How to correctly understand the range ratio of a differential pressure flow meter!
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The method for calculating the range ratio of differential pressure-type flow meters should be as follows: first, determine the differential pressure corresponding to the maximum flow rate of this type of flow meter; then identify the minimum differential pressure permitted by it. The range ratio of such a flow meter is obtained by taking the square root of the ratio between these two values. To refer to the square root of the differential pressure transmitter’s range as the range ratio of the differential pressure-type flow meter is nothing but a misrepresentation of concepts. Considering only the square root of the differential pressure transmitter’s range, without taking into account the minimum differential pressure required by the throttling device for different fluids, is purely baseless. Let’s discuss this together!
The range ratio is the ratio of the maximum range to the minimum range that can be measured while maintaining measurement accuracy.
You may not be familiar with the product technology of our company. We are orifice flow meters that calculate the discharge coefficient in real time, point by point; therefore, the transmitter range (taken to the power of one half) is our flow measurement range. A standard orifice plate flow meter indeed cannot do it.
Correct, Pig Brother. A orifice plate generates a differential pressure simply because the fluid flowing through it causes jetting; when the flow velocity drops to a certain level, no jetting occurs at all, so where does the differential pressure come from?
It seems you’re too confident in your company’s product technology. In our natural gas industry, orifice plate flow meters are used to measure natural gas flow (in compliance with the standard GBT 21446-2008 \"Measurement of Natural Gas Flow Using Standard Orifice Plate Flow Meters\"); industrial computers are employed as flow computers to carry out iterative calculations (compensation is provided for almost all influencing factors). The other configurations are similar to those used by your company. The flow range recognized in this industry is usually within a ratio of 10:1, and no one dares claim that it can exceed this value (this is also approved by the technical supervision authorities). As for the transmitter aspect, “1111111” (whom we usually call Pig Brother) is already a rare expert (he has great expertise in pressure measurement); he shared a lot of relevant knowledge with you, but you just didn’t pay attention.
Our company has just had it tested at the **Measurement Institute in Yantai, and the accuracy is 1% within 1:30. Already certified
If all parameters are correct, the differential pressure range ratio can reach 10:1, which is the limit; there is nothing more to discuss.
It has been calibrated by the **Metrology Institute, with a precision of 1% at a ratio of 1:30. Of course, the measurable range should be at least 1:70.
No matter how low the speed is, that is, no matter how low the flow rate is, a pressure difference will always exist. This is because the orifice plate flow equation derived from Bernoulli’s equation does not impose a lower limit on the flow rate. The existence of something and whether it can be measured are two different things. The prerequisite is that the fluid must fill the pipe.
It depends on the throttling element you use; a range ratio of 20:1 is quite normal in some cases