|
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 a measure of the relative density of a petroleum liquid and the density of water, but it is used to compare the relative densities of 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 graduated in degrees on a hydrometer instrument and was designed so that most values would fall between 10 and 70 API gravity degrees. The American Petroleum Institute, commonly referred to as API, is the main U.S. trade association for the oil and natural gas industry, representing about 400 corporate members involved in all aspects of the industry. ...
A hydrometer is an instrument used for determining the specific gravity of liquids. ...
History of development
The U.S. National Bureau of Standards in 1916 established the Baumé scale (see degrees Baumé) as the standard for measuring specific gravity of liquids less dense than 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. A hydrometer scale developed by French pharmacist Antoine Baumé to measure density of various liquids. ...
Relative density (also known as specific gravity) is a measure of the density of a material. ...
API gravity formulas The formula used to obtain the API gravity of petroleum liquids is thus: Pumpjack pumping an oil well near Lubbock, Texas Ignacy Åukasiewicz - inventor of the refining of kerosene from crude oil. ...
- API gravity = at 60°F - 131.5
Conversely, the specific gravity of petroleum liquids can be derived from the API gravity value as Pumpjack pumping an oil well near Lubbock, Texas Ignacy Åukasiewicz - inventor of the refining of kerosene from crude oil. ...
- SG at 60 °F =
(Further tables give adjustments for temperature).
(See ASTM D1298)
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:
- - 131.5 = 10.0 degrees API.
Classifications or grades Generally speaking 40 to 45 API gravity degree oils have a greatest commercial price and values outside this range have lower commercial price. Above 45 degrees API gravity the molecular chains become shorter and less valuable to a refinery.
Crude oil is classified as light, medium or heavy, according to its measured API gravity. Pumpjack pumping an oil well near Sarnia, Ontario Petroleum (from Greek petra – rock and elaion – oil or Latin oleum – oil ) or crude oil is a thick, dark brown or greenish liquid. ...
Light crude oil is defined as having an API gravity higher than 31.1 °API
Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API
Heavy oil is defined as having an API gravity below 22.3 °API.
Not all parties use the same grading.[1] The US Geological Society uses slightly different definitions at [2] Simply put, bitumen sinks in fresh water, while oil floats.
Oil which will not flow at normal temperatures or without dilution is named bitumen and the API gravity is generally less than 10 °API. Bitumen derived from the oil sands deposits in the Alberta, Canada area has an API gravity of around 8 °API. It is 'upgraded' to an API gravity of 31 °API to 33 °API and the upgraded oil is known as synthetic crude. In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ...
Ewer from Iran, dated 1180-1210CE. Composed of brass worked in repoussé and inlaid with silver and bitumen. ...
Ewer from Iran, dated 1180-1210CE. Composed of brass worked in repoussé and inlaid with silver and bitumen. ...
Open pit mining Tar sands, also referred to as oil sand or bituminous sand, is a combination of clay, sand, water, and bitumen. ...
Synthetic crude is a type of crude oil developed by upgrading bitumen (a tar like substance found in tar sands). ...
External links | 
Feeds |
Contact