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Api Equation:
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The API (American Petroleum Institute) gravity equation is a measure of how heavy or light a petroleum liquid is compared to water. It provides a standardized way to express the density of petroleum products in the oil and gas industry.
The calculator uses the API equation:
Where:
Explanation: The equation converts specific gravity measurements into the API gravity scale, which is inversely related to density - higher API values indicate lighter (less dense) petroleum products.
Details: API gravity is crucial in the petroleum industry for classifying crude oils, determining product quality, calculating taxes and duties, and facilitating trading and transportation of petroleum products.
Tips: Enter the specific gravity measurement in g/mL. The value must be greater than 0. Typical crude oils range from 10° to 70° API, with lighter oils having higher API values.
Q1: What is the relationship between API gravity and specific gravity?
A: API gravity is inversely related to specific gravity. Higher API values correspond to lower specific gravity (lighter fluids), while lower API values indicate higher specific gravity (heavier fluids).
Q2: What are typical API gravity ranges for different petroleum products?
A: Light crude oils: >31.1° API, Medium crude oils: 22.3-31.1° API, Heavy crude oils: <22.3° API. Water has an API gravity of 10°.
Q3: Why is API gravity important in the oil industry?
A: API gravity helps classify crude oils, determine refining processes, calculate product yields, and establish pricing since lighter oils typically command higher prices.
Q4: How is specific gravity measured for API calculation?
A: Specific gravity is typically measured using a hydrometer at standard conditions of 60°F (15.6°C), following ASTM D1298 standard test method.
Q5: Can API gravity be negative?
A: Yes, API gravity can be negative for very dense materials. Substances denser than water (SG > 1) will have negative API values, though this is uncommon for petroleum products.