A customer uses 20-meter high silos to store contaminated activated carbon from industrial carbon filters. The carbon often contains unknown substances and gases. To prevent reactions with oxygen, a nitrogen blanket is placed over the carbon under slight overpressure.
The customer asked us to develop a system to monitor the nitrogen blanket safely and accurately. A standard oxygen detector was not suitable due to dust formation in the silos, which would lead to contamination and frequent cleaning. In addition, maintenance would disrupt the closed nitrogen system, with the associated risks.
Together with the customer, we developed a solution: a sampling system that draws a sample through a filter. This is analyzed by our MSA UltimaX5000 Low Range O2 detector to ensure that oxygen levels remain safe. The sample passes two oxygen sensors for increased reliability.
To keep the filter clean, the measurement cycle begins with a pulsed cleaning of the filter with nitrogen. If the filter is contaminated, it is cleaned from the inside by backfiring. A PLC controls these processes, communicates with the customer’s operating system and provides live status updates. If the oxygen level is too high or the filter is clogged, an alarm is automatically triggered.
A dirty filter can easily be replaced by closing the ball valve at the top of the silo. The PLC also monitors this crane, so that maintenance can be carried out safely without disturbing the nitrogen blanket.
Our system developed and tested in-house was transported to the customer, installed and commissioned. This tailor-made solution shows how collaboration and thinking lead to safe and efficient systems in difficult situations.