Hatch Cover

A hatch cover is the movable cover that closes off a cargo hatch, the large opening in the deck of a cargo ship through which cargo is loaded into and discharged from the hold below. Bulk carriers and general cargo ships have wide hatch openings so that grabs, cranes and shore equipment can reach the cargo, and these openings must be closed and sealed at sea to keep water out and protect the cargo, which is the job of the hatch covers. On modern ships they are large steel structures, and they do far more than simply cover the hole: when closed and secured they must be weathertight, keeping out the sea and rain that break over the deck, and they form part of the strength deck, contributing to the longitudinal strength and watertight integrity of the hull.

Modern hatch covers are usually mechanised for speed and safety. Common types include folding covers, where panels are hinged and fold up against each other or the hatch end, and rolling or side-rolling covers that run on rails, both operated hydraulically so that a large hatch can be opened and closed quickly. When shut, the covers are pressed down onto rubber seals and secured with cleats and locating devices to make them weathertight.

The watertightness of hatch covers is a serious safety matter, because water entering a hold through leaking covers can damage cargo and, in the worst case, threaten the ship's stability and survival; failures of hatch covers have contributed to the loss of bulk carriers. For this reason the covers and their seals and securing arrangements are inspected and tested, for example by hose testing or ultrasonic testing, and maintained carefully, and Port State Control and cargo surveyors pay close attention to them. The hatch cover is thus both a cargo-protection device and a key element of the ship's structural and watertight integrity.