Re {HEAD ~ opening} of the main valve is accomplished with {TAIL ~ the aid} of a bypass system connecting the upstream side of the metering valve to the main valves first chamber 
is accomplished with
Re { HEAD ~ opening } of the main valve is accomplished with { TAIL ~ the aid } of a bypass system connecting the upstream side of the metering valve to the main valves first chamber
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH