Abstract: An apparatus for measuring a multiphase fluid stream which flows in a pipe (2) comprising: a measuring unit (11), coaxial to the pipe, consisting of an isokinetic sampling device (1) suitably configured for allowing the equidistribution of the flow at the inlet in n channels (6) having an area A, of which m are sampling channels and a flow restriction (13) both equipped with differential pressure measuring means (12, 14), a phase separator (15), connected to the sampling device, measurers and regulation means downstream of said separator. A method in accordance with said apparatus which comprises: the isokinetic sampling of a portion q of the multiphase flow Q at the inlet, measuring the flowrates of the liquid qL and gas qG of the portion sampled and calculating the liquid and gas flow-rates (QL and Q0) from the sampling sections according to the equations QG=n/tn qG and QL=n/m qL. The method provides isokinetic sampling for portions of flow removed ranging from 5% to 20%.

Abstract: A compact inertial gas-liquid separator including: a stratification mechanism including a first horizontal pipe and a second pipe having a larger diameter possibly slightly tilted with respect to the horizontal, for example of ?10°, connected to each other by a suitable connection gate; a cylindrical body with a vertical development, on which the stratification mechanism is tangentially inserted, wherein the inertial gas-liquid separation is performed, in whose upper part an arrangement of finishing elements can be optionally inserted for further separation of drops of liquid entrapped in the gaseous stream; two outlets for the liquid stream and for the gaseous stream.

Abstract: A method for measuring the liquid and gas flow rates (QL and QG) of a multiphase fluid stream which comprises: withdrawing a portion of the overall flow rate (Q) under isokinetic conditions, measuring the liquid and gas flow rates (qL, qG) of the withdrawn portion, measuring the pressure drop in correspondence of a t least one of the constricted sections located upstream and downstream of the sampling section and calculating said liquid and gas flow rates (QL, QG) from the sampling section and calculating said liquid and gas flow rates (QL, QG) from the relation QL=(A1/A2) qG, where A1 and A2 are the areas of the constricted section and of the sampling section respectively.