Marine Engineering and Naval Architecture

One of the major concerns during a towing operation is how much load is being put on the towline and the fittings used to secure it. There is a way of approximately calculating this – and it will at least give an indication of when the tow line is getting close to or has reached its safe working load. Maximum safe working load is usually taken to be 50% of the rated strength of the rope. The rated strength or break load being the load at which the line will probably part. Any rope manufacturer or supplier should be able to give not just the rated strength of a rope, but also its ‘elongation at break’ or ‘stretch at breaking’. For example Polyester 3 strand 20 mm Diameter - break load 6300kgs - elongation at break 30%. Using the above example a cheap & easy ‘eyeball’ method of gauging loads on the towline can be set up.   If the elongation at break is 30%, then the elongation at the ropes max safe working load (50%) will be approx 15%. A preset length is measure...

Single buoy or single point mooring :  Often larger ships which cannot approach ports and terminal are berthed outside the port limits or in sheltered anchorages and the cargo transfer carried out with the help of Single point or single buoy moorings. The basic principle of the buoy is to keep the position of the vessel with respect to the buoy steady and at the same time allowing vessels to swing to wind and sea.. Often a tug is provided at the aft to keep the ship at a fixed angle and distance from the buoy. The buoy is fixed by positioning it in the centre of four anchors connected to it. The ship is made fast to the buoy with the help of a single chain or two which is secured onboard to the bow stopper. In general while approaching Single point or single buoy moorings weather is a major criteria in determining whether to berth the vessel or not. Calm seas with low swell and wind force below 15kts are considered favorable to make an approach. Presence of strong tidal curren...