main valve means comprising a movable member cooperating with said main valve cavity for enclosing and varying in size a main valve chamber and having sealing means facing said seat, said {HEAD ~ main valve chamber} being connected to {TAIL ~ said outlet} and to said second by pass conduit, 
main valve means comprising a movable member cooperating with said main valve cavity for enclosing and varying in size a main valve chamber and having sealing means facing said seat , said { HEAD ~ main valve chamber } being connected to { TAIL ~ said outlet } and to said second by pass conduit ,
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 OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH