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Moored vessels breaking out from their berths

By Jeffery Rodriguez,2014-05-09 21:04
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Moored vessels breaking out from their berths

Protank Management S.A , takes into account all “loss prevention” circulars

    and share findings with its crew.

    Officers and crews onboard are encouraged to participate with their comments after discussing those topics in safety meetings. Our aim is to avoid recurrence of similar incidents.

    As a continuous improvement effort, Company manuals are subject to review and

    amendment taking into account those industry circulated loss prevention and

    lessons learnt circulars.

Moored vessels breaking out from their berths

    Gard P&I club, has investigated several P&I and H&M incidents involving moored vessels breaking out from their berths, following a recent increase in the frequency of such incidents.

    The consequences of these incidents range from personal injury, significant contact damage to the vessel including ranging and grounding damage, damage to adjacent vessels, shore/terminal structures to pollution damage to the environment. The majority of these incidents occurred during periods of adverse weather, with high winds acting on vessels with large windage areas.

    Wind speeds recorded in the above incidents ranged from 63 km/h to 120 km/h (Beaufort force 7- 12), although in one case the actual wind speed was estimated to have been much higher due to the funnelling effect of container stacks ashore. In many cases additional mooring lines were deployed in anticipation of high winds, ultimately to no avail. In one case the vessel moorings were even supplemented by shore lines with load monitoring, however, the vessel still broke free due to excessive loads on the lines, seemingly as a result of abnormal tidal flow caused by restricted under keel clearance. Even tugs could not prevent her from ultimately grounding.

    In another case, the vessel did get tugs to hold her alongside the berth, only to stand them down prematurely. The second time the vessel came off the berth she grounded resulting in substantial bottom damage.

    Ports around the world have various berth layouts and mooring facilities and are exposed to different wind, tidal and swell conditions. It is important that the Master takes into consideration the key critical aspects of any given port along with the vessel’s characteristics, in order to ensure that the vessel is adequately

    moored to withstand the anticipated mooring forces, even in normal conditions.

    It is equally important that the Master is ready to take extra precautions to keep the vessel alongside in adverse weather, tidal and swell conditions and is ready and able to vacate

    the berth safely when conditions make it difficult for moorings to cope.

Risk Assessments

    Whilst incidents of this nature may involve reports of defective mooring equipment or lack of attention to moorings, investigations suggest that in many incidents a proper risk assessment was not undertaken. It is recommended that appropriate risk assessments are carried out, taking into consideration the vessel’s characteristics, type, size, trading pattern and the prevailing weather conditions.

    Factors to be taken into consideration include, but should not be limited to, the following:

    Examples of wind, tidal, swell and weather related factors

• Wind loads exerted onto a vessel’s superstructure and hull above the waterline, which can

     form a large proportion of the total load on the mooring system depending on the moored

     vessel’s location and characteristics.

    • Wave loads on a vessel, which can vary depending on the vessel’s response to waves of

     varying periods and heights. Of special concern are moorings in relatively shallow water

     depths, in low tide and high wave conditions. These conditions can lead to violent vessel

     behaviour at the moorings (breaking waves, excessive motions, snatch loads etc.) and in

     extreme cases, loss of under-keel clearance in wave troughs for larger, deeper draft vessels.

• Forces resulting from steady currents in combination with other loadings, especially at low

     water levels in breaking wave conditions, which can also exert substantial loads on a ship’s

     mooring system.

    • The effect of wind against tide or current and the effect of a change in tide direction on moorings.

    • Tidal surges before, during and after storms, which may be well away from the area in which

     the vessel is berthed, causing unusually large tidal ranges and lower than expected water levels.

Examples of port/berth related factors

• Characteristics and history of the port and berth and any unusual occurrences.

    • Peculiar features of the berth such as overhanging berthing arrangements, obstruction by

     gantry cranes, wind funnelling effects from shore structures.

    • Design/type, position, quality and adequacy of shore mooring equipment, including storm

     moorings and fenders, and of tugs.

    • Exposure at the berth to wind, tide and swell conditions.

    • Delay in the availability of shore mooring equipment, mooring gangs, pilots and tugs etc. in

     normal as well as emergency situations.

    • Proximity of other vessels and hazards in the vicinity of the berth.

    • Effect of passing vessels on vessels moored alongside. (surging)

    • Availability of storm bollards, which may not be useable during cargo operations if moorings

     restrict working on the berth.

    • Port/terminal procedures in the event of extreme conditions and their suitability.

    - possibility of vessel to take a list due to excessive tightening of ropes.

Examples of vessel related factors

• Size/type of vessel, notably the windage area (including windage area due to cargo or

     containers if applicable) and the related effects of the same with changes in wind, tidal and

     swell conditions.

    • Design/type and condition of mooring equipment, its limitations and weaknesses.2

    • Suitability of the mooring pattern - number of lines, lengths, angles and leads and the ability

     to maintain even tension on the lines.

    • Manning level/crew availability for normal as well as adverse weather conditions.

    • Weather forecast and warnings - reliability and frequency.

    • Readiness of engines, thrusters, anchors and power on deck.

    • Availability, condition and readiness of additional moorings.

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