Excavator load and a low bridge clearance
You are to move a 22 t tracked excavator on a low-bed trailer from Sohar to a site inland. The trailer deck is 1.25 m above the road when loaded. The excavator measures 3.85 m from the deck to the top of its boom, and timber packing under the tracks adds 0.15 m. The load is 3.4 m wide and the combined vehicle length is 18.5 m. The permit states a maximum height of 5.3 m. The proposed route includes a reinforced concrete bridge with a posted clearance of 5.1 m at a wadi crossing, and an underpass signed at 5.5 m. The excavator driver says the boom can be lowered by about 0.4 m if the bucket is removed, but this takes two hours and needs a crane. No alternative route has been surveyed.
1. Calculate the actual load height and decide whether the vehicle can use the proposed route as loaded.
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Loaded height is deck 1.25 m + excavator 3.85 m + packing 0.15 m = 5.25 m. The bridge clearance is 5.1 m, so the load is 0.15 m too high. That is only the static measurement; suspension movement, tyre deflection, road camber and load settling can reduce the margin further, so passing under a 5.1 m bridge with a 5.25 m load is not acceptable. The permit limit of 5.3 m is not a guarantee that every structure on the route is high enough; it is the maximum authorised height, and the route must still be checked structure by structure. The 5.5 m underpass would clear, but the bridge does not. Therefore the vehicle cannot use the proposed route as loaded.
2. What are the safe options, and which would you choose?
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Options are: remove the bucket and lower the boom to reduce height by about 0.4 m, bringing the load to roughly 4.85 m; survey and use an alternative route avoiding the 5.1 m bridge; or reduce the trailer deck height, which is usually impractical. Lowering the boom is the most controllable option, but it must be done with a crane or suitable lifting equipment, the boom secured against movement, and the new height measured after packing. A 4.85 m load still needs a route survey for other low structures, wires and trees, and the permit may need amendment if dimensions change. I would not rely on “it will probably fit” or on deflating tyres. Choose the lowering option only if the new height gives a safe margin, then re-measure and confirm the route.
3. What height and load checks should be made before departure and during the journey?
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Before departure, measure the highest point with the machine settled on its packing, not from the manufacturer's brochure. Use a straight edge and tape, record the figure, and compare it with every structure on the surveyed route, allowing a safety margin for suspension and road camber. Confirm width and length against the permit, fit height marker boards or a height pole if required, and check that the boom, bucket and any attachments are secured. Check tyre pressures and trailer suspension because these affect height. During the journey, re-check restraints and height after the first few kilometres and at each stop, especially after rough roads. Approach bridges and wires slowly, and if any clearance is doubtful, stop and verify rather than commit. Record the measurements and route survey with the permit.