The Overweight Container and the Rated Capacity Plate
You are assigned to unload a 40-foot container at a freight depot. The forklift you are given is a 2.5-tonne counterbalance diesel unit fitted with a side-shift and 1,200 mm forks. Its capacity plate states a rated capacity of 2,500 kg at a 500 mm load centre. The container holds palletised bagged fertiliser; the manifest lists each pallet as 1,150 kg, with 20 pallets in total. Each pallet is 1,200 mm deep, so when loaded against the fork heel the load centre sits at roughly 600 mm. The side-shift carriage adds about 80 kg of attachment weight ahead of the mast. A colleague says the forklift is rated to 2.5 tonnes so any 1,150 kg pallet is fine. The yard supervisor wants the job finished before the afternoon truck arrives.
1. Determine whether the forklift can safely lift one pallet as configured. Show your reasoning and state what you would do before starting.
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The rated 2,500 kg applies only at a 500 mm load centre on the bare carriage. Two things reduce actual capacity here.
First, load centre. The pallet is 1,200 mm deep, so the centre of gravity sits about 600 mm from the fork face, not 500 mm. Capacity falls roughly in proportion to the increase in load centre distance from the front wheel axis, so a 600 mm load centre reduces the rating by roughly 500/600, giving about 2,080 kg.
Second, the side-shift attachment. It adds about 80 kg of weight ahead of the mast and moves the load forward, further reducing net capacity. A reasonable de-rating takes the figure well below 2,000 kg.
Against a 1,150 kg pallet, the calculated capacity is still above the load, but the margin has shrunk from 1,350 kg to a few hundred kilograms, and the machine's stability is now governed by the tyres, ground condition and mast height rather than the headline rating. That is exactly the situation where a plate reading is not enough.
Before starting I would: check the machine's own load chart for the attachment and load centre (many plates list reduced capacities for attachments); confirm the actual pallet weight by weighing one rather than trusting the manifest, since bagged product absorbs moisture; keep the load as low as possible and the mast tilted back; check tyre condition and ground bearing; and if the chart does not cover a 600 mm load centre with side-shift, refuse the lift and request a larger machine or break the pallets down. The colleague's reasoning is wrong because rated capacity is conditional, not absolute.
2. The manifest later proves inaccurate and a pallet weighs 1,450 kg. Explain the consequence and the control you would apply.
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At 1,450 kg the pallet is still under the headline 2,500 kg, so nothing on the plate appears to be breached. But applying the same de-rating - roughly 2,080 kg for load centre, then a further allowance for the side-shift attachment - the margin is now thin or negative depending on the chart. The real risk is not a clean overload but a marginal one: the machine will lift the pallet, then tip forward when the mast is raised or when the load is tilted forward, or when travelling over an uneven surface.
The consequence of a marginal overload is loss of rear-axle stability. The forklift pivots on the front axle; once the combined centre of gravity passes ahead of that line, the counterweight cannot save it. The operator has no warning other than the rear wheels lifting.
Controls: stop the job, weigh a sample pallet, and re-plan against the actual chart rather than the manifest. Options are to use a machine with adequate capacity at the real load centre, reduce pallet size, or reposition the load hard against the fork heel to pull the centre back. I would document the discrepancy with the consignor, because the manifest is a safety document, and record the decision. I would not proceed on the basis that 'it lifted last time' - marginal overloads fail intermittently, which is why they kill experienced operators.