Common Mooring Methods Used For Ships

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 current limits the interval for berthing and unberthing. The headway approach has to be slow often less than while at the same time approaching at a smaller angle to the buoy and then gradually hauling in the buoy messenger rope and pulling the vessel slowly towards the buoy using engine kicks at short intervals to control and maintain headway along with mooring winches to haul in the vessel when she nears about 150-200 meters from the buoy. For unberthing the chain is released from the bow stopper and a short kick on the engines going astern swings the bow to starboard for right handed propellers thus clearing the vessel of the buoy. Tug’s assistance can also be sued to pull the vessel astern and clear it of the buoy.

 

 

Conventional buoy or multi buoy mooring : In this method the bow of the ship is secured using both her anchors whereas the stern is secured to buoy around it . In the approach firstly vessel approaches the final berthing position from forward at an angle of 90 degrees to her final direction of berthing. The starboard anchor is then let go first at a pre decided spot while the ship is making headway. Required amount of cable is paid and the astern propulsion too operated simultaneously to stop the vessel. Once the vessel is stopped in water port anchor is let go and thus vessel positions her stern along the centerline bifurcating the buoys . For aligning the vessel along this centerline port cable is paid out and starboard cable heaved in with astern propulsion . The helm and engines to be carefully used during this maneuver to ensure the stern is swinging clear of any of the buoys. During unberthing the anchor cables are heaved in to move the vessel forward and the weight is taken on windward lines while casting off other lines to prevent swinging of the stern into the other buoys. This manoeuvre requires skill and efficient operation of ship’s crew as well as of the mooring equipments as often weight of the lines can be immense.