Interfac Transmitter Calibration

Height of tank and location of D/P cell is critical to calibration range and must be known in order to answer the question.

Some thoughts:

1). Since the measurement is interface, for the sake of discussion let's use 'water' for the one medium in the tank, and the word 'oil' for other medium.

2). Interface is typically a level measurement: 'what is the level of the interface between water (on the bottom) and oil (on the top)?', so units of mm H2O or m H2O water column (wc) would be nearly intuitive. But kPa could be converted to percentage of maximum level by an HMI/indicator/read-out.

3). If the tank were filled to the top (same level as the low side wet leg level) with pure water, what would a properly ranged transmitter read as a percentage of maximum level?

Hint: DP reading is high side minus low side (remember, wet leg is water filled)

4). Would this 'all water/no oil' situation represent an 'interface' of 0% or 100% or some in-between percentage?

5). If the tank were filled to the top with pure oil (no water) with a density/specific gravity of 0.8, what would a properly ranged DP transmitter read?

6). Would this 'all oil/no water' situation represent an 'interface' of 0% or 100% or some in-between percentage?

7). If the tank were half full of water, the other half oil, what would the interface level be?

8). What process condition(s) is/are necessary for this interface by DP to function?

9). What other data would be necessary to determine the proper scaling/ranging for the DP transmitter?

10). What has HiTekRednek had to say about similar situations?

http://instrumentationtools.com/level-measurement-terminology/

Go back to the design documentation for the plant. In there will be an Instrument Specification document for the instrument, a mechanical Hook-up Drawing for the instrument, and a Commissioning Record for the instrument. Further, there will be periodic maintenance Calibration Check documents, dated at intervals from when the instrument was first brought into use. There may well be an HazOp Study record document that mentions it. In a well-managed facility these documents should answer all the questions.

Come back when there is anything on those documents that is not understood, please.