Bulk products level measurement in silos

Level measurement in dusty environment causes problems. Many of methods fail, readings are unreliable or specific technologies do not fit applications at all because of principle of operation. Interesting, immune to dust, moisture and fumes solution are accoustic wave level transmitters Sultan.

The customer had previous problems, where the level transmitters were unstable during filling operations. The customer had used electro-mechanical level systems, where cables had broken off and gone through the feeder, causing major maintenance cost. They wanted to be provided a low cost communications package for the control room PLC’s. The instruments had to conform to dust ignition certification.

Solution

Akustyczny przetwornik poziomu Sultan - montaż od góry

The transmission of high powered acoustic waves ensures minimal losses through the environment where the sensor is located. Due to the high powered emitted pulse, any losses have far less effect than would be experienced by traditional ultrasonic devices. More energy is transmitted hence more energy is returned. Advanced receiver circuitry is designed to identify and monitor low level return signals even when noise levels are high. The measured signal is temperature compensated to provide maximum accuracy to the outputs and display.

The silos were sizes 90 ft (27.5 m) and 50 ft (15 m) with pneumatic filling. The products being measured were corn flour, wheat flour, rice flour, pre-mixes, grains, wheat, rice, oil seeds, canola, rape seed, offal etc. For taller silos 5 kHz transducers were provided and for shorter 10 kHz transducers. The transducers were all non-intrusive and maintenance accessible, from the top of the silo. The transducers were self cleaning. Accordingly to customers requirement low cost ModBus communications was provided, to reduce installation costs. This also provided the client, additional diagnostic information in the control room, such as temperature levels in each silo, as well as levels etc. All provided transducers had Ex dust ignition certification, to comply with the local code. The transmitters were mounted in a remote location 2950 ft (900 m) away from the transducers.

There are several methods of level measurement being used in silos, but the most reliable in dusty environment are accoustic wave transmitters - Sultan. Strong, low frequency signal penetrates dust and fumes and makes the sensor cleans itself. Transducers emits 5-15 kHz accoustic wave which should not be confused with ultrasonic wave with frequency above 20 kHz.