A further broad aspect relates to a valve having {HEAD ~ structure} for pneumatically or hydraulically closing {TAIL ~ the valve}, and a back up structure for resiliently or mechanically closing the valve 
for pneumatically closing
A further broad aspect relates to a valve having { HEAD ~ structure } for pneumatically or hydraulically closing { TAIL ~ the valve } , and a back up structure for resiliently or mechanically closing the valve
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH