METHOD FOR DETERMINING THE ERROR OF A FLOW METER DURING NORMAL OPERATION WITHOUT DISCONNECTING IT FROM ANY PIPES

摘要

The invention is a system (1) for measuring the flow rate of a base gas that flows along a duct (2), comprising: a feeding unit (3) of a secondary gas containing a tracer gas; a feeding duct (4) for the introduction of the secondary gas in the duct (2) under thermodynamic supply conditions; a unit (6) for measuring the flow rate of the secondary gas that flows in the feeding duct (4); a duct (7) suited to extract the mixture of base gas and secondary gas from the duct (2) downstream of the point of introduction of the secondary gas; a device (9) for detecting the concentration of tracer gas in the mixture; a processing unit (10) operatively connected to the measuring unit (6) and to the detector device (9) and configured to calculate the flow rate of the base gas as a function of the concentration of both the secondary gas and the tracer gas flowing in the mixture. The feeding duct (4) comprises a converging nozzle (11) and the feeding unit (3) is configured so that the secondary gas reaches sound speed in the nozzle (11). The measuring unit (6) comprises a sensor unit (12a, 12b) suited to detect the thermodynamic supply conditions of the secondary gas and means (13) for calculating the flow rate of the secondary gas based on the thermodynamic supply conditions and the geometric shape of the nozzle (11).