During “routine maintenance”, a process operator was cleaning an inline filter connected to pipework below a thickener tank. He opened the drain valve to verify isolation before undoing four bolts to open the inline filter door. On opening the inline filter door, the operator found the screen/filter full of material. As he pulled the screen/filter out of its housing, a blockage upstream of the screen/filter box dislodged. The operator was engulfed in 203°F (95°C) caustic solution, receiving thermal and caustic burns to his body and face. An emergency responder found the main isolation valve open. Here’re more details…