Working principle and maintenance precautions of turbine flowmeter

Turbine flowmeter is a typical velocity type flowmeter. It has the characteristics of high measurement accuracy, fast response, and high pressure resistance, so it is increasingly widely used in industrial production.
The turbine flowmeter operates based on the principle of conservation of fluid moment of momentum. The measured fluid drives the turbine blades to rotate, and within a certain range, the turbine speed is proportional to the average flow rate of the fluid. The turbine speed is converted into an electric pulse signal through a magnetoelectric conversion device, which is amplified and sent to a display and recording instrument. The instantaneous flow rate and cumulative flow rate of the measured fluid can be deduced.
The turbine flowmeter should pay attention to the following points in daily maintenance:
(1) The flow meter sensor should be used in accordance with the flow range, nominal pressure, and flow direction indicated on the certificate of conformity.
(2) The temperature and environmental conditions of the tested liquid should comply with the provisions of this user manual.
(3) Power up the flow totalizer. When the downstream valve is closed, the flow totalizer should display zero flow.
(4) When the flowmeter sensor is put into use, all bypass valves should be opened first, followed by slowly opening the downstream valve of the flowmeter sensor, then slowly opening the upstream valve until it is fully open, and then slowly closing the bypass valve. If there is no bypass valve, the upstream valve can be slowly opened, and then the downstream valve can be slowly opened. Be careful not to suddenly reach a high speed on the impeller.
(5) When measuring liquefied gas and gasoline, it is necessary to maintain a pressure of 0.1MP higher than the vapor pressure of the liquid, which is close to the flowmeter sensor ɑ， To prevent excessive wear of bearings in a short period of time due to excessive impeller speed caused by increased volume during liquid gasification.
(6) Under normal usage, the flow meter sensor is generally inspected and calibrated once every six months to one year, with the cycle depending on the severity of the working conditions. If severe wear is found on the shaft and bearings, they should be replaced in a timely manner and recalibrated.
(7) During maintenance, unscrew the compression rings at both ends of the flow sensor and remove the guide seat and impeller from the main body in sequence.
a. Check for foreign object adhesion and wear of various components. When removing foreign objects, be careful not to damage the parts. After replacing the components, recalibration is necessary.
b. Magnetization of impeller blades can affect the modulation of signal voltage and cause errors. Therefore, do not allow strong magnets to approach the impeller.
c. After the maintenance is completed, install the front and rear guide seats and impeller in the original position and direction, and tighten the compression ring. And confirm that the impeller rotates flexibly, the gap between the top of the impeller and the inner wall of the main body is uniform, and the amplifier has signal output.
(8) Due to changes in the impedance of the detection coil over time, it is necessary to compare the conduction impedance and insulation impedance (greater than 2M) of the coil with normal values.
(9) After recalibration, when the constant K of the flow sensor instrument changes, do not forget to change the set value of the display instrument.
(10) It is strictly prohibited to allow steam to pass through the flow sensor during shutdown and line cleaning.