The anchoring operation of a ship is a complex activity, especially when it is being carried out in busy anchorages or in ports’ outer limits where traffic is heavy. It involves the use of critical shipboard equipment and requires high level of situational awareness. A number of accidents have been caused due to failure of anchor to hold the vessel under medium or heavy weather conditions.
In particular, anchor and chain loss can often lead to collisions and grounding, which can result in additional damage to a vessel. Adding to the costs of anchor loss is the increasingly common requirement from port authorities that lost anchors are recovered. Therefore, the loss of anchor is a common issue for the industry resulting in delays and costs of replacement for the companies such as anchor recovery and removal expenses.
Types of anchoring failures
The problems related to anchoring operations may be technical due to the size, weight of anchor, the type and condition of anchor chain and the condition of equipment which supports anchors (winches, links, stoppers etc), or they may be operational depending on the use of anchors and the procedures supporting the operations.
There many different sizes and weights to choose from; it is the size and the potential cargo of the vessel which determine the appropriate anchor and chain for each vessel. In merchant marine shipping, ordinary and high or super high holding anchors are often being used. This article features an analysis of a single anchor use.
Maintenance and inspections should be frequent both to anchor and to chain. The quote ‘a chain is only as strong as its weakest link’ makes sense in anchoring operations, considering that in moments of tensions (during heavy weather and swell) the pressure on the chain links is multiple. A weak link may easily break and lead to loss of chain and anchor. Winches and stoppers should be inspected and maintained as per manufacturer’s instructions and crew should be familiar on how to operate and use them. By minimizing structural problems, the possibility of an anchor loss incident is decreasing.
What needs to be considered during anchorage plan
Anchoring operation should be carefully planned, executed and monitored in order to avoid any operational failure. Therefore, during planning stage, an anchorage plan should be prepared by the navigation officer taking into account:
- The vessel’s loading condition (in order to calculate draught and Under Keel Clearance)
- The available depth and type of ground (holding ground)
- The proximity of navigational hazards
- The weather forecast
- The prevailing tide and currents in the anchorage area
- The cables that are going to be used in accordance with anchorage depth and weather
- The safety Swinging Circle of the vessel
An alternative anchorage should also be prepared (taking in to account all the above) in case the initial selected anchoring position is not available.
What needs to be considered during anchorage operation
During execution stage the following items should be considered:
- Proper and efficient communication between the bridge and the anchor station is the most important aspect of anchoring operations. Before starting the operation, the officer must clarify: the anchor to be used (Port or Starboard); how many shackles are to be lowered and; how the anchor should be lowered (letting go or walking on gear)
- Presence of crew members wearing proper PPE for assisting the anchor station
- The anchor lashings and bow stopper are removed prior commencing the operations
- When using hydraulic windlass, make sure the pumps are started prior operation
- Check the working of windlass and its controls
- Visually check the anchor and its chain
A well-executed anchoring operation holds the vessel steady in the required position: the chain lays across the seabed, making the strain from the anchor more parallel to the sea bed, thus, causing it to hook better into the sea floor.
What needs to be considered during anchorage monitoring
During anchorage monitoring, an anchor watch is to be established in order to check the position of vessel during anchorage.
- Plot the swinging circle and check vessel’s position frequently.
- Follow the Master’s Standing Orders
- Keep a Check on your own Ship and other Ships in the Vicinity.
- Keep continuous communication with local Vessel Traffic service and port authorities in order to notify and be notified for any emergency.
- Keep appropriate daily signals and night lights.
The most critical part of the operation is when the anchor is ready to be detached from holding sea bottom while the vessel is ready to depart from the anchorage. The windlass has to overcome the weight of the chain from hawsepipe to bottom plus the anchor weight plus the resistance from holding ground. In case of tide / current or severe weather conditions additional tension may be added. The appropriate use of windlass and vessel’s propulsion is the solution to overcome the pick of anchor and chain tension at this stage.
Good maintenance, planning, safe execution and detailed monitoring are the keys for appropriate anchoring operations and minimize the risk of incident which may lead to multiple un desirable results such as grounding, pollution, anchor loss and relevant costs.
