SUPERVISOR WAS CHECKING THE NORTH COOLER FOR A LACK OF COOLING WATER. FROM THE PLATFORM'S LADDER, HE SAW WATER COMING OFF PIPE & HAD OPERATOR START BACK UP. A POOL OF WATER FORMED IN THE COOLE R WHILE IT WAS DOWN & WHEN THEY STARTED UP, THE HOT GRANULES MIXED W/ THE WATER CREATING A BURST OF STEAM THAT BURNED THE SUPERVISOR'S FACE & HANDS.