How to adjust the flow rate of Weiliba?
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The factory used several VeriBa flow meters to measure air volume. After installation, the flow rate reading was not 0 when the system was at rest; it showed 260 within the range of 0–1300 m3/H, and in some cases it even reached 500. There was current flowing in the circuit. This makes me question whether flowmeters of the Weibah type are reliable or not; this is already the second time it’s happened. There was another instance as well, where the instrument was from Rosemount while the probe came from Jiangyin.
This is the Wiliba principle; just compare it and you’ll understand. . . With this flow rate, changes in temperature, pressure, and humidity will all affect the density, and naturally, changes in density will affect the flow rate as well
I understand the principle, but in actual use it doesn’t seem very accurate; there’s already a flow rate of several hundred cubic meters even when the system is at rest
If the reading is too high, use HART to adjust the zero point of the Rosemount differential pressure transmitter down to 0
I tried this method to zero it out yesterday
Consider the issue with the differential pressure transmitter again; or disconnect the differential pressure transmitter from the Wilo unit and check whether it outputs 0 when in a stationary state. If not, perform zero calibration. After calibration, observe the transmitter – if there is no change over an extended period of time, then reinstall the transmitter along with the flow meter. Observe again; if there is a value indicated, it means there is gas flow inside the pipe. There’s nothing that can be done about this; it’s not a problem with the instrument. Let’s tackle it from a technical perspective. Zeroing must be carried out in accordance with the specifications; otherwise, the calibrated zero point will be inaccurate.
This detail can be tried out; I discussed this matter with a senior engineer yesterday. Since the Weiliba flow meter has a market, it should be usable. Another detail is that this type of flowmeter probe requires a purging function, which isn’t installed here{:3_47:}
Weibiba and average velocity tubes are not suitable for every operating condition; many of their differential pressure ranges are only a few hundred Pa, or even less. If the normal flow rate is low and the flow velocity is too low, it becomes difficult for the differential pressure transmitter to make measurements; since the differential pressure is already small, it’s also not possible to filter out low-level signals, which results in the flow rate being displayed even when there is no gas flow. Even if the transmitter zero point is verified, it is prone to recurring issues. Using Weiba is not recommended when the pipeline flow velocity is below 10 m/s. If the gas is relatively clean, an average velocity tube is a better choice than a Venturi tube, as the pressure difference generated by an average velocity tube under the same operating conditions is approximately twice that of a Venturi tube. For differential pressure transmitters, either EJA or Rosemount models with a low range diaphragm should be chosen; if the required differential pressure is below 1 KPa, a more expensive micro-differential pressure transmitter is necessary.