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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.

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Presentation on theme: "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."— Presentation transcript:

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 party building a house/factory planning 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 time and 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 TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8 EErect walls10 FPlaster ceiling2 GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

9 Some of these activities must be completed before others can start. TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8 EErect walls10 FPlaster ceiling2 GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

10 You can’t erect the roof (G) before you have erected the walls (E) TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8 EErect walls10 FPlaster ceiling2 GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

11 Precedence

12 D must follow E TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10 FPlaster ceiling2 GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

13 E must follow A and B TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2 GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

14 F must follow D and G TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5 HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

15 G must follow E TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5E HInstall door and windows8 IFit gutters and pipes2 JPaint outside3

16 H must follow G TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5E HInstall door and windows8G IFit gutters and pipes2 JPaint outside3

17 I must follow C, F TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5E HInstall door and windows8G IFit gutters and pipes2C, F JPaint outside3

18 J must follow H and I TaskDuration (days) Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5E HInstall door and windows8G IFit gutters and pipes2C, F JPaint outside3I

19 We call this a precedence table TaskDuration (days) Precedence Aprepare foundations7 BMake and position door frame2 CLay drains, floor base and screed15 DInstall services and fittings8E EErect walls10A, B FPlaster ceiling2D, G GErect roof5E HInstall door and windows8G IFit gutters and pipes2C, F JPaint outside3I

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 ATask B Task A Task B Task C Task B Task A Task B depends upon Task A; B cannot start until A is finished Task C depends upon Task A and B; C cannot start until both A and B are finished Tasks B and C depend on Task A; neither can start until A is finished, but B and C are independent of each other

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

23 Drawing a NETWORK – how do we get here?

24 Algorithm

25 Draw in the links TaskPrecedence A B C DE EA, B FD, G GE HG IC, F JI

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

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

28

29 STEP 1- original vertices with no arcs STEP 2 - delete all arcs incident on E and redraw as shown STEP 3 - repeat iteration

30

31 STEP 1- original vertices with no arcs STEP 2 - delete all arcs incident on D, G and redraw as shown STEP 3 - repeat iteration

32

33 STEP 1- original vertices with no arcs STEP 2 - delete all arcs incident on F and H and redraw as shown STEP 3 - repeat iteration

34

35 STEP 1- original vertices with no arcs STEP 2 - delete all arcs incident on I and redraw as shown STEP 3 - STOP

36

37 Converting to a usable diagram

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

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

40 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.

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

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

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

44 Practice 1 Task 06 2 Task Task Task 03 3 Task 08 2 Task Task 09 1 Task 05 3 Task

45 Practice 1 Task 06 2 Task Task Task 03 3 Task 08 2 Task Task 09 1 Task 05 3 Task

46 Practice 1 Task 06 2 Task Task Task Task Task Task 09 1 Task Task

47 Practice 1 Task 06 2 Task Task Task Task Task Task 09 1 Task Task

48 Practice 1 Task 06 2 Task Task Task Task Task Task 09 1 Task Task Take the largest value

49 Practice 1 Task 06 2 Task Task Task Task Task Task 09 1 Task Task

50 Practice 1 Task 06 2 Task Task Task Task Task Task 09 1 Task Task Take the largest value

51 Forward pass complete Duration = 18 Task 06 2 Task Task Task Task Task Task Task Task

52 Backward pass Task 06 2 Task Task Task Task Task Task Task Task

53 Task 06 2 Task Task Task Task Task Task Task Task Float

54 Task 06 2 Task Task Task Task Task Task Task Task

55 Task 06 2 Task Task Task Task Task Task Task Task

56 Task 06 2 Task Task Task Task Task Task Task Task

57 Forward pass complete Task 06 2 Task Task Task Task Task Task Task Task Take the smallest

58 Critical Path – float = 0 Task Task Task Task Task Task Task Task Task

59 Your turn Task A 7 Task B 2 Task C 15 Task E 10 Task D 8 Task G 5 Task F 2 Task H 8 Task I 2 Task J 3 Finish

60 Example 1 – Forward pass Task A 7 0 Task B 2 0 Task C 15 0 Task E 10 Task D 8 Task G 5 Task F 2 Task H 8 Task I 2 Task J 3 Finish

61 Example 1 – Forward pass Task A 7 0 Task B 2 0 Task C 15 0 Task E 10 Task D 8 Task G 5 Task F 2 Task H 8 Task I 2 Task J 3 Finish

62 Example 1 – Take the largest value Task A 7 0 Task B 2 0 Task C 15 0 Task E 10 7 Task D 8 Task G 5 Task F 2 Task H 8 Task I 2 ? Task J 3 Finish

63 Example 1 – Take the largest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D 8 17 Task G 5 17 Task F 2 Task H 8 Task I 2 ? Task J 3 Finish

64 Example 1 – Take the largest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F 2 Task H 8 Task I 2 ? Task J 3 Finish

65 Example 1 – Take the largest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F 2 25 Task H 8 22 Task I 2 ? Task J 3 Finish

66 Example 1 – Minimum 32 Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish 32

67 Example 1 – Backward pass Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish 32

68 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

69 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

70 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

71 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

72 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

73 Example 1 – Take lowest value Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

74 Example 1 – Critical Path – zero float Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

75 Example 1 – Critical Path – A-E-D-F-I-J Task A 7 0 Task B 2 0 Task C 15 0 Task E Task D Task G Task F Task H Task I Task J Finish

76 Using the outputs Gantt Charts optimising the schedule

77 Gantt: Critical path in red

78

79 Scheduling: Move the critical path along the top

80 Now fit the other activities like a puzzle

81

82 Schedule

83 Any delay on the critical path causes a delay in the entire project

84 There is a 2-day float on the non-critical path

85 Definitions Critical Path Those activities that can not over run without effecting the total length of the project, are those where the EST = LFT (Total float = 0). Total Float LFT of the activity- the duration- EST of the activity. This shows how much ´slack´ there is on a particular route of the network. If the total float is 0 then an activity lies on the critical path. Free Float EST of the next activity – Duration – EST of this activity. This shows the ´slack´ on an individual activity before it delays the start of the next activity.

86 EES = Earliest early start time LLF = latest late finish time Free float: The amount of time that a schedule activity can be delayed without delaying the early start date of any immediately following schedule activities. Free Float = EES successor – EF

87 EES = Earliest early start time LLF = latest late finish time Independent float is that portion of the total float within which an activity can be delayed for start without affecting the float of the preceding activities. Independent Float = EES successor -LLF predecessor -duration


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