At approximately 8:30 AM, a maintenance team was troubleshooting a metal detector that was continuously rejecting product. The directional air valve and piping had been disassembled during sanitation and were not re-installed correctly. Maintenance team members disassembled a 3-foot section of piping to visually identify the issue. The injured employee was removing some product from the pipe when the directional air valve actuated. The employee's left little finger was pinched by the valve, amputating the fingertip.