1 Scope
This International Standard gives guidance on the selection, installation, commissioning, calibration and verification of hybrid tank measurement systems (HTMS) for the measurement of level, static mass, observed and standard volume, and observed and reference density in tanks storing petroleum and petroleum products in fiscal or custody transfer application. As it is a matter for the user to decide which measurements (i.e. volume, or mass or both) are used for custody transfer purposes, this International Standard includes an uncertainty analysis, with examples, to enable users to select the correct components of an HTMS to address the intended application.
This International Standard is applicable to stationary, vertical cylindrical tanks storing liquid hydrocarbons with a Reid Vapour Pressure (RVP) below 103,42 kPa.
This International Standard is not applicable to pressurized tanks or marine applications.
NOTE 1 The term “mass” is used to indicate mass in vacuum (true mass). In the petroleum industry, it is not uncommon to use apparent mass (in air) for commercial transactions. Guidance is provided on the calculation of both mass and apparent mass in air (see Annex A).
NOTE 2 The calculation procedures in this International Standard can also be applied to tanks with other geometries, which have been calibrated by a recognized oil-industry method (e.g. ISO 7507). Examples of uncertainty analysis for spherical and horizontal cylindrical tanks are given in Annex B.