The operation method 5, {HEAD ~ wherein the first valve} and the second valve are {TAIL ~ a control valve} 
are
The operation method 5 , { HEAD ~ wherein the first valve } and the second valve are { TAIL ~ a control valve }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL