An employee was working to connect a tote-size sac of crystalline chemical to the iris of a process feed chute. The crystals feed down the chute through the iris, then through a rotating vane valve. There are two panels covering the vane valve. The sac of crystalline chemical emptied down the chute just halfway before the crystalline chemical got blocked. The employee opened the panel covering the vane valve to unblock the material. The valve vane amputated the employee's right index finger down to the knuckle.