To ensure that leakage of tank gas, particularly through
                           the hatch centre-line joints, is eliminated or minimized, it is essential
                           that the hatch covers are inspected frequently to determine the state
                           of their seals, their alignment, etc. When the hatch covers have been
                           opened, particularly after the ship has been carrying a dry bulk cargo,
                           the seals and trackways should be inspected and cleaned to remove
                           any foreign matter.