The ManicaPost
In The Classroom With Stephen Mutsongodza
Network analysis indicates the shortest possible time in which a project can be completed. It is a technique used in the planning and controlling of complex projects.
The following are the activities that must be completed to establish the critical path.
- Identify the objective of the project (e.g the construction of a bridge within a month)
- Put the task (activities needed) into the right sequence to draw up a network diagram.
- Add the durations of each of the activities to identify the critical path.
- Use the network as a control tool when problems occur during the project.
NB: An arrow represents/indicates each activity. An activity takes up time and resources.
A node (circle) indicates an event (transition between activities- the start or end of each activity).
A dotted line indicates a dummy activity. A dummy activity is imaginary, it takes neither time nor resources.
It is meant to show logical dependency of activities.
The length of each arrow does not represent duration of the activity.
Network diagrams are drawn from left to right.
Example
Activity Order/Sequence Duration (Days)
A 1
B Follows A 1
C Follows A 2
D Follows C 3
E Follows B 1
F Follows E 1
G Follows D and F 2
(a) Draw a network diagram
(b) Calculate the critical path
ABEFG = six days
ACDG = eight days
ACDG is the critical path (there is no float or spare time on the critical path. Activities on the critical path, i.e A, C, D and G are called critical activities. These activities give the shortest time in which the project can be completed (eight days). If you delay any of the critical activities, you will not be able to complete the project on time.
ABEFG is a non-critical path- there is a float (two days).
Earliest Start Time (EST)
It is the earliest time each activity can begin taking into account all the preceding activities e.g activity.
B cannot start before one day because activity A will not be finished then; D cannot start before three days because A and C have to be completed first.
Verify the ESTs by working through the diagram from left to right, taking the longest route to each node.
Latest Finish Time (LFT)
It is the latest time an activity can finish without delaying the whole project e.g D must finish by Day 6, or the whole project may take longer than eight days.
The easiest way to calculate the LFTs is to work from right to left- where there is a choice of routes back to the node, the aim is to achieve the lowest number of the LFT, e.g LFT for Node 2 to one day, achieved by working back through D and C instead of FEB.
These activities that no spare time are the critical activities- they are shown by nodes where ESTs are equal to LFTs.
Float
Any spare time available in performing other activities.
It is the difference between ESTs and LFT and is often shown by splitting the work.
Total float
This is the amount of time a path of activities can be delayed without affecting the overall project completion.
Free float
This is the amount of time an activity can be delayed without affecting the commencement of the next activity at its EST.
There is no float on critical, but on non-critical activities.
Float is important in planning projects where resources are limited. The resources can be rescheduled to critical activities without delaying completion of the project.
Dummy Activity
This activity does not consume either time or resources.
This is an imaginary activity which shows a clear logical dependency between activities. It is shown by a dotted line.
Example: A and B are the start of the project; C follows A; D follows A and B.
This represents the information on a network diagram.
Advantages of network analysis
It facilitates the planning and co-ordination of large projects.
Identifies critical activities which determine the total duration of the project.
Identifies activities which cause or are likely to cause bottlenecks and delays.
Determines when resources and components are needed.
Forces managers to plan the use of resources.
Reduces and eliminates idleness.
Improves communication.
Facilitates the taking of corrective action when performance falls below plan specifications.
Efficiency – It produces a network that helps a business to operate efficiently, e.g identifying tasks which can be carried at the same time can save time and resources.
Decision making. Network analysis aids and improves decision making, e.g network analysis models are more scientific and objective methods of making decisions.
Working capital control – Identifying when resources will be needed in projects can help a business to manage its working capital.
Time-based management. These are techniques to minimise the length of time in business processes. Identifying tasks which can be done together, those that have to be done in their order and those that may delay the whole project. This helps to ensure that the least time is taken to complete an operation.
Disadvantages of network analysis
Projects must be specific enough to time them accurately.
Not practicable for routine planning, e.g flow production.
If emphasis is purely on time and not cost, its value diminishes (time is not the only important factor in the success of project completion).
It is a planning and control technique and cannot solve production problems on its own.
Requires skilled and motivated staff to put it into effect.
