In the absence of {HEAD ~ an open configuration} of {TAIL ~ the second valve apparatus, fluid pressure increases} in the second flow path 
In the absence of { HEAD ~ an open configuration } of { TAIL ~ the second valve apparatus , fluid pressure increases } in the second flow path
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH