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Ship Anchoring Operation

Updated: May 25


Ship Anchoring Operation


📍 When and Where to Anchor

You may be required to anchor in various situations:

  • Awaiting berth or pilot at port

  • Offshore cargo operations

  • Shelter from bad weather

  • Emergency stop due to engine failure

  • Routine drills

⚠️ Always check Chart Notes, Port Guidelines, NAVTEX warnings, and local anchor restrictions.

🛠️ How to Drop Anchor – Step by Step

  1. Prepare Equipment and Crew

    • Inform bridge and engine

    • Power windlass

    • Put brake in "on" position

    • Remove bow stopper

    • Confirm chain is clear and positioned for letting go

  2. Approach Heading

    • Head into wind/current at 0.3 – 0.5 knots

    • Reduce speed well in advance

  3. Let Go or Walk Back

    • Let Go (free fall): Used in emergency or deep water anchoring

    • Walk Back (by gear): Controlled lowering, preferred in port

❗ Use “walk back” method if close to other ships or underwater cables — it allows better control.

🔢 How to Calculate Required Shackles – Normal Anchoring

To determine how many shackles to drop, use the water depth and apply a scope ratio.

Formula: Shackles = (Depth × Scope) ÷ 27.5

Where:

  • Depth = depth at anchorage (in meters)

  • Scope = ratio of chain length to depth (6:1 to 10:1 depending on weather)

  • 27.5 = length of one shackle in meters

📊 Recommended Scope Based on Conditions:

Conditions

Scope Ratio

Notes

Calm weather, good holding

6:1

Minimum safe scope

Moderate wind/current

7–8:1

Good practice for most ports

Heavy weather or poor bottom

9–10:1

Ensures strong holding

🔢 Example:

  • Depth = 20 m, Scope = 7:1

  • Shackles = (20 × 7) ÷ 27.5 = 5.1 shackles✅ Drop 5 to 5.5 shackles in this case.

💡 Add 0.5–1 shackle if strong wind, long stay, or poor bottom conditions.

⛓️ Drop or Walk Back – Which to Use?

Method

Use Case

Drop

Emergency anchoring, open sea

Walk Back

Controlled ports, near traffic, cables

⏱️ How to Keep Anchor Watch

Once the anchor is dropped, keeping a proper anchor watch is mandatory.


🧭 How to Know If Anchor Is Holding

✅ Anchor Is Holding:

  • Ship stays within swing circle

  • Chain is taut but not leading astern

  • No steady movement on radar or GPS

  • Heading varies naturally with wind/tide

❌ Anchor Is Dragging:

  • Vessel moves steadily in one direction

  • Heading remains constant despite movement

  • Chain stretched and leading astern

  • Alarms from ECDIS swing circle

  • Bottom sediment seen rising (visual)

✅ If dragging is suspected: increase shackles, start engine on standby, be ready to heave up and re-anchor.

🚨 Emergency Anchoring – Dragging Anchor to Stop the Ship

Emergency anchoring is a last-resort action to slow or stop a ship when propulsion is lost and immediate danger (e.g., grounding or collision) is near.

The anchor must not bite immediately — instead, it should drag along the seabed to create resistance and reduce the ship’s momentum gradually.

🔧 Key Points:

  • Anchor must intentionally drag to absorb energy

  • Do not drop the normal full scope (e.g., 6–10 shackles)

  • Drop limited shackles (3–5) to prevent sudden stop or damage

  • Once the ship slows, more chain can be paid out if needed for holding

🧮 How Many Shackles to Drop in Emergency?

Drop 3 to 5 shackles, depending on depth and vessel speed

Depth (m)

Emergency Shackles

Purpose

10

2.5 – 3.5

Immediate drag, fast effect

20

3.5 – 4.5

Controlled deceleration

30

4.5 – 5.0

Slower drag start

> 50

⚠️ Not recommended

Chain may not bite in time

⚠️ Too much chain may cause anchor to hold too suddenly — risking loss of anchor or gear failure.

🧠 Signs Anchor Is Slowing the Ship:

  • Speed dropping steadily on Doppler log or ECDIS

  • Anchor chain taut with vibration or load on brake

  • Bow sheering or shifting due to drag

  • Engine can assist once vessel is under control

📌 Final Reminders

  • Always log anchoring time, shackles, and position

  • Monitor anchor bearings and GPS

  • Never leave anchor watch unattended

  • Regularly inspect anchor windlass and brakes


💬 Share Your Best Practice

How do you handle anchoring in poor weather or crowded roads?👉 Log in to your Master Work Station account and leave a comment below to share tips or ask questions!


📂 Follow for More

Stay up to date with real onboard practices —Follow the “Shipboard Practice & Experience” category on Master Work Station for future posts on anchoring, mooring, pilotage, and more!


💡 Anchoring done right keeps the ship safe and steady — even when everything else moves.








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