Transcription of Calculating Critical Path & Float for a Network Diagram
1 Task Name, Duration (D) Late Finish (LF) Early Finish (EF) Late Start (LS) Early Start (ES) Calculating Critical path & Float for a Network Diagram Find out the length of all the paths in the Network Diagram The longest path is the Critical path Float = EF - LF = ES - LS Calculating Critical path for a Network Diagram Task 1 4 days Task 2 5 days Task 3 3 days Task 4 7 days Task 5 4 days Identify tasks, durations & dependencies. Step 1: Draw a Network Diagram Task 1, 4 days Task 2, 5 days Task 3, 3 days Task 4, 7 days Task 5, 4 days 0 4 4 9 14 18 4 7 7 14 Task 5 is dependent on Task 2 and Task 4 being complete. So, ES for Task 5 is 14 days (dependent on Task 4, which is the longer task. For forward pass, calculate the Early Start (ES) and Early Finish (EF). Step 2: Determine Critical path Length of all tasks: Task1 Task2 Task5 = 4 + 5 + 4 = 13 days Task1 Task3 Task4 Task5 = 4 + 3 + 7 + 4 = 18 days The longest path is the Critical path Critical path = longest path = 18 days Critical path = Task1 Task3 Task4 Task5 To determine Critical path , calculate length (durations) of all the paths: Step 3.)
2 Calculate Float in all tasks Backward Pass Task 1, 4 days Task 2, 5 days Task 3, 3 days Task 4, 7 days Task 5, 4 days 18 14 14 9 14 7 7 4 For all tasks on Critical path (Task1, Task 3, Task 4, Task 5), EF = LF & ES = LS Thus, Float (slack) for tasks on Critical path = LF EF = 0 Float for Task 2 = LF EF = 14 9 = 5 days 0 4 0 4 4 9 4 7 ES = Early Start EF = Early Finish LS = Late Start LF = Late Finish 7 14 14 18 Step 4: Calculate Project Float Customer requests an end date of 25 days. Project Float is the total amount of time that the project can be delayed without delaying the project completion date required by the customer. 25 days 18 days = 7 days. Project Float can be negative when the date imposed by the customer is before the duration required in the project schedule.
3 For negative project Float , the project must be crashed or fast-tracked. Crashing is a technique used to decrease the duration of the project by assigning additional resources to tasks and decreasing the duration required for those tasks. Fast Tracking is a technique used to shorten project time by scheduling some activities concurrently that were originally scheduled sequentially.
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