|
|
| Line 1: |
Line 1: |
| The [[American Petroleum Institute]] gravity, or '''''API gravity''''', is a measure of how heavy or light a [[petroleum]] 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. API gravity is thus an inverse measure of the relative density of a petroleum liquid and the density of water, but it is used to compare the relative densities of [[List of crude oil products|petroleum liquids]]. For example, if one petroleum liquid floats on another and is therefore less dense, it has a greater API gravity. Although mathematically, API gravity has no units (see the formula below), it is nevertheless referred to as being in "degrees". API gravity is gradated in degrees on a [[#Direct Measurement of API gravity (Hydrometer method)|hydrometer instrument]]. The API scale was designed so that most values would fall between 10 and 70 API gravity degrees.
| | I'm Mercedes (29) from Zenon Park, Canada. <br>I'm learning French literature at a local college and I'm just about to graduate.<br>I have a part time job in a college.<br><br>my page ... [http://Wheretoshopmilan.com/?page_id=2%FFsac+%C3%A0+main+celine%FFnofollow%FFcheap+nike+air+max+sale%FFnofollow how to get free fifa 15 coins] |
| | |
| ==History of development==
| |
| The U.S. [[National Bureau of Standards]] in 1916 accepted the [[Baumé scale]], developed in France in 1768, as the U.S. standard for measuring the [[specific gravity]] of liquids less dense than [[Density of water|water]]. Investigation by the U.S. National Academy of Sciences found major errors in [[salinity]] 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 [[American Petroleum Institute]] was to create the API Gravity scale, recognizing the scale that was actually being used.
| |
| | |
| ==API gravity formulas==
| |
| The formula to obtain API gravity of [[petroleum]] liquids, from [[specific gravity]] (SG), is:
| |
| | |
| :<math>\text{API gravity} = \frac{141.5}{\text{SG}} - 131.5</math>
| |
| | |
| Conversely, the specific gravity of [[petroleum]] liquids can be derived from the API gravity value as
| |
| | |
| :<math>\text{SG at}~60^\circ\text{F} = \frac{141.5}{\text{API gravity} + 131.5}</math>
| |
| | |
| Thus, a heavy oil with a specific gravity of 1.0 (i.e., with the same density as pure water at 60°F) would have an API gravity of:
| |
| | |
| :<math>\frac{141.5}{1.0} - 131.5 = 10.0^\circ\text{API}</math>
| |
| | |
| ==Using API gravity to calculate barrels of crude oil per metric ton==
| |
| In the oil industry, quantities of crude oil are often measured in metric tons. One can calculate the approximate number of barrels per metric ton for a given crude oil based on its API gravity:
| |
| | |
| :<math>\text{barrels of crude oil per metric ton} = 1\div\bigg[\frac{141.5}{\text{API gravity}+131.5} \times 0.159\bigg]</math>
| |
| | |
| So, for example, a metric ton of [[West Texas Intermediate]] (39.6° API) would contain about 7.6 barrels.
| |
| | |
| ==Measurement of API gravity from its density==
| |
| | |
| To derive the API gravity from the [[density]], the density is first measured using either the [[hydrometer]], detailed in [[ASTM]] D1298 or with the [[oscillating U-tube]] method detailed in ASTM D4052.
| |
| Density adjustments at different temperatures, corrections for soda-lime glass expansion and contraction and [[meniscus]] corrections for opaque oils are detailed in the [[Petroleum Measurement Tables]], details of usage specified in ASTM D1250.
| |
| The specific gravity is then calculated from the formula below and the API gravity calculated from the first formula above.
| |
| | |
| :<math>\mbox{SG oil} = \frac{\rho_\text{oil}}{\rho_{\text{H}_2\text{O}}}</math>
| |
| | |
| ==Direct Measurement of API gravity (Hydrometer method)==
| |
| | |
| There are advantages to field testing and on-board conversion of measured volumes to volume correction.
| |
| This method is detailed in ASTM D287.
| |
| | |
| ==Classifications or grades==
| |
| Generally speaking, oil with an API gravity between 40 and 45 commands the highest prices. Above 45 degrees the molecular chains become shorter and less valuable to refineries.<ref>{{cite web|title=Comments on Crude Oil Gravity Adjustments|url=http://dnr.louisiana.gov/sec/execdiv/techasmt/oil_gas/crude_oil_gravity/comments_1989.htm|publisher=Louisiana Department of Natural Resources|accessdate=6 January 2014|archiveurl=http://web.archive.org/web/20070118001025/http://dnr.louisiana.gov/sec/execdiv/techasmt/oil_gas/crude_oil_gravity/comments_1989.htm|archivedate=18 January 2007}}</ref>
| |
| | |
| [[Crude oil]] is classified as light, medium or heavy, according to its measured API gravity.
| |
| | |
| * [[Light crude oil]] is defined as having an API gravity higher than 31.1 °API (less than 870 kg/m<sup>3</sup>)
| |
| * Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API (870 to 920 kg/m<sup>3</sup>)
| |
| * [[Heavy crude oil]] is defined as having an API gravity below 22.3 °API (920 to 1000 kg/m<sup>3</sup>)
| |
| * Extra heavy oil is defined with API gravity below 10.0 °API (greater than 1000 kg/m<sup>3</sup>)
| |
| | |
| Not all parties use the same grading.<ref>Crude oil grades, Crudemonitor.ca, web PDF file: [http://www.crudemonitor.ca/quickfacts/misc/grades.pdf CMonitor-Gr-PDF]</ref> The [[United States Geological Survey]] uses slightly different definitions.<ref>USGS FS2006-3133_508, web PDF file: [http://pubs.usgs.gov/fs/2006/3133/pdf/FS2006-3133_508.pdf USGS-508-PDF]</ref>
| |
| | |
| Crude oil with API gravity less than 10 °API is referred to as [[extra heavy oil]] or [[bitumen]]. Bitumen derived from the [[oil sands]] deposits in the Alberta, Canada area has an API gravity of around 8 °API. It can be diluted with lighter hydrocarbons to produce [[diluted bitumen]], having an API gravity of lower than 22.3 API, or further "upgraded" to an API gravity of 31 °API to 33 °API as [[synthetic crude]].<ref>Canadian Centre for Energy Information. [http://www.centreforenergy.com/AboutEnergy/ONG/Oil/Overview.asp?page=2 "What is crude oil?"]. Retrieved on: 2012-09-10.</ref>
| |
| | |
| ==See also==
| |
| * [[Density]]
| |
| * [[Specific gravity]]
| |
| * [[Specific weight]]
| |
| | |
| == References ==
| |
| {{Reflist}}
| |
| | |
| ==External links==
| |
| *[http://www.koehlerinstrument.com/products/hydrometer.html Link to hydrometer]
| |
| *[http://dnr.louisiana.gov/assets/docs/oilgas/productiondata/comments_1989_rev.pdf Comments on API gravity adjustment scale]
| |
| *[http://www.globalsecurity.org/military/library/policy/army/fm/10-67-1/APPI.HTML Instructions for using a glass hydrometer measured in API gravity]
| |
| *[http://www.sizes.com/units/hydrometer_api.htm API Degree history]
| |
| | |
| [[Category:Units of density]]
| |
| [[Category:Physical quantities]]
| |
| [[Category:Petroleum geology]]
| |
| [[Category:Petroleum production]]
| |
I'm Mercedes (29) from Zenon Park, Canada.
I'm learning French literature at a local college and I'm just about to graduate.
I have a part time job in a college.
my page ... how to get free fifa 15 coins