Introduction To Network Diagram
Network Diagram is flow chart that indicates the process of completing a project in sequence of tasks linked to each other. Network diagram for the project of Hansdon Ltd is a below:
Determining the timing of activities and the total float
The EST of A is zero as it is starting point of the project and by adding duration in it, the EFT is calculated. The EFT of predecessor is EST of current activity. If there are more than two predecessors like activity G than highest EFT like 18 of C will be the EST of that activity.
EST = EFT of predecessor (in case when there are more than one predecessors that highest EFT will be considered).
EFT = EST + Duration (for example EFT of A = 0 + 4 = 4).
The calculation of LFT starts from last activity. In this present case LFT of last activity is equals to EFT of the same activity and LST is of this activity is calculated by deducting the duration form LST (Beheshti, 2006). Total float is the time by which project completion date is not affected. The total float is calculated by EST and duration is deducted from LFT.
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LST = LFT – Duration
Total Float = LFT – (EST + Duration).
In case when there are more than 1 successive activity the LFT is determined as lowest LST among them.
Determining the project duration and critical path
The last activity of this network diagram is indicating the EFT and LFT of 76 that means the project duration will be 76 days.
Critical path is contains of those activities which do not have any float. These activities should not be delayed to finish the project on targeted time. In this present case the critical path is: A, B, C, G, H, J, K, L, N, O, P, Q, R.
Effect on the dates of the project
- If the activity D is delayed by 1 day there will be no effect on project as activity D is not included in critical path.
- If the activity M is delayed by 1 day there will be no effect on project as activity M is not included in critical path.
- If the activity Q is completed 1 day earlier than the project duration will be decreased to 75 days and it will complete on Monday, 29th July, 2013.
Limitations of network diagram
Network diagram is a comprehensive tool to estimate the project duration and completion but it has some limitations too, such as:
Due to limited resources parallel path is not possible in network diagram that means two tasks cannot take place together (Jedd, 2005).
Each activity has their specific start and end so if one task is delayed than all the reaming tasks may have to suffer.
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- If the length of project is too long than creation of network diagram requires a long time. It is appropriate for small projects only.
- It provides an estimate only.
- It can only show finish to start dependencies (Schwalbe, 2009).
- Cleland, D.I., and Ireland, L.R. 2004. Project Management Strategic Design and Implementation, 4th Ed. NY: McGraw-Hill.
- Jedd, M. 2005. Risking Less. PMNetwork. 19(9), pp. 76-80.
- Schwalbe, K. 2006. Introduction to project management. Boston: Course Technology.
- England, D. Crawford, L. And Pollack, J. 2006. Uncovering the trends in project management: Journal emphases over the last 10 years. International Journal of Project Management. 24, pp. 175–184.
- White, D. and Fortune, J. 2002. Current practice in project management – anempirical study. Int J Project Manage. 20(1), pp. 1–11.