ASTM D6822 for Density, Relative Density and API Gravity of Petroleum Products
ASTM D6822 Standard Test Method for Density, Relative Density, and API Gravity of Crude Petroleum and Liquid Petroleum Products by Thermohydrometer Method
1. Scope
1.1 This test method covers the determination, using a glass thermohydrometer, of the density, relative density (specific gravity), or API gravity of crude petroleum and liquid petroleum products with Reid vapor pressures of 101.325 kPa (14.696 psi) or less. Values are determined at existing temperatures and corrected to 15°C or 60°F by means of international standard tables.
1.2 The values stated in either SI units or inch pound-units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1298 Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method (API MPMS Chapter 9.1)
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
E 100 Specification for ASTM Hydrometers
2.2 API Standards:
MPMS Chapter 9.1 Hydrometer Test Method for Density, Relative Density (Specific Gravity) or API Gravity of Crude Petroleum and Liquid Petroleum Products (ASTM Test Method D1298)
MPMS Chapter 11.1 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils
2.3 ASTM Adjuncts:
Adjunct to D1250, Guide for Use of the Petroleum Measurement Tables (API MPMS Chapter 11.1)
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 API gravity (°API), n - a special function of relative density 60/60°F, represented by:
°API = [141.5 / (relative density 60/60°F)] - 131.5
3.1.1.1 Discussion - No statement of reference temperature is required, as 60°F is included in the definition.
3.1.2 density, n - the mass of liquid per unit volume at 15°C and 101.325 kPa with the standard unit of measurement being kilograms per cubic metre (kg/m3).
3.1.2.1 Discussion - Other reference temperatures, such as 20°C may be used for some products or in some locations. Less preferred units of measurement; for example, kg/L or g/mL, are still in use.
3.1.3 observed values, n - hydrometer readings observed at a temperature other than the defined reference temperature.
3.1.3.1 Discussion - These values are only hydrometer readings and not density, relative density, or API gravity at the temperature.
3.1.4 relative density, n - the ratio of the mass of a given volume of liquid at a specific temperature to the mass of an equal volume of pure water at the same or different temperature. Both reference temperatures shall be explicitly stated.
3.1.4.1 Discussion - Common reference temperatures include 15/15°C, 60/60°F, 20/20°C, and 20/4°C. The historic term specific gravity may still be found.
3.1.5 thermohydrometer, n - a glass hydrometer with a self-contained thermometer.
