When the pressure is reduced, {HEAD ~ the inert gas} is exhausted from {TAIL ~ the casting furnace} by an exhaust line, the feed line having a check valve to prevent gas which is contaminated by magnesium from entering the feed line 
When the pressure is reduced , { HEAD ~ the inert gas } is exhausted from { TAIL ~ the casting furnace } by an exhaust line , the feed line having a check valve to prevent gas which is contaminated by magnesium from entering the feed line
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL 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