Detecting and Correcting for Coriolis Meter Calculated Fluid Density Drift due to Ambient Temperature Variation

Coriolis metering technology is now widely implemented throughout industry and is considered to be one of the most effective methods to monitor the mass flow rate of fluid within a pipeline. It is also well known that Coriolis meters have the
ability to determine the density of the fluid present within its internals. There is now an increased interest from the Oil and Gas industry in utilising this density measurement capability as the primary process value to be output from the technology in applications such as precision control for fluid property conditioning as well as fluid contamination monitoring and control applications. However, within the industrial environments in which these applications tend to be required it is common for there to be considerable fluctuation in the ambient conditions in which the meter is installed. This paper details research data obtained using NEL’s ‘Very Low Flow’ single phase
facility. The rig has been modified to include a programmable temperature enclosure. The results clearly show significant drift in the calculated fluid density output by a Coriolis meter when it is subject to fluctuations in the surrounding ambient air. The fluid properties of the test medium were confirmed to be stable
using NEL’s UKAS standard reference instrumentation. Using the high-resolution data sets obtained from this research programme, a modified density correction model to better compensate for these ambient temperature effects has been
developed and the improved performance from said model is demonstrated. The rig and test matrix which form the basis of the results were developed over two distinct research phases with input from several meter manufacturers and end users. The model demonstrates that correcting the reported fluid density for ambient variations is viable so that any system using the density value e.g. a PID control system, will not lose efficiency when the ambient air temperature varies. The resulting cost savings are therefore considerable. Previous temperature corrections for Coriolis meters have focussed on the process fluid temperature and there is little published data on systematic investigations of
ambient temperature. This work forms part of a 4-year doctoral research program investigating the influence of ambient conditions on Coriolis meter accuracy.