Abstract: AT ABOUT 4 P.M. ON JULY 31, 1992, EMPLOYEE #1, A WELDER, WAS INSTALLING A NEW CENTER SHAFT SUPPORT WELDMENT INTO THE END OF A DRUM-TYPE ROLLER USED IN A MODEL 596 OWATTANA HAY BALER. THE ROLLER'S OLD WELDMENT HAD BEEN REMOVED WITH A CUTTING TORCH AND THE ROLLER HAD BEEN PREPARED FOR THE NEW PART BY GRINDING. AT SOME POINT, EMPLOYEE #1 USED A SPRAY GREASE FROM A PRESSURIZED CAN TO COAT THE INSIDE OF THE ROLLER WHERE THE WELDMENT HAD TO SLIP IN. THE PRODUCT CONTAINED 46 PERCENT CHLORINATED SOLVENTS AND PETROLEUM DISTILLATES, GREASE, AND PROPANE/ISOBUTANE/N-BUTANE PROPELLENT. A COWORKER ASSISTED EMPLOYEE #1 IN THE INSERTION OF THE WELDMENT INTO THE END OF THE ROLLER AND THEN LEFT THE SCENE. EMPLOYEE #1 STOOD THE ROLLER ON END, CLIMBED A WORKSTAND, AND BEGAN WELDING WITH A WIRE FEED WELDER. HE MADE ONE SPOT WELD FOR POSITIONING, THEN STOPPED AND ASKED A FELLOW WORKER IF HE HAD SEEN THE "POOF" THAT HAD JUST OCCURRED. EMPLOYEE #1 THEN PROCEEDED AND WAS MAKING THREE MORE SPOT WELDS WHEN THE VAPORS INSIDE THE ROLLER EXPLODED, CAUSING THE WELDMENT TO BE PROPELLED VIOLENTLY UPWARD. THE WELDMENT STRUCK EMPLOYEE #1 IN THE FACE AND HEAD AND CONTINUED UPWARD UNTIL IT STRUCK THE 16-FOOT CEILING AND FELL TO THE FLOOR. EMPLOYEE #1 WAS THROWN BACKWARD TO THE FLOOR.