Of course, you could rely on luck — or try to rein in the element of chance. But, as Müller pointed out, “if you don’t start thinking about the potential risks until the shutdown is underway, then the battle is already lost.” Planners often work with best-case and worst-case scenarios for this purpose based on assumptions as to the shortest or longest possible duration of a given subsection. This information — as helpful as it may be — is only of limited use in the case of complex projects as it does not allow any statements to be made about probability and interdependence. It does not take into account how milestones may be delayed and if deadlines will be exceeded along the way, as refinery boss Kroll knows only too well. “If delays continue and then the next project comes along, the additional costs incurred on account of poor assessment will ultimately run into millions”, he said.
Plant Turnaorund: It’s no Gamble
It may be worth shifting the focus to a place where people have experience with random numbers: to the roulette wheels in Monte Carlo. Not that we are suggesting that the turnaround should become a game of chance — but because the Monte Carlo method offers a stochastic way of analyzing the statistical probability of chance events which permits conclusions to be drawn in relation to complex situations. The analysis encompasses every aspect of the project that can be quantified, including sustained risks and delays.
The scenarios arrived at in the calculations can be plotted on a scale between the best case and the worst case, allowing a determination of the probability of meeting deadlines or reaching conclusions — or not, as the case may be. This approach makes it possible not only to draw up a realistic timetable but also to identify the risks which have the greatest influence on the project aims.
Müller recommends aiming for a probability of 70 % at the project finish date. This figure is not set in stone, however: If the envisaged time frame proves to be over-optimistic, additional resources should be set aside in preparation or adjustments made to the scope and deadlines — allowing the operator to stockpile products in order to be in a position to deliver if restart is delayed.
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