Patent ID: 8852440
Filing Date: 2014-10-07
Classification: B01D

Abstract:
1. A filter unit comprising: an inlet ( a first filter cartridge ( a second filter cartridge ( a switching device ( the first filter cartridge being implemented as a main cartridge ( the second filter cartridge being implemented as an auxiliary cartridge ( a differential pressure switch ( wherein the pressure loss in the auxiliary cartridge is set to a same threshold value as the pressure loss in the main cartridge with a contaminated fine filter, at which the differential pressure switch reacts and triggers an alarm such that, during changing of the main filter, the pressure loss of the flow medium flowing through the coarse filter of the second filter element, when the course filter is in a clean state, causes the differential pressure switch to continue triggering the alarm, and the differential pressure switch only discontinues triggering of the alarm once the first filter cartridge is replaced and the flow medium again flows through the first filter cartridge at a reduced pressure loss following changing the filtering back to the fine filtering operation.