DP level transmitter calibrated range

[frogcurry]

Currently planning on using a DP cell for a level transmitter. The level is in a static line on the outlet from a vessel. My question is this, for specifying that item I have been asked to supply a range of barg pressures for a "calibrated range". My expectation was that the range would be a differential pressure for the maximum density of fluid and height that the cell needs to measure. Also this would not any cause issues with different pressures in different operations as I have, whereas quoting barg values requires picking a case to quote the barg values from.

i.e. max fluid density is 1100 kg/m3, height is 1m, so P=pgh, etc.

I would like to know what others make of this and in particular where I am going wrong (if I am).

 

[quark]

The DP transmitter might have been calibrated with respect to barg initially and now it may be adjusted for meters of liquid column.

It is better if you stick to your point. Just provide the maximum liquid column height and the liquid density. If your process pressure changes during the process, your dp should read the liquid column height with respect to vapor space pressure. Change in density does effect the accuracy of the meter and you may have to go for alternate technologies.

Regards,

 

[frogcurry]

Thanks.

 

[underpressure1]

frogcurry,
As far as I understood you need to measure a liquid level in a tank (or chamber) that is under an X static pressure (not an atmospheric tank).
Your fluid max spec. gravity is 1.1 kg/lt;
Being your application not atmospheric you have to use a DP transmitter and connect the negative side of the transmitter to the top of the tank / line that have to be dry.
The calibrated span will be 4 mA=0 mmH2O and the 20 mA = 1100 mmH2O.
In the case you can connect the negative leg to the top side of the tank, what you have to look for is only the max static pressure you have in the tank as the process flanges will need a compatible rating (and obviously the max working pressure of the transmitter have to be compatible too).