{HEAD ~ The liquid oxygen stream} after {TAIL ~ purification} by the guard bed is vaporised to form a gas stream at 16 
after
{ HEAD ~ The liquid oxygen stream } after { TAIL ~ purification } by the guard bed is vaporised to form a gas stream at 16
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH