Mechanical filters:

There are two kinds of mechanical filters in use, gravity and pressure.  Pressure filters are the most hugely used since they could be installed in a pressurized system, thereby eliminating the required for additional pumps (gravity filters needs pumps to provide a motive force).  Further, in a pressurized filter system, flow rate and other related parameters could be better controlled.

Another method used for the removal of suspended corrosion products within facility fluid systems is the electromagnetic filter. Those are gaining popularity in PWR feed and condensate systems whereas they have proven effectual in reducing the crud loading of these systems, by decreasing the inventory of corrosion products within steam generators.

Ion exchangers also function as filtration units through virtue of the size of the resin beads and the torturous path the water must follow in passing by the resin.  The filtration effectiveness, therefore, is significantly less than the ion exchange efficiency (90 percent or less for filtration versus approximately 100 percent for most ion exchange reactions).  Filtration effectiveness depends hugely on the size of the suspended materials, along with greater effectiveness for the larger particles.  Adverse effects of this filtration procedure are same to those occurring in other categories of filters.  Within a radioactive system, the buildup of filtered particles (crud) could increase the radiation to prohibitive levels or cause flow reductions which might necessitate removal or backwash of the resin.