A mechanical-engineering company regularly machines cast components. Coolant flushes the chips out of the machines; coarse chips settle in a collection tank and are removed by a scraper-belt conveyor.
Large quantities of small chips and particles were pumped with the coolant to a belt filter. Coarser chips settled on the filter belt and were removed, but the fine particles produced when machining cast iron—especially those below 50 µm—passed through.
These particles accumulated in the clean tank beneath the belt filter. After several months, black deposits covered the machine interior, and coolant analysis confirmed a high particle load despite the existing filtration.
During a coolant change, a layer of black sludge several centimetres deep was found on the tank floor. The sludge and high particle concentration promoted severe bacterial growth, making repeated additions of biocide necessary.
The operator evaluated several alternatives, including a magnetic drum. Conventional magnetic drums typically generate only 2,500–3,500 gauss. This is sufficient for particles around 50 µm and larger, with reliable separation generally beginning above 70 µm, so the expected improvement would have been limited.
The company therefore tested a FRIESS FMF 310/3 magnetic filter. Its field strength exceeds 10,000 gauss, and the housing flow path is optimised for fine-particle separation. The filter can remove magnetisable particles down to approximately 1 µm.
During the initial trial, the magnetic filter had to be cleaned after only a few hours because it collected so much accumulated contamination.
As the system became cleaner, the maintenance interval increased first to 24 hours and later to 48 hours. Fine particles that had previously remained in circulation were now separated safely and reliably.
The machine interior became visibly cleaner and the black deposits disappeared. Even after more than one year, the bacterial count in the coolant remained stable at a low level without additional biocide.
Following this result, other machines at the company were also equipped with FMF 310/3 magnetic filters.
