Abstract: ON JUNE 22, 1992, EMPLOYEES #1 AND #2 WERE CHANGING A LEAKING EXPANSION JOINT AND REDUCER SPOOL CONNECTED TO THE DOWNSTREAM SIDE OF A TUFLINE 6-INCH TAPERED PLUG VALVE. THIS 6-INCH VALVE WAS THE PRIMARY VALVE ON A 200,000-GALLON STORAGE TANK HOLDING APPROXIMATELY 80,000 GALLONS OF SULFONATION ACID SLUDGE, A HIGHLY CORROSIVE AND FLAMMABLE LIQUID CONSISTING OF APPROXIMATELY 60 PERCENT SULFURIC ACID AND APPROXIMATELY 40 PERCENT HYDROCARBONS. AN ACTIVATOR BRACKET ON TOP OF THE 6-INCH TAPERED PLUG VALVE HAD BEEN MODIFIED, MAKING IT IMPOSSIBLE TO ACCESS 2 OF THE 8 FLANGE BOLTS CONNECTING THE VALVE TO THE LEAKING EXPANSION JOINT. WHEN EMPLOYEES #1 AND #2 REMOVED THE ACTIVATOR BRACKET ON TOP OF THE PLUG VALVE, THE ENTIRE VALVE BONNET AND PLUG WERE EXTRACTED FROM THE VALVE BODY, CAUSING THE SUDDEN RELEASE OF 80,000 GALLONS OF SULFONATION ACID SLUDGE. EMPLOYEE #1 SUFFERED SECOND-, THIRD- AND FOURTH-DEGREE CHEMICAL BURNS AND DIED AS A RESULT OF HIS INJURIES. EMPLOYEE #2 IS RECOVERING FROM SECOND- AND THIRD-DEGREE CHEMICAL BURNS OVER HIS BODY. CONTRIBUTING FACTORS TO THE ACCIDENT INCLUDE: THE MODIFICATION TO THE ACTIVATOR BRACKET WAS A POOR ENGINEERING DESIGN; NEITHER EMPLOYEE WAS TRAINED IN MAINTENANCE WORK ON A TAPERED PLUG VALVE; NEITHER EMPLOYEE WAS WEARING APPROPRIATE PPE; AND THE FAIL-SAFE MECHANISM, THE INTERNAL EMERGENCY PLUG INSIDE THE TANK, HAD BEEN DISCONNECTED OR WAS INOPERATIVE.