EE WAS PUMPING #2 TRAY CAUSTIC TO #2 SECONDARY USING THE NORTH HOSE LIQUOR PUMP & JUMPING TO #2 TRAY FEED LINE. WHILE THE NORTH HOSE LIQUOR PUMP WAS STILL RUNNING, HE DISCONNECTED THE AIR SUPP LY TO THE CLARKSON VALVE ON THE ST MANIFOLD BEFORE OPENING THE GATE VALVES TO THE LINE, CAUSING PRESSURE TO BUILD UP & BLOW A GASKET IN THE INSPECTION WINDOW COVER. HOT CAUSTIC SPRAYED ON HIM