{HEAD ~ at least one drive unit} for {TAIL ~ at least one shut off device} for at least one fluid pipe; and, 
for
{ HEAD ~ at least one drive unit } for { TAIL ~ at least one shut off device } for at least one fluid pipe ; and ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH