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