When hiring a lorry crane, it is easy to focus entirely on the headline figure—like a “10-tonne” or “18-tonne” crane. But experienced project managers know that a crane’s maximum capacity is only true under ideal, specialized conditions.
In the real world, physics dictates how much weight a crane can actually lift safely. That is where Load Diagrams and Load Charts come in. Misinterpreting these charts can lead to severe safety hazards, costly equipment stress, or project delays.
To make heavy logistics simpler and safer, here is a breakdown of how to read and understand a lorry crane load chart.
- Understand the Golden Rule: Radius is King
The single biggest misconception in heavy lifting is assuming a crane can lift its maximum weight anywhere. In reality, a crane’s capacity changes based on the Operating Radius (the horizontal distance from the center of the crane’s rotation to the center of the suspended load).
The Arm Analogy: Think of holding a heavy toolbox. Holding it right against your chest requires very little effort. But if you extend your arm straight out, that same toolbox feels exponentially heavier.
The Chart Impact: As the boom extends further outward or flatter, the lifting capacity drops sharply. A crane that handles massive weight close to the truck may only lift a fraction of that weight at maximum reach.
- The Three Core Pillars of Every Load Chart
Before looking up numbers on a chart, you must lock in three critical parameters:
Boom Length: How far the telescopic sections of the boom are extended. Longer booms give you more reach but lower your overall lifting capacity.
Operating Radius / Angle: The distance or elevation angle of the boom. Steeper boom angles provide higher lifting power.
Outrigger Configuration: For truck-mounted lorry cranes, outriggers (stabilizing legs) must be fully deployed and set correctly. Charts assume specific outrigger setups; partial deployment changes everything.
- Step-by-Step: How to Read the Matrix
When you open a manufacturer’s load chart, you will see a grid or matrix intersecting boom lengths and operating radiuses:
Select the Right Table: Ensure you are looking at the page matching your exact equipment configuration (outrigger setup and boom setup).
Find Your Radius: Locate your required horizontal distance on the left column or axis.
Find Your Boom Length: Locate the matching boom length on the top row.
Read the Intersection: Where the row and column meet, you will find the Rated Capacity (the maximum total weight the crane can safely lift at that exact geometry).
- Don’t Forget the Rigging Weight (The Hidden Trap)
A common oversight is forgetting to calculate the weight of the accessories. The numbers on a load chart represent the total allowable weight.
You must subtract the weight of the hook block, steel slings, shackles, and lifting beams from the chart’s maximum capacity to find your true Net Payload Limit.
Leave the Complex Calculations to the Experts
Reading load diagrams accurately requires precision, experience, and strict adherence to safety margins. If calculating radiuses, tonnages, and site constraints sounds like a headache, you don’t have to do it alone.
At Lintasan Setia, we specialize in taking the heavy burden off your shoulders. With 28 years of industry expertise, we handle site assessments, load chart calculations, and end-to-end transport from pick-up to drop-off.
[ Contact us today ] for a seamless, hassle-free lifting solution tailored to your project.
How to Read a Crane Load Chart (Step-by-Step)
This video provides a helpful visual breakdown of how to track working radiuses, boom lengths, and configurations when calculating crane lifting capacities.