DNV-ST-0378 Load Cases: The Lift Is More Than the Weight

A crane can be structurally strong and still have a design basis that does not represent the real offshore lift.

This is one of the most important distinctions in lifting-equipment engineering: capacity on a nameplate is not the same thing as understanding the load case.

The lift is more than the lifted weight

Offshore lifting appliances operate in an environment where geometry, motion, acceleration, reeving, machinery behaviour and the interaction between the appliance and its supporting structure can matter. The applicable DNV-ST-0378 requirements depend on the equipment and intended operation, so the project basis has to describe the actual use case rather than a convenient nominal figure.

Start with the operating envelope

Before detailed calculations, the team should understand the working range of the equipment. Where can the load be positioned? What configurations are possible? Which operating conditions are intended? What limits will be imposed?

This matters because a lifting appliance is a system. A critical condition may occur at a particular geometry or operating state rather than at the condition that looks most severe at first glance.

Do not isolate the crane from what supports it

The forces do not disappear at the pedestal, foundation or mounting interface. The appliance and its supporting structure have to be treated as connected parts of the load path.

That interface is also a project interface. If one party designs the appliance and another designs the supporting structure, assumptions must be exchanged clearly and kept consistent as the design develops.

Good calculations begin with good inputs

Detailed analysis cannot rescue an unclear design basis. Before spending time refining a model, make sure the load definitions, geometry, boundary conditions and operating assumptions are controlled.

For a fast-track project, this is especially valuable. Every assumption that has to be reopened after fabrication release costs more time than one resolved during concept and design.

GravityX can coordinate the engineering interface

Where a lifting appliance requires structural engineering, mechanical integration, fabrication and compliance coordination, GravityX can help bring those activities into one execution plan.

See the complete DNV-ST-0378 series, our engineering solutions or discuss the design basis with us.

Need the lifting operation translated into a controlled design basis? Resolve the load cases and interfaces before detailed engineering is locked.