Non-contact flow measurements for marine research
Continuous flow measurements on board a research vessel to support sound velocity measurements and the calibration of acoustic echo-sounder systems for ocean mapping.
KATflow supports oceanographic research on board the FS METEOR
Research vessels carry out a wide range of tasks on the world’s oceans. They are scientific laboratories on the high seas and indispensable tools when it comes to understanding the Earth system. They cover a wide range of marine research fields in the areas of biology, geology, geophysics, glaciology, geochemistry, oceanography and meteorology.
The FS METEOR is a globally operating, multidisciplinary research vessel owned by the Federal Republic of Germany, operated and co-ordinated by the LEITSTELLE DEUTSCHE FORSCHUNGSSCHIFFE / the University of Hamburg and managed by BRIESE SCHIFFAHRTS GmbH & Co. KG / Research Vessel Division. The METEOR’s missions are overseen by the Federal Ministry of Education and Research and the German Research Foundation, on whose behalf it conducts research into the world’s seas and oceans.
In this context, the FS METEOR fulfils, amongst other things, two specific tasks: Firstly, using a so-called thermosalinograph system, it measures typical oceanographic parameters such as conductivity, salinity, temperature and density of the surface water (to a depth of approx. 6 m) and makes the results available to scientific databases and analysis systems on land. Research institutions and groups active in marine research can make use of this data at a later date. For example, temperature changes measured in a delta provide insights into how freshwater inflows into seawater vary. This enables conclusions to be drawn about changes in climate and ocean currents and ultimately leads to an accurate picture of today’s ocean circulation.
The second task of the METEOR is, on the other hand, to continuously measure the sound velocity at the ocean’s surface—which varies between 1,400 m/s and 1,800 m/s due to fluctuating oceanographic parameters— so that acoustic echo sounder systems can be calibrated with the corrected sound speed and, consequently, the seabed can be accurately surveyed and mapped. Incorrectly calculated sound speeds lead to errors in echo sounder calibration and, ultimately, to inaccurate ocean mapping.
The operator imposed several requirements on the flow measurement system. The most crucial characteristic for the research was non-contact flow measurement of the seawater; in other words, avoiding contact with invasive measuring probes, metals or plastics, so as not to chemically alter the seawater and thereby distort the analysis results. The process sensor system also needed to be as compact as possible to allow for the design of short pipework runs, free from geometries that could affect the flow. As several higher-level systems needed to be supplied with measurement results from the process via interfaces, the challenge was to find devices offering a wide range and flexibility of interfaces.
The shipping company found what it was looking for at Katronic and, following the consultation that took place during the process, procured a suitable flow measurement system. Consequently, two non-invasive KATflow 100 clamp-on ultrasonic flowmeters were installed on PVDF pipework with nominal diameters of DN 25–40 mm on board the METEOR.
Oceanographic parameters essential for accurately determining the speed of sound – such as conductivity, salinity, temperature and density of the seawater medium – are continuously measured and recorded whilst the METEOR is underway. To this end, seawater at a temperature of 8–18 °C is continuously pumped through measuring containers in flow systems. The process parameters of flow rate and pressure are of fundamental importance for the control and monitoring of the plant’s technical systems; these are also monitored and recorded for the subsequent validation of the data. Without valid process parameters, there can be no valid measurement results. Additionally, optical measurement methods in operation require continuous flow rates to prevent turbulence in front of the sensors’ optics. Constant, drift-free and temperature-stable flow rate measurements are an absolute prerequisite for the control of these measuring systems. As the shipping company itself explains: “Whilst the high-precision and exotic scientific sensors often behave like diva-like devices during ongoing operations, the process-related sensors should be exactly the opposite. Stability, reliability and robustness are essential here.”
Generally speaking, the results of the continuous flow measurements on the METEOR provide insights into the condition of the system with regard to organic fouling and sedimentation in the pipework and on sensors, and, of course, whether pump and valve controls are set correctly. “Overall, the flow meter plays a central role. Without flow measurement, everything we measure in these systems is essentially meaningless,” says Mr Wolf, one of the shipping company’s senior technical inspectors.
“BRIESE SCHIFFAHRTS GmbH & Co. KG has found a reliable partner for this purpose in Katronic’s flow measurement systems. Since 2014, scientists have been able to use them to carry out reliable validation and classification of the data collected without any failures.” To this day, the system measures flow rates in scientific analysis systems for freshwater and archives these as evidence for research.
Image credit: CONTROL CENTRE FOR GERMAN RESEARCH VESSELS / University of Hamburg
