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When the discharge berth is occupied, or the vessel's draft is too deep to berth on arrival, the tanker will go to anchor and await berth availability or lighter to docking draft.

5.6.1 Anchoring
The selected anchorage should be carefully reviewed for the presence of:

  • Prevailing or tidal currents.

  • Exposure to severe weather.

  • Available water depth.

  • Submarine pipelines, cables.

  • Charted anchorage restrictions.
  • All advice received from local authorities should be viewed with suspicion, the master being guided primarily by the actual conditions observed, indications of the admiralty/coast pilot, the sailing directions and navigation chart information. If the observed water depths are less than those indicated by local pilots, receivers, or facility operators, then the master has the right and obligation to abort the mooring operation and request that supplementary soundings be made to verify the adequate safe depth.
    The anchorage must provide sufficient depth under the keel for all stages of the tide and anticipated vessel trim. Sufficient clearance must be available for the ship to passover its own anchors safely. If significant tidal currents will be experienced, an allowance for the squat of the ship at maximum current must be included. The anchorage must provide sufficient room for the ship to swing clear of all shoals, obstructions and other vessels. Anchors should be equipped with a marker buoy, especially where there is a record of anchors being lost.
    Despite having a pilot embarked, the master and watch officers must regularly fix the position of the ship while approaching the anchorage and verify that the ship is making the agreed courses to the anchorage. The speed over the ground and depth of water under the keel should be frequently verified and the depth alarm used, (if fitted).
    The chief officer normally handles the anchor, ensuring well before hand that all the anchoring equipment is available and the windlass is in all respects ready for use. Preparations must always be supervised by a deck officer and only experienced crew members should handle the anchor machinery. Protective goggles and helmets must be worn by the men operating the windlass brake. The anchor pawl or stopper should be in place until immediately before the anchor is lowered.
    To ensure the minimum opportunity for accident or damage when anchoring, the ship should be fitted with a doppler speed log, with the transducer mounted under the forepeak. The speed log should have a 'ground lock' capability which will indicate the speed of the ship over the bottom (rather than the speed through the water).
    The anchor should be backed out (not dropped). When the master and chief officer are in agreement that the vessel is at or near zero speed over the bottom the anchor should be landed on the bottom and chain backed out to the desired scope. The chief officer must keep the master regularly advised of the length (scope), of chain out and the direction the chain is tending. On smaller vessels, the anchor may be walked out to one half of the water depth and then dropped. On larger tankers and in any depth of water over 40 meters, the anchor should be walked out under power to the desired scope. See the OCIMF publication Anchoring systems and procedures for large tankers for additional guidance.
    Anchor bearings should be carefully taken and verified before the anchoring party is released from their duties. The doppler speed log set on ground lock provides a second indication that the vessel is not dragging. Anchor signals should be properly displayed.

    5.6.2 Anchor watch
    An anchor watch must be set with clear instructions to use all available means to verify that the vessel is not dragging its anchor. Enter anchor bearings in the log and plot the anchored position on the chart. Plot a 'bridge turning circle' using the scope of chain and the ship's length. Use cross bearings to regularly verify that the bridge is remaining within the circle drawn on the chart.
    The ship should remain at least 0.8 miles clear of all obstructions.
    Engines should be maintained ready for manoeuvring if necessary and the watch officer clearly instructed that he is required to use the engines if necessary to avoid danger to the vessel.
    The anchor watch must keep a vigilant, all around lookout. Approaching vessels should be tracked by radar and visual bearings as if own vessel were under way. The master must be called if it appears that a closing ship will not pass clear and the watch officer should attempt to make early radio or visual contact with closing vessels with small CPA's, to determine their intentions.
    If the vessel yaws excessively in river or narrow channel, it is sometimes possible to minimise or eliminate the motion by use of the automatic steering. Alternatively, if sufficient water depth permits, a second anchor may be lowered on a short scope to reduce the motions of the bow due to wind or sea.
    The required anchor signals must be displayed and if the weather closes in, the required sound signals made. The stage of the tide and current should be closely observed. The master must be notified if there is a significant change in the weather.
    The deck watch should be assigned to make frequent rounds of the ship and accommodation and the result entered in the log. Pilot ladders and gangway must be raised to deck level except when in use. The deck watch must keep a good watch for strange boats approaching and unauthorised persons attempting to board the ship.
    While at anchor in Angola, Brazil, Malaysia, the South China Sea, or Singapore, special precautions are needed to prevent pirates from boarding the ship. The master must seek recommendations from owners and the P&I Club when en route to those areas. Further guidance is available from the International Shipping Federation publication, Pirates and armed robberies - A master's guide.
    Tankers should not anchor in ice unless there is no alternative.

    5.6.3 Lightering by barge
    Most lightering operations are conducted in fairly sheltered waters by barge. The barges are manned by experienced crews and are rigged for going alongside, with all the necessary transfer equipment. Nevertheless, a large measure of the responsibility for a safe lightering operation rests with the crew of the tanker.
    The operation should be conducted according to a written procedure prepared by the chief officer and approved by the master. All applicable recommendations of the OCIMF Ship-to-ship transfer guide (petroleum) should be complied with and the publication (only 18 pages in length), should be read by the chief officer and cargo officers prior to each lightering operation. The OCIMF guide includes a series of checklists which should be used for the lightering operation.
    When the barge arrives alongside, it is the responsibility of the chief officer to determine if it will be accepted for the lightering operation. The fendering, mooring wires, winches and the transfer hoses should be carefully examined. If any of those items or any other equipment appears to be neglected, or otherwise present a safety hazard, then the barge should be refused and turned away from the ship.
    If the barge is accepted and no independent petroleum inspector is available, then the chief officer must inspect the barge's tanks and piping system to determine that the vessel is suitable to receive the ship's cargo. If the barge is found unsuitable for any reason, it should be instructed to depart and the owners and charterer's notified. At the end of the lightering operation, the chief officer must again attend the barge (absent any petroleum inspector attendance), to observes the gauging of barge tanks and witness the barge report.
    The quantity to lighter will have been calculated and agreed prior to the vessel's arrival. If sea conditions in harbour permit and if a shore boat or the barge tug is available, then the chief officer may be able to visually check the draft of his ship near the end of the lightering. Otherwise, the lightering will be completed by calculated ullages, with the hope that they are correct.

    5.6.4 Mooring at SPMs
    The vessel may be required to discharge at a single point mooring (SPM). If that is the case, the vessel's mooring wires and ropes will not be used. In most cases, the operators of the SPM facility will use their own equipment and mooring crew to connect the mooring.
    Before proceeding to the SPM, the charterers and operators should be fully aware of the vessel's suitability to secure and discharge at the facility.
    The ship owner's responsibility is to provide:

  • A means of securing the chafe chain. This would be a bow chain stopper or an acceptable SMIT type towing bracket.

  • Bow fairleads of the correct shape and size to pass the chafe chain.

  • Pedestal roller fairleads and winch drums/capstans correctly positioned to provide the proper leads and clearances for the messenger lines.
  • Further details of procedures to be used at SPM moorings may be obtained in the OCIMF publication Recommendations for equipment employed in the mooring of ships at single point moorings.

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