Those responsible for handling chromium-containing process wastewater must take great care to prevent overflows in collecting tanks. Laurent Roumieux of Belgian water and wastewater service provider, ENGIE Solutions, talks about why his company chose the new VEGAPULS 21 compact radar level sensor to minimise this risk.
Belgian company, ENGIE Solutions, specialises in industrial wastewater treatment for reuse as drinking or process water. A large engineering company in the Liège region of Belgium asked ENGIE for help with its fluid treatment plant, which was taking care of the treatment of wastewater and other fluids from various processes.
An especially difficult challenge was the chromium-containing wastewater coming from a process for treating the surfaces of metal parts. The chromium in the chromic acid solution first had to be extracted from the wastewater before the wastewater was sent for further treatment.
Chromium is not easy to handle because it is dangerous due to its possible effects on health and the environment. The collected chromic acid solution had be stored in a double-walled HDPE tank to prevent leakage and thus environmental damage. The plant was also looking for a reliable measuring system to accurately track the level of the aggressive chromium solution in the tank. The tank capacity needed to be used to the fullest extent, but under no circumstances could the maximum safe level be exceeded.
Until recently, ultrasonic technology was generally used for level measurement in wastewater treatment plants, basically for economic reasons. However, when VEGA launched a new sensor series based on radar measurement technology in early 2020, new perspectives opened up. The compact radar instrument VEGAPULS (Series 10, 20 and 30) are comparable with ultrasonic instruments in terms of cost, but are much more reliable and user-friendly.
VEGAPULS 21: Ideal for safety critical applications
“I was looking for a level solution that would pose no risk to my employees,” explains Laurent Roumieux, team leader at ENGIE. “Up to that point we had been using an ultrasonic measuring system, but I had installed a non-contact radar sensor on an HDPE tank filled with hydrochloric acid (HCl). My VEGA contact helped me to select the instrument and set it up. I was quite impressed because I was able to check the level just by mounting the sensor over the top of the HDPE tank. This solution was very simple and, above all, safe and worry-free. The sensor has provided reliable measurement data ever since it was put into operation.”
Due to this positive experience, Roumieux considered installing this radar sensor on the tank holding the aggressive chromium solution. The application was not identical; in fact it was much more complex because the tank was cylindrical and double walled.
Nevertheless, due to the experience gained from the new VEGA radar measuring instruments on the HCL tank, Roumieux decided to go ahead and install a VEGAPULS 21 for the chromium application.
The VEGAPULS 21 is part of the new compact series of radar level sensors from VEGA. The beating heart of these new sensors is a radar microchip that was newly developed by VEGA and specially optimised for the requirements of level measurement. Thanks to the small design, very compact sensors are now possible.
80-GHz technology means that the radar beam can be aimed at the measured medium with pinpoint accuracy. The technology enables real level signals to be better distinguished from interfering signals. The measuring process itself thus becomes much easier and more precise than other measuring methods. No incorrect measurements arise from deposits or internal installations, such as pipes, probes or pumps, in double-walled tanks or in narrow shafts.
This means that – in contrast to ultrasonic sensors – no false signal suppression is necessary. Besides being unaffected by temperature fluctuations, vacuum or high pressures, radar sensors are, most importantly, not sensitive to build-up on the sensor. These are all factors that can often cause other types of measuring devices, such as ultrasonic level transmitters, to malfunction. What is more, radar sensors have a wide dynamic range, which guarantees reliable level measurement even if there is strong signal damping.
The installation experience
These features made the VEGAPULS 21 ideal or this application. “I didn’t need to make any openings in the double-walled tank to install the sensor. This is important for several reasons. For one thing, the measuring system is very safe because, when handling the sensor, my staff never comes into contact with the chromium solution and thus there is no risk of an accident happening during installation,” says Roumieux, highlighting a most important advantage. “And for another thing, I didn’t need to drill holes in the tank to install a mounting flange for the sensor. This prevents damage and also eliminates the cost of fitting a suitable flange.”
Another advantage is that the new compact sensors measure right up to the edge of the container without a blocking distance. With ultrasonic sensors, on the other hand, the optimal adaptation of the sensor is made more difficult because the blocking distance is greater and the maximum range is thus reduced. This is not an issue with radar sensors – the blocking distance is much smaller and even heavily soiled sensors can deliver exact measurement values. This allows the maximum volume of the tank to be utilised.
The VEGA Tools App
For the technical team at ENGIE, the new sensor not only delivered more safety in handling, it also made installation faster. Thanks to the VEGA Tools App, which makes use of the tilt sensor integrated into smartphones, it was easy to align the radar sensor perfectly to the cylindrical tank. Technician Yannick Crouquet, who was in charge of installation and commissioning, found this application extremely practical. “It meant that I didn’t need to bring along a spirit level or a scaffold onto the tank to align the sensor.”
But Crouquet is also enthusiastic about the app for other reasons. “I can connect directly via my smartphone using the free VEGA Tools App.” Sensors that have the display/adjustment module, PLICSCOM with Bluetooth, can also be wirelessly adjusted using the app. The intuitive user interface of the app makes it easy to configure a sensor and put it into operation. What is more, the user can read the current level measurement and the sensor status at a glance. And all relevant information about the VEGA instrument can be retrieved just by entering the serial number. This makes later maintenance work much easier.
The VEGAPULS 21 is an ideal level sensing solution for the chromic acid tank, which is difficult to access because mounting and movement on the cylindrical HDPE tank should be avoided. Yannick Crouquet explains: “Thanks to the VEGA Tools application, I was able to monitor the liquid level of the tank and the signal quality of the probe remotely during the first few days of operation. After a few days of observation, I knew that the VEGAPULS21 was working and I could concentrate on other tasks again. It’s also much easier to access the parameters later and reconfigure the new level sensors, if necessary. It’s a real time saver and far less restrictive,” he says.
Looking to the future, Roumieux says that ENGIE will be gradually replacing all of its ultrasonic devices with this radar instrument, especially in applications where foam occurs – because radar is much less sensitive to foam – and also where space is very limited and the open path for a measuring beam is very narrow.
“We’re going to use this same radar model as standard for all of our installations so that we only need to keep one sensor type in stock for all level measuring applications. Then our technicians will no longer need to learn different installation routines for multiple brands,” he concludes.
