Section 14.1 Anchoring Procedures for Large Vessels (Site Selection, Execution, Monitoring)

Anchoring is a routine yet critical operation for bulk carriers, whether it’s for waiting for a berth, seeking shelter from heavy weather, or for other operational or emergency reasons. While seemingly straightforward, anchoring a large, heavily laden or high-windage ballast bulk carrier requires careful planning in site selection, precise execution of the anchoring maneuver, and diligent monitoring once at anchor to ensure the vessel remains secure. Errors in anchoring can lead to dragging anchor, collision with other vessels or obstructions, grounding, or damage to the anchor equipment itself.

1. Purposes of Anchoring:

Bulk carriers may need to anchor for various reasons:

Waiting for Berth (WFB): The most common reason. Ports are often congested, and vessels may need to wait at a designated anchorage for their turn to berth.

Waiting for Orders (WFO): Awaiting further commercial instructions.

Waiting for Favorable Weather: Seeking shelter from storms or waiting for weather conditions to improve before proceeding to sea or entering port.

Waiting for Tide or Daylight: If port entry or transit is restricted by tidal height or requires daylight.

Bunkering, Stores, or Crew Change: Some of these operations can be conducted at anchor.

Emergency Situations: Such as engine failure, loss of steering, or to avoid an imminent collision or grounding (though anchoring in an emergency is a high-risk maneuver itself).

Holding Ground for Port Formalities: Completing customs, immigration, or health clearance before proceeding to berth.

2. Site Selection for Anchoring – Critical Considerations:

Choosing a suitable anchoring position is paramount for safety. This is a key part of the “Appraisal” and “Planning” stages of passage planning if anchoring is anticipated.

A. Designated Anchorages:

Most ports have designated anchorage areas clearly marked on charts and described in Sailing Directions/Pilot Books. These are usually selected by port authorities for their suitability in terms of depth, holding ground, and clearance from fairways and dangers.

Always use designated anchorages if available and instructed to do so.

Be aware of any specific regulations for anchoring within these areas (e.g., minimum spacing between vessels, reporting requirements).

B. Depth of Water:

Sufficient Depth: The depth must be adequate to provide safe under-keel clearance (UKC) at all states of the tide (especially Low Water) throughout the expected period at anchor, accounting for potential changes in draft if cargo operations or ballasting are planned at anchor (rare for bulkers, but possible).

Not Too Deep: Excessively deep water (e.g., >80-100 meters for conventional anchoring systems) can:

Put excessive strain on the windlass when heaving anchor.

Require a very long scope of cable, potentially leading to a large swinging circle.

Increase the risk of the anchor dragging if the weight of the cable itself lifts the anchor shank.

Make it difficult to detect if the anchor is dragging.

Ideal Depth: Often considered to be in the range of 15-50 meters, allowing for a reasonable scope of cable and good holding.

C. Nature of Holding Ground:

Good Holding Ground: Provides strong resistance to the anchor dragging. Ideal types include:

Mud, Clay, Stiff Mud/Clay: Generally offer excellent holding.

Sand, Sand/Shell, Sand/Mud: Can provide good holding, but some types of fine, loose sand might be less reliable.

Poor Holding Ground:

Rock/Rocky Bottom: High risk of the anchor snagging or fouling, making recovery difficult or impossible, and potentially damaging the anchor or windlass. Also, anchors may “skate” over smooth rock.

Very Soft Silt/Ooze: Anchor may drag through it easily.

Gravel/Shingle: Can be variable; anchor may drag.

Information Sources: Charts often indicate the nature of the seabed. Sailing Directions provide more detailed descriptions of holding ground in specific anchorages.

D. Shelter from Wind and Sea:

Choose a position that offers maximum protection from prevailing and forecast strong winds, high seas, and swell. Lee shores (where the wind blows directly onto the land from the sea) should be avoided.

Consider the effect of headlands, islands, or breakwaters in providing shelter.

E. Swinging Room:

A vessel at anchor will swing around its anchor due to changes in wind and tidal stream direction.

Calculate Swinging Circle: Radius ≈ √(Scope² – (Depth + Freeboard to Hawsepipe)²) or more simply, Scope + Ship’s Length Overall (LOA) as a conservative estimate for initial planning.

Sufficient Sea Room: Ensure there is ample clear water all around the intended anchoring position for the vessel to swing safely without coming dangerously close to:

Other anchored vessels.

Shallow water / navigational dangers (reefs, wrecks, shoals).

Shorelines or fixed structures.

Fairways or channels.

Consider the swinging circles of other vessels already at anchor. Maintain a safe distance.

F. Proximity to Fairways and Channels:

Anchor well clear of established fairways, channels, and port approaches to avoid obstructing navigation for other vessels. Designated anchorages are usually sited to ensure this.

G. Tidal Streams and Currents:

Strong tidal streams or currents can put considerable strain on the anchor and cable, increasing the risk of dragging.

They will also affect the vessel’s orientation at anchor and its swinging pattern.

If possible, anchor in an area with moderate or weak streams.

H. Submarine Cables, Pipelines, and Other Obstructions:

Charts indicate the presence of submarine cables, pipelines, restricted areas, and other underwater obstructions. Anchor well clear of these to avoid damage and potential legal liabilities.

I. Local Regulations and VTS Requirements:

Comply with all local port regulations regarding anchoring, including any requirements to obtain permission, report anchoring position, or maintain a listening watch on specific VHF channels.

Follow instructions from Vessel Traffic Services (VTS).

3. Execution of Anchoring Maneuver:

This requires careful preparation, good communication, and precise ship handling.

A. Pre-Anchoring Preparations (Bridge and Deck):

Briefing: Master briefs the bridge team and the anchor party (Chief Officer, Bosun, ratings) on the selected anchoring position, approach plan, depth of water, nature of holding ground, amount of cable to be used, method of letting go (walk back or let run), and safety precautions.

Anchor Ready:

Clear the anchor for letting go (remove cement from hawsepipe, release chain stopper lashings, ensure anchor is free to run).

Windlass tested and ready (power on, brake tested, clutch disengaged if letting go under gravity).

Chain stopper ready to be applied once anchored.

Communication: Establish reliable communication between the bridge and the forecastle anchor station (VHF radio, sound-powered telephone, hand signals as backup).

Day/Night Signals: Prepare to display the anchor ball (day) or anchor lights (night) immediately upon anchoring.

Engine Room Notified: Engine room on standby, main engine ready for maneuvering.

Steering Gear Tested.

Navigational Equipment: Radar, ECDIS, echo sounder operational. Position plotted on chart/ECDIS.

B. Approach to Anchoring Position:

Against Wind or Current: Approach the chosen anchoring position slowly, heading into the predominant wind or current (whichever is stronger). This gives better control over the vessel’s speed and heading.

Monitor Speed Over Ground (SOG): Reduce speed gradually. Aim to be almost stopped over the ground (or making slight sternway if letting go and snubbing) at the “let-go” position.

Use Echo Sounder: Continuously monitor the depth of water.

Position Fixing: Use all available means (GPS/DGPS, Radar bearings/ranges, visual bearings) to accurately determine the vessel’s position relative to the intended drop point.

C. Letting Go the Anchor:

“Let Go” Order: When the vessel is in the correct position and nearly stopped (or with slight sternway), the Master gives the order to “let go port/starboard anchor.”

Method of Letting Go:

Letting Run (Under Gravity): The windlass brake is released, and the anchor and cable run out freely. This is quick but can put high stress on the brake if not controlled, especially in deeper water. The chain should be checked (briefly braked) periodically as it runs out to prevent it from piling up on the anchor.

Walking Back: The anchor and cable are paid out slowly using the windlass motor. This provides better control, reduces stress on the brake and windlass, and is preferred in deep water or when precise positioning is critical. It also helps the anchor to embed properly.

Amount of Cable (Scope):

Definition: Scope is the ratio of the length of anchor cable paid out to the depth of water (measured from the hawsepipe to the seabed). Scope = Length of Cable / Depth.

General Rule: A common rule of thumb is a scope of 5 to 7 in moderate conditions. (e.g., Depth 20m, Cable 120m (approx. 4.5 shackles) => Scope 6:1).

Factors Influencing Scope:

Depth of Water: More cable is needed in deeper water for the same scope.

Holding Ground: Poorer holding ground may require a longer scope.

Weather Conditions: In strong winds or currents, or if heavy weather is anticipated, a longer scope (e.g., 8:1 or more) is necessary to increase holding power and reduce yawing.

Swinging Room: A longer scope means a larger swinging circle.

Length of Stay: For a short stay in calm conditions, a shorter scope might be acceptable. For a prolonged stay, a more robust scope is prudent.

The amount of cable is usually measured in shackles (1 shackle = 15 fathoms = 27.5 meters or 90 feet, though this can vary slightly).

Paying Out Cable: Pay out the desired length of cable, observing the lead and weight on the chain.

D. Bringing the Vessel Up (Setting the Anchor):

Once the desired length of cable is paid out, gently apply the windlass brake to snub the chain and allow the anchor to dig into the seabed.

The vessel will gradually swing to lie head to wind or current.

Observe the anchor cable: It should lead out ahead and have a slight catenary (sag). If it becomes taut and leads directly downwards or starts to “jump,” the anchor may be dragging.

Apply the chain stopper securely once the anchor is holding and the vessel has settled. The load should be taken by the chain stopper, not just the windlass brake.

E. Confirming Anchor Position and Holding:

Fix the Vessel’s Position: Once the vessel is brought up, take an accurate fix of its position and plot it on the chart/ECDIS. This is the “anchored position.”

Check Bearings/Ranges: Take bearings and ranges to prominent shore objects or navigational marks to monitor for dragging.

Monitor GPS/DGPS Position: Set an “anchor watch alarm” or “drag circle” on the GPS/DGPS or ECDIS. This will alarm if the vessel moves outside a pre-set radius around its anchored position.

Observe the Anchor Cable: Periodically check the lead and feel of the cable.

Echo Sounder: Note the depth.

4. Monitoring While at Anchor:

Maintaining a vigilant anchor watch is crucial, even in apparently calm conditions.

A. Regular Position Checks:

At frequent intervals (e.g., every 15-30 minutes initially, then hourly if holding well, but more often in strong winds/currents or if other vessels are close).

Use GPS/DGPS anchor alarm, visual bearings, Radar ranges/bearings, and comparison of charted position with actual.

B. Monitoring for Dragging Anchor:

Signs:

Vessel position moving consistently outside the drag circle.

Changes in bearings/ranges to fixed objects.

Anchor cable “jumping,” leading directly up and down with no catenary, or feeling excessive vibration.

Unusual yawing or sheering of the vessel.

Sudden shallowing of water on the echo sounder if dragging towards shallower areas.

Action if Dragging:

Alert Master immediately.

Engine room on standby, main engine ready.

Pay out more cable (if sea room permits and it’s safe to do so – this can sometimes help the anchor to dig in again).

If dragging continues or if danger is imminent, prepare to heave up anchor and re-anchor in a safer position, or maneuver using main engine if necessary. This requires quick and decisive action.

C. Swinging Circle Awareness:

Be constantly aware of the vessel’s swinging circle and the proximity of other anchored vessels, navigational dangers, and shallow water.

Monitor changes in wind and tidal stream that will cause the vessel to swing.

D. Weather Conditions:

Keep a close watch on the weather forecast and current conditions. If conditions deteriorate significantly, consider paying out more cable or even heaving anchor and proceeding to sea or a more sheltered location if safety is compromised.

E. Anchor Watch Alarms (ECDIS/GPS): Ensure these are correctly set and understood by the OOW.

F. Readiness of Main Engine: Keep main engine on appropriate standby (e.g., 30 minutes, 1 hour notice) as per Master’s instructions and prevailing conditions. In very exposed anchorages or with doubtful holding, engines might be kept on immediate standby.

G. Anchor Lights/Shapes and Sound Signals:

Display correct anchor lights (all-round white lights) at night and anchor ball (black ball) by day.

Make appropriate sound signals in restricted visibility (bell forward, gong aft, plus optional whistle signal).

H. Security: Maintain appropriate security watches, especially in areas prone to piracy or theft.

I. Logbook Entries: Record all anchoring operations, position checks, weather conditions, cable paid out, and any incidents (e.g., dragging) meticulously in the deck logbook.

5. Master’s Key Responsibilities in Anchoring:

Site Selection Approval: Final decision on where to anchor.

Supervision of Maneuver: Often conns the vessel during the approach and letting go, or closely supervises the officer doing so.

Decision on Scope of Cable:

Ensuring Proper Anchor Watch: Setting clear instructions for the OOW regarding monitoring and actions if dragging.

Decision to Re-Anchor or Proceed to Sea: If conditions at anchor become unsafe.

Compliance with all Local and International Regulations.

Safe anchoring of a bulk carrier relies on careful planning, precise execution, and unwavering vigilance once at anchor. It is a testament to the Master’s seamanship and their commitment to the safety of the vessel, its crew, and other vessels in the vicinity.