Regarding the issue of the drum liquid level
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I would like to ask the experts why, when using a differential pressure transmitter to measure the level of the drum, the range is set to -300mm to +300mm?
I don’t know either; I want to figure it out as well. Where exactly is 0mm in relation to the boiler drum? . . . Brother is so confused; he is in pain and confused.
For the pressure difference, calculate the range based on the density of the medium, and determine whether -300 corresponds to the zero point or 0 corresponds to the zero point.
-300–300 mm is a value used for process considerations; it refers to the center plane of the drum. At this point, the evaporation surface is at its maximum size, and there are also requirements regarding control at the drain outlet. Speaking of instrument settings, the drum level is generally measured using a double-chamber balance vessel with a range of 0.6 meters; under actual operating conditions the specific gravity is less than 1. The pressure P is determined using the pressure formula, and the transmitter is set to the range -P to 0 ； The system side is set to 4–20mA, corresponding to 0–100%. The above assumptions are only accurate under design conditions; there are deviations when water is supplied. Using DCS for compensation is a bit more complicated.
The setting for the transmitter using a two-chamber equilibrium vessel should be P~0.
0 corresponds to the centerline of the boiler drum. It is mostly instructions regarding operating procedures. As for practical use, what has been seen is that percentages are used, with 0 corresponding to the lower sampling port and 100% corresponding to the upper sampling port.
*It’s just a habit; it’s a matter of different perspectives.
Are you still playing your one-on-one dedicated posts? . .
It should be to add or subtract at the 50% position, right?
This midpoint can only be set at 12 mA – it’s just an approximate value. Upon closer examination, it becomes clear that the pressure of saturated water and steam is highly dependent on temperature, which makes things complex. Moreover, the level of water in the steam drum doesn’t need to be that precise either.