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Definitions
Density is defined as the mass of a substance per unit volume at a specific temperature and atmospheric pressure or equilibrium vapor pressure This measurement is often referred to as "true density" or "density in vacuo." When reporting density, it is essential to specify the units of mass and volume, as well as the temperature at which the measurement was taken, such as kilograms per cubic meter or grams per millimeter at a given temperature in Fahrenheit or Celsius In the oil industry, if the temperature is not specified, a standard temperature of 60 °F or 15 °C is typically assumed.
API gravity is a key term in the petroleum industry that indicates the relative density of petroleum liquids The connection between API gravity and relative density, previously known as specific gravity, is illustrated in Equation (1) As a dimensionless number, API gravity is derived from absolute density and is measured "in vacuo."
Apparent weight of a substance occupying unit volume.
An expression of density in SI (metric) units, also equal to grams per millilitre.
An expression of density in SI (metric) units, also equal to grams per cubic centimetre.
An expression of density in SI (metric) units, numerically equivalent to grams per litre This is the common unit of density currently used in the oil industry.
Mass is an absolute measure of the quantity of matter in an object, defined relative to a standard mass It remains constant regardless of location, unlike weight, which changes with altitude The standard unit of mass in the metric system is the kilogram (kg).
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 3
The density ratio of a substance at a given temperature compared to a reference substance at a specified reference temperature is crucial for accurate reporting It is important to clearly indicate the temperatures used, such as 20 °C/4 °C This measurement was previously referred to as specific gravity.
The density ratio of a liquid at a specific temperature \( t \) and pressure \( p \) compared to its density at standard conditions (60 °F and 14.696 psia or 15 °C and 101.325 kPa) is crucial for accurate measurements To convert a liquid's volume at temperature \( t \) to its volume at reference temperature, one must multiply the volume at temperature \( t \) by the Volume Correction Factor (VCF) for that temperature For detailed guidelines, consult API MPMS Chapter 11.1 on temperature.
Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils.
Gravitational force acts on an object, and its strength decreases with distance from the Earth's center, making weight relative to mean sea level It's important to distinguish weight from mass, as mass remains constant regardless of gravity and correlates directly with the quantity of atoms or molecules In the United States, the standard unit of weight is the pound (lb).
When weighing a liquid in air using standardized commercial weights, the apparent weight of the liquid is influenced by buoyancy This buoyancy force is determined by the difference between the mass of air displaced by the liquid and the mass of air displaced by the weights For further details, refer to Section B.4.
The weight of a mass in a vacuum, with no air buoyancy effect.
Abbreviations
°API degrees API gravity bbl barrel (42 U.S gallons) cm 3 cubic centimetre
D a 15 density in air (apparent density) at 15 °C
D a 60 density in air (apparent density) at 60 °F
D 60 60 relative density at 60 °F g gram gal U.S gallon gal/lb U.S gallons per pound g/cm 3 grams per cubic centimetre g/mL grams per millilitre
LT long ton m 3 cubic metre
MT metric ton (1000 kilograms, 1 million grams)
ST short ton ρ 60 density of water at 60 °F
VCF t volume correction factor at temperature t (°F in this standard) and one atmosphere pressure unless otherwise specified.
Derivations of the equations below are presented in Annex B API MPMS Ch 12 governs all rounding Absent specific direction from API MPMS Ch 12, results should be rounded as indicated below.
Relative Density (60/60 °F) Equivalent to API Gravity at 60 °F
The following equation (see Section B.1) expresses the relationship between API gravity at 60 °F and relative density at 60 °F (D 60 60 ):
Solve Equation (1) with values of °API at 60 °F and round the result to five places past the decimal for further use.
Absolute Density at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.2) defines the relationship between API gravity at 60 °F and density D 60 in kilograms per cubic metre at 60 °F:
(2) Solve Equation (2) with values of °API at 60 °F and round the result to two places past the decimal for further use
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 5
What is the absolute density at 60 °F for gasoline equivalent to a 60 °F API gravity of 58.61?
Absolute Density at 15 °C Equivalent to API Gravity at 60 °F
The following equation (see Section B.3) expresses the relationship between API gravity at 60 °F and density at 15 °C in kilograms per cubic meter:
To solve Equation (3) using °API values at 60 °F, round the result to two decimal places for subsequent applications This calculation is specific to the product due to the inclusion of a VCF59 For crude oils, generalized products, and lubricants, refer to API MPMS Ch 11.1-2004, while other products may require different tables.
What is the absolute density at 15 °C for gasoline equivalent to a 60 °F API gravity of 58.61? Using Table 6B from API
Pounds per U.S Gallon at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.4) expresses the relationship between API gravity at 60 °F and the corresponding density in pounds per U.S gallon in vacuo:
The following equation (see Section B.4) expresses the relationship between API gravity at 60 °F and the corresponding density in pounds per U.S gallon in air:
Solve Equation (4) or Equation (5) with values of °API at 60 °F and round the result to nine places past the decimal for further use.
A tank car of gasoline having a 60 °F API gravity of 58.61 is determined to contain 24,386 gal at 60 °F What is the in vacuo weight in pounds of the cargo?
Use Equation (4) to calculate the in vacuo intraconversion factor:
D 60 in lb/gal = × 0.999016 × 8.345404452 = 6.205421857 lb/gal
The 24,386 gal of gasoline is then equivalent to (rounding as indicated in Table 1):
Weight in vacuo = 6.205421857 lb/gal × 24,386 gal = 151,325 lb
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in pounds of the cargo?
Use Equation (4) to calculate the in vacuo intraconversion factor:
D 60 in lb/gal = × 0.999016 × 8.345404452 = 6.205421857 lb/gal
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Weight in vacuo= 6.205421857 lb/gal × 361,901 bbl × 42 gal/bbl + 94,321,432 lb
U.S Gallons per Pound at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.5) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per pound in vacuo:
The following equation (see Section B.5) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per pound in air:
Solve Equation (6) or Equation (7) with values of °API at 60 °F and round the result to ten places past the decimal for further use.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 94,321,432 lb What is the 60 °F volume in U.S gallons?
Use Equation (6) to calculate the in vacuo intraconversion factor:
The 94,321,432 lb of gasoline is then equivalent to (rounding as indicated in Table 1):
60 °F gal = 0.1611493986 gal/lb × 94,321,432 lb = 15,199,842 gal
= S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 7
Short Tons per 1000 U.S Gallon at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.6) expresses the relationship between API gravity at 60 °F and the corresponding short tons per 1000 gal in vacuo:
The following equation (see Section B.6) expresses the relationship between API gravity at 60 °F and the corresponding short tons per 1000 gal in air:
Solve Equation (8) or Equation (9) with values of °API at 60 °F and round the result to nine places past the decimal. EXAMPLE
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in short tons?
Use Equation (8) to calculate the in vacuo intraconversion factor:
D 60 in ST/1000 gal = × 0.999016 × 4.172702226 = 3.102710928 ST/1000 gal
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Weight in vacuo = 3.102710928 ST/1000 gal × 361,901 bbl × 42 gal/bbl = 47,160.7159 ST
U.S Gallons per Short Ton at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.7) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per short ton in vacuo:
The following equation (see Section B.7) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per short ton in air:
Solve Equation (10) or Equation (11) with values of °API at 60 °F and round the result to seven places past the decimal for further use.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 47,160.7159 ST What is the
Use Equation (10) to calculate the in vacuo intraconversion factor:
The 47,160.7159 ST of gasoline is then equivalent to (rounding as indicated in Table 1):
Short Tons per Barrel at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.8) expresses the relationship between API gravity at 60 °F and the corresponding short tons per barrel in vacuo:
The following equation (see Section B.8) expresses the relationship between API gravity at 60 °F and the corresponding short tons per barrel in air:
Solve Equation (12) or Equation (13) with values of °API at 60 °F and round the result to ten places past the decimal for further use.
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in short tons?
Use Equation (12) to calculate the in vacuo intraconversion factor:
The 361,900.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Barrels per Short Ton at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.9) expresses the relationship between API gravity at 60 °F and the corresponding barrels per short ton in vacuo:
= 60 °F gal = 322.2987971 gal/ST 47,160.7159 ST× = 15,199,842 gal
= Weight in vacuo = 0.1303138590 ST/bbl 361 901 bbl× , = 47 160.7159 ST,
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 9
The following equation (see Section B.9) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per short ton in air:
Solve Equation (14) or (15) with values of °API at 60 °F and round the result to nine places past the decimal for further use.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 47,160.7159 ST What is the 60 °F volume in barrels?
Use Equation (14) to calculate the in vacuo intraconversion factor:
The 47,160.7159 ST of gasoline is then equivalent to (rounding as indicated in Table 1):
Long Tons per 1000 U.S Gallons at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.10) expresses the relationship between API gravity at 60 °F and the corresponding long tons per 1000 gal in vacuo:
The following equation (see Section B.10) expresses the relationship between API gravity at 60 °F and the corresponding long tons per 1000 gal in air:
Solve Equation (16) or (17) with values of API at 60 °F and round the result to nine places past the decimal for further use.
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in long tons?
Use Equation (16) to calculate the in vacuo intraconversion factor:
= 60 °F bbl = 7.673780883 bbl/ST 47,160.7159 ST× = 361,901.00 bbl
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Weight in vacuo = 2.770277615 LT/1000 gal × 361,901 bbl × 42 gal/bbl = 42,107.7820 LT
U.S Gallons per Long Ton at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.11) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per long ton in vacuo:
The following equation (see Section B.11) expresses the relationship between API gravity at 60 °F and the corresponding U.S gallons per long ton in air:
Solve Equation (18) or (19) with values of °API at 60 °F and round the result to seven places past the decimal for further use.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 42,107.7820 LT What is the 60 °F volume in U.S gallons?
Use Equation (18) to calculate the in vacuo intraconversion factor:
The 42,107.7820 LT of gasoline is then equivalent to (rounding as indicated in Table 1):
60 °F gal = 360.9746527 gal/LT × 42,107.7820 LT = 151,199,842 gal
Long Tons per Barrel at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.12) expresses the relationship between API gravity at 60 °F and the corresponding long tons per barrel in vacuo:
The following equation (see Section B.12) expresses the relationship between API gravity at 60 °F and the corresponding long tons per barrel in air:
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 11
Solve Equation (20) or Equation (21) with values of °API at 60 °F and round the result to ten places past the decimal for further use.
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in long tons?
Use Equation (20) to calculate the in vacuo intraconversion factor:
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Barrels per Long Ton at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.13) expresses the relationship between API gravity at 60 °F and the corresponding barrels per long ton in vacuo:
The following equation (see Section B.13) expresses the relationship between API gravity at 60 °F and the corresponding barrels per long ton in air:
Solve Equation (22) or Equation (23) with values of °API at 60 °F and round the result to nine places past the decimal for further use.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 42,107.7821 LT What is the 60 °F volume in barrels?
Use Equation (22) to calculate the in vacuo intraconversion factor:
The 42,107.7821 LT of gasoline is then equivalent to (rounding as indicated in Table 1):
= Weight in vacuo = 0.1163516598 LT/bbl 361,901 bbl× = 42,107.7820 LT
= 60 °F bbl = 8.594634588 bbl/LT 42,107.7821 LT× = 361,901.00 bbl
Metric Tons per 1000 U.S Gallons at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.14) expresses the relationship between API gravity at 60 °F and the corresponding metric tons per 1000 gal in vacuo:
The following equation (see Section B.14) expresses the relationship between API gravity at 60 °F and the corresponding metric tons per 1000 gal in air:
Solve Equation (24) or Equation (25) with values of °API at 60 °F and round the result to nine places past the decimal for further use.
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in metric tons?
Use Equation (24) to calculate the in vacuo intraconversion factor:
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Metric Tons per Barrel at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.15) expresses the relationship between API gravity at 60 °F and the corresponding metric tons per barrel in vacuo:
The following equation (see Section B.15) expresses the relationship between API gravity at 60 °F and the corresponding metric tons per barrel in air:
Solve Equation (26) or (27) with values of °API at 60 °F and round the result to ten places past the decimal for further use.
= Weight in vacuo = 2.814732007 MT/1000 gal 361,901 bbl 42 gal/bbl× × = 42,783.4818 MT
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 13
A tanker of gasoline having a 60 °F API gravity of 58.61 is determined to contain 361,901.00 bbl at 60 °F What is the in vacuo weight in metric tons?
Use Equation (26) to calculate the in vacuo intraconversion factor:
The 361,901.00 bbl of gasoline is then equivalent to (rounding as indicated in Table 1):
Barrels per Metric Ton at 60 °F Equivalent to API Gravity at 60 °F
The following equation (see Section B.16) expresses the relationship between API gravity at 60 °F and the corresponding barrels per metric ton in vacuo:
The following equation (see Section B.16) expresses the relationship between API gravity at 60 °F and the corresponding barrels per metric ton in air:
Solve Equation (28) or Equation (29) with values of °API at 60 °F and round the result to nine places past the decimal for further use.
A tanker of gasoline having a 60 °F API gravity of 58.61 is invoiced at 42,783.4818 MT What is the 60 °F volume in barrels?
Use Equation (28) to calculate the in vacuo intraconversion factor:
The 42,783.4818 MT of gasoline is then equivalent to (rounding as indicated in Table 1):
= Weight in vacuo = 0.1182187443 MT/bbl 361,901 bbl× = 42,783.4818 MT
= 60 °F barrels = 8.458895467 bbl/MT 42,783.4818 MT× = 361,901.00 bbl
Cubic Metres per Short Ton at 15 °C Equivalent to API Gravity at 60 °F
The following equation (see Section B.17) expresses the relationship between API gravity at 60 °F and the corresponding cubic metres at 15 °C per short ton in vacuo:
The following equation (see Section B.17) expresses the relationship between API gravity at 60 °F and the corresponding cubic metres at 15 °C per short ton in air:
To solve Equation (30) or Equation (31) using °API values at 60 °F, round the result to nine decimal places for subsequent applications This calculation incorporates a VCF 59, making the result specific to the product Crude oils, generalized products, and lubricants should refer to API MPMS Ch 11.1-2004, while other products may utilize alternative tables.
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 47,160.7159 ST What is the
Use Equation (30) to calculate the in vacuo intraconversion factor:
The 47,160.7159 ST of gasoline is then equivalent to (rounding as indicated in Table 1):
Cubic Metres per Long Ton at 15 °C Equivalent to API Gravity at 60 °F
The following equation (see Section B.18) expresses the relationship between API gravity at 60 °F and the corresponding cubic metres at 15 °C per long ton in vacuo:
The following equation (see Section B.18) expresses the relationship between API gravity at 60 °F and the corresponding cubic metres per long ton in air:
To solve Equation (32) or Equation (33) using °API values at 60 °F, round the result to nine decimal places for subsequent applications This calculation incorporates a VCF 59, making the result specific to the product Crude oils, generalized products, and lubricants should refer to API MPMS Ch 11.1-2004, while other products may utilize alternative tables.
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 15
An incoming shipment of gasoline having a 60 °F API gravity of 58.61 is invoiced at 42,107.7821 LT What is the
Use Equation (32) to calculate the in vacuo intraconversion factor:
The 42,107.7821 LT of gasoline is then equivalent to (rounding as indicated in Table 1):
U.S Gallons at 60 °F to Litres at 15 °C Dependent on API Gravity at 60 °F
The following equation (see Section B.19) expresses the relationship between U.S gallons at 60 °F and litres at
To calculate the volume correction factor (VCF) at 59 °F, utilize the liquid's API gravity and solve the parenthetical part of Equation (34), rounding the result to nine decimal places for accuracy This calculation is specific to the product, as it incorporates VCF 59 For crude oils, generalized products, and lubricants, refer to API MPMS Ch 11.1-2004, while other products may require different tables.
A quantity of gasoline having a 60 °F API gravity of 58.61 is determined to be 15,199,842 gal at 60 °F What is the volume in litres at 15 °C?
Use Equation (34) to calculate the intraconversion factor:
The 15,199,842 gal of gasoline at 60 °F is then equivalent to (rounding as indicated in Table 1):
Barrels at 60 °F to Litres at 15 °C Dependent on API Gravity at 60 °F
The following equation (see Section B.20) expresses the relationship between barrels at 60 °F and litres at 15 °C:
To determine the VCF at 59 °F using the liquid's API gravity, solve the parenthetical part of Equation (35) and round the result to seven decimal places for future reference This calculation is specific to the product, as it incorporates a VCF59 Crude oils, generalized products, and lubricants should refer to API MPMS Ch 11.1-2004, while other products may require different tables.
A quantity of gasoline having a 60 °F API gravity of 58.61 is determined to be 361,901 bbl at 60 °F What is the volume in litres at 15 °C?
Use Equation (35) to calculate the intraconversion factor:
The 361,901 bbl of crude at 60 °F is then equivalent to (rounding as indicated in Table 1):
Data Level
The unit relationships in Annex A and their application in Annex B feature different significant figures For this standard, the intermediate constants obtained in Annex B from these precise relationships are rounded to 10 significant figures.
API MPMS Ch 12 governs all rounding Absent specific direction from API MPMS Ch 12, the implementation procedures detailed in Section 4 specify the rounding for each intraconversion
According to the current API MPMS Ch 12, rounding during the use of intraconversion factors is influenced by the data source, such as when container capacity tables are in whole gallons, necessitating that all subsequent gallon values be recorded accordingly In the absence of other limiting factors, operators should refer to Table 1, which is designed for bulk liquid quantities For smaller quantities, while Table 1 suggests rounding the calculated weight of bulk cargo to whole pounds or kilograms, users may opt to calculate the weight of a barrel of product to two or three decimal places The significant digits in Table 1 ensure consistency within this standard, which may slightly differ from the current API MPMS Ch 12.
Rounding of Numbers
Chain calculations must be executed without any rounding or truncation When rounding a calculation result to a specific number of decimal places, it should be done in a single step to the desired number of figures, rather than through multiple successive steps If the digit to the right of the last retained place is less than
5, the figure in the last place retained should be unchanged When figure to the right of the last place to be retained is
5 to 9, the figure in the last place should be increased by 1.
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 17
Table 1—Significant Digits for Bulk Quantities a
Cubic metre xxx,xxx.xxx
Short tons xxx,xxx.xxxx
Long tons xxx,xxx.xxxx
Metric tons xxx,xxx.xxxx
VCF x.xxxxx a Densities and relative density are presented with six significant figures to reflect values obtainable with modern high precision instrumentation.
This annex is included for documentation purposes only and is not necessary for implementation of this standard.
Exact Constants and Factors Used in Calculations (NIST Handbook 44, Appendix C) *
1 L = 1.000000 dm 3 [12th General Conference on Weights and Measures (1964)]
* The volume factors are solely for conversion at the same temperature.
According to NIST Handbook 44 Appendix B and Handbook 105-1, brass is no longer utilized for balance weights due to its softness An internationally agreed generic reference weight density of 8.0 g/cm³ at 20 °C is now employed As a specific material is not designated, calculating density at the reference temperature is not feasible.
NIST Handbook 44 Appendix B and Handbook 105-1 establish that air buoyancy calculations should be conducted at a standard temperature of 20 °C The most recent Air Density Executable File from the International Committee of Weights and Measures (CIPM) indicates an air density of 0.001199228 g/cm³ at 760 mm pressure and 50% humidity at this temperature For more information, the program can be accessed at the NIST website.
The equation of Patterson and Morris [Metrologia, 31, 277 – 288 (1994)] yields a density of water at 60 °F of 999.016 kg/m 3 , or 0.999016 g/mL (API MPMS Ch 11.4.1).
This annex serves solely for documentation and is not required for the implementation of this standard All conversion factors provided are based on precise relationships detailed in Appendix C of Handbook 44.
B.1 Relative Density (60/60 °F) Equivalent to API Gravity at 60 °F
The relationship between API gravity at 60 °F and relative density at 60 °F (D 60 60 ) is defined as: which can be expressed as:
API gravity and relative density are dimensionless terms.
B.2 Absolute Density at 60 °F Equivalent to API Gravity at 60 °F
A liquid’s relative density D t t1 is defined as its absolute density D t at temperature t divided by the absolute density of water ρ t1 at temperature t1 Relative density at reference temperature 60 °F (D 60 60 ) is therefore:
The density of water can be found in Annex A, ensuring that the units of density are consistent, such as g/mL, kg/m³, or lb/gal Relative density is a dimensionless quantity By substituting Equation (B.1) into Equation (B.2) and using 999.016 kg/m³ for ρ₆₀, the calculations can be completed.
B.3 Absolute Density at 15 °C Equivalent to API Gravity at 60 °F
A volume correction factor (VCF) is calculated by dividing the density of a liquid at a specific temperature (D t) by its density at a reference temperature, which is 60 °F in the United States.
To convert the density of a liquid at 60 °F to its density at 15 °C, multiply by the volume correction factor for that liquid at 59 °F Crude oils, generalized products, and lubricants should refer to API MPMS Ch 11.1-2004, while other products may utilize different tables By substituting Equation (B.3) into Equation (B.4) with t = 59 °F (15 °C), the result is °API 141.5.
B.4 Pounds per U.S Gallon at 60 °F Equivalent to API Gravity at 60 °F
Conversion of API gravity to various units of density in vacuo is a straight unit conversion of Equation (B.3) using 0.999016 g/mL as the density of water:
(B.5) where f is a constant for converting grams per millilitre to any other density units.
To convert grams per millilitre to pounds per U.S gallon, Equation (B.5) is used with f being:
Converting API gravity to pounds per U.S gallon in air involves accounting for the buoyancy of air When measuring mass \(d\) on a scale in a vacuum, it is balanced by an equal reference mass \(b\) In this balanced state, the forces acting on the system cancel each other out, resulting in the force \(F_d = m_d \times a\) (where \(a\) is the acceleration due to gravity) being equal to the force \(F_b = m_b \times a\) on the reference mass \(m_b\).
According to Archimedes's principle, when balanced in air, each mass experiences a force that is equal to the weight of the air it displaces This can be expressed as \$F_{ad} = m_{ad} \times a\$ and \$F_{ab} = m_{ab} \times a\$, where \$m_{ad}\$ represents the mass of air displaced by mass \$m_d\$ and \$m_{ab}\$ denotes the mass of air displaced by mass \$m_b\$.
Multiplying the right side of the equation by one in the form of m b / m b gives:
Similarly, multiplying each side of the equation by the volumes involved (V d for mass m d , V b for mass m b ) gives:
At 60 °F, the specified ratios represent densities; however, for air buoyancy corrections, the reference weight densities should be based on 20 °C (68 °F) as per international agreement The difference between the densities at 20 °C and 60 °F is deemed negligible.
1 mL 231 in.⁄( 3 /gal 16.387064 mL/in.× 3 )
F d –F ad = F b –F ab m d ×a–m ad ×a = m b ×a–m ab ×a m d –m ad = m b –m ab m d –m ad m b –m ab m b
S ECTION 5, P ART 1—C ONVERSIONS OF API G RAVITY AT 60 °F 21 where
D 60 is the density of liquid at 60 °F in vacuo, m d / V d ;
A 68 is the density of standard air at 68 °F in vacuo, m ad / V d or m ab / V b ;
B 68 is the density of the weights at 68 °F in vacuo, m b / V b ;
(m b / V d ) 60 is the density of liquid at 60 °F in air
Choosing the correct conversion factor is essential for converting units between different systems, such as from grams per milliliter to pounds per U.S gallon, or any other density expression.
D 60 can be converted to relative density D 60 60 with Equation (B.2)
Inserting Equation (B.1) provides a relationship between API gravity and density in air:
Substituting D a 60 for [m b / V d ] 60 and values from Annex A, we obtain:
(B.6) Conversion of grams per millilitre to pounds per U.S gallon is again determined using f as calculated above.
B.5 U.S Gallons per Pound at 60 °F Equivalent to API Gravity at 60 °F
The relationship between API gravity at 60 °F and the volume in U.S gallons occupied by 1 lb in vacuo is given by the reciprocal of Equation (B.5) with f determined as in Section B.4.
The relationship between API gravity at 60 °F and the volume in U.S gallons occupied by 1 lb in air is given by the reciprocal of Equation (B.6) with f determined as in Section B.4.
B.6 Short Tons per 1000 U.S Gallons at 60 °F Equivalent to API Gravity at 60 °F
To convert API gravity at 60 °F to the weight in short tons in vacuo for 1000 gallons, use Equation (B.5) This involves changing the measurement from grams per milliliter to short tons per U.S gallon by calculating the factor \( f \).
Conversion of API gravity at 60 °F to the weight in short tons in air of 1000 gal is accomplished with Equation (B.6), using f as calculated above. m b ⁄V d
1 mL 231 in.⁄( 3 /gal 16.387064 mL/in.× 3 )
B.7 U.S Gallons per Short Ton at 60 °F Equivalent to API Gravity at 60 °F
The relationship between API gravity at 60 °F and the volume in U.S gallons occupied by 1 ST in vacuo is established through the reciprocal of Equation (B.5), with the factor \( f \) defined in Section B.6, and then multiplied by 1000.
The relationship between API gravity at 60 °F and the volume in U.S gallons occupied by 1 short ton in air is established through the reciprocal of Equation (B.6), with the factor \( f \) determined as outlined in Section B.6, and then multiplied by 1000.
B.8 Short Tons per Barrel at 60 °F Equivalent to API Gravity at 60 °F
To convert API gravity at 60 °F to the weight in short tons in vacuo for 1 barrel, use Equation (B.5) This involves changing the measurement from grams per milliliter to short tons per barrel by calculating the factor \( f \).
Conversion of API gravity at 60 °F to the weight in short tons in air of 1 bbl is accomplished with Equation (B.6), using f as calculated above
B.9 Barrels per Short Ton at 60 °F Equivalent to API Gravity at 60 °F
The relationship between API gravity at 60 °F and the volume in barrels occupied by 1 ST in vacuo is given by the reciprocal of Equation (B.5) with f determined as in Section B.8.
The relationship between API gravity at 60 °F and the volume in barrels occupied by 1 ST in air is given by the reciprocal of Equation (B.6) with f determined as in Section B.8.
B.10 Long Tons per 1000 U.S Gallons at 60 °F Equivalent to API Gravity at 60 °F