The external DE 1 oil filter is directly integrated into the oil circuit of rotary vane pumps and comes with a cartridge containing activated alumina. Optional replacement cartridges with cellulose or activated carbon are available depending on the application. Activated alumina is especially suitable for mineral acids and polar media, activated carbon for chlorinated substances and ammonia, while cellulose removes solids from the oil. The filter extends oil life and provides lasting protection for the pump.