A NEW OXYGEN BOTTLE WAS CONNECTED TO A REGULATOR. A MILLWRIGHT CRACKED THE OXYGEN BOTTLE VALVE. FLAMES BEGAN COMING OUT OF THE REG.BODY (THRU VENT HOLES). THE FLAMES BURNED APPROX. 40 SECONDS & THEN SELF-EXTINGUISHED. THE VALVE ON OXYGEN BOTTLE WAS THEN CLOSED. A REGULATOR BURN-OUT. NO INJURIES.