Abstract: Employee #1, a shipfitter, was instructed to install a bulkhead penetration insert in the grey water tank of a tug. It was known by his supervisor that Employee # 1 sometimes tightened his oxygen/propylene hose couplings hand tight. Employee #1 assembled his hoses and torch and told his tacker to lower his torch and hose and the welding lead into the tank. The tacker lowered the torch and hose into the tank but couldn't lower the welding lead because it fell short of reaching the tank opening. While the tacker went to look for more welding lead, Employee #1 charged the oxygen and propylene lines at the manifold and proceeded to the vessel. Employee #1 placed his feet on the ladder to descend into the tank when the tank exploded. Employee #1 was blown upwards 30 feet from the tank opening and fell 45 feet to the dry-dock floor. Employee #1 died instantly from his injuries.