Calculating Fluid Density Changes in Foundation Fieldbus Devices

I received this question on density measurement and wanted to share what I found out.

I understand all dP flow measurements are affected by the density of the fluid (liquid or gas) flowing through orifice, annubar, pitot tube, etc. Most dP measurements in process measurements make an assumption of the density of the fluid. I understand the measurement of density is a complicated and expensive.

My question to you concerns Foundation Fieldbus systems.

  1. Are the math blocks for calculating liquid flow using a Differential Pressure Transmitter available in a Foundation Fieldbus network? I know there are flow computers for this calculation. I was hoping FF would absorb the flow computer functionality.
  2. If this capability exists, does the calculation allow for the input of density over the FF network for realtime correction of the flow measurement for changes in fluid density?


I turned to Emerson’s Sudhir Jain who has lots of experience in the oil & gas industry and with the Foundation fieldbus protocol technology in his role as a Senior Industry Consultant.

Sudhir pointed me to the Rosemount 3051S Series product data sheet. On page 119, it describes a fully compensated mass flow block option:

Calculates fully compensated mass flow based on differential pressure with external process pressure and temperature measurements over the Fieldbus segment. Configuration for the mass flow calculation is easily accomplished using the Rosemount Engineering Assistant software.

3051smv-eng-assistantThis software enables configuration of the Rosemount 3051S MultiVariable transmitter and is available either standalone or as AMS Snap-On application. The software includes:

  • Comprehensive fluids and primary element database
  • Instant validation with test calculation
  • Compliance with industry standards including API, ISO 5167, AGA Report #3 & #8, and ASME, MFC-3M
  • Status and quality reported on all process variables for enhanced diagnostics

Ultimately, depending on the parameters of the application, this solution or the use of Micro Motion Coriolis Flow and Density meters might be the best fit.

You can connect and interact with other oil & gas and flow measurement experts in the Oil & Gas and Flow groups in the Emerson Exchange 365 community.

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