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