Installing Offshore Wind turbine video

[Keith_McClary]

TL;DR Summary

Installing Offshore Wind Turbine
Two minute time lapse video.

 

[berkeman]

Very cool, thanks for sharing.

Do they raise the ship like that to make it a steadier platform for the crane?

 

[anorlunda]

Very cool, thanks for sharing.

Do they raise the ship like that to make it a steadier platform for the crane?

I presume so, yes. Here's a case from 10 years ago. In the first picture, you see them lifting cargo using the crane on a docked ship that did not have those 4 feet. 10 seconds later, it was capsized.

 

[Dr.D]

Remarkably still water in the video. How smooth does the water have to be for this assembly to happen?

 

[Keith_McClary]

How smooth does the water have to be for this assembly to happen?

I think they would be concerned about wind.

 

[Lnewqban]

Please, see:
https://en.wikipedia.org/wiki/Jackup_rig

https://en.wikipedia.org/wiki/Wind_turbine_installation_vessel

"A jackup rig is a barge fitted with long support legs that can be raised or lowered. The jackup is maneuvered (self-propelled or by towing) into location with its legs up and the hull floating on the water. Upon arrival at the work location, the legs are jacked down onto the seafloor. Then "preloading" takes place, where the weight of the barge and additional ballast water are used to drive the legs securely into the sea bottom so they will not penetrate further while operations are carried out. After preloading, the jacking system is used to raise the entire barge above the water to a predetermined height or "air gap", so that wave, tidal and current loading acts only on the relatively slender legs and not on the barge hull.

Modern jacking systems use a rack and pinion gear arrangement where the pinion gears are driven by hydraulic or electric motors and the rack is affixed to the legs.

Jackup rigs can only be placed in relatively shallow waters, generally less than 120 metres (390 ft) of water. However, a specialized class of jackup rigs known as premium or ultra-premium jackups are known to have operational capability in water depths ranging from 150 to 190 meters (500 to 625 feet)."

 

[Dr.D]

I think they would be concerned about wind.

I'm sure that is true, but I was hoping someone could quantify the situation in terms of what is an acceptable sea state.

 

[Keith_McClary]

I'm sure that is true, but I was hoping someone could quantify the situation in terms of what is an acceptable sea state.

Once it's jacked up it shouldn't matter.

 

[berkeman]

It does seem like if there were much wave action that would make the rig too unstable to drop the jack stands cleanly onto the seafloor.

 

[anorlunda]

It does seem like if there were much wave action that would make the rig too unstable to drop the jack stands cleanly onto the seafloor.

Look at the first 4 seconds of the video in the OP. Those yellow jack stands were in place before this ship arrived. We don't know from the video how or when they were placed.

I think an interesting question would be how those jack stands are attached to the sea bottom, and what kind of bottom preparation was needed. A concrete slab would be difficult to do but maybe not impossible. Also, it's not obvious whether those jack stands need to be absolutely rigid relative to the sea bottom, or if some rock and roll is permissible.

 

[Keith_McClary]

how those jack stands are attached to the sea bottom

It appears there are various designs depending on depth.
https://www.google.com/search?q=offshore+turbine+foundation&tbm=isch