Copyright © 2008 by ASME. The analysis of this modified
system leads to a failure probability of 8.3 %, a decrease in the
system failure probability by about 50 %. To improve the
system reliability further, additional redundancies could be
introduced and the effect calculated. For instance, another
bottle neck is the pilot control valve, which could also be
replicated.
Also, the effect of substituting components by more
reliable can be easily analysed. Assuming that the actuators can
be substituted by ones with a significantly lower probability of
blockage (5.09·10-7). For this case, the system failure
probability is calculated as 8.2 %, which is nearly the same
effect as in the first modification.
Alternatively, if a failure probability of 17 % is assumed to
be acceptable, an operation time of about 2.0·104 hrs (≈ 2.3 a)
is achieved.
The introduction of an additional actuator leads to a small
increase of the system reliability of about 5 %.[QUOTE=Earl Boebert;43637]Re: alcor’s 5747
There’s a bit more to unity of command than just the notion of having one superior. A useful discussion of the concept in the military domain can be found here:
www.strategicstudiesinstitute.army.mil/pdffiles/pub889.pdf
Like all management principles, it’s subject to interpretation and following it does not guarantee success – but ignoring it does raise the chances of failure.
I must confess that I have seen command/management structures that fill me with more confidence than those described in the alcor’s post, but that topic is going to be pecked to death by the lawyers so I’ll let it pass.
I do have some questions (real questions, not disguised assertions) in regard to the operations of these rigs:
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How much time does a Driller have to react to an anomalous flow/pressure/volume reading? Minutes? Hours?
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How is an order to activate the BOP issued, verified, and executed?
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Anybody know the deepest depth at which a BOP has been activated, either operationally or under test?
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Is it really true that BOP technology hasn’t evolved significantly since 1946? This paper:
www.iti.de/fileadmin/Ressourcen/Paper_und_Fachartikel/OMAE_Proceedings.pdf
draws some interesting conclusions.
Cheers,
Earl[/QUOTE]