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On 24 May 2019, IHC Systems from Sliedrecht has introduced its latest product, a radio frequency (RF), non-radioactive, density measurement system.
IHC Systems managing director, Quentin van Ballegooie; sales manager, Rens Klootwijk; and R&D manager, Jacco Osnabrugge, spoke to DPC about the development and the characteristics of the product and what it will mean for the dredging market.

Klootwijk explained, this development marks the culmination of a period of 15 years of extensive research, testing, and validation. Most suction dredgers nowadays are equipped with tools to measure the velocity and concentration of the dredging mixture in the pipeline, using a radioactive source, the so-called RA meter.

Despite the robustness of the RA system, making it industry standard, it has considerable disadvantages, predominantly due to the radioactive materials involved and therefore crew members having to be certified before being allowed to operate and manage the system.

IHC Systems therefore decided to develop a non-radioactive, environmental-friendly density meter. The company wanted the resulting product to be installed on board a dredger in a similar situation as current tools. Another aim was to make it possible to exchange the existing RA gauge without major adaptations to the dredger’s configuration. The new gauge had to be limited in size as well as applicable in horizontal and vertical pipe sections.

After the assessment, IHC Systems concluded that RF was the most promising technique to meet all requirements. A RF meter is fitted with one or more transmitting and receiving antennas, for each transmitting antenna, there is a receiving antenna on the opposite side of the pipe. Its working principle is based on measuring the phase shift and attenuation between transmitted and received signal.

The system consists of a few key components: a measurement pipe, radio electronics, and a signal conditioner. IHC Systems’ patented design consists of a pipe section of 1,200 mm. The antennas are placed behind irathane layers in such a way that they can be easily replaced. In 2015, the first field tests were carried out on board an operational trailing suction hopper dredger (TSHD). This was the 560 m3 inland hopper dredger Cornelis Sr of Baggerbedrijf De Boer/Dutch Dredging’s subsidiary Van der Waal from Papendrecht.

Van der Waal uses the Cornelis Sr for the mining of sand in the Rhine and Meuse river delta. Tests were carried out during a period of 11 months on seven inland river waters locations, both coarse and fine sand was dredged. The Cornelis Sr tests gave similar results to those from the laboratory, that is not more than 1% difference with the RA meter.

With the success of the initial tests, the next round started in 2016 in sea water conditions. The sea water tests were carried out with an RF meter with four antennas in a pipe section with a diameter of 900 mm. This was installed on DEME’s 5,600 m3 TSHD Artevelde.

The testing took place in different locations with challenging environments, including the port of Zeebrugge, and Maasvlakte 2 in the port of Rotterdam. The results were positive with only minor differences between RF and RA ranging within 1–5%.

Currently, Artevelde still operates with the RF meter on board and after two years of operation, negligible wear was found on the RF pipe section. The product is immediately available for existing dredgers.