200851 Ramp door malfunction

On joining an elderly ro-ro vessel, I was somewhat surprised to see two chain blocks permanently rigged near the quarter ramp door external cleats. I was told by the CO and Bosun that the hinged ramp door could not be hove in fully, and that the final heaving and tightening was done with two crew members jointly hauling on the two chain blocks hooked on to the hinged flap. Besides the safety risks involved in two crew members leaning awkwardly from the securing platforms on the stern while trying to 'hook on' the chain blocks to the ramp, uneven tightening of the chain blocks could impose high torsional loads on the hinges and in turn, compromise the effective sealing of the ramp door against the hull.

During a day-long experiment on a rare day at anchor, we worked the ramp door in and out several times and eliminated diverse causes such as possible wrong rigging, elongation of wire ropes, malfunction or wrongly adjusted limit switches etc. We finally identified the cause. In the original design, the hinged flap section had a series of triangular wedges welded along the inboard edge. These were meant to engage against the outboard edge of the main ramp section during the final folding movement of the hinged section, slowly tilting the ramp door so that the securing lugs would come closer to the drop cleats. These 'contact areas' were considerably worn down and the plate edge even torn in some places, but being on the lower side of the ramp when landed on the shore, the defect was not readily noticeable.

 

 

Making the ramp door operable

A new set of wedges and small doublers was quickly fabricated in the engine room workshop and immobilisation and hot work permits were obtained at the next berth the following day. Soon after cargo operations were completed, with the ramp suspended sufficiently clear over the wharf, the ship's staff went under it and quickly cropped away the small damaged sections and welded on the new inserts. For the first time in many years, the ramp door was operable normally and the unsightly chain blocks were returned to the store.