SHUNTING FLOWMETER

Japanese Patent JP3757009

B2

PROBLEM TO BE SOLVED: To estimate flow rate in a main pipe accurately by measuring the differential pressure in the main pipe across a joint of a shunt pipe to the main pipe, determining a shunt ratio therefrom and then multiplying the flow rate in the shunt pipe by the shunt ratio. SOLUTION: A shunt pipe 2 is jointed to a main pipe 1 at an upstream side joint 11 and a downstream side joint 12 and a flowmeter 3 is fixed and then the difference of static pressure introduced into the main pipe 1 through pressure introduction pipes 6, 6\' is measured by means of a differential pressure gauge 4. The pressure introduction pipes 6 is jointed to the main pipe 1 at a pressure introduction port 13 on the upstream side of an upstream joint 11 of the main pipe 1 and the shunt pipe 2 while the pressure introduction pipes 6 is jointed to the main pipe 1 at a pressure introduction port 14 in the downstream of the upstream joint 11 and in the upstream of a downstream side joint 12. Subsequently, the differential static pressure across the upstream joint 11 in the main pipe 1 is measured. A signal processor 8 calculates the shunt ratio between the main pipe 1 and the shunt pipe 2 based on the outputs from the flowmeter 3 and the differential pressure gauge 4 and then calculates the flow rate in the main pipe 1 which is indicated on an indicator 9. According to the arrangement, flow rate in the main pipe 1 can be measured accurately regardless of variation of shunt ratio due to variation of flow conditions.