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Is there any impediment to run a Risk analysis using a PDM schedule?

2 replies [Last post]
Armando Ugarte
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Joined: 4 Feb 2008
Posts: 11

Hello All:   I had a brief discussion with one of our collegues about running pertmaster with a PDM schedule some equipment setting are not logically tied at this moment because the P&IDs are not finished, is there any restiction or misscalculation doing it?


Dennis Hanks
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Joined: 17 Apr 2007
Posts: 310


If I understand your question, you are asking if it makes sense to model equipment setting (construction) with incomplete P&IDs?  Without knowing your logic or what stage of development the P&Is are, a definative answer is not likely.  That said, the primary drivers to equipment setting are equipment delivery and foundations.  Equipment purchase requires only the material requistion that often preceeds P&Is but follows block/process flow diagrams.  The foundations are another thing, they almost always follow P&I "Issue for Approval".  If I was forced to model construction this early in the game (before the Construction Estimate, I assume) and I knew my expected delivery dates, I think it could be done, you would just have to extend your uncertainty range to account for insufficient design.

Short answer: Yes, it can be done, you just will have more uncertainty now than later.  Personally, I would not model beyond the level of my current estimate.  I would insist that all activities be 'tied-off' - no open ends, before attempting this exercise.  If you can't, then it is probably too soon for this level of detail.  "No estimate, no schedule.  No well crafted schedule/plan, no risk analysis".  I think it is too early.

Note: 'All' current scheduling is PDM (precedence diagraming method).  ADM 'died' years ago with the widespread usage of computers.

Rafael Davila
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Joined: 1 Mar 2004
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Is there any impediment to run a Risk analysis using a PDM schedule?

If your risk software is the same you are using to manage your schedule there shall be no problem unless the model is wrong or the software have bugs. Ask yourself the question, is my risk software PDM? If yes I believe this shall answer your question.

You shall be aware that if lags are subject to variation and your software does not model variations in lag then you shall model lag using activities.

Remember that because risks do vary as a job progress there is much value in modeling jobs in progress.

Good Luck