Lifting & Heavy-Lift Engineering

Every lift is engineered around three questions: what does the object weigh and where is its centre of gravity, how much will the load be amplified by the sea state and crane dynamics, and can the object, the rigging and the crane all take that load with the required factors. We answer them in that order.

Weight control feeds the dynamic amplification factor. The lifted object is then analysed in the lift condition, where members that were designed for in-place loads often see very different stresses at the padeyes. Rigging is sized with the sling-angle, skew-load and consumable factors required by DNV-ST-N001, and the crane vessel is checked for hook load, radius and stability with the load off the deck.

For riser, conductor, davit and deck-equipment installations offshore we add the interface engineering: lift-off from the supply vessel or barge, motion compensation where relevant, set-down clearances, temporary supports and sea-fastening for the transit. Our team supported a four-platform riser installation campaign with sixteen lifts, assessed feasibility for more than thirty riser lifts, and engineered four 50-tonne davit installations on a vessel in Nigeria.

• DNV-ST-N001 Section 16 Lifting operations (the successor to DNV-OS-H205 / Noble Denton 0027)
• ISO 19901-6, API RP 2A and AISC for the lifted structure
• LOLER, IMCA and client lifting procedures for rigging and equipment certification
• Classification-society rules for lifting appliances on vessels and cranes