A crane’s capacity is not a single number. It is a chart, and the figure that
applies is the one at the radius and height the lift actually happens at.
From the load chart
- What radius is needed — not just at the load, but along the whole path
- What configuration the crane is in: boom length, counterweight, support
- What the capacity is there, not in its best position
- What counts as part of the load: hook, block, slings, beam, chains
See the article Load charts aren’t suggestions and
crane models for manufacturer documentation.
The gear
Gear is chosen for the load, the attachment points and the geometry — not for
what is nearest the container door.
- Is the WLL legible, and does it apply to the hitch being used
- Sling angle increases the force in each leg. See the
sling calculator and the article
Sling angles multiply load - Is the gear within its inspection date and undamaged — see
maintenance - Does the material suit the load: edges, heat, chemicals
- Are connectors and shackles the right type, fitted the right way
Margin
How much margin is appropriate is a judgement that belongs to the plan and to
those with the competence — there is no figure here. But the margin should be
larger when the weight is uncertain, when the centre of gravity is unclear, when
the load catches wind, or when conditions may change during the operation.
If it is tight, that is not an invitation to try. It is a message that the
crane or the method is wrong for this lift.
The plan is the employer's. Under § 18-6 lifting operations must be planned and carried out properly, with the necessary organisation and competence, and that duty sits with the employer. These pages explain how a plan is built and what each element means — they are not a plan, and nothing here substitutes for an assessment made by someone competent for the specific lift. Where a figure is needed — capacity, distance, bearing pressure, wind limit — it comes from the crane's documentation, the equipment certificate or the relevant specialist, never from this site.