Noncontact Flow Measurements for Marine Research
Continuous flow measurements aboard a research vessel to support sound velocity measurements and the calibration of acoustic echo sounder systems for ocean mapping.
KATflow supports oceanographic research aboard the FS METEOR
Research vessels perform a wide range of tasks on the world’s oceans. They serve as scientific laboratories on the high seas and are indispensable tools for understanding the Earth system. They conduct research across a wide range of marine fields, including 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 coordinated by the LEITSTELLE DEUTSCHE FORSCHUNGSSCHIFFE / 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 (DFG), on whose behalf it conducts research in the world’s seas and oceans.
In this context, the FS METEOR fulfills, among other things, two specific tasks: First, using a so-called thermosalinograph system, it measures typical oceanographic parameters such as conductivity, salinity, temperature, and density of the surface water (down to a depth of approximately 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 later. For example, temperature changes measured in a delta provide insights into how freshwater inflows into seawater vary. This allows 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 to continuously measure the sound speed at the ocean 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, as a result, the seafloor can be precisely 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 critical characteristic for the research was non-contact flow measurement of seawater—that is, avoiding contact with invasive measurement probes, metals, or plastics—to prevent chemical alterations to the seawater that could distort analysis results. The process sensors also needed to be as compact as possible to allow for the design of short piping runs free of geometries that could affect flow. Since several higher-level systems need to be supplied with measurement results from the process via interfaces, the challenge was to find devices that offer a wide range and flexibility of interfaces.
The shipping company found what it was looking for at Katronic and, through the consultation that followed, procured a suitable flow measurement system. Consequently, two non-invasive KATflow 100 clamp-on ultrasonic flow meters were installed on PVDF piping with nominal diameters of DN 25–40 mm aboard 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 while the METEOR is underway. To this end, seawater at a temperature of 8–18 °C is continuously pumped through flow systems via measurement containers. The process parameters of flow rate and pressure are of fundamental importance for controlling and monitoring the system’s operation; 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 use 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 controlling these measuring devices. As the shipping company itself explains: “While high-precision and exotic scientific sensors often act like divas during ongoing operations, the process-engineering 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 system conditions regarding organic fouling and sedimentation in the piping systems 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 responsible 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 reliably validate and classify the collected data without any interruptions.” To this day, the system measures flow rates in scientific analysis systems for freshwater and archives these measurements as evidence for research.
Photo credit: CONTROL CENTER FOR GERMAN RESEARCH VESSELS / University of Hamburg
