It is well known that turbine flowmeters, positive displacement flowmeters, and Coriolis mass flowmeters in flowmeters are three types of products with relatively high levels of repeatability and accuracy, and turbine flowmeters have their own characteristics, such as a simple structure and processed parts. Small, light weight, easy maintenance, large flow capacity and adaptability to high parameters.
Because of the small changes in the eccentricity of the turbine and the mechanical frictional resistance torque, the turbine flowmeter will experience periodic speed changes in the same rotation cycle. This also makes it very difficult for the turbine to have extremely low speeds because it is extremely susceptible to disturbances. Stop turning.
The effect of the viscosity of the measured medium on the turbine flowmeter :
1. For low production wells with higher production fluid viscosity, a more sensitive turbine of the acquisition system should be used to enable accurate acquisition of low-speed (less than 0.01 r/s) signals.
2. Before entering the linear segment of the turbine response, the K value continues to increase, and the Reynolds number at the entrance of the flow meter increases exponentially.
3. As the viscosity increases, the K value of the turbine flowmeter will decrease, and the linearity will also deteriorate.
4. As the viscosity increases, the start-up displacement of the turbine flowmeter will decrease, and the minimum speed of response will also decrease.
5. Turbine flowmeters used to measure different viscous fluids only perform a calibration with different flow Reynolds numbers at high viscosity conditions. The relationship between K value and Reynolds number of the turbine flowmeter can be approximated, and the turbine is reversed. Response curves for different viscous fluids.
What are the factors that affect the measurement accuracy of turbine flowmeters?
1, the media generally have some impurities, wear on the bearings, shafts, so that the gap between the two increases, the dynamic balance of the moving parts is destroyed, the speed is reduced, or dirt into the gap, so that the resistance to increase the movement , Speed ​​drops. All of these reasons cause the display value of the instrument to decrease, causing a negative error, which is detrimental to the fluid supplier.
2. The fibrous or viscous impurities in the fluid are attached to the rotating part of the flowmeter , which increases the rotational resistance, causing the indicator value of the instrument to decrease, causing negative errors, and adverse to the fluid supplier.
3. Changes in fluid temperature and pressure may cause air contained in the pipeline to escape, or the pressure in the pipeline is lower than the saturation vapor pressure of the fluid, making part of the liquid into steam, or it may be caused by the negative pressure of the medium. The gas is sucked into the pipeline. These gases flow along with the measured fluid, causing the indicator value of the instrument to increase, causing a positive error, which is detrimental to the demand of the fluid.
4, the working environment is rather harsh, for example, electromagnetic interference, dust , high temperature, vibration, humidity, etc., may cause malfunction or failure of the turbine flow sensor , directly causing the turbine flowmeter error, the error is positive or negative The value may not be obvious or it may completely fail. For the above phenomenon, when it is more serious, problems can be found in the comparison of process working status and it is easy to take corresponding measures. However, in the early stages of the problem, problems could not be discovered without special measures.
Turbine flowmeter maintenance should pay attention to the following points:
1. When used, the measured media should be kept clean, free from impurities such as fibers and particles.
2. When the turbine flow sensor is used, the sensor should be filled with medium slowly, and then the outlet valve should be opened (the valve should be installed at the back end of the flowmeter ). It is strictly prohibited that the sensor is exposed to high-speed fluid when it is in the non-medium state.
3, the maintenance cycle of turbine flow sensor is generally six months. During maintenance cleaning, please be careful not to damage the parts in the measuring chamber, especially the impeller. Please pay attention to the positional relationship between the guide and the impeller when assembling.
4. When the turbine flow sensor is not in use, the internal medium should be cleaned, and after drying, a protective sleeve should be added at both ends of the sensor to prevent dust from entering and then stored in a dry place.
5, equipped with the filter should be cleaned regularly, when not in use should clean the internal media, with the same sensor, add the dust jacket, placed in a dry place.
6. Before the sensor is installed, use the mouth blow or dial the impeller to make it rotate quickly to see if there is any display, and then install the sensor when it is displayed. If there is no display, check the relevant parts and troubleshoot.
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