Superheated steam flow totalizer problem
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The field instrument has a temperature and pressure compensation of 4-20ma and is connected to the calculator. The range is correct, but the display is inconsistent with the field flow meter. I just want the function of accumulating flow. The k coefficient and density in the calculator are not necessary.
If DCS you are connected traffic is sending signals. It's equivalent to sending the signal directly. How can it be different? If they are two separate systems and the calculator performs on-site calculations, and your DCS only collects the differential pressure signal, then converting the differential pressure signal into flow rate requires temperature and pressure compensation calculations, etc., not just the measurement range.
What is output to the calculator on site is the current corresponding to the differential pressure signal. If the meter header does not have a square root, then the square root must be set on the calculator side, and the K coefficient and density must be set.
Even if it is the same signal, the accumulated value of the flow meter head and the calculator may be different. It may be due to inconsistent sampling periods, or it may be a slight deviation of the transmission signal, but this amount will become larger and larger as the accumulated value becomes larger, so the accumulated value can only be calibrated with a standard and cleared regularly.
The flow totalizer is the accumulated flow after temperature and pressure compensation, while the on-site flow meter has not been temperature and pressure compensated or has manually set temperature and pressure, so the two displays cannot be consistent.
It has a lot to do with your primary element. It also involves the flow coefficient C and the expansion coefficient β. It is not just a simple Bernoulli equation. The internal part is an iterative equation about C and β as well as differential pressure and static pressure, so the measurement is not as simple as you think.
Thanks for the reply. You don’t need to change the meter header. Just change the coefficients and density in the calculator to 1.
The calculator only accepts 4-20MA and makes a total without calculating the coefficient or density. Measure whether the output current is consistent with the field meter display. The output current cannot avoid errors, so there will be errors accumulated over a long period of time. It is best to use RS485 communication to avoid errors.
Superheated steam is a very special medium that requires accurate temperature and pressure compensation. This needs to be corrected according to the actual parameters of the superheated steam. Only by performing compensation calculations with an integrator can more accurate flow data be obtained. Let your designers or technicians who understand steam measurement check and set the parameters of the calculator. Because the density of superheated steam is a nonlinear binary function of temperature and pressure, simple density calculations are inaccurate.
No matter what communication method is used, it cannot solve the factors affecting the density of superheated steam due to temperature and pressure. You probably don’t understand the special characteristics of superheated steam
The range corresponding to 20 mA is not set consistently, 13193756695