Answer / valluri066

Range is Negative mmWC to Zero because we are using "Wet leg configuration" arrangement. In which LP side of transmitter is contains a Condesate Pot always filled-in with water.

Wet leg configuration is used when the tanks contain CONDENSABLE VAPOURS, these vapours when entered impulse lines may be condensed over time and get accumulated. This accumulated liquids in impulse line creates Pressure head resulting error in level measurement. to avoid this suituation we initially fill LP side impulse line with water ( or a condensate pot is used to condense vapour and fill impulse line automatically).

Answer / mithilesh kumar

actually wht happen there..
level is totally depend upon vessel/drum/tank type..
means that it is open or close..
if it's open then range is in positve..
but if it's fully closed then range is start with negative..
by using level formula..
u can mail me if this formula or step is required..
email id: mithilesh.barnwal30@gmail.com

Answer / sam

In both cases you are using a wet leg configuration with the
DPT. In the steam drum if you use the old fashion way by
changing the HP and LP legs around you will get a positive
mmH2O reading. If you use a piped SMART Tx or a SMART
capillary type DPT, you will get this negative mmH2O readings.
I have already done a writeup on this so go and look at
previous questions.
In the deaerator there is a vacuum but again the same wet
leg is done. I have already done a writeup on this vacuum
applications as well so go and look at previous questions.
Good luck

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