[BITList] Riser Tensioners (Ruckers)

[fs]

The Larger yellow units are for the riser and the Smaller units are for 
the BOP (blow out preventer) and are also used as guides for the sub-sea 
TV assembly ,before one unlatches the riser the drill pipe is pulled and 
layed down, if time does not allow for the pipe to be pulled the shear 
rams in the BOP are activated which cuts the pipe At the BOP and allows 
for the pipe to be pulled to the surface and layed down the BOP Holding 
lines are then unlatched (Depending on the depth the BOP is operated 
using ether a pneumatic multi-cored umbilical line or in deep water 
(1000ft plus where pneumatics are no longer fast enough ) by sonar 
signals to a sub-sea controller mounted on the stack) allowing the 
vessel to move off location. Normally the riser is then also pulled and 
layed down if conditions allow, it gets very interestingly when one 
try's to go back onto location and re-enter the well being drilled even 
more so if flotation riser is being used because of deep water. When the 
BOP and ball joint is being run a sub-sea sonar beacons are attached to 
them along with a attached captive buoy which can be theoretically be 
released  by sending a coded sub-sea signal to it, the odds of a false 
signal being received is up in the millions, but while drilling in the 
straights of Taiwan we were for ever having to jump the divers to repack 
it after the buoy popped up in the moonpool or along side depending on 
the tides, only happened in Taiwan though
frank

On 1/11/2010 4:57 AM, HUGH wrote:
> 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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