Regarding the range ratio of vortex flow metering
Thread Content
This post was last edited by Lalaa2 on 2018-8-14 at 11:30. Hello everyone, today I came across an article; as shown in the picture, if the maximum velocity of (saturated) steam is 35 and the minimum allowable velocity for vortex flow is 5, shouldn’t the range ratio be 7:1? And now, many vortex flowmeters have a very large range ratio; so is the problem with the maximum velocity?
Is everyone busy today? :time:
Your range ratio does not refer to the absolute maximum and minimum flow rates; it is merely a reference value, and your range should include these two values.
I don’t quite understand what you mean. Could you explain it again? Maybe I haven’t figured it out yet; the range isn’t it just the maximum flow rate/minimum flow rate? In the case of the same pipeline, it should be possible to think of it as the maximum flow velocity/minimum flow velocity, right?
For example, my maximum flow rate is 15 and the minimum is 5. I can choose a range of 2 to 20
The article states that \"the lowest steam flow rate that can be measured by a typical vortex flow meter is 5 m/s\". Since the range of such meters starts at 2, does that mean they cannot achieve their accuracy within the range of 2–5?
Accuracy below the minimum flow rate cannot be guaranteed. The concept of range ratio seems a bit misleading to me, as manufacturers generally specify the maximum range ratio; the problem is that this may not apply to all media, as temperature, pressure, and density also affect the flow rate depending on the medium used. Therefore, it can be observed that the accuracy decreases sometimes after expanding the range.
Just understand them separately; don’t take it too seriously. Beyond the limit, the measurement error becomes so large that it’s unacceptable.
This parameter is one of the parameters of the flow meter; if the range ratio is high, it indicates that its actual measurement range is wide. This information is provided in the flow meter’s technical documentation, and the minimum flow rate is not zero. The advantage of a high range ratio is that one spare part can replace several original spare parts; there are no other advantages
This post was last edited by myface on 2018-8-15 08:46. Take another close look at the text: what he said is that the maximum flow rate affects the noise and erosion in the steam system, which is why the value of 35 is used; it’s not that this flow rate represents the upper limit for the accuracy of vortex flow meters. The above is an explanation based on the text you posted. In fact, what matters for vortex flow meters is the Reynolds number, rather than just the flow rate. In practice, this 7:1 range is exactly the normal range for vortex flow meters. From the examples of vortex flow meters I’ve seen, the generally recommended range is around 7-10; only for pipes with a diameter of over 200 mm is a range of around 20 applicable, and I’ve never seen such a range for pipes with a diameter of 30 mm. So it’s probably just pure theoretical data that doesn’t take operating conditions into account.