Abstract: A hatch cover for deployment over a hatchway formed in a floating roof liquid storage tank permits rapid loading and unloading of inspection or maintenance equipment and minimizes vapor emissions from the tank. The portable hatch cover has two base plates movably connected at a hinge and each defining complementary recesses. A circular flange extends from the bottom surfaces of the base plates to seat the hatch cover in the hatchway. Two door panels are movably connected at hinges to the top surfaces of the base plates. When one or both of the door panels are opened, equipment may be loaded into the tank through the complementary recesses. When closed, the door panels cover the recesses in the base plates. Complementary notches in the door panels provide an opening through which equipment tubing or wiring may extend when the door panels are closed. A collar gasket optionally may be wrapped around the tubing or wiring as a further means to limit vapor emissions from the tank.