The application of coarse oil filters is practically self-explanatory. These devices are used to remove 0.04 to 0.09 mm particles from circulating oil. Filter elements for a coarse filter are mostly slotted strainers. The pressure drop is low enough to allow all flow to pass through the filter. Construction material is usually steel or brass.
Filter elements should be inspected visually every day. If the filter is clogged, it should be rinsed with diesel fuel or kerosene. Cleaning of filters should be performed daily as well.
A slotted belt filter is a goffered cylinder with a brass belt wrapped around it. The ledges form 0.04 to 0.09 mm slots. Oil passes through the slots, while large particles are trapped on the surface of the filter.
To increase throughput and to extend operation time without rinsing, filters may be arranged one inside another.
A coarse filter is used only for pre-filtering of oil. To remove fine particulate matter, fine filters are installed in systems.See more video about transformer oil purification