Every seasoned seafarer knows how precarious a dragging anchor can be.
It’s one thing that keeps captains awake at night, especially when the weather gets bad, and you’re anchored close to the shore or with other vessels nearby.
If your anchor drags, it’s not just the Master’s problem; it’s the whole crew’s. Damage to property, the environment, and even loss of life could result if this situation isn’t handled well.
This article will help you address the signs of dragging and the best response when met with one.
- Stronger external forces from wind/currents and poor holding ground cause most failures of the anchor to hold.
- Continuous position monitoring, visual cues, and sensing tension changes are critical to detecting anchor dragging early.
- Informing the bridge team and deploying crews to address the situation swiftly minimizes accident risk from uncontrolled drift.
What is dragging an anchor?
Dragging Anchor is an expression used to describe a vessel moving over the ground when its anchor is not dug in and holding.
In simpler terms, dragging will occur if the environmental forces acting on a ship are stronger than an anchor can withstand.
Holding Power < External Force = Dragging
Consider it a tug-of-war between your ship and the anchor where your ship prevails, except in this case, it’s a bad idea!
This dangerous situation leads to failure to maintain position and accidents if the vessel hits structures or other ships.
Signs that your anchor is dragging
It doesn’t guarantee it will hold out even if you drop the anchor safely and properly. There is also no formula for predicting when the anchor will drag.
That’s why continuous monitoring is necessary to check if the vessel drifts, especially during bad weather.
Here are the signs of dragging.
1. Your ship is outside the swinging circle.
2. The ship’s side against the wind has not changed.
3. You hear extraordinarily unusual significant vibrations and tensions from the anchor chains.
4. Anchor watch alarm in ECDIS, GPS, and radar fire off.
5. Irregular depth soundings may imply drifting rather than holding steady at a fixed seabed position.
6. Bearing of landmasses and navigational markers shift in relation to your vessel.
7. The ship picks up speed according to its Speed Over Ground (SOG).
8. Changes in the position and distance of other vessels nearby.
9. Sometimes, your hunch tells you, “It just doesn’t feel right!“.
10. The radar’s Variable Range Marker (VRM) changes when set to a fixed target ashore.
11. The yaw and sway motion of the ship forms a “figure-of-eight” pattern. This was discovered by Capt. Takuzo Okada in his P&I Loss Prevention Bulletin.
12. You get a call from the Vessel Traffic Services (VTS) or other ships that you are dragging.
Actions to take during dragging
All type of ships drag their anchors at some point in their sailing life. It’s part of sea life, and there’s no need to panic when it happens.
What matters most is what we do about it because sometimes, they happen unexpectedly.
As an Officer of the Watch, here are your best course of action when your anchor drags.
- Inform the key people in this order: 1st is the Master. Second is the Engineer on duty, Third is the Chief Mate and lastly is the Bosun. The AB on duty should also be aware of this point.
- Send the anchor party forward (Bosun, AB, Chief Mate).
- Start the main engines to gain immediate control and maneuverability of the vessel.
- When ready, start heaving up the anchor.
- Inform the VTS that you’re heaving up and repositioning your anchor.
- Drop the anchor in another location and increase the scope of the chain for increased holding.
- Reset the anchor watch alarms and monitor your ship’s position.
The composition of the anchoring party depends on the system and company policy, so you should consult this one with the master.
Some Captains may add more shackles to the water before heaving it up, while others reposition it directly. It depends on their assessment.
Another technique they employ is to assist the anchor with the main engine. Lastly, some ships proceed to drifting areas until the weather calms down.
What causes anchor dragging?
Usually, anchor dragging is caused by a combination of factors that interact on the ship’s hull. It usually happens during bad weather, when these forces are stronger than average.
Here are the most common causes.
- Strong Winds – Storm-strength winds delivering force beyond the anchor system’s maximum load capacity is a prime cause.
- Inadequate Scope – The length of shackles deployed should depend on the expected meteorological conditions. Small scope (4:1) during inclement weather is a recipe for dragging.
- Poor Holding Ground – Rock, grass, coral, and some sand bottoms provide sub-optimal grip for anchors compared to sticky mud seabeds.
- Changing Weather Conditions – Sudden shifts in wind direction and strength can exert lateral forces on the ship, causing it to drag.
- Strong and Shifting Current – This happened to us in Lisbon, where we almost hit the bridge after the current shifted its direction, causing the anchor to drag.
- Equipment Failures – Any anchor part could break, like the chain, fluke, etc.
- Fouling with Another Ship – If another vessel gets its chain tangled with yours, expect your ship to drag.
Dangers and risks
When a vessel’s anchor fails to maintain its grip on the seafloor and begins dragging, several severe risks and dangers can rapidly escalate if not addressed swiftly:
- Grounding – As the ship drags, it can be pulled towards shallow waters, reefs, or even on the beach!
- Collision – Drifting vessels pose a significant collision risk to other nearby ships, potentially resulting in maritime accidents, property damage, and endangering lives.
- Loss of anchor and chain – In extreme cases, the sheer force of dragging can cause the anchor and even a significant portion of the anchor cable to break free.
- Environmental damage – It can cause significant damage to the seabed ecosystem as the anchor scrapes the sea bottom.
- Entanglement and fouling – The anchor and chain may become entangled with underwater structures such as submarine cables, pipelines, and other vessels.
- Safety risks to crew – The crew could be in danger as the ship runs aground and gets damaged while tossed by the waves.
- Financial consequences – Shipowners could face fines, penalties, and financial obligations for fixing the damages. Marine insurance may even refuse to pay the total price if caused by negligence.
I experienced a lot of anchor dragging in Biscay and Ijmuiden anchorage, but we managed it well.
However, the one that gave us much worry was when the ship ahead of us started dragging heading towards us.
Have you faced anchor dragging situations? Share your experiences in the comments below! Your insights could offer valuable lessons to the maritime community.
May the winds be in your favor.