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Critical Path Analysis

Critical Path Analysis. There are no pre-requisites for this Achievement Standard so it can be placed in any course. No knowledge is pre-supposed. Methods include a selection from those related to:. precedence tables network diagrams critical events scheduling float times.

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Critical Path Analysis

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  1. Critical Path Analysis

  2. There are no pre-requisites for this Achievement Standard so it can be placed in any course. No knowledge is pre-supposed.

  3. Methods include a selection from those related to: precedence tables network diagrams critical events scheduling float times

  4. Critical Path Analysis (CPA) A complex project must be well planned, especially if a number of people are involved. CPA is used to ensure that the complete scheme is completed in the minimum time. It is used to schedule the projects.

  5. Any activity can be represented as a project:planning a partybuilding a house/factoryplanning a conference So what is a project?

  6. What do the projects have in common? Each project can be broken down into tasks. Each task takes timeand uses resources. Tasks are structured

  7. Step 1 – Precedence table • To identify actual tasks that make up a project • To identify the order these tasks need to be in • To decide how long each task will take

  8. Example: Constructing a garage

  9. Some of these activities must be completed before others can start.

  10. You can’t erect the roof (G) before you have erected the walls (E)

  11. Precedence

  12. D must follow E

  13. E must follow A and B

  14. F must follow D and G

  15. G must follow E

  16. H must follow G

  17. I must follow C, F

  18. J must follow H and I

  19. We call this a precedence table

  20. Precedence diagrams are not that useful. • A useful visual representation of a project is a network diagram.

  21. Sequence the most common sequences / dependencies Task B depends upon Task A; B cannot start until A is finished Task A Task B Task B Tasks B and C depend on Task A; neither can start until A is finished, but B and C are independent of each other Task A Task C Task A Task C depends upon Task A and B; C cannot start until both A and B are finished Task C Task B

  22. more unusual links and relationships so far all links have been finish-start links... 3 days Task B depends upon Task A, but with a 3 day delay; B cannot start until 3 days after A is finished Task A Task B Task A The start of Task C depends on the start of Task A; this is a start-to-start link; it may also incorporate a delay Task C Task A The finish of Task C depends upon the finish of Task A Task C

  23. Drawing a NETWORK – how do we get here?

  24. Algorithm

  25. Draw in the links

  26. Draw in A, B, C on a rough diagram

  27. STEP 1- original vertices with no arcsSTEP 2 - delete all arcs incident on A, B, C and redraw as shownSTEP 3 - repeat iteration

  28. STEP 1- original vertices with no arcsSTEP 2 - delete all arcs incident on Eand redraw as shownSTEP 3 - repeat iteration

  29. STEP 1- original vertices with no arcsSTEP 2 - delete all arcs incident on D, G and redraw as shownSTEP 3 - repeat iteration

  30. STEP 1- original vertices with no arcsSTEP 2 - delete all arcs incident on F and H and redraw as shownSTEP 3 - repeat iteration

  31. STEP 1- original vertices with no arcsSTEP 2 - delete all arcs incident on Iand redraw as shownSTEP 3 - STOP

  32. Converting to a usable diagram

  33. early finish time early start time duration task number and/or name late finish time late start time float Proposed method Now draw the network diagram using boxes slack

  34. 7 8 2 15 2 10 2 8 3 5 Task J Task F Task A Task B Task C Task I Task D Task H Task G Task E Example Duration Finish

  35. Critical Path • Find the earliest possible start for each activity, by going forwards through the network. • Secondly, the latest possible start time for each activity is found by going backwards through the network. • Activities which have equal earliest and latest start time are on the critical path.

  36. 3 4 Task 02 Task 03 5 Task 07 1 3 6 3 Task 01 Task 04 Task 05 Task 09 2 Task 06 Task 08 Practice 1 2

  37. 3 4 Task 02 Task 03 5 Task 07 0 1 3 6 3 Task 01 Task 04 Task 05 Task 09 2 Task 06 Task 08 Practice 1 2

  38. 3 4 Task 02 Task 03 5 Task 07 1 3 6 3 0 3 Task 01 Task 04 Task 05 Task 09 2 Task 06 Task 08 Practice 1 2

  39. 3 3 4 Task 02 Task 03 5 Task 07 3 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 2 Task 06 Task 08 Practice 1 3 2

  40. 3 7 3 4 Task 02 Task 03 5 Task 07 3 9 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 2 Task 06 Task 08 Practice 1 3 5 2

  41. 3 7 7 3 4 Task 02 Task 03 5 Task 07 3 9 9 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 5 2 Task 06 Task 08 Practice 1 3 5 2

  42. 3 7 7 10 3 4 Task 02 Task 03 5 Task 07 3 9 9 12 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 5 7 2 Task 06 Task 08 Practice 1 3 5 2

  43. 3 7 7 10 3 4 Task 02 Task 03 12 5 Task 07 3 9 9 12 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 5 7 2 Task 06 Task 08 Practice 1 Take the largest value 3 5 2

  44. 3 7 7 10 3 4 Task 02 Task 03 12 5 17 Task 07 3 9 9 12 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 5 7 2 Task 06 Task 08 Practice 1 3 5 2

  45. 3 7 7 10 3 4 Task 02 Task 03 12 5 17 Task 07 3 9 9 12 3 1 3 6 3 0 Task 01 Task 04 Task 05 Task 09 5 7 2 Task 06 Task 08 Practice 1 Take the largest value 3 5 2

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