Abstract: At 10:00 a.m. on October 7, 2023, three employees were preparing to install a male threaded pipe sleeve into a female threaded factory installed coupling on a flange to interconnect three battery tanks from the tank roof. Two days prior to welding, there was a liquid leak from one of the tanks. The supervisor was instructed by the plant manager to open the vessel to purge the mud. The supervisor instructed his employees to shut off the valves once they were installed. However, there still appeared to be fluid leaking from the tank, as stated by the plant manager. The supervisor's crew installed the valves upside down, thus leaving the valves open. This occurrence led to gas leaking into the tanks. There were three employees working on top of the tank. The supervisor did not conduct any flammable testing prior to welding. There was an explosion. During the explosion, the lid and two of the employees were thrown. Employee #1 and Employee #2 were pronounced dead at the scene. A coworker jumped over to the other tank prior to the explosion; he was rescued alive with no injuries. Only one of the three employees was utilizing fall protection at the time of the incident. The aerial lift that was being utilized had a burned and wilted basket with a missing gate. The tank that the employees were installing flanges on was missing the lid.