On 15.12.2021 at 0855hrs installation of the new mud agitator gear box was in progress. The Asst. Mechanic entered the suction tank in order to install the foundation bolts. The Rig Sr. Mechanic and HIAB Operator were attempting to align the gear box. While doing so, the gear box unexpectedly jerked and the Asst. Mechanic received the injury of his left-hand inner palm. The work was stopped immediately, and the Asst. Mechanic was shifted to the clinic for medical assistance Why it happened/Finding : The Asst. Mechanic placed his hands in the line of fire The Asst. Mechanic was not wearing impact gloves at the time of the incident The communication between the parties was inadequate The supervision was inadequate The Lift Plan was inadequate and did not address the risks and controls of the lift The PTW controls were not properly implemented