Methods of Securing Hatch Pontoons:-
Positioning of Hatch Covers:-
- Every precaution must be taken to ensure that the hatch panels are correctly positioned when they are lowered onto the coaming.
- If a panel is wrongly positioned the cleats will not meet truly. They should not be forced, instead the panel should be repositioned.
- With Single pull covers it is imperative when closing that the leading panel is positioned correctly, the hauling wire is then shifted to the trailing panel and again pulled tight to ensure that ultimately all the sections are properly mated together so that the transverse compression bars are in the center of the gaskets. Failure to above this could result in leakage in the way of cross joints.
- In folding type hatch covers, correct positioning of the panel is ensured by placing longitudinal stoppers fitted on panel side & corresponding locator pads on the coaming side.
- There are various ways of securing the hatch covers once they are in place. The hatch panels are held in position by cleats of varying design.
- Because of the need for an elastic joint between adjoining panels and between panels and coamings due to flexing of ship structure at sea and conditions of loading resulting in a hog or sag there by arising the need that the decks is to restrict the vertical movement of the hatch panels in heavy seas and also achieve watertightness by physical compression of gaskets against the rounded profile of compression bars.
- Modern covers may be self-cleating or secured by hydraulically operated cleats or wedges.
- But the most common type an older vessel is the manual quick-acting cleat, having a cam at the upper end, which is forced onto a snug on the hatch cover panels. A rubber disc between two steel washers at the lower end of the cleat has enough elasticity for the cam to be placed on the snug by using a portable lever. Thus the hatch covers are restrained from lifting, but are allowed some movement on the hatch coaming in the transverse and longitudinal directions.
- When hatch cover panels are not sufficiently linked together by hinges, they also need cleats across the cross joints of the panels. These cleats are termed as cross joint wedges/ screw cleats. Some covers may have torsion bars/ internal cleats operated manually or automatically.
- The manufacturers recommended sequence for fastening of cleats should be followed, since uneven tightening of cleats might after the flexing & watertightness of hatch cover.