Emerson Exchange 365

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Scaling level % and Volume for Conical Tank

We currently have 2 Conical tanks that have level pads (pressure) on the straight wall side of them. Operations wants to move them to the bottom where the piping connects.

The Rosemount 3051 transmitter will move to the bottom and be scaled in the transmitter for 0-230 inches H2o which then will output a 0-100% (4-20mA). this is what I will use for our DeltaV level %. This will be LI040200

I need to figure out a way to convert that to volume. We have never done this style tank before, so I am here to ask for help.

They would like the volume to be in liters.

With the tank being a conical shape I am not sure the calculation that I need or if there is a way to do multiple scales in DeltaV.

Just so I am being clear the tank is a total of 188 inches tall the conical cone shape is 47 inches tall and the cylindrical straight wall is 141 inches tall.

Thank you in advance for all the help.

Adam Villhauer

• 13 Feb 2024 8:33 PM
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2 Replies

• KeithStThomas

  

  • 13 Feb 2024 9:01 PM

  Hi Adam,
  
  There isn't a built-in method to characterize the scale other than the linear or square root options. However, you could use the "raw" signal and apply your own calculation and/or characterization to it. The trick will be how to connect this new calc signal back to a graphic and faceplate for the operator to see. One way is using 2 AI blocks and a Calc block in between. Call the 1st AI block AI_RAW, assign the DST to this block and scale it 0-188 inches. Connect AI_RAW/PV to a calc block, calculate the volume based on the level signal and output to OUT1. Then connect the CALC1/OUT1 to the simulate input of the 2nd AI block, called AI1. Scale is set to match your volume range and simulate is enabled. This AI1 block will be accessible to the standard faceplates.
  
  You will need to know the radius of the upper and lower parts of the cone and use the formula V = πH/3 (R2 + Rr + r2), where V=volume, H = height, R = radius at top of cone, and r = radius at bottom of cone. This formula applies until the level reaches 47 inches, then use a standard cylinder formula for the remaining volume.
  
  Hope this helps.

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• Brian Hrankowsky

  

  • 14 Feb 2024 5:12 PM

  In reply to KeithStThomas:

  another approach can be to add an AI and signal characterizer to an alarm block based module. bring the input in through the AI, wire the AI1/OUT to the SGCR input. set the characterization as needed. wire the SGCR to the ALM block input. This avoids needing anything in simulate or other unusual block mode/status.
  
  I do not know the features of a 3051, but another approach used with other level transmitters is to use a strapping table in the transmitter itself. It may depend a bit on your instrument shop and calibration practices (or other) how well this would fit for you.

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