Patent ID: 8065923

Claim:
A flow rate measuring method for a multiphase fluid mixture flowing in a line, the fluid mixture comprising at least a first and a second phase, the method comprising the steps of: passing the fluid mixture through a first measuring device permanently installed on the line in which the fluid mixture is subjected to a pressure drop, continuously measuring with said first measuring device a differential pressure across the first measuring device and a line pressure of the fluid mixture in the line, calibrating the line with a second measuring device removably installed on an empty portion of the line, punctually measuring at a determined instant with the second measuring device removably installed on a throat portion of the line at least one measured parameter of the fluid mixture correlated to the first phase quantity relatively to the second phase quantity, continuously determining at least one estimated parameter of the fluid mixture correlated to the first phase quantity relatively to the second phase quantity based on the punctually measured parameter and an extrapolating scheme, determining at least one phase flow rate based on the differential pressure across the first measuring device, the line pressure of the fluid mixture into the line and the at least one measured parameter of the fluid mixture when the second measuring device is installed on the line, setting a flag that defines the determined instant when the second measuring device is installed on the line, the determined instant being defined when the flag has reached a determined flag value, determining at least one phase flow rate based on the differential pressure across the first measuring device, the line pressure of the fluid mixture into the line and the at least one estimated parameter of the fluid mixture when the second measuring device is removed from the line.