{HEAD ~ A separation tray}, suitable for mounting in {TAIL ~ a vertical column}, for separating liquid/gas mixtures 
suitable for mounting in
{ HEAD ~ A separation tray } , suitable for mounting in { TAIL ~ a vertical column } , for separating liquid / gas mixtures
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH