The overused topic of flow meter range setting!
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This post was last edited by wtkmail on 2012-4-4 19:50. Our facility has dozens of flowmeters, including vortex, mass, electromagnetic, differential pressure, and others! The brands include E+H, KRONHE, SIMENS, HONEYWELL, ROSEMOUNT, and more! Taking one of the Cologne mass flow meters as an example: the data sheet provided by the design institute indicates a range of 0–40 t/h, with a minimum value of 18 t/h, a normal value of 25 t/h, and a maximum value of 32 t/h. The primary flow meter selected is the OPTIMASS 1300C S40, with a range of 0–60 t/h. Since the conveying capacity of the pump in use on site is 25 t/h, what should be the appropriate range for this meter?
Reply to 1# wtkmail: Your range is quite inconsistent; it’s 40T one moment and 60T the next.
The range of a single gauge is related to the current signal fed into the control room; what’s important is that the value set for the single gauge is 60. So, the configuration in the control room should be set to 60. 40 is the same in this case as well. Either one is fine!
The flow rate of the flow meter is related to the following concepts: The minimum flow rate of 18 T/h specified by the design institute refers to the minimum flow rate required for the process； The normal flow rate of 25 T/h refers to the usual flow rate in the process, while the maximum flow rate of 32 T/h represents the highest flow rate possible in that process. Additionally, the design institute specified the measurement range of the flow meter, which is 0–40 T/h for the calibrated flow meter. However, many flow meters have corresponding flow ranges for different diameters; in other words, they also have their own minimum flow rate of 380 kg/h, a typical flow rate, a maximum flow rate, as well as a flow range set at the time of manufacture. Here, 0-60 T/h represents the maximum flow rate that this flow meter can measure. Today’s flow meters are essentially smart devices; through their menus, it is possible to set the output scale for 4-20mA signals. Here, a flow rate of 0-40 T/h corresponds to a 4-20mA signal. You can also set 0-60 T/h to correspond to 4-20 mA. But it must be consistent with the calibrated flow rate in the design institute and the DCS. If you have any further questions, please contact us.
Was the output forced to 20mA or the maximum frequency during the circuit testing?
As you said, I set both the flowmeter gauge and the DCS to 40 t/h as specified in the data sheet, but the process team believes that the pump’s capacity is only 25 t/h; therefore, they consider the measured value of 40 t/h to be inaccurate!
Please don’t get it wrong, friends – once the pump starts running, the flow meter shows a value of around 40. I deliberately changed the range to 20, and the reading on the gauge became 20! The DCS hasn’t changed; it’s still 40. That’s easy to understand! So once the flow measurement range is designed, it can’t be changed arbitrarily?
For example, with another Cologne electromagnetic pump, the range specified in its data sheet is 2400; each pump has a capacity of 950. When one pump is in use, the reading is 1209, and when two pumps are used, the reading is 2413. According to the process requirements, the pump’s capacity should be 1900 only – the error is too large. I had to explain to him that the capacity of the pump is only an approximate value, and the gauge should be taken as the accurate figure! I deliberately set the range to 1900, yet it shows 1902! Since it can’t be changed arbitrarily, why not set the range to a fixed value? ? Time to go to work
Regardless of the range, as long as 20% of this gauge’s reading matches is sufficient
Reply to 9# SHY0528: It’s extremely easy for the primary meter and the secondary meter to show the same reading! What I pursue is accurate traffic display! Exact!
According to the design institute, 0 to 40 tons