Sewage sludge is a product of wastewater treatment. The drier it is, the better it can be utilised downstream. The key basic treatment of the sludge takes place in the thickeners. Their operational safety, in turn, depends on reliable force measurement in the drive system.
Wastewater treatment plants are a central element in the water cycle. They treat and purify wastewater in several mechanical, biological and chemical processes. During these processes, sewage sludge is produced at various stations. This “waste product” can be used at the approved quality, for example to fire coal and lignite power plants, to supply energy to cement works and to fertilise arable land.
Sewage sludge requires a high dry-matter content for utilisation
A high dry-matter content is a prerequisite for any utilisation. The most important preliminary treatment to achieve this goal takes place in the thickeners. These devices work with an agitator system, the rabble rake. It rotates at a very low speed. This process encourages water to rise so that more and more solids are deposited at the bottom.
Force transducer protects the sewage sludge thickener’s rabble rake drive from overload
The model F2301 force transducers from WIKA enable indirect monitoring of the torque of rabble rake drives by measuring the load via the torque support (diagram on the left). The instruments can be easily installed using two threads and swivel heads.
As the core task of sewage sludge thickening is carried out by the rabble rakes, the measurement instrumentation is focused on their drive. This means that the torque must be monitored continuously to protect the motor from potential overload. Such a critical situation can arise if, for example, a solid body jams in the rabble rake and the drive motor runs hot as a result.
Patented thin-film technology
The model F2301 tension/compression force transducer from WIKA has proven itself for such monitoring. Its patented thin-film technology features long-term stability, even in dynamic applications – as in the case of the rabble rakes. Here, permanent force measurement is carried out with varying loads of up to 1 kN, depending on the sludge feed and consistency.
The force transducer, made of corrosion-resistant stainless steel, is highly resilient having been tested to 20 million operating cycles, and its amplified output signal is correspondingly stable over the long term. The plant operator can therefore rely on being informed in good time when a critical threshold value is reached. The model F2301 can also be combined with a limit switch to stop the motor in the event of an overload, and thus protect it from damage.
Uncomplicated installation and measurement free from transverse forces
However, the measuring instrument is not only notable for its robustness and reliability. The adaptation using two threads enables uncomplicated installation. The model F2301 is self-aligning in the direction of force. This means that there are no transverse forces that could affect the measuring result. As the force transducer is supplied with a calibrated output signal, the operator only needs to install it, set the defined limit value – and the instrument is ready for operation.
Note
On the WIKA website you will find further information on the model F2301 tension/compression force transducer. We also present further measurement solutions for the water and wastewater industry there. Should you have any further questions, your contact will gladly help you.
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