Steel hatch covers made their first appearance in 1929 as a design by the MacGregor brothers. Since then, steel hatch covers have become the standard equipment for General cargo ships, Bulk-carriers, and Refrigerated cargo carriers. In addition to these hatch covers they design and build covers for other types of vessels.
There are a number of different types of hatch covers and they fall into categories designed for those that are to be fitted on the weather decks of a ship and those to be fitted in a ship’s tween decks.
The main types of hatch covers that are designed to be fitted on the weather deck of a deep-sea going, dry cargo ship are
(1) folding type
(2) rolling type
(3) piggyback type
(4) reefer type
(5) stacking hatch covers
The main types of hatch covers that are designed to be fitted on the tween deck of a deep-sea going, dry cargo ship are
(6) folding type
(7) sliding type
(1) Weather deck covers—folding type.
These covers are designed as high stowing types, with two, three, or four panels. These panels stow either at one end of the hatch or both. Single-pull compact-stow covers may have any number of panels. Their usage depends on the opening size of a hatch, the height of a hatch coaming and the length of stowage. The covers are operated by wire or by hydraulic means.
All covers are built specifically for one ship, depending on the requirements of the owners and the Class, as part of Load Line requirements.
Their configuration is for
(a)
high-stowing/two-panel covers/twofold. These afford economical stowage, optimum hatch width.
(b)
high-stowing/three-panel covers/direct pull. These are easy to install, with simple, economic operation of the ship’s gear and they require minimum maintenance.
(c)
high-stowing/three-panel covers/foldtite. These have the actuating equipment outside the panels of the hatch covers, with minimum stowage length and easy maintenance.
(d)
high-stowing/four-panel covers/foldlink. These are suitable for long hatch coamings, with four or six panels stowing at each end. They feature minimum stowage length.
(2)
Weather deck covers—rolling type.
These covers roll to stow on the sides of a hatch (side-rolling) and are mainly used by bulk-carriers. The usual arrangement is for one panel to stow on the port side, while the other stows on the stbd side. They roll on rails and they are driven by a rack and pinion mechanism. Alternatively, they can be driven by wires or chains.
The covers of this type offer simplicity of operation and independent panel-rolling. They can be made to be fully automatic. The external drive unit is always accessible with the panel closed and the operation is hydraulic, thus providing positive continuous and smooth movement.
(3)
Weather deck covers—piggyback type.
Piggyback type covers can be fitted on a lot of different ship types. They stow one on top of the other and they can do so under fully automated conditions. They can stow on the ends or on the side of the hatch and can remain partially open. Their cleating can be fully automated.
(4)
Weather deck covers—reefer type.
Reefer ships are designed to allow for the loading of 40 in. containers, with four containers being able to stow within the hatch opening.
The hatch covers are hydraulically operated, high-stowing folding type. These covers are easily operated and require little stowing-length.
Two panels stow on each end and their quick acting cleats can be manually or automatically operated. The sealing of these covers is important if the cargo holds are capable of maintaining a controlled atmosphere. The hatch covers have additional openings to facilitate pallet movements.
(5)
Weather deck covers—stacking hatch covers.
Stacking hatch covers are of the multipanel type that can stow at the end of the hatch, but within the opening of the hatch. As an alternative the covers can be moved to any position on the hatch. These covers provide for fully automatic stacking at various locations. The number of covers that can be stacked in one location is, in theory, unlimited.
(6)
Tween deck covers—folding type.
The hatch covers of this type fit flush so that the vessel benefits from a large area that can handle trailers, pallets and containers. The opening and closing of these covers is by means of hydraulic devices. Two panel covers are operated by wire arrangements, whereas four-panel covers are hydraulically operated. This enables the possibility of having the covers open on the port and stbd sides.
(7)
Tween deck covers—sliding type.
The sliding hatch covers for tween decks can be
fitted on both general cargo ships and in refrigerated cargo ships, especially
where the decks are non-insulated. The panels slide, one under the other, as
the hatch opens and they stow slightly sloping. Rack and pinion devices and
wire arrangements can be employed in both the opening and the closing of these
covers. These covers can be stiffened to carry containers, if this is required.