A large steel structure fitted over a hatch opening to prevent the ingress of water into the cargo hold. It may also be the supporting structure for deck cargo. Various designs exist for particular applications. The hatch cover has to be weatherproof and has to remain so when conditions change as a result of waves, temperature and cargo.
- Folding hatch covers – Folding hatch covers for weather decks can be either of the low or high stowing type. The low stowing version and single pull hatch covers are designed in a number of panel configurations. The high stowing versions are also available in a number of configurations: for example, with two to six panels and with stowing taking place at one or both ends of a hatch.
- Lift-and-roll Piggy-Back covers – One panel of each pair is operated by high-lifting hydraulic cylinders for vertical movement. The horizontal movement of the other panel is achieved by traction drive via electric motor, planetary gear and hydraulic brake after it has been raised by a wheel-lifting device.
- Lift-away hatch covers – Usually multi-panel units designed so that there are several panels for each hatch opening. They can be opened in an independent order and they allow partial hatch opening. Hatches are opened with a spreader using the vessel cranes or container cranes on shore. After removal, the panels can be stowed on top of adjacent covers which are placed on the quay or on the ship deck. The weight of the cover, and any cargo stowed on it, is transferred to the ship structure by bearing pads.
- Pontoon hatch covers – Pontoon type hatch covers feature a flat top and flat bottom plate and are weathertight.
- Rolling hatch covers – Rolling covers are divided into two main types considering opening direction. Side-rolling covers open sideways and end-rolling covers lengthwise. Both types are well suited to act as weatherdeck covers for dry bulk carrier and, when designed to sustain internal liquid loads, also for OBO and Ore/Oil ships.