When the pressure is reduced, {HEAD ~ the inert gas} is exhausted from the casting furnace by an exhaust line, {TAIL ~ 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 the casting furnace by an exhaust line , { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH