|ultimate heat sink
||The atmosphere, a body of water or ground water (or a combination of these), to which generated heat is transferred.
||See vacuum pumps. Ultra high quality vacuum has a gas pressure lower than 1 µbar .
|unscheduled down time
||The down time of the plant not according to plan.
|unscheduled non-operating state
||When the plant or component is down according to plan for the length of the unscheduled down time due to an off-normal event.