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Our customer manufactures heavy-duty cranes especially designed for marine applications both ship-board and off-shore. They were designing a marine deck crane of fixed boom type with a load carrying capacity of 8 tons. The design was done based on the past experience over old legacy cranes. The customer wanted to check the compliance of the new design with Bureau Veritas (BV) Rules for lifting appliances on board ships.

Zeus Numerix thoroughly studied the crane design and prepared all necessary hand calculations. As a first step, the strength of the crane pedestal and plates were checked and verified with BV rules. Then all the loads are calculated by considering dead weight, influence of self-motions (hoisting and slewing motion), influence of external conditions (list and trim) and other environmental conditions. The obtained loads are scaled up by using appropriate correction factors as suggested in BV.

Typical construction of marine deck crane.

Using the loads obtained, the stability criterion of crane jibs is checked. Then the strength criterion for lifting structure is checked by using the bending moments. Other components like pedestal and slewing rings are checked for failure. Finally the customer is supplied with detailed document and areas of improvement wherever the design is marginally close to the allowable value as per BV Rules.