Brake control, runaway chain, and why anchoring accidents happen in seconds
Estimated read time: 55–65 minutes
Skill level: Cadet → AB → Junior Officer → Chief Mate
Contents
- Introduction – Anchoring Is Not “Dropping Weight”
- The Windlass–Brake–Cable System
- Let-Go Anchoring: What Actually Happens
- Walk-Back Anchoring: Why It Exists
- Brake Physics: Holding, Slipping, Burning
- Runaway Chain Events (Real Failure Sequences)
- Human Positioning During Let-Go & Walk-Back
- Weather, Way On, and Load Shock
- Decision Rules: Which Method, When
- Key Takeaways
1. Introduction – Anchoring Is Not “Dropping Weight”
Anchoring looks simple from the outside.
On deck, it is one of the most violent energy transitions on the ship:
- a moving vessel
- a massive chain
- friction-based braking
- seabed engagement
- human proximity
Most anchoring injuries and near-fatalities occur before the anchor ever touches bottom.
The problem is not the anchor.
It is loss of control during energy release.
2. The Windlass–Brake–Cable System
Anchoring is a system, not a piece of equipment.
It consists of:
- windlass motor & gearbox
- band brake (or disc brake)
- cable lifter / wildcat
- chain
- anchor
- seabed
The brake is the only thing preventing gravity and ship momentum from winning instantly.
A brake does not “stop” a chain.
It converts kinetic energy into heat.
This matters — because heat destroys brakes quietly.
3. Let-Go Anchoring: What Actually Happens
In a let-go:
- brake is eased
- anchor and chain run under gravity
- speed is controlled manually
- ship’s way must be minimal
What goes wrong in reality
A common real-world sequence:
- Ship still has slight way on
- Brake eased “a bit more”
- Chain accelerates
- Brake overheats within seconds
- Brake glaze forms
- Operator loses friction
- Chain runs uncontrollably
At this point:
- the chain is a moving weapon
- nobody can stop it
- people panic and step where they shouldn’t
This is how fingers, limbs, and lives are lost.
4. Walk-Back Anchoring: Why It Exists
Walk-back anchoring uses the windlass motor to:
- control chain speed
- limit acceleration
- protect the brake
- manage energy gradually
It is not “slow anchoring”.
It is controlled anchoring.
Walk-back is safer when:
- water is deep
- weather is marginal
- ship handling is complex
- brake condition is uncertain
How walk-back still fails
Failures occur when:
- motor is overloaded
- operator fights the brake
- communication breaks down
- crew assume “motor will handle it”
Motors stall.
Brakes still matter.
5. Brake Physics: Holding, Slipping, Burning
A windlass brake works by:
- friction
- surface area
- pressure
Under rapid chain movement:
- friction generates heat
- heat reduces friction
- friction loss accelerates runaway
A burned brake often:
- looks intact
- smells “hot”
- fails next time — not immediately
This is why many runaway incidents happen on the second anchoring, not the first.
6. Runaway Chain Events (Real Failure Sequences)
Typical real-world pattern:
- anchoring went “a bit fast” last time
- brake adjusted tighter to compensate
- next anchoring loads brake harder
- brake fails catastrophically
- chain runs to bitter end
- securing arrangement fails
- structure damaged / people injured
Runaway chain events escalate too fast for reaction.
The only defence is preventing them entirely.
7. Human Positioning During Let-Go & Walk-Back
During anchoring:
- nobody stands in line with the cable
- nobody steps over the chain
- nobody reaches across the wildcat
- nobody “just clears something quickly”
Most serious injuries happen when:
“It was nearly finished.”
The danger peaks at:
- brake adjustments
- final scope
- stopping the run
8. Weather, Way On, and Load Shock
Anchoring with way on multiplies load instantly.
Wind, swell, or current can:
- snatch the cable
- lift chain off seabed
- reintroduce shock loads
- overwhelm brake friction
Anchoring is not static — it is dynamic until the ship is settled.
9. Decision Rules: Which Method, When
Let-go is acceptable when:
- way on is minimal
- conditions are calm
- brake is proven
- crew are clear and disciplined
Walk-back is preferred when:
- depth is significant
- conditions are variable
- traffic is heavy
- brake condition is uncertain
Choosing the wrong method is a judgement failure, not bad luck.
10. Key Takeaways
- Anchoring is energy release, not weight drop
- Brakes fail through heat, not neglect
- Let-go failures escalate instantly
- Walk-back controls acceleration, not risk
- Human positioning decides injury outcomes