Mobile Crane: Stability of Cranes

The suitability of ground conditions is the responsibility of the Contractor, who must ensure that all crane standing positions are prepared in accordance with the loading provided by the Company Representative. The stability of mobile cranes relies on the following factors:

• That the ground is suitably compacted and levelled. Underground services or constructions may suffer damage or collapse due to a crane passing over or nearby, which in turn may lead to the crane overturning. Arrangements must be made to avoid underground services and constructions, basements and embankments.
• That the outrigger beams on the crane are extended to the required lengths or positions in accordance with the crane manufacturer’s specified duties and dimensions.
• That the outrigger jacks are extended to raise the crane wheels off the ground and free of weight.
• That adequate support material has been positioned under the outrigger jacks to prevent them sinking into the ground whilst lifting loads.
• That the crane carries out lifting strictly in accordance with the manufacturer’s tables of Safe Working Loads, i.e. Duty Charts.
• The outrigger jack loading tables are for guidance only and show the maximum theoretical loads for a selection of various cranes in each category. Loadings for other crane models and specific outrigger loadings are available from the Crane Owner.
• The Crane Supervisor and Crane Operator must monitor ground conditions during the course of erection, paying attention to deterioration as a result of usage and adverse weather.
• If there is doubt about the ground condition, the Crane Operator should be instructed to fully retract the main boom derrick to minimise radius and then slew the counterweight in the direction of each outrigger in turn for two minutes to simulate actual lift.

Source: www.precastfloors.info

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