VEGAPULS 69 level sensor secures coal supply in an Indonesian power plant

Without a reliable supply of coal, even the best of all power plants couldn’t deliver the required energy. Reliable monitoring of the coal reserves is therefore absolutely essential. The coal is delivered by sea and unloaded into bunkers up to 30 m high. The coal is transported to these bunkers from the stockpiles of the power plant via conveyor belt systems above or below ground. From there, the coal has to be transported to the mills, where it is ground into a fine powder for subsequent combustion in the combustion chamber of the furnace. Reliable level sensors are required everywhere to ensure uninterrupted charging of the combustion chamber and to prevent overfilling of the bunkers. Especially critical is the continuous monitoring of the minimum level in the coal dust silos, because an interruption of supply to the furnaces must be avoided at all costs.
The problem: The ambient conditions that prevail in coal bunkers are not the easiest to deal with – logically, all sensors quickly get covered with dust and dirt. At the power plant in Tanjung, too, the company was constantly struggling with a measuring point that was supposed to display the precise height and thus the quantity of the coal reserves. However, the opposite was the case: again and again the reading jumped to the 100% value, although the actual level was completely different, often being close to zero. It was not only the dusty environment and the loud filling noises that caused problems for the measuring instrument, but also the typical bulk material distribution in the bunkers.

Since the power company had already had good experiences with VEGA products at other measuring points in the plant, for example with a VEGAWAVE 62 in the fly ash silo, a VEGAPULS WL S 61 for wastewater measurement and a VEGAPULS 64 for measuring the level in the chlorine tank, the Schiltach radar experts were asked for advice. They recommended VEGAPULS 69, which offers great reliability especially in dusty and dirty environments due to its high measuring frequency of 80 GHz. Interestingly, the system was first demonstrated in a small seminar room with the help of a canopy as the level and books as objects causing interfering signals. The presentation was nonetheless convincing despite the improvised setup and the company decided to take a shot at it with VEGAPULS 69.
Ever since its market launch, VEGAPULS 69 has been regarded as a very robust problem solver. With a measuring range up to 120 m and an accuracy of ± 5 mm, the sensor has sufficient performance reserves even for the most challenging applications. The height of nine metres here in the bunkers was therefore no big problem for VEGAPULS 69.

The antenna system of the sensor is made of the robust material PEEK, which has high temperature and chemical resistance. Its lens antenna is also non-sensitive to build-up and dirt and shows no signs of wear. Another great advantage in this application is that the 80-GHz microwaves easily penetrate the dense clouds of coal dust. Since the sensor has a flushing air connection as a standard feature, it can clean itself quickly at any time and "dispose" of any build-up. Even in this difficult application, VEGAPULS 69 is completely unaffected by the deposits of fine coal dust on the antenna and has been delivering correct measured values continuously since its installation. The supply of coal is thus no longer at risk.

The power company was also enthusiastic about another VEGA idea: configure all sensor parameters conveniently via PLICSCOM with Bluetooth with a tablet or mobile phone. Bluetooth wireless communication was developed especially for hard-to-reach places, harsh industrial environments and Ex hazardous areas, but it also facilitates everyday work in conventional applications. The user can configure and parameterize his plics® sensors from a safe distance with a smartphone or tablet, regardless of whether it is an Apple or Android device. Display and diagnostic functions are also at the user's disposal.
The operator appreciates this practical solution not only because of its sophisticated technology. PT PLN also values the fast and unbureaucratic support that VEGA has provided during the nearly ten years of collaboration, whether it was in the form of technical advice, spare parts or special help with problematic measurements.