Vortex flowmeters operate by measuring pressure variations associated with vortices shed from a ‘bluff body’ in the flowline. Traditional devices use piezoelectric sensors which require associated electronics, so limiting their application in harsh and hazardous environments. SmartFlow addresses this limitation by combining vortex shedding flow measurement techniques with FBG sensing advantages. The result is a meter capable of withstanding extremes of temperature, vibration, magnetic field and radiation, whilst operating in hazardous areas without expensive associated Ex rated electronics. This then enables more affordable and practical flow measurement in such applications as steam plants, subsea and downhole oil & gas, LNG flowlines and nuclear reactors.
SmartFlow was tested in dry gas at pressures between 1 and 40 bar, showing linear performance at various pressures and demonstrating good accuracy across a range of Reynolds numbers. The meter was also tested in wet gas at up to 30% mass fraction of liquid, achieving accuracies better than 10% for wet gas.
A further, unique SmartFlow feature comes from the FBG data processing scheme. For conventional, electronic-based vortex flowmeters, sensor data is typically encoded into a simple 4-20mA signal at the point of measurement, at which point all further, detailed measurement data is lost. For SmartFlow, high-frequency signals from the FBG sensors are transferred to the remote instrument and fully analysed for data content. This data was found to contain a signal representing the Eigenfrequency of the sensor plate that correlates directly with the density of the flowing fluid. For steam flow applications, this leads to the highly sought after capability of combined steam flow and steam quality measurement from a single, inexpensive meter.
The multiplexing capability of FBG technology allows for a system wherein dozens of SmartFlow meters across a facility can be simultaneously interrogated with a single SmartScan interrogator, ATEX certified as required. For use in a surface facility, the interrogator can be located in a safe area control room. For downhole or subsea use, the interrogator can be located in a suitable surface location some tens of kilometres distant from the point of measurement.