In case of rigid sludge such as fibrous, pulpy strong sludge, higher pressure(2㎏/㎠~3㎏/㎠) can be applied for lower moisture content in cake.  The higher tension is created  by tensioning a metal mesh belt hydraulically.And this higher tension produces higher pressure around the high press roller which compresses the sludge between the belts resulting in further dewatering in discharge cake.
 

Drainage Zone

Wedge Zone

Squeeze Zone

High Pressure Zone