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Explanation of factors affecting the accuracy of vortex flowmeter

1. Dryness change
The vortex flowmeter requires a saturated steam dryness of not less than 85% when measuring saturated steam. However, the actual situation on the site is that the saturated steam dryness is less than 100% in the boiler, and after a certain distance is transmitted through the pipeline, the dryness will be less than 85%, which makes the measured value.
decline.
2. Pressure changes
There are many valves and pressure reducing valves in the heat network piping that can change the piping pressure. Vortex flowmeters are not mass flowmeters. The metering of steam quality depends on the pipe flow rate and the vapor density. The density is determined by the pressure. Changing the pressure means changing the density. When the valve is just opened, the pipe flow rate is also changed. error.
Pressures often fluctuate at industrial sites, and pressure fluctuations can affect saturated vapor density. When the pressure is lower or higher than the calibration value, it directly affects the high or low mass flow value.
3. Pipe and flow meter vibration
The instrument coefficient error of the vortex flowmeter becomes larger as the vibration acceleration of the pipeline increases, and the overall seismic performance is poor. Under the same pipe vibration acceleration condition, no matter how the vibration frequency changes, the instrument coefficient error of the vortex flowmeter decreases with the increase of the flow rate, and the small flow is most affected by the pipeline vibration. At the same time, the meter coefficient of the vortex flowmeter decreases as the vibration frequency of the pipeline increases. Pipes and flowmeters are not well reinforced, or the flowmeters are vibrating near the motor. The vibration will cause interference to the vortex flowmeter, causing the flowmeter to measure too high or cause traffic misjudgment.
4. The outlet side of the flowmeter leads to the atmosphere
The exit side of the vortex flowmeter leads to the atmosphere, and there is a phenomenon that the pressure difference between the front and the back is too large, which causes the flow rate to reach the upper limit, so the flow change cannot be correctly reflected. This situation is mainly caused by the zero drift and unreasonable arrangement of the pressure tube.
5. The straight pipe section before and after the flowmeter installation does not meet the requirements
The installation of the vortex flowmeter has certain requirements for the straight pipe sections before and after. If it does not meet the requirements, it will affect the correct formation of the Karman vortex street, thus affecting the measured value of saturated steam. For example, for the LUGB-2310 vortex flowmeter, when installing an elbow upstream of the pipeline, a straight pipe section with a length greater than or equal to 20D (D is the nominal diameter of the flowmeter) should be placed on the upstream side of the vortex flowmeter, and the downstream side should be configured with a length. Straight pipe segment greater than or equal to 5D.

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