HATCH COAMING

Hatch coaming is a steel structure welded on the weather deck, along the perimeter of the opening on the deck. On top of the coaming plate a bulb end flat bar is welded termed as the table top of the coaming.

The table top is mounted with a compression bar on Port and starboard side coaming, and bulb angle bar at the forward and aft end for providing surface of compression enable achieve weather

tightness of the hatch covers; a track way is mounted for providing a surface for movement of the pontoon eccentric wheels, and flat bar for housing of quick acting cleats.

The hatch coaming plates are adequately strengthened by stays welded at intervals of not exceeding two meters, on all the four sides of the coaming, in addition longitudinal stiffeners may be welded.

The weather deck is fitted with doubler I insert plates at each corner of the hatch opening.

The deck opening corners are rounded off to avoid point of stress concentration; the radius of the corner rounding within the region of 0.3 length from fore and aft end, must be not less than 305 mm, else where not less than 150 mm.

To achieve weather tight joint between the pontoon end and table top of the coaming, each pontoon houses rubber packing along its perimeter; the rubber packing is compressed against the

compression bar on the table top under the pressure of its own weight, additional pressure is exerted by the quick acting cleats and cross wedges; minimum Two quick acting cleats must be provided on each pontoon, the quick acting cleat must nit be more than 30 Cms, away from each corner.

As per load line rules, hatch coaming in position 1 must not be less than 600 mm, else where not less than 450 mm; however, to comply with factory act requirements the height of the coaming is usually not less than 760 mm.

The purpose of hatch coaming is to prevent any water from deck entering the cargo compartment or through the pontoon overlap end, hatch coaming also forms a barrier to prevent accidental fall of

personnel while working on deck.