Bubbler Level Measurement in Closed Vessel Vacuum


Thread Starter


Dpt make is abb and model no is 266MST-F-MBAR-CBAR-K-A-6-J-1E1L1-MM-B2-M51L C1 H. Vessel is under vacuum 70 kpa A and level material specific density is 1129 kg/m3. Vessel length is 1938 mm.

Please provide the information how I calculate the transmitter urv and lrv. I have dpt and constant n2 plow though rotameter and differential constant relay.
DP transmitter's Low side port connects to vapor/vacuum port.

DP transmitter's High side port connects to the output of the N2 differential relay (constant flow regulator) anywhere along the line (can be at the top of the dip tube).

Specific Gravity: 1129 kg/m3 / 1000 kg/m3 = 1.129

I'll use DP transmitter engineering units in mmH2O

If the level measurement is to be made to the top of the tank and the maximum tank height is 1938 mm, then

LRV = 0.000 mm H2O (bottom of the dip tube)
URV = 1938 * 1.129 = 2188.0 mmH2O

The host system converts the mA signal to actual level over a range of 0.0 to 1938 mm level.

If the dip tube does not reach the bottom, the elevation distance between the dip tube and the bottom can not be measured and will represent a fixed offset error.
Very simple, connect the LP connection to the headspace and HP connection to the bubble tube.

Low range for length of tube under fluid at zero level x density.
High range for length of tube under fluid at 100% level x density.
The units will be inches or mm Water Column.
The output will be zero to 100% level.

You can forget about the static pressure, the DP cell takes care of that.