5 Safety Precautions Associated with Ballast Water Exchange

  5.1 Three methods of carrying out ballast water exchange at sea have been identified as acceptable by the Organization. Each has particular safety aspects associated with it that should be considered when selecting the method(s) to be used on a particular ship.

  5.2 When identifying the ballast water exchange method(s) for the first time for a particular ship, an evaluation should be made which should include:

• .1 the safety margins for stability and strength contained in allowable seagoing conditions, as specified in the approved trim and stability booklet and the loading manual relevant to individual types of ships. Account should also be taken of the loading conditions and the envisaged ballast water exchange method or methods to be used;

• .2 the ballast pumping and piping system taking account of the number of ballast pumps and their capacities, size and arrangements of ballast water tanks; and

• .3 the availability and capacity of tank vents and overflow arrangements, for the flow through method, the availability and capacity of tank overflow points, prevention of under and over pressurization of the ballast tanks.

  5.3 Particular account should be taken of the following:

• .1 stability which is to be maintained at all times and not less than those values recommended by the Organization or required by the Administration;

• .2 longitudinal stress, and where applicable torsional stress values, not to exceed permitted values with regard to prevailing sea conditions;

• .3 exchange of ballast in tanks where significant structural loads may be generated by sloshing action in the partially filled tank to be carried out in favourable sea and swell conditions such that the risk of structural damage is minimized;

• .4 wave-induced hull vibrations when carrying out ballast water exchange;

• .5 limitations of the available methods of ballast water exchange in respect of sea and weather conditions;

• .6 forward and aft draughts and trim, with particular reference to bridge visibility, slamming, propeller immersion and minimum forward draft; and

• .7 additional work loads on the master and crew.

  5.4 Having undertaken an evaluation for a particular ship and the exchange method or methods to be used, the ship should be provided with procedures, advice and information appropriate to the exchange method(s) identified and ship type in the Ballast Water Management Plan. The procedures, advice, and information in the Ballast Water Management Plan, may include but is not limited to the following:

• .1 avoidance of over and under-pressurization of ballast tanks;

• .2 free surface effects on stability and sloshing loads in tanks that may be slack at any one time;

• .3 maintain adequate intact stability in accordance with an approved trim and stability booklet;

• .4 permissible seagoing strength limits of shear forces and bending moments in accordance with an approved loading manual;

• .5 torsional forces;

• .6 forward and aft draughts and trim, with particular reference to bridge visibility, propeller immersion and minimum forward draft;

• .7 wave-induced hull vibrations when performing ballast water exchange;

• .8 watertight and weathertight closures (e.g. manholes) which may have to be opened during ballast exchange must be re-secured;

• .9 maximum pumping/flow rates – to ensure the tank is not subjected to a pressure greater than that for which it has been designed;

• .10 internal transfers of ballast;

• .11 admissible weather conditions;

• .12 weather routeing in areas seasonably affected by cyclones, typhoons, hurricanes, or heavy icing conditions;

• .13 documented records of ballasting and/or de-ballasting and/or internal transfers of ballast;

• .14 contingency procedures for situations which may affect ballast water exchange at sea, including deteriorating weather conditions, pump failure and loss of power;

• .15 time to complete the ballast water exchange for each tank or an appropriate sequence thereof;

• .16 continual monitoring of the ballast water operation; monitoring should include pumps, levels in tanks, line and pump pressures, stability and stresses;

• .17 a list of circumstances in which ballast water exchange should not be undertaken. These circumstances may result from critical situations of an exceptional nature or force majeure due to stress of weather, known equipment failures or defects, or any other circumstances in which human life or safety of the ship is threatened;

• .18 ballast water exchange at sea should be avoided in freezing weather conditions. However, when it is deemed absolutely necessary, particular attention should be paid to the hazards associated with the freezing of overboard discharge arrangements, air pipes, ballast system valves together with their means of control, and the build up of ice on deck; and

• .19 personnel safety, including precautions which may be required when personnel are required to work on deck at night, in heavy weather, when ballast water overflows the deck, and in freezing conditions. These concerns may be related to the risks to the personnel of falling and injury, due to the slippery wet surface of the deck plate, when water is overflowing on deck, and to the direct contact with the ballast water, in terms of occupational health and safety.

  5.5 During ballast water exchange sequences there may be times when, for a transitory period, one or more of the following criteria cannot be fully met or are found to be difficult to maintain:

• .1 bridge visibility standards (SOLAS V/22);

• .2 propeller immersion; and

• .3 minimum draft forward.

  5.6 As the choice of acceptable ballast water exchange sequences is limited for most ships, it is not always practicable to dismiss from consideration those sequences where transitory noncompliance may occur. The practical alternative would be to accept such sequences provided an appropriate note is placed in the Ballast Water Management Plan to alert the ship's master. The note would advise the master of the nature of the transitory non-compliance, that additional planning may be required and that adequate precautions need to be taken when using such sequences.

  5.7 In planning a ballast water exchange operation that includes sequences which involve periods when the criteria for propeller immersion, minimum draft and / or trim and bridge visibility cannot be met, the Master should assess:

• .1 the duration(s) and time(s) during the operation that any of the criteria will not be met;

• .2 the effect(s) on the navigational and manoeuvring capabilities of the ship; and

• .3 the time to complete the operation.

  5.8 A decision to proceed with the operation should only be taken when it is anticipated that:

• .1 the ship will be in open water;

• .2 the traffic density will be low;

• .3 an enhanced navigational watch will be maintained including if necessary an additional look out forward with adequate communications with the navigation bridge;

• .4 the manoeuvrability of the vessel will not be unduly impaired by the draft and trim and or propeller immersion during the transitory period; and

• .5 the general weather and sea state conditions will be suitable and unlikely to deteriorate.

  5.9 On oil tankers, segregated ballast and clean ballast may be discharged below the water line at sea by pumps if the ballast water exchange is performed under the provisions of Regulation D-1.1 of the International Convention for the Control and Management of Ships' Ballast Water and Sediments, provided that the surface of the ballast water has been examined either visually or by other means immediately before the discharge to ensure that no contamination with oil has taken place.