Is marine growth thickness on a riser pipe included for Buoyancy loads and Wave loads for AutoPIPE analysis?
Marine growth thickness usually varies with depth. Also, from AutoPIPE online help:
Marine Growth: Enter the amount of marine growth attached to the submerged structure. This value is used to calculate the effective diameter to be used in force calculations. Marine growth is assumed zero above still water level.
No, AutoPIPE does not consider marine growth thickness (under Load> Wave) in the calculation of buoyancy.
Recommend one of the following modeling approaches:
For a given PipeID apply marine growth as insulation of the correct thickness and density, and enter a small value for marine growth on the Wave Loading dialog.
AutoPIPE does consider insulation around the pipe in the buoyancy load which can be used to simulate marine growth over a section of pipe and also capture additional weight of riser pipe marine growth. However, multiple pipeID's are needed with different insulation thickness to capture the marine growth as the thickness varies with depth.
Also, by entering a small marine growth value on the Wave Loading dialog (where the pipe + marine growth OD is mostly accounted for by the insulation settings on the pipe property dialog) a current profile can still be applied.
Account for marine growth weight with Insert> Distributed load and enter the correct value for marine growth on the Wave Loading dialog.
Assuming marine growth is linearly increasing with depth, Suggest modeling as distributed load down the riser pipe. After selecting the riser pipe from the surface to the ocean floor, press Insert> Distributed load> enter a smaller distributed load near the surface and a larger distributed load near the ocean floor, all points between them will be linearly adjusted accordingly.
On the Wave dialog, enter the correct marine growth profile to account for the wave forces.
Only drawback to this approach is that there is no method of correctly accounting for the buoyancy of the marine growth on the pipe. If buoyancy due to marine growth is believed to be significant, model with option #1 above.
Model Subsea (Underwater) Piping