Custody transfer measurements

The trading of gases, liquids and energy is done on the basis of flow measurements. Naturally, the necessary requirements are imposed on this type of flow measurement. First of all, the instrument must be accurate. But also issues such as fraudworthiness are taken into account. And external influences must be nil, such as sensitivity to ambient temperature and electromagnetic radiation.

The metrology law

Because the reliability of such a flow measurement must be so high, this type of measurement is regulated by law. The law that applies to calibration measurements is the Metrology Law and the guideline that the law uses for this is the MID.

Not every flow meter is suitable for settlement purposes. The choice of a flow meter depends on the medium to be measured, the size of the pipe, the design pressure and temperature and the accuracy class specified.

Common calibrated flowmeter applications

The above mentioned measurement methods are common combinations of flow application and flowmeter choice. But depending on the process parameters, other choices are made in specific situations. For example, when measuring bulk gas in a semiconductor plant, where one especially wants no particles in the gas, instruments with moving parts are not an option. In that case a thermal gas mass flow meter in UHP execution is the most obvious choice.

Incidentally, MID does not apply to large gas flows.