EE SUSTAINED FIRST AND SECOND DEGREE BURNS TO HIS LEFT ARM, RIGHT ARM, CHEST/NECK, LEFT LOWER LEG, AND FACE. HE WAS ATTEMPTING TO CLEAR A PLUGGED LINE AND HAD THE SCREEN BOX OPEN. THE SYSTEM H AD BEEN DRAINED, SUCTION AND DISCHARGE VALVES WERE CLOSED AND THE PUMP HAD BEEN SHUT OFF. HE WAS INCREMENTALLY CLEANING THE SCREEN BOX WITH A HOSE (WAQTER HOSE) WHEN STEAM AND MUD BLEW OUT ON