Standard Test Method for Density, Relative Density, and API Gravity of Crude Petroleum and Liquid Petroleum Products by Thermohydrometer Method

Importancia y uso:

5.1 Accurate determination of the density, relative density, or API gravity of petroleum and its products is necessary for the conversion of measured volumes to volumes or masses, or both, at the standard reference temperatures of 15 °C or (60 °F) during custody transfer.

5.2 This procedure is most suitable for determining the density, relative density, or API gravity of low viscosity transparent liquids. This procedure can also be used for viscous liquids by allowing sufficient time for the hydrometer and temperature measuring device to reach temperature equilibrium, and for opaque liquids by employing a suitable meniscus correction. Additionally for both transparent and opaque fluids the readings shall be corrected for the thermal glass expansion effect on the hydrometer body and alternative calibration temperature effects before correcting to the reference temperature.

5.3 When used in connection with bulk oil measurements, volume correction errors are minimized by observing the hydrometer reading at a temperature close to that of the bulk oil average temperature.

5.4 Density, relative density, or API gravity is a factor governing the quality and pricing of crude petroleum. However, this property of petroleum product is an uncertain indication of its quality unless correlated with other properties. Crude petroleum prices are frequently posted against values in kg/m³ (or in degrees API). This correlation may be used to give approximate hydrocarbon composition and heat of combustion.

5.5 Density is an important quality indicator for automotive, aviation and marine fuels, where it affects storage, handling and combustion.

5.6 Typical Field of Application—The procedure is convenient for gathering or main trunk pipelines and other field applications where limited laboratory facilities are available. The thermohydrometer method may have limitations in some petroleum density determinations. When this is the case, other methods such as Test Method D1298 (API MPMS Chapter 9.1) should be used.

5.7 Density thermohydrometers conforming to Specification E2995 are not suitable for custody transfer measurements unless they are calibrated and provided with certification by the manufacture stating that they meet the permissible scale errors specified in Specification E100.

Note 6: Specification E2995 in essence allows the doubling of the temperature scale error. Therefore, while thermohydrometers meeting the specifications of E2995 may be used, they shall be calibrated to meet the requirements of Specification E100 and Annex A3 of this standard and the temperature scale error shall meet the requirements of Specification E100.

Subcomité:

D02.02

Referida por:

D0287-22, D0287-22, D6074-15R22, D7777-24, D6448-24, D0287-22

Volúmen:

05.03

Número ICS:

75.040 (Crude petroleum), 75.080 (Petroleum products in general)

Palabras clave:

API gravity; density; digital contact thermometers; hydrometer; hydrometer cylinder; relative density; thermohydrometer; thermometer;