North Sea, trial rig transfers by boat instead of helicopters

[Self loading bear]

This thread is most interesting to me. (not being a pilot myself, I am occasionally one of your passengers on the (mostly Dutch) North Sea.
The improved capsule to which Diginiagain is referring is the Frog. It has shock breakers under de seats. I found it very comfortable but as a passenger you have less self-control in case of emergency (immersion or tipping over) as you are strapped in. Offshore Personnel & Cargo Transfer Solutions | Reflex Marine | Reflex Marine


The Billy Pugh is still on board almost every drilling rig and occasionally used in the North Sea. The oil companies keep it as a last resort. Helicopter is the preferred and prescribed way of transfer (and perceived the safest) The risks with Billy Pugh transfer are in the possibility of snagging of the guide lines; the high impact at rough seas and last but not least: crane operator induced oscillation.
Operating a Offshore Crane - The Wrong Way

Operating a Offshore Crane - The Wrong Way - YouTube

Oscillation is best dampened by dipping the Billy Pugh in the sea but that does not make the passengers more happy. I only have been transferred to a boat by Billy Pugh after 3 days of mist. But after 3 days of mist the sea is dead calm so very little risk on high impact.
The DP Gezina which is being used by Perenco does not uses the Billy Pugh or Frog but has an “Ampelmann”. http://www.ampelmann.nl/products/s2s/



This is a gangway which is mounted on a wave motion compensating hydraulic suspension. This is a Dutch development which originates from the idea to mirror the hydraulic suspension of flight simulators! As already mentioned by EESDL this works up to about 2,5 Hs significant wave height. (with 2 m hydraulic cylinders, it should be able to expand the envelope but would need larger cylinders) Ampelmann suggests/mentions on their website that this would give 87% up time in the Southern (Dutch) North Sea. I question that.



Fact is that it is nothing new. As far as I know in 2006 the Smit Kamara was the first supply vessel on the North Sea equipped with a wave motion compensated gangway operating for NAM/Shell. The gangway requires a docking station/step-over platform on the fixed platform or windmill, which can be up to 20 m above sea (but usually lower). At this moment the REM Star and the REM Mermaid have such gangways and are operating from Den Helder.



These vessel are specifically NOT intended for crew transfer to larger Manned platforms far away but are used as smaller mobile maintenance stations to serve NUI’s which have no proper accommodation. This eliminates that maintenance crews loose much hours by heli transfer every morning and evening. In Southern North Sea NAM/Shell have 3 satellites which are so small that they do not even have a heli deck! These are designed to be visited for maintenance solely by these “Walk to Work” vessels and they plan to do so only every two years!

It is true that a lot of the maintenance people do not love this way of “Walk to Work” as when they are working they are on a stable platform, but when they go to bed they are subjected to the wave motions of the vessel. Sea-sickness is indeed very common! I think it will only be a few years before dedicated SWATH type (fast semi-submersibles) are fitted with an Ampelmann and will reduce those complaints. These SWATHS are already been introduced in Windfarm maintenance and Pilot vessels.
http://www.loodswezen.nl/nl/materieel/swath/1823/
http://www.odfjellwind.com/

So yes it is a thread for some helicopter operations.
But also something good may have come out of it:
Another Dutch company Barge Master has copied the idea and first developed it into a motion compensated crane foundation. Lately they have teamed up with aluminium helideck producer Bayards to introduce a motion compensated helideck on board ships.
http://www.barge-master.com/products/motion-compensated-helideck.html



I was not able to find any data on significant wave heights or maximum amplitudes which can be absorbed, but I think you would need pretty long cylinders to compensate the full motion of a ship in conditions where this is beyond the ability of helicopters to land. Can anybody give some answers on the maxima which can be handled by an helicopter without any compensation? I guess it will aim to reduce maximum amplitudes too, say, 50% to increase operational limits.



SLB