Choosing a crane
How to read a crane load chart
Written by The FORTZA team Published:
The short answer
How do you find out how much a crane can lift at the distance you need?
From the model’s load chart: find the crane configuration (the jib length actually fitted), then the radius at which the load has to go, and read the permitted load at that radius. The maximum load can only be lifted close to the tower; towards the jib tip the capacity drops to the tip load. The real load, plus slings and accessories, must stay below the value you read.
“How much does the crane lift?” has no single answer. The capacity depends on how far the load is from the tower. That is why every model has a load chart, published by the manufacturer.
Why capacity drops towards the jib tip
A crane works like a lever. The counterweights balance the moment produced by the load, that is, its weight multiplied by its distance from the tower. The same weight pulls harder when it is far from the tower. So as the trolley moves out along the jib, the permitted load decreases.
Two values appear in almost every listing:
- Maximum load: the heaviest weight, permitted only on the part of the jib close to the tower.
- Load at jib tip: the weight permitted at the end of the jib, at maximum radius.
Between those two points, the chart shows the permitted value for each radius.
How to read the chart, step by step
- Choose the configuration. Many cranes can be fitted with jibs of different lengths. The chart has a curve or column for each jib length. Use the one for the configuration that will actually be erected.
- Find the radius. Measure on the site plan the horizontal distance from the crane axis to the furthest point where the load must be set down or picked up.
- Read the permitted load at that radius.
- Compare with the real load. Add the slings, extra hook, bucket or pallet fork to the weight of the material. The total must stay below the value you read.
A worked line of reasoning
You need to take 1,000 kg pallets 25 m from the crane. A model with a 2,000 kg maximum load may look sufficient, but what matters is the value at 25 m. If the chart shows 900 kg there, the crane cannot make the lift, and the answer is a larger model, a different crane position or lighter loads.
What else affects capacity
- Wind: work stops at the speeds set by the manufacturer; the crane’s anemometer measures them.
- Ground and base: a correctly built base or foundation is the condition for the values on the chart.
- Safety devices: the moment limiter and the load limiter stop movements that would exceed capacity.
A quick check before asking for an offer
The crane selector estimates from the published data which catalogue models can lift a load at a given radius and height. It is a pre-selection. Before the offer, the FORTZA team confirms the choice with the manufacturer’s load chart and the exact crane configuration.
Frequently asked questions
What does “load at jib tip” mean in a listing?
The weight the crane can lift at the end of the jib, at the maximum radius. It is the lowest value on the load chart and the most important one if you need to take materials to the edge of the site.
Can I use the selector’s estimate instead of the load chart?
No. The selector makes a cautious estimate from the published maximum load and tip load, useful for choosing which models to ask about. The decision is made with the manufacturer’s chart for the exact crane configuration.
Sources
- Crane selector – how the estimate works – FORTZA.RO SRL
- Crane rental – what you need to know – FORTZA.RO SRL
Useful links
General, indicative information. Crane erection, operation and inspections must be carried out only by authorised staff, following the manufacturer’s documentation and the applicable regulations (ISCIR in Romania).