Djenane Jeanty Project Management Context Professor C. Lennon Module V 11. 17. 12 Abstract Project managers carefully manage slack on sensitive resource-limited projects (Larson and Gray, p. 295). If possible, they will add slack at the end of the project by committing to a completion date that goes beyond the scheduled date. Eliyahu Goldratt (1997) advocates an alternative approach to managing slack. He championed the “theory of constraints” and has coined the term “critical-chain” recognizing that the project network may be constrained by both resource and technical dependencies (Larson and Gray, p. 95). Projects often can exceed their planned schedule by a certain percentage, sometimes even 50 to 100 percent. Often this is attributed to uncertainty or the unforeseen. Managers and project personnel have learned to compensate to this dilemma by adding additional time to their schedule estimates (Larson and Gray, p. 302). Yet even when they do, projects still overrun their schedules. Goldratt (1997) argues that there is a natural tendency for people to add safety time, just in case, to their estimations. One of the key problems identified in this case was the project time estimate.
Even when management added 10 percent time to all activities or added 10 percent project estimates to ensure project durations would be met, the issues still remained (Larson and Gray, p. 302). Then, Pinyarat explained that the activity durations had gotten squeezed down to less than the 50 percent guideline and that the estimates were impossible. Pinyarat also mentioned that she was allowed to put in a big enough project buffer and other members of the firm had no idea why management would use CCPM scheduling in these projects (Larson and Gray, p. 303).
It is believed that project managers who estimate activity times provide an estimate that has about an 80 to 90 percent chance of being completed on or before the estimated time (Larson and Gray, p. 295). Using the Critical Chain Method, projects can be completed more quickly and with greater scheduling reliability. The difference between traditional and Critical Chain scheduling is in how uncertainty is managed. Applying the CCPM approach to the projects To resolve these issues listed, I will report to Pinyarat that in Critical Chain scheduling, uncertainty is primarily managed by some or all of these methods. ) using average task duration estimates; (b) scheduling backwards from the date a project is needed (to ensure work that needs to be done is done, and it is done only when needed); (c) placing aggregate buffers in the project plan to protect the entire project and the key tasks; and (d) using buffer management to control the plan. In my report I will list these specific steps which Pinyarat can use in order to manage a CCPM: 1. Reduce activity duration estimates by 50%. Activity durations are normal estimates, which are known to be high probability and contain excessive safety time.
Let’s estimate the 50% probability by cutting these in half. (The protection that is cut from individual tasks is aggregated and strategically inserted as buffers in the project) (DRM, 2012). 2. Eliminate resource contentions by leveling the project plan. The Critical Chain can then be identified as the longest chain of path and resource dependencies after resolving resource contentions (DRM, 2012). 3. Insert a Project Buffer at the end of the project to aggregate Critical Chain contingency time (initially 50% of the critical chain path length) (DRM, 2012). . Protect the Critical Chain from resource unavailability by Resource buffers. Resource buffers are correctly placed to ensure the arrival of Critical Chain resources (DRM, 2012). 5. Size and place Feeding Buffers on all paths that feed the Critical Chain. Feeding buffers protect the Critical Chain from accumulation of negative variations, e. g. excessive or lost time, on the feeding chains. This subordinates the other project paths to the Critical Chain (DRM, 2012). 6. Start gating tasks as late as possible. Gating tasks are tasks that have no predecessor.
This helps prevent multitasking (DRM, 2012). 7. Ensure that resources deliver Roadrunner performance. Resources should work as quickly as possible on their activities, and pass their work on as they complete it (DRM, 2012). 8. Provide resources with activity durations and estimated start times, not milestones. This encourages resources to pass on their work when done (DRM, 2012). 9. Use buffer management to control the plan. Buffers provide information to the project manager, for example, when to plan for recovery and when to take recovery action (DRM, 2012).
The Critical Chain approach is perhaps the most important new development in project scheduling in the last 30 years. Used properly, the Critical Chain approach is an extremely powerful means of gaining more predictability, productivity and speed from your project plans (DRM, 2012). References Erik w. Larson, Clifford F. Gray (2011) Project Management – The Managerial Process 5th ed. Eliyahu Goldratt (1997) Critical Chain (Great Barrington, MA: North River Press). DRM Associates – Critical Chain Project Management from http://www. npdsolutions . com/ critical. html Retrieved 11. 17. 12
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