall be used
A3.1.2 Certified—The process and documentation whereby as the reference standard guide for the calibration of Tempera-
a device or material is accepted as a reference standard, ture Digital Contact Thermometers.
accurate within prescribed limits, and traceable to a NMI. A3.2.2.3 Temperature instruments shall be verified at two or
more test points on the temperature scale. Test points shall be
A3.1.3 The calibration shall be performed on an annual chosen to bracket the range of use.
basis:
A3.3 Handling, Shipping, and Documentation of Density

A3.1.3.1 If the calibrated instrument is not placed into and Temperature Measuring Instruments:
service immediately after the user receives it back from the
calibration laboratory, the calibration remains in effect for one A3.3.1 All density and temperature measuring instruments
year from the original calibration date on the calibration shall be securely packaged whether being shipped from the
certificate. calibration laboratory or to it to prevent any damage from
occurring during the shipping process.
A3.1.3.2 Once the calibrated instrument is placed into
service, providing it is done within the one year grace period A3.3.2 All calibrated instruments shall be supplied with a
after original calibration or any subsequent re-calibrations, the calibration certificate that provides at a minimum the following
annual calibration time period begins. information:

A3.1.3.3 Once an instrument exceeds the one year calibra- A3.3.2.1 ASTM number,
tion grace period, without being placed in service, the calibra- A3.3.2.2 Range of instrument over which it was calibrated,
tion certificate is void and the instrument shall be re-calibrated. A3.3.2.3 Serial number,
A3.3.2.4 Name of manufacturer,
A3.1.3.4 These instruments should be properly stored in a A3.3.2.5 Name of calibration laboratory.
climate-controlled space and not exposed to extreme weather. A3.3.2.6 Calibration certified date, and
Devices should also be kept in a controlled and secure A3.3.2.7 Calibration results/documentation in accordance
environment to maintain the integrity and accuracy of the with the applicable calibration protocol.
device.
NOTE A3.1—Column separation may occur during the shipping process
Warning—Instruments which will be calibrated by defini- which does not affect the calibration or certification of the instrument. If
tion have a shelf life and the calibration and certification of the user experiences this then follow the procedure in Annex A1,
these instruments is typically preformed when ordered. Ad- A1.4.1.1.1 of Test Method D287, to rejoin column, this does not affect the
equate lead time should be allowed when requesting a cali- overall certification.
brated or certified instrument.

A3.2 Calibration Test Points

A3.2.1 Density Instruments:

11

D287 − 22

SUMMARY OF CHANGES

Subcommittee D02.02 has identified the location of selected changes to this standard since the last issue
(D287 – 12b (2019)) that may impact the use of this standard. (Approved Dec. 1, 2022.)

(1) Revised title. (6) Added definitions for observed values and PRT to Section
(2) Revised subsections 1.1, 1.2, 4.2, 4.3, 6.1, 6.1.1, 6.2 (and 3.
subsections), 6.3, 6.3.2, 8.1, 8.5, 8.8, 8.9, 8.10, 9.2.1, 9.2.2, (7) Added Note 1, Note 2, Note 3, Note 4, and Note 9, and
10.2, and 10.5. renumbered subsequent.
(3) Added subsections 6.2.3, 6.3.1, 6.3.3, 7.2, 8.1.1, 8.1.2, 8.2, (8) Deleted former Note 3 and renumbered subsequent.
8.3, 8.7, 8.7.1, 8.9.1, 8.9.2, and 8.11. (9) Revised Note 5.
(4) Deleted former subsections 9.2, 9.3, and 9.4 and renum- (10) Revised Table 1.
bered subsequent. (11) Added Table 2.
(5) Added Practice D7962, Guide D8164, Test Method E77, (12) Added Figs. 1-5.
Test Method E126, Terminology E344, Specification E2251, (13) Added Annex A1, Annex A2, and Annex A3.
and Guide E2877 to Section 2.

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