The Overloaded Container Unload
You are operating a 2.5 tonne counterbalance truck with a rated capacity of 2,500 kg at 500 mm load centre. The load chart in the cab shows a derated capacity of 1,900 kg when the load centre is extended to 600 mm, and 1,600 kg at 700 mm. A pallet of bagged sand is presented. The delivery note states a gross weight of 1,750 kg, and the pallet is 1,200 mm deep with the load evenly distributed so its centre of gravity sits roughly 600 mm from the heel of the forks. The yard is level and dry. A colleague suggests you just 'lift it a bit and see if the back wheels come up'. The truck has no load moment indicator fitted.
1. Using the figures given, decide whether the lift is within capacity and explain the reasoning step by step.
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Step 1 - Establish the actual load centre. The pallet is 1,200 mm deep and evenly loaded, so the centre of gravity is about 600 mm from the fork heel. That is the load centre that applies, not the nominal 500 mm on the rating plate.
Step 2 - Read the correct figure off the chart. At 600 mm the truck is rated at 1,900 kg, not 2,500 kg.
Step 3 - Compare. Load is 1,750 kg; capacity at that load centre is 1,900 kg. There is only 150 kg (about 8%) margin.
Step 4 - Consider the real-world derates the chart does not show. Tyre condition, mast wear, any side shift or attachment, and dynamic loads from lifting/lowering all eat into that margin. A 150 kg margin on a 1,750 kg load is thin.
Conclusion: The lift is technically within the static rating, but only just. The correct action is to lift slowly, keep the load low, avoid any tilt while raised, and be prepared to stop. If the load were even slightly heavier or shifted forward, it would be over capacity. The colleague's 'lift and see' method is unacceptable - it tests stability by creating an uncontrolled tipping moment.
2. Explain why 'lifting it to see if the back wheels come up' is an unsafe way to check capacity, and state what a competent operator does instead.
Read the worked answer
Why the 'wheel lift' test is unsafe:
- It deliberately creates a condition where the truck's centre of gravity moves outside the stability triangle. If the load is too heavy, the truck tips rather than giving a warning.
- Counterbalance trucks can tip forward with no gradual warning; the rear wheels lifting is already the point of no return on a slope or with momentum.
- It stresses the mast, chains and hydraulic system beyond design loads.
- It provides no measurement - you learn nothing usable for the next lift.
What a competent operator does instead:
- Confirm the load weight from documentation or a weighbridge; if unknown, treat it as too heavy until proven otherwise.
- Measure or estimate the load centre and read the correct derated capacity from the data plate/chart.
- Account for any attachment (which further reduces capacity).
- If in doubt, do not lift - split the load, use a larger truck, or get the load weighed.
- Report to the supervisor and record the decision.