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1. Will there be data fluctuations when using a vortex flowmeter to measure liquid flow during blowdown?
When using a vortex flowmeter to measure liquid flow during blowdown, there is a high probability that data fluctuations will occur. The amplitude and duration of the fluctuations are directly related to the blowdown pressure, gas-liquid mixing ratio, and flow field stability..
1. Core reasons for fluctuations 1 Flow field is directly interfered: The measurement principle of vortex flowmeter is based on the linear relationship between vortex shedding frequency and flow velocity in a stable single-phase flow field. During blowing, high-speed airflow will destroy the original laminar or stable turbulent state of the liquid, forming a turbulent flow field in the vortex shedding area, resulting in irregular changes in vortex shedding frequency and directly outputting fluctuating flow data. 2. Mismatch of two-phase flow conditions: Compressed air is mixed into the process liquid during blowing, forming gas-liquid two-phase flow, while the calibration parameters of vortex flowmeter are only suitable for single-phase liquid conditions. The flow resistance and vortex generation conditions of two-phase flow are significantly different from those of single-phase liquid, and the flowmeter cannot accurately match the working conditions, inevitably resulting in reading fluctuations. 3 Abnormal amplification of blowing pressure fluctuations: If the blowing gas source pressure is unstable, it will cause the gas-liquid mixing ratio to change constantly, further exacerbating the turbulence of the flow field and amplifying the amplitude of data fluctuations.
2. Fluctuations in Different Blowing Scenarios 1
2. Online pressurized blowing: If the blowing pressure is strictly controlled slightly higher than the process liquid pressure, the gas-liquid mixing ratio is reduced, and the fluctuation amplitude is relatively controllable, but instantaneous reading jumps may still occur during periods with more bubbles mixed in.
III. Compliance Operation Suggestions 1 Prioritize offline blowing: Remove the flowmeter from the process pipeline and clean the blowing shell and front and rear straight pipe sections separately, which will not interfere with the online measurement flow field and can thoroughly clean the internal impurities. 2. Optimize parameters during online blowing: adjust the blowing gas source pressure to slightly higher than the liquid pressure in the pipeline, reduce the gas-liquid mixing ratio, and reduce the degree of flow field disorder. 3. Standardize data recording: During the blowing process, mark the abnormal data period separately, wait for 10-30 minutes after the blowing is completed (the larger the pipe diameter, the longer the waiting time), and then restore normal flow recording after the process liquid returns to a stable single-phase flow state Safety operation requirements: During operation, it is necessary to strictly follow the compressed air usage specifications, ensure that the blowing pressure does not exceed the design pressure value of the pipeline and flow meter, and avoid equipm
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