2016 WODCON - New Technology for Dredging Mixture Velocity Measurement
New Technology for Dredging Mixture Velocity Measurement
Passive sonar based mixture velocity measurement was evaluated on a DEME trailing suction hopper dredger. A conventional electro-magnetic flow meter served as the velocity reference. Evaluation was carried out over a period of several months and included various operating conditions; i.e. trailing, turning and dumping of both sand and silt type mixtures. Velocity of the mixture ranged from 2 m/s to 10 m/s at densities varying from 1 t/m3 to 1.8 t/m3. Results show very good agreement between passive sonar based measured velocities and the reference.
Passive sonar based technology allows a velocity meter to be clamped around existing pipework without any modification. Existing liner material, paint or rust does not influence the measurement. Unlike clamp-on ultrasonic meters, either Doppler or transit-time based, sonar based metering is a passive technology which works equally well in pure fluids as in mixtures. The sonar based meter on this trailing suction hopper dredger was installed by a crew of two in less than six hours during a bunkering stop.
Flow metering technology based on passive sonar has been available for years in slurry plant and pipeline management in a variety of industries. Applications such as a velocity meter on cutter suction dredgers have shown that the technology is a viable, robust and low-cost alternative to conventional electro-magnetic flow meter technology. Without any wetted parts and with no moving parts the passive listening employed in a clamp-around embodiment has proven to withstand harsh, ambient and operating, conditions for periods in excess of 10 years without any maintenance or recalibration.