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
8. Reports
8.1 Reporting of Observed Readings:
8.1.1 Apply any relevant corrections to the observed thermohydrometer reading.
8.1.1.1 For opaque samples, make the appropriate correction to the observed thermohydrometer scale reading given in 7.2.5.
8.1.2 Record this corrected hydrometer scale reading to the nearest 0.5 kg/m3 density or 0.1°API and record the thermometer reading to the nearest 0.5°C or 1.0°F.
8.2 Correction to Standard Temperatures:
8.2.1 To correct density or API gravity to standard temperatures at 15°C or 60°F respectively, use the following Petroleum Measurement Tables.
8.2.1.1 When a density scale thermohydrometer was employed, use Tables 53A, 53B, or 53D from the appropriate adjuncts to Guide D1250 (API MPMS Chapter 11.1) to obtain density at 15°C.
8.2.1.2 When an API scale thermohydrometer was employed, use Tables 5A, 5B, or 5D from the appropriate adjuncts to Guide D1250 (API MPMS Chapter 11.1) to obtain the gravity in °API.
8.2.1.3 When a relative density scale thermohydrometer was employed, use Tables 23A and 23B from the appropriate adjuncts to Guide D1250 (API MPMS Chapter 11.1) to obtain the relative density at 60/60°F.
8.3 Unit Conversions:
8.3.1 When a value is obtained with a thermohydrometer scaled in one set of units and a result is required in another set of units, convert by use of the appropriate Petroleum Measurement Tables.
8.3.1.1 For conversion from density at 15°C to other units, use Table 5 in the appropriate adjunct to Guide D1250 (API MPMS Chapter 11.1).
8.3.1.2 For conversion from API gravity to other units, use Table 3 in the appropriate adjunct to Guide D1250 (API MPMS Chapter 11.1).
8.4 Reporting of Final Value - Report the final value as density at 15°C to the nearest 0.5 kg/m3, relative density 60/60°F to the nearest 0.0005, or as °API to the nearest 0.1°API, whichever is applicable.
9. Precision and Bias
9.1 Precision - The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
9.1.1 Repeatability - The difference between two results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test method, exceed 0.6 kg/m3 or 0.2°API only in one case in twenty.
9.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories and on identical test material would, in the long run, in the normal and correct operation of the test method, exceed 1.5 kg/m3 or 0.5°API only in one case in twenty.
NOTE 3 - The precision of this test method was not obtained in accordance with Practice D6300. The precision statement applies only to measurements made at temperatures of 15 more or less 10°C or 60 more or less 15°F.
9.2 Bias - Bias for this test method has not been determined. However, to determine that the bias is within acceptable limits, ensure the hydrometer and the thermometer have been verified using standards traceable to International Standards before the thermohydrometer or hydrometer and thermometer are placed into service. Periodic re-verification may be required.
10. Keywords
10.1 API gravity; density; hydrometer; hydrometer cylinder; relative density; thermohydrometer; thermometer
