How loads really move — and why most lifting injuries start before the crane lifts
Category: ON DECK → Lifting Operations
Estimated read time: 60–75 minutes
Audience: Zero knowledge → competent AB → junior officer → senior deck officer
Introduction – Why lifting feels controlled right up to the moment it isn’t
Lifting operations on deck are deceptive. The crane moves slowly, the load appears stable, and everyone involved believes the danger is contained within the hook and the slings. This creates a powerful illusion of control. In reality, the most dangerous part of any lift happens before the load leaves the deck, when geometry, friction, and human assumptions quietly set the conditions for failure.
Most lifting injuries are not caused by cranes collapsing or slings snapping without warning. They are caused by load shift, unexpected rotation, or sudden tension transfer—events that happen because the rigging was misunderstood, not because the equipment was weak. To learn lifting from zero knowledge, the first thing to abandon is the idea that strength alone makes a lift safe.
What rigging actually does to a load
Rigging does not simply connect a crane to an object. It defines how forces enter the load and how the load is allowed to move once tension is applied. The moment the hook takes weight, every sling begins competing for load share. Small differences in length, angle, or stiffness determine which sling tightens first and how the load reacts.
This is why a load that looked balanced on the deck can suddenly tilt or rotate as it lifts. The rigging did not “fail”; it revealed the true centre of gravity only after friction with the deck was removed. Experienced riggers expect this behaviour. Inexperienced ones are surprised by it.
Slings: strength is not the same as safety
Slings are usually chosen by capacity—wire, chain, or synthetic, each rated well above the expected load. That rating assumes straight, evenly loaded conditions. On deck, those conditions almost never exist. Slings bend over edges, twist under rotation, and see rapidly changing angles as the crane booms or slews.
A sling overloaded by geometry will not look overloaded. It will simply accept the load until internal damage accumulates or a sudden movement pushes it beyond its limit. This is why sling failures feel “instantaneous”. The weakness was introduced earlier, quietly, when the rigging geometry was accepted without question.
🔻 Real-World Failure: Offshore Heavy Lift Vessel Orion — Crane Load Test Collapse (2020)
During routine load testing at the port of Rostock, the offshore wind installation vessel Orion suffered a catastrophic crane failure when its newly installed 5,000-tonne Liebherr heavy lift crane collapsed under test load. The vessel was alongside, stationary, and not engaged in offshore operations. This was not a storm event, a DP failure, or a dynamic lift — it was a controlled engineering test.
At the time of the incident, the crane was carrying a test load of approximately 2,600 tonnes, less than half of its intended maximum test load. Despite operating well below its ultimate capacity, the main lattice boom suddenly flipped backward, and the hoist hook failed. Two personnel were hospitalised and ten more were treated on site for minor injuries.
Initial statements confirmed that the failure originated at the crane hook, which had been sourced from an external supplier. Investigators ruled out errors in the crane’s primary structure and focused instead on component-level failure under load — a reminder that in lifting operations, the system always fails at its weakest interface, not its strongest element.
What makes the Orion incident particularly instructive for deck crews is that nothing looked abnormal until the instant of failure. The load was static. The lift was controlled. The equipment was new. All certification was valid. Yet the failure was sudden, violent, and irreversible.
This is the reality of lifting operations:
Safe Working Load does not mean safe behaviour.
It means safe only if every component behaves exactly as assumed.
For deck crews, the lesson is not about crane design — it is about respecting system fragility. Every shackle, hook, sling, pin, and termination is part of the load path. When one of those elements behaves differently than expected, failure does not negotiate.
The Orion incident reinforces a core deck principle:
Lifting systems do not fail gradually.
They fail when hidden margins disappear.
Shackles, hooks, and the danger of “it fits”
Shackles and hooks fail less often than slings, but when they do, the consequences are severe. The most common error is not exceeding the rated load, but misusing the connection. Side-loading a shackle, crowding multiple slings into a hook, or allowing a shackle pin to rotate under load all change how forces flow through the metal.
From zero knowledge, the key concept is this: lifting hardware is designed to be loaded in one specific way. If the load path deviates from that design, the rating no longer applies. Experienced deck officers do not ask whether a shackle “fits”; they ask whether it is being loaded as intended.
Angle effects: where lifts quietly double in force
One of the least intuitive aspects of rigging is how sling angles multiply load. As sling legs spread outward, the vertical component of force decreases and the tension in each sling increases dramatically. A load that seems modest can impose forces far beyond expectation when lifted on wide angles.
This is not a calculation exercise for specialists only. On deck, understanding angle effects is about recognising when a lift looks wrong. Wide, flat slings pulling almost horizontally should immediately trigger concern, regardless of what the paperwork says.
Tag lines and the myth of “just steadying it”
Tag lines are meant to control rotation and position, not to restrain force. Many injuries occur when crew instinctively try to steady a moving load with their bodies instead of allowing the crane to do the work. When a load swings, the instinct to grab or brace is strong—and often fatal.
A person holding a tag line must always assume that the line could tighten suddenly. Standing in line with a potential snap-back path or wrapping a line around a hand removes any margin for escape. Skilled deck crews treat tag lines as guides, never as restraints.
Real-world pattern: the lift that went wrong slowly
In many accident investigations, the lift did not fail immediately. The load lifted cleanly, moved a short distance, and only then shifted or dropped. The root cause was almost always present from the start: an off-centre lift, a poor sling angle, or a connection under side-load.
What failed was not the equipment. What failed was the assumption that “if it lifts, it must be safe.”
Knowledge to Carry Forward
Rigging is about force direction, not just force magnitude. Loads move according to geometry, not intention. Slings fail because of angles, shackles fail because of misuse, and people get hurt because they stand where the load will move, not where they hope it will. A competent deck operator reads a lift before it starts and expects movement rather than being surprised by it.
Tags
On Deck, Lifting Operations, Rigging, Slinging, Shackles, Angle Factor, Tag Lines, Stored Energy, Deck Safety, Human Factors, Failure Modes