OrcaFlex Examples - F Payload Handling

F01 Lowering Hydrodynamics.zip (85.5 MB) – Description PDF

In these three examples, we consider a number of effects that often need to be taken into account when doing a lifting or lowering analysis through the sea surface, and show how to model them in OrcaFlex.

The examples illustrate:

  • The effect of object size on the modelling method selected
  • Using multiple connected objects to model a complex structure
  • Modeling slam loads
  • Modelling trapped water

F01 Lowering Hydrodynamics

F02 Passive Compensation.zip (4.7 MB) – Description PDF

During the lowering process the heave of the vessel can result in severe motions of the payload and/or high loads on the crane.

To reduce these effects, heave compensation devices are often used. These can be active systems that adjust winch payout to keep the payload at a constant depth or passive systems where the payload is allowed to move but there is additional compliance with damping to reduce the loads on the crane when it heaves upwards.

This example considers the passive system, using a CRANEMASTER device as an example. The principles can also be applied to other devices.

F02 Passive Compensation

F03 PID Controlled Active Winch.zipDescription PDF

This package-lowering example uses a winch to model an active heave compensation device.

An external function written in Python is used to provide a feedback loop which controls the winch in response to the package's position, holding it at a constant depth.

Note: using the Python API to OrcaFlex requires a licenced copy of OrcaFlex.

F03 PID Controlled Active Winch

F07 Suction Anchor Lowering.zip (133.2 MB) – Description PDF

In this example we show how to model a suction anchor lowering operation.

Lowering of a suction anchor vertically through the sea surface requires careful consideration of how to account for the change in axial added mass and inertial loads as the suction anchor cap hits the sea surface, trapping a volume of water inside.

F07 Suction Anchor Lowering

Examples  |  A Production Risers  |  B Drilling Risers  |  C Moorings  |  D Riser Installation  |  E Pipelay and Recovery  |  F Payload Handling  |  G Deployment  |  H Offloading Systems  |  I Towed Systems  |  J Defence  |  Z Miscellaneous