The first and second valve apparatus may be used in {HEAD ~ conjunction} with {TAIL ~ throttling apparatus} applied to one or both of the first and second flow paths 
with
The first and second valve apparatus may be used in { HEAD ~ conjunction } with { TAIL ~ throttling apparatus } applied to one or both of the first and second flow paths
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH