553:
457:
official density of water at 60 °F according to the 2008 edition of ASTM D1250 is 999.016 kg/m. The 1980 value is 999.012 kg/m. In some cases the standard conditions may be 15 °C (59 °F) and not 60 °F (15.56 °C), in which case a different value for the water density would be appropriate (
456:
With the formula presented in the previous section, the API gravity can be readily calculated. When converting oil density to specific gravity using the above definition, it is important to use the correct density of water, according to the standard conditions used when the measurement was made. The
646:
Report on the
Development, Construction, Calculation and Preparation of the ASTM – IP Petroleum Measurement Tables (ASTM D1250; IP 200), 1960, published by the Institute of Petroleum, 61 New Cavendish Street, London, W.1 and American Society for Testing Materials, 1916 Race Street, Philadelphia 3,
88:
and temperature controls that had caused serious variations in published values. Hydrometers in the U.S. had been manufactured and distributed widely with a modulus of 141.5 instead of the Baumé scale modulus of 140. The scale was so firmly established that, by 1921, the remedy implemented by the
345:
451:
216:
147:
273:
297:
382:
563:
Generally speaking, oil with an API gravity between 40 and 45° commands the highest prices. Above 45°, the molecular chains become shorter and less valuable to refineries.
391:
515:: The API gravity is read at the point where the surface of the liquid intersects the hydrometer scale. For maximum accuracy, the reading is taken at the bottom of the
797:
158:
503:: An appropriate API gravity hydrometer is chosen based on the expected range of the sample. These hydrometers are typically calibrated to read API gravity directly.
532:
The hydrometer method is widely used due to its simplicity and low cost. However, it requires a relatively large sample volume and may not be suitable for highly
475:
The hydrometer method is a standard technique for directly measuring API gravity of petroleum and petroleum products. This method is based on the principle of
877:
552:
528:: If the measurement is not performed at the standard temperature, a correction factor is applied to adjust the reading to the equivalent value at 60°F.
857:
461:
509:: The hydrometer is gently lowered into the sample contained in a cylindrical vessel. It is allowed to float freely until it reaches equilibrium.
42:
liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.
472:
There are advantages to field testing and on-board conversion of measured volumes to volume correction. This method is detailed in ASTM D287.
111:
701:"Standard Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method"
227:
57:. For example, if one petroleum liquid is less dense than another, it has a greater API gravity. Although API gravity is mathematically a
826:
221:
Thus, a heavy oil with a specific gravity of 1.0 (i.e., with the same density as pure water at 60 °F) has an API gravity of:
917:
746:
801:
656:
API Manual of
Petroleum Measurement Standards, Chapter 11.1 – 1980, Volume XI/XII, Adjunct to: ASTM D1250-80 and IP 200/80
611:
deposits in
Alberta, Canada, has an API gravity of around 8°. It can be diluted with lighter hydrocarbons to produce
494:
362:
To derive the API gravity, the specific gravity (i.e., density relative to water) is first measured using either the
340:{\displaystyle {\text{barrels of crude oil per metric ton}}={\frac {{\text{API gravity}}+131.5}{141.5\times 0.159}}}
882:
593:
912:
377:
Density adjustments at different temperatures, corrections for soda-lime glass expansion and contraction and
902:
90:
69:
61:(see the formula below), it is referred to as being in 'degrees'. API gravity is graduated in degrees on a
31:
854:
907:
615:, which has an API gravity of less than 22.3°, or further "upgraded" to an API gravity of 31 to 33° as
497:, usually 60°F (15.6°C), to ensure consistency in measurements across different samples and conditions.
54:
17:
897:
541:
152:
Conversely, the specific gravity of petroleum liquids can be derived from their API gravity value as
674:"Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer/Method)"
557:
446:{\displaystyle {\mbox{SG oil}}={\frac {\rho _{\text{crudeoil}}}{\rho _{{\text{H}}_{2}{\text{O}}}}}}
385:, details of usage specified in ASTM D1250. The specific gravity is defined by the formula below.
728:
540:
fluids. Proper cleaning and handling of the hydrometer are crucial to maintain accuracy, and for
351:
211:{\displaystyle {\text{SG at}}~60^{\circ }{\text{F}}={\frac {141.5}{{\text{API gravity}}+131.5}}}
58:
842:
65:
instrument. API gravity values of most petroleum liquids fall between 10 and 70 degrees.
8:
544:
liquids, special precautions may be necessary to prevent evaporation during measurement.
93:
was to create the API gravity scale, recognizing the scale that was actually being used.
823:
288:
371:
742:
516:
378:
278:
76:, which had been developed in France in 1768, as the U.S. standard for measuring the
773:
734:
102:
81:
77:
50:
588:
Extra heavy oil has an API gravity below 10.0° (i.e., greater than 1000 kg/m)
861:
830:
616:
612:
600:
582:
579:
Medium oil has an API gravity between 22.3 and 31.1° (i.e., 870 to 920 kg/m)
573:
635:
569:
is classified as light, medium, or heavy according to its measured API gravity.
84:. Investigation by the U.S. National Academy of Sciences found major errors in
73:
891:
700:
738:
283:
In the oil industry, quantities of crude oil are often measured in metric
467:
480:
363:
357:
62:
777:
765:
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608:
566:
533:
142:{\displaystyle {\text{API gravity}}={\frac {141.5}{\text{SG}}}-131.5}
39:
27:
Measure of how heavy or light a petroleum liquid is compared to water
576:
has an API gravity higher than 31.1° (i.e., less than 870 kg/m)
268:{\displaystyle {\frac {141.5}{1.0}}-131.5=10.0^{\circ }{\text{API}}}
476:
85:
279:
Using API gravity to calculate barrels of crude oil per metric ton
883:
Instructions for using a glass hydrometer measured in API gravity
604:
537:
46:
291:
per metric ton for a given crude oil based on its API gravity:
45:
API gravity is thus an inverse measure of a petroleum liquid's
284:
585:
has an API gravity below 22.3° (i.e., 920 to 1000 kg/m)
800:. Louisiana Department of Natural Resources. Archived from
599:
Crude oil with API gravity less than 10° is referred to as
367:
766:"Characterization and Properties of Petroleum Fractions"
486:
The procedure typically involves the following steps:
396:
468:
Direct measurement of API gravity (hydrometer method)
394:
300:
230:
161:
114:
358:
Measurement of API gravity from its specific gravity
592:However, not all parties use the same grading. The
483:to determine the API gravity of a liquid sample.
445:
339:
267:
210:
141:
822:Crude oil grades, Crudemonitor.ca, web PDF file:
889:
462:standard conditions for temperature and pressure
381:corrections for opaque oils are detailed in the
354:(39.6° API) has a volume of about 7.6 barrels.
287:. One can calculate the approximate number of
547:
519:formed by the liquid on the hydrometer stem.
798:"Comments on Crude Oil Gravity Adjustments"
101:The formula to calculate API gravity from
556:API gravity of crude oil produced in the
49:relative to that of water (also known as
878:Comments on API gravity adjustment scale
853:Canadian Centre for Energy Information.
551:
726:
493:: The petroleum sample is brought to a
96:
38:, is a measure of how heavy or light a
14:
890:
730:Handbook of Petroleum Product Analysis
53:). It is used to compare densities of
841:USGS FS2006-3133_508, web PDF file:
760:
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722:
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695:
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479:and utilizes a specially calibrated
303:barrels of crude oil per metric ton
24:
25:
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717:
690:
659:
727:Speight, James G. (2014-12-12).
596:uses slightly different ranges.
847:
835:
594:United States Geological Survey
374:method detailed in ASTM D4052.
816:
790:
650:
640:
629:
13:
1:
622:
350:For example, a metric ton of
918:American Petroleum Institute
383:Petroleum Measurement Tables
91:American Petroleum Institute
70:National Bureau of Standards
32:American Petroleum Institute
7:
864:. Retrieved on: 2012-09-10.
80:of liquids less dense than
10:
934:
548:Classifications or grades
829:October 8, 2007, at the
558:contiguous United States
607:. Bitumen derived from
352:West Texas Intermediate
560:
447:
341:
269:
212:
143:
59:dimensionless quantity
739:10.1002/9781118986370
733:(1 ed.). Wiley.
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448:
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213:
144:
913:Petroleum production
855:"What is crude oil?"
501:Hydrometer selection
495:standard temperature
392:
298:
228:
159:
112:
97:API gravity formulas
903:Physical quantities
860:2014-07-10 at the
636:API Degree history
561:
491:Sample preparation
443:
400:
372:oscillating U-tube
370:D1298 or with the
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68:In 1916, the U.S.
908:Petroleum geology
748:978-1-118-36926-5
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55:petroleum liquids
16:(Redirected from
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898:Units of density
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103:specific gravity
78:specific gravity
51:specific gravity
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613:diluted bitumen
601:extra heavy oil
583:Heavy crude oil
574:Light crude oil
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804:on 2 May 2006
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843:USGS-508-PDF
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806:. Retrieved
802:the original
792:
781:. Retrieved
770:www.astm.org
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708:. Retrieved
705:www.astm.org
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681:. Retrieved
678:www.astm.org
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35:
34:gravity, or
29:
523:Temperature
507:Measurement
314:API gravity
196:API gravity
117:API gravity
74:Baumé scale
36:API gravity
892:Categories
783:2024-08-07
710:2024-08-07
683:2024-08-07
623:References
526:correction
481:hydrometer
364:hydrometer
63:hydrometer
18:Degree API
808:6 January
609:oil sands
567:Crude oil
419:ρ
409:ρ
329:×
256:∘
242:−
176:∘
134:−
105:(SG) is:
40:petroleum
858:Archived
827:Archived
542:volatile
517:meniscus
477:buoyancy
413:crudeoil
379:meniscus
86:salinity
605:bitumen
534:viscous
513:Reading
289:barrels
47:density
745:
538:opaque
398:SG oil
168:
332:0.159
326:141.5
321:131.5
245:131.5
234:141.5
203:131.5
191:141.5
164:SG at
137:131.5
126:141.5
82:water
810:2014
743:ISBN
368:ASTM
285:tons
252:10.0
30:The
774:doi
735:doi
647:Pa.
603:or
536:or
464:).
459:see
262:API
237:1.0
894::
772:.
768:.
757:^
741:.
719:^
703:.
692:^
676:.
661:^
619:.
172:60
129:SG
812:.
786:.
776::
751:.
737::
713:.
686:.
436:O
430:2
425:H
403:=
318:+
307:=
248:=
200:+
186:=
182:F
121:=
20:)
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