Colin Ryan (X) Jun 29, 2010:

In this case, the oil rig must be able to provide its own electricity under extreme weather conditions and even in the event of a failure of the means of electricity production.
From the wikipedia article for "fault-tolerant system": "Fault-tolerance or graceful degradation is the property that enables a system (often computer-based) to continue operating properly in the event of the failure of (or one or more faults within) some of its components."
Note the subtle distinction made between failure and fault in this definition: "in the event of the failure of (or one or more faults within) some of its components".
In retrospect, I regret submitting my own answer; I should have just agreed with yours and tweaked "fault" to "failure". Won't happen again.

meirs Jun 29, 2010:

fault versus failure There is a fine line, albeit entirely different than that in our colleague's explanation, and it depends on the scope of supply like this. Failure is understood as one in the goods you supplied whereas fault can be there or in goods/services supplied by others (that your system interfaces with/needs them). For example, if the external power (supplied by others - their fault) fails, your system can still operate if it is fed from two independent power sources and one is still OK. In the broader perspective, redundant system where one or even two failures (of their components) do not prevent them from operating at 100% functionality exist and are used in critical industries (The latter are called "triple-redundant").