While deformable particles can push through a monoflament textile, they are held back in three-dimensional needle felts.
Needle felts have a three-dimensional flter structure, whe- reby the flter properties apply both on the surface and th- roughout the depth. This enables deep fltration for very large accumulations of solids and higher fow rates. The needle felt is heattreated on the surface in order to virtually prevent fb- res getting into the fltered material. The specifed pore size is practically unmeasurable; a nominal flter fneness that is based on empirical values is specifed here.