Abstract: DIES AND PUNCHES AT THE ALUMINUM OGIVE (POINTED TOPS FOR 155 MM PROJECTILES) AND BASE FORGING PRESSES HAVE TO BE PREHEATED TO ABOUT 400 DEGREES FOR PROPER OPERATION. STATIONARY PROPANE HEATERS HEAT THE DIES AND PORTABLE PROPANE "TIP" BURNERS HEAT THE PUNCH FOR ABOUT 2 HOURS PRIOR TO THE 7 AM PRODUCTION STARTUP. THE STATIONARY DIE HEATER AT THE BASE (MIDDLE) PRESS WAS TURNED OFF PRIOR TO START-UP BECAUSE OF EXCESSIVE SMOKE. THAT PROPANE HEATER WAS RELIT 30 MINUTES BEFORE START-UP BY ANOTHER EMPLOYEE, AS DIRECTED BY THE FOREMAN. EMPLOYEES IN THE VICINITY OF THESE TWO PRESSES RECALL A STRONG ODOR OF PROPANE BEFORE START-UP. THE PRESSES STRADDLE A 15 FOOT WIDE BY 35 FOOT LONG BY 15 FEET DEEP PIT. PRODUCTION BEGAN NORMALLY, BUT WAS SHUT DOWN PRIOR TO 8 AM TO ALLOW THE PUNCH TIP AT THE OGIVE (NORTH) PRESS TO BE CHANGED. SHORTLY AFTER RESUMING PRODUCTION, AND AFTER FORMING THE 138TH OGIVE, AN EXPLOSION OCCURRED. AFTERWARDS, AN INVESTIGATION TEAM FOUND THAT THE TWO BALL VALVES WHICH CONTROL THE FLOW OF GASEOUS PROPANE TO THE LIGHTING WAND AT THE BASE (MIDDLE) PRESS WERE IN THE OPEN (ON) POSITION. APPARENTLY, PROPANE LEAKED AT THE MIDDLE PRESS AND GOT MIXED IN SWIRLING AIR CURRENTS NEAR THE TOP OF THE PIT UNDER THE THREE ALUMINUM PRESSES. IT PROBABLY WAS CARRIED TOWARD THE NORTH (OGIVE) PRESS, WHERE IT WAS IGNITED. IT THEN FLASHED BACK SOUTH TOWARD THE MIDDLE AND SOUTH PRESSES. SIX EMPLOYEES WERE INJURED.