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Content Level Measurement Detection in Seawater Tank

12 Dec 2019  |
In Malaysia, a plant operator in the power generation field was looking for a smart solution for continuous level monitoring of its seawater tanks.

To meet the challenges of space constraints and the salty atmosphere within the containers with robust accurate content detection, the NivoRadar® NR 3000 contact-free radar sensor with robust stainless steel housing was used.

Contact-free radar sensor as the innovative solution in cooling processes

The Malaysian energy producer is part of an energy development company that organizes the generation, transmission and distribution of electricity for the largest state on the island of Borneo in northwestern Malaysia. Due to the abundance of indigenous resources such as water, coal and gas, the power supply for more than 2 million inhabitants in an area of 124,451km2 is provided by a combination of hydropower, thermal energy and alternative energy. The company uses existing natural resources to generate predominantly renewable hydropower, supplemented by heat from gas and coal.

In the energy industry, safety and efficiency come first. For the coal-fired power plant, which is a major electricity supplier to the southern and central regions of Borneo, with a total output of 270 megawatts, the plant operator was looking for a robust and reliable level monitoring solution in its seawater pump cooling vessels. Due to the geographic location within easy reach of the South China Sea, seawater can be fed into the cooling system and used to effectively control the temperature of the boiler turbines. The tanks are 15 meters high and contain 86,000 cubic meters of water. The level sometimes changes very quickly and must be recorded reliably as a full and empty message. In this part of the world, the average salinity of the seawater is around 3.3%, which corresponds to a salt content of 33 grams per kilogram of seawater, which is slightly below the general average of 3.5%. Nevertheless, there is a sufficiently large salt content to exert a corrosive effect on sensor technology, which is in permanent contact with the seawater.

The local UWT partner, situated near the Malaysian capital Kuala Lumpur, worked in partnership with the energy producer to produce a reliable solution for continuous level measurement on site. The non-contact radar created an optimal solution for the application. Radar sensors are often used in addition to electromechanical plumb bobs for continuous level measurement in storage processes. They measure distances up to 100 meters and, thanks to their high sensitivity, can also be used in different liquids and pastes, except very fine bulk solids.

The radar sensor works with a high-frequency 78 GHz signal, which is emitted with a very narrow beam of only 4°, reflected by the sea water and received again by the sensor. The frequency difference, which is directly proportional to the distance, is then further processed and output as a fill level signal.

Optimum positioning with specially designed protective housing made by the UWT Partner

The mainly tropical rainforest climate is humid and warm with a constant temperature of around 25°C all year round. The sun is high in the sky at noon, which produces a tremendous amount of evaporation. Depending on the degree of build-up, the measurement result can be distorted. This, in turn, can affect the entire finishing process when overfilling or idling occurs. Constant and consistent cooling by the seawater is crucial.

The advantage here is, of course, the use of non-contact technology. In addition, due to the integrated lens flush for the cleaning of the lens antenna, the application was completely problem-free. Even the formation of condensation or salt deposits, the flushing connection ensures a reliable measurement. The device uses two-wire technology and is easily put into operation via a local programming device with display and a quick start wizard. The free-radiating radar sensor has a completely sealed construction and delivers reliable measurement results at process temperatures from -40°C to +200°C.

In order to properly position the radar within the seawater tanks so as to ensure accurate level monitoring, a special housing construction was designed in which the device was installed. This acts like an adjusting flange by means of which the radar sensor could be optimally aligned in accordance with the container conditions and the beam lobe could be fixed to the desired point.

The entire installation kit was made entirely of sturdy stainless steel to provide the sensor with additional protection against heat, high humidity and corrosion due to the high salt content and, moreover, it could be installed very space-saving inside the tank container. UWT has further equipped the radar with an extra-narrow beam, which allows use in tanks and containers where space is tight and facilitates the installation and placement of the sensor.

Keeping a constant eye on the contents of the tank

The NivoRadar® can easily be combined with the Nivotec® visualization system and offers a good combination option as an element for level determination. The data visualization provides the detected levels in height, percentage, weight or volume. Trends are saved, emails via fill levels or silo messages can be activated. The remote retrieval of the data obtained can also be done via a GSM modem. Here, the current measured values can be retrieved via the Nivotec® visualization software on every Ethernet PC via Internet browser. Data access is particularly swift, because the visualization controllers are integrated directly in the company Ethernet. System installation is straightforward and can be done by our own service staff. The fact that all detected fill levels are currently available at all times ensures a certain degree of planning security for the plant operator.

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