[BITList] Fwd: Centaur identified with video footage

[HUGH]

Very interesting stuff.  A blast from the past - the yellow stabilisers are Riser Tensioners, attached bottom end to the structure round the moonpool, one at each corner, and top end to a wire rope round the top of a pulley that goes down to the slip joint whence the riser casing round the drill string is supported.  The pulley sits on a ram that slides inside the cylinder.  These are quick response (or were, last time I was involved with them on a vessel like the one on the photo) pneumatic/hydraulic very high pressure.  When the ship falls they reel in, and when she rises they reel out, at least that's the theory, so they only operate between these limits.  The object is to isolate the riser from ship movement up and down - shock absorbers or stabilisers, if you like.  As far as I recall, if seas are bigger than the designed range, the riser is disconnected from the blowout preventer on the sea bed and just hangs there till conditions improve.  Don't ask me what happens to the drill string.

Hugh.
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