The principle of turbine flowmeter to measure flow_flow range of turbine flowmeter

　　The principle of turbine flowmeter to measure flow

　　Working principle of turbine The turbine flowmeter consists of a turbine, bearings, preamplifier, and display instrument. The principle of the turbine flowmeter is to place a turbine in the center of the pipeline, supported by bearings at both ends. When the fluid passes through the pipeline, it impacts the turbine blades, generating a driving torque on the turbine, causing the turbine to overcome the friction torque and fluid resistance torque and rotate. Within a certain flow range, for a certain fluid medium viscosity, the rotational angular velocity of the turbine is proportional to the fluid flow rate. Therefore, the fluid flow rate can be obtained through the rotational angular velocity of the turbine, so that the fluid flow through the pipeline can be calculated. The speed of the turbine is detected by a sensor coil installed outside the casing. When the turbine blades cut the magnetic lines of force generated by the permanent magnets in the casing, it will cause the magnetic flux in the sensor coil to change. The sensor coil sends the detected magnetic flux period change signal to the preamplifier, amplifies and shapes the signal, generates a pulse signal proportional to the flow rate, and sends it to the unit conversion and flow integration circuit to obtain and display the cumulative flow value; at the same time, the pulse signal is also sent to the frequency current conversion circuit to convert the pulse signal into an analog current, thereby indicating the instantaneous flow value.

　　1. The horizontally installed sensor of the turbine flowmeter requires that the pipeline should not have a visually perceptible tilt (within 5°). The vertical deviation of the vertically installed sensor pipeline should be less than 5°, and the fluid direction should be downward and upward.

　　2. In places where the flow cannot be stopped, bypass and stop valves should be installed. If the fluid contains impurities, a filter should be installed on the upstream side; if it contains gas, a degasser should be installed on the upstream side. The sewage outlet and degasser outlet of the filter and degasser should lead to a safe place.

　　3 The flow control valve should be installed downstream of the sensor, and the upstream stop valve should be fully open during measurement, and no vibration or leakage should occur. For processes that may produce reverse flow, a check valve should be added to prevent the fluid from flowing in reverse.

　　4 The sensor should be concentric with the pipeline, and the sealing gasket should not protrude into the pipeline. The sensor should not be at the highest point of the horizontal pipeline to prevent the gas accumulated in the pipeline (such as air mixed in when the flow stops) from staying at the sensor and being difficult to discharge, thus affecting the measurement.

　　Turbine flowmeter flow range

　　Selection of flow range of turbine flowmeter

　　The selection of flow range of turbine flowmeter has a great influence on its accuracy and service life, and each caliber flowmeter has a certain measurement range, and the selection of flowmeter caliber is also determined by the flow range. The principle of selecting flow range is: the minimum flow rate during use shall not be lower than the minimum flow rate allowed by the instrument, and the maximum flow rate during use shall not be higher than the maximum flow rate allowed by the instrument.

　　For intermittent working occasions where the actual operation time of the instrument does not exceed 8 hours per day, 1.3 times the maximum flow rate during actual use is selected as the upper limit of the flow range; for continuous working occasions where the actual operation time of the instrument is not less than 8 hours per day, 1.4 times the maximum flow rate during actual use is selected as the upper limit of the flow range. The lower limit flow rate of the instrument is appropriately 0.8 times the minimum flow rate in actual use.