Abstract: At 12:30 p.m. on April 2, 2002, Employee #1, a mill operator for a chemical fertilizer manufacturer, was performing his routine duties of processing items through a mill to decrease their grain size (increase fineness). The equipment used for this process consisted of several components: a mill proper (a rotary valve approximately 8.5 inches by 8.5 inches and 7.5 inches deep), an impeller shaft, located inside the proper chamber (1 inch in diameter), and a screw plug (1 inch diameter), located at the center of the mill. Although the screw plug is not to be opened, it is an aperture through which air, under pressure, can be injected into the impeller from outside. The grain powder is fed to the impeller through vertical ducting above it and the powder is discharged into a drum below. Occasionally, the powder gets wet leading to improper travel through the ducts of the impeller. Therefore, it is routine for the mill operator, after conducting the Energy Control Procedure of lockout/block-out, to use a hammer to strike the mill equipment. This enables the powdered to be released, allowing for better flow. While Employee #1 was operating the mill, the powder became stuck, requiring him to hammer on the mill. Unexpectedly, the screwed plug became loose and separated from the mill. Employee #1, who was holding a hammer with his right hand, tried to re-install the plug with his left hand, but the plug slipped and his index finger got caught in the rotating impeller. Employee #1's left index finger was severed. The Energy Control Procedure (lockout/block-out) was not followed. Employee #1 was treated at both Kaiser Permanente Hospital and Long Beach Memorial Hospital.