ISO 12185 Crude petroleum and petroleum products - Determination of density - Oscillating U-tube method
1 Scope
This International Standard specifies a method for the determination, using an oscillating U-tube density meter, of the density of crude petroleum and related products within the range 600 kg/m3 to 1100 kg/m3 which can be handled as single-phase liquids at the test temperature and pressure.
This International Standard is applicable to liquids of any vapour pressure as long as suitable precautions are taken to ensure that they remain in single phase with no loss of light ends and subsequent changes in composition and density during both the sample handling and the density determination.
NOTE 1 If the determined density is to be converted to a density at some reference temperature using petroleum measurement tables, the determination should be carried out at a temperature as close as possible to the reference temperature in order to minimize uncertainties due to the use of generalized tables.
This method is not intended for use in calibrating online density meters.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 91-1:1992, Petroleum measurement tables - Part 7: Tables based on reference temperatures of 15 °C and 60 degrees F.
ISO 91-2:1991, Petroleum measurement tables - Part 2: Tables based on a reference temperature of 20 °C.
ISO 3015:1992, Petroleum products - Determination of cloud point.
ISO 3016:1994, Petroleum products - Determination of pour point,
ISO 3170:1988, Petroleum liquids - Manual sampling.
ISO 3171:1988, Petroleum liquids - Automatic pipeline sampling.
ISO 3696:1987, Water for analytical laboratory use - Specification and test methods.
ISO 3838:1983, Crude petroleum and liquid or solid petroleum products - Determination of density or relative density - Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods.
IP 389/93, Determination of wax appearance temperature of middle distillate fuels by differential thermal analysis or differential scanning calorimetry.
IP 1995, Standard methods for analysis and testing of petroleum and related products, Appendix G Density of water; Appendix H Density of ambient air.
BIPM Tables, Density of water and Density of ambient air, to replace, when published, the corresponding IP tables.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 density: Mass of the substance, expressed in kilograms, divided by its volume, expressed in cubic metres.
3.2 reference temperature: Temperature at which the sample density is to be reported.
NOTE 2 This temperature should be either 15 °C or 20 °C.
4 Principle
A small (typically less than 1 ml) portion of the test sample is introduced into a temperature-controlled sample cell. The oscillation frequency is noted, and he density of the test sample calculated using cell constants previously determined by measuring the oscillation frequencies when the cell is filled with calibration fluids of known density.
