The valve protects the ink in {HEAD ~ the ink supply} from {TAIL ~ contaminants} that can migrate up the ink line during shut down periods 
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The valve protects the ink in { HEAD ~ the ink supply } from { TAIL ~ contaminants } that can migrate up the ink line during shut down periods
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH