ly ▁steel ), ▁cer am ic ▁or ▁pl astic ▁( such ▁as ▁poly ure th ane , ▁poly pro py l ene , ▁or ▁other ▁types ). ▁Metal ▁or ▁cer am ic ▁hydro cy cl ones ▁are ▁used ▁for ▁situations ▁requiring ▁more ▁strength , ▁or ▁dur ability ▁in ▁terms ▁of ▁heat ▁or ▁pressure . ▁When ▁there ▁is ▁an ▁occurrence ▁of ▁much ▁ab ras ion ▁( such ▁as ▁occurs ▁with ▁sand ▁particles ) ▁poly ure th ane ▁performs ▁better ▁than ▁met als ▁or ▁cer am ics . ▁Metal ▁l ined ▁with ▁poly ure th ane ▁is ▁used ▁in ▁cases ▁of ▁combined ▁ab ras ion ▁and ▁high ▁pressure . ▁ ▁In ▁a ▁susp ension ▁of ▁particles ▁with ▁the ▁same ▁density , ▁a ▁relatively ▁sharp ▁cut ▁can ▁be ▁made . ▁The ▁size ▁at ▁which ▁the ▁particles ▁separate ▁is ▁a ▁function ▁of ▁cy clone ▁diameter , ▁exit ▁dimensions , ▁feed ▁pressure ▁and ▁the ▁relative ▁characteristics ▁of ▁the ▁particles ▁and ▁the ▁liquid . ▁E ffic iency ▁of ▁separation ▁is ▁a ▁function ▁of ▁the ▁sol ids ' ▁concentration : ▁the ▁higher ▁the ▁concentration , ▁the ▁lower ▁the ▁efficiency ▁of ▁separation . ▁There ▁is ▁also ▁a ▁significant ▁difference ▁in ▁susp ension ▁density ▁between ▁the ▁base ▁exit ▁( f ines ) ▁and ▁the ▁a pe x ▁exit , ▁where ▁there ▁is ▁little ▁liquid ▁flow . ▁ ▁If ▁the ▁size ▁range ▁of ▁the ▁particles ▁is ▁limited , ▁but ▁there ▁are ▁differences ▁in ▁density ▁between ▁types ▁of ▁particles , ▁the ▁dens er ▁particles ▁will ▁exit ▁prefer entially ▁at ▁the ▁a pe x .