{HEAD ~ Closure} of the first valve apparatus prevents {TAIL ~ fluid communication} along the first flow path, whereby fluid communication may be diverted to the second flow path, provided the second valve apparatus is in an open configuration 
{ HEAD ~ Closure } of the first valve apparatus prevents { TAIL ~ fluid communication } along the first flow path , whereby fluid communication may be diverted to the second flow path , provided the second valve apparatus is in an open configuration
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH