RF Density Meter
Kris Zych, IHC Merwede
Dredging is crucial to maintain commercial waterways for ships and barges around the world. Nowadays it is done by means of a hydraulic transportation, where sand is sucked in and pumped away through a pipeline. The in-line density of this water-sand mixture i crucial for the efficiency of this process.
At IHC an innovative density measurement method was developed, where a high frequency radio wave (RF) propagating across a pipeline is used. Laboratory measurements showed that the density of the mixture can be calculated from the measured signal phase velocity. Trials onboard a ship revealed however that salt content of estuary water seriously disturbs the measurement, causing the RF prototype to give erratic result.
The task of the project was to investigate and tackle the problem caused by salty water,
including the development of an operational prototype. First a series of carefully designed
experiments were performed on the existing prototype. We investigated all aspects of the signal path, including the signal-processing electronics and EM field measurements inside the pipe, followed by physical modeling of influence of salinity on the signal propagation.
The main experimental actions were performed using a dedicated pump setup (Fig. 1.). We were able to create a flow of water-sand mixture with full control over the density and the salinity. We discovered that not only the signal level and phase accuracy but also the frequency spectrum are crucial for correct determination of the density. A vast body of experimental data was obtained, and a measurement algorithm was derived, allowing for real time measurements of density, regardless of the variations of salinity of the mixture (Fig. 2.).
At the end of the graduation project we delivered a working prototype of the RF density meter. Obtained results show that the RF method has a potential to outperform the current density measurement methods. As a result, IHC Systems is ready to built a first device which can be offered to customers and revolutionize the market of inland dredging vessels.
Kris followed the DTI program. His graduation project was the design of a slurry density meter. The project was carried out at IHC Systems in Sliedrecht under supervision of dr.ir. Martijn van Eeten, (IHCS) and prof. Herman Beijerinck (TN TU/e).
Now he continues the full development of that device as an R&D engineer at IHCS and simultaneously as a PhD in Design candidate, tutored by prof. Ward Cottaar (TN TU/e).