This Technical Report describes the measurement of wet gas with differential pressure meters. It applies to two-phase flows of gas and liquid in which the flowing fluid mixture consists of gas in the region of 95%volume fraction or more (the exact limits on the mixture are defined in 6.4.3, 6.4.5, 7.5.3 and 7.5.5). This Technical Report is an extension of ISO5167. The ranges of gases and liquids from which the equations in this Technical Report were derived are given in 6.4.1 and 7.5.1. It is possible that the equations do not apply to liquids significantly different from those tested, particularly to highly viscous liquids.
Although the over-reading equations presented in this Technical Report apply for a wide range of gases and liquids at appropriate gas-liquid density ratios, evaluating gas flowrates depends on information in addition to that required in single-phase flow: under certain conditions, a measurement of the pressure loss is sufficient; tracers can be used to measure the liquid flow; the total mass flowrate may be known (this is more likely in a wet-steam flow than in a natural gas/liquid flow); in a wet-steam flow a throttling calorimeter can be used.
Wet-gas measurement using Venturi tubes or orifice plates is covered in this Technical Report.
This Technical Report is only applicable to wet gas flows with a single liquid and is not intended for the oil and gas industry.