A vessel may be described as having two 80-tonne cranes, while the heaviest cargo unit weighs only 60 tonnes. At first sight, the lifting arrangement appears sufficient.
That conclusion can be wrong.
The safe working load stated in the vessel’s particulars normally applies under defined operating conditions. The crane’s lifting capacity may decrease as the outreach increases. A crane capable of lifting the cargo close to the ship’s side may not have sufficient capacity to reach a unit positioned farther away on the quay.
For project cargo, crane capacity must therefore be assessed together with outreach, hook height, cargo position and the complete lifting arrangement.
Maximum capacity is not available everywhere
Ship cranes normally have load charts showing the permitted lifting capacity at different outreach distances.
The advertised maximum safe working load may only be available at the shortest radius. As the jib is extended, the permissible load can fall significantly.
The relevant question is not simply:
How much can the crane lift?
It is:
How much can the crane lift at the outreach required for this operation?
Without the complete crane load chart, the vessel’s headline crane capacity is insufficient for a proper suitability assessment.
The cargo’s position on the quay matters
The required outreach depends on where the cargo can be positioned before loading.
A heavy unit may have to remain:
- on a transport trailer;
- behind other cargo;
- outside the terminal’s safety zone;
- beyond bollards or quay equipment;
- at a distance imposed by the terminal;
- on a barge alongside the vessel.
The vessel’s beam, the distance between the crane pedestal and ship’s side, and the position of the cargo relative to the quay edge all affect the required working radius.
A few additional metres can materially reduce the crane’s available lifting capacity.
Hook height and lifting accessories
The crane must have sufficient hook height to clear the ship’s rail, hatch coaming and any other obstruction.
The complete lifting height includes:
- cargo height;
- slings;
- shackles;
- spreader beams;
- lifting frames;
- clearance above the cargo;
- clearance above the hatch coaming.
The weight of lifting accessories must also be included in the total load applied to the crane. A 60-tonne cargo unit with a heavy lifting beam and rigging arrangement may impose a materially higher load than the cargo weight alone suggests.
Tandem lifting requires separate verification
When two cranes are used together, their stated capacities cannot simply be added without further examination.
The feasibility of a tandem lift depends on:
- whether simultaneous crane operation is permitted;
- the cranes’ combined lifting capacity at the required outreach;
- the distance between the cranes;
- the cargo’s lifting points;
- the centre of gravity;
- load sharing between the cranes;
- vessel stability during the lift;
- the approved lifting procedure.
Unequal load distribution can overload one crane even when the combined headline capacity appears sufficient.
The vessel’s owner, master and technical representatives must confirm that the proposed tandem lift is permitted and operationally feasible.
Shore crane availability should not be assumed
If the vessel’s own cranes cannot complete the operation, a mobile harbour crane or floating crane may be considered. This alternative can materially change the transportation cost.
Before relying on shore equipment, the parties should verify:
- crane availability;
- permitted working radius;
- lifting capacity;
- quay bearing limits;
- mobilisation costs;
- terminal approval;
- working hours;
- weather limitations;
- responsibility for delays.
A shore crane solution that has not been confirmed before fixing can expose the charterer to additional costs and lost time.
Documents required before nomination
For a meaningful vessel assessment, cargo interests should provide:
- dimensions and weight of every significant unit;
- maximum weight of a single piece;
- lifting points;
- centre of gravity;
- technical drawings;
- photographs;
- lifting frame or spreader requirements;
- proposed quay position;
- information about available shore cranes.
The shipowner should provide crane load charts, outreach information, hook height, crane certificates and confirmation of any tandem lifting arrangement.
The commercial conclusion
A vessel’s crane capacity cannot be assessed as a single number. The cargo must be liftable at the actual working radius and through the complete movement from quay to final stowage position.
Best Break Bulk considers crane outreach, cargo geometry, lifting points, terminal conditions and the proposed stowage arrangement when assessing tonnage for project cargo chartering. These checks should be completed before the vessel is fixed, not after it arrives at the loading port.