Description: The article centers on the main idea and topic of fxnetworks-activate. The content is related to an overview of an example of how we make changes to networks which affect the critical path, it contains network analysis which is about the delays and changes to the Critical Path and network diagrams.
Today we’re going to extend our understanding of network analysis by taking a quick look at what happens, when there are delays to activities in a network diagram, a project and consider the implications for the critical path, don’t forget that as we draw our network diagrams, the golden rules to follow that which make it much easier to complete the diagram and work out where the critical path is.
Firstly when we’re working out the earlier start time for each node, we work from left to right, we always calculate the first node and work from left to right.
As we calculate the earlier start time, it’s always the highest calculated figure, we have to wait for the activity with the longest duration to finish before the next series of activities, the next node can start and when we’re working backwards to work out the latest finishing time again.
We reverse that we go from right to left, we take a calculated figure, at this time, the lowest calculated figure, I hope you all become clear, as we have a look at this diagram, let’s work through this, this is our original network diagram and we’re going to firstly calculate what the earliest start times are to work out the project completion time.
Then we’ll work backwards very quickly to show the latest finishing times and spot the critical path, what will then do? We’ll introduce some delays to the project and see what the effect is now.
You may want to pause here and have a go yourself at working out the earliest start times and the project completion time, if you want to do, so pause at this stage before we start going through it, we’ll use the highlighter circle here to help us guide our way through this network at node one.
We have two activities that begin activity A and activity B, they converge on node, we have to wait for activity A and B to be finished, before we can start the next series of activities and we have to wait for the longest activity to finish first.
So B is the longest activity, therefore the earliest start time we can start C D or E b4 where’s to wait for B to finish A would have finished a week earlier looking at node 2 now, we can see that 3 activities can start and before we can move on to the next series of activities which go beyond node 3, we have to wait for D to finish.
The longest C will finish before D e will finish before D therefore the earliest start time at node 3, we always take the highest figure of those three activities must be 4 plus 6 equals 10 and moving on from node 3, we can see three more activities, begin F G and H and they converge on to node 4 and we have to wait for G to finish, that will be the last to finish one to F will finish a week before H will finish first two weeks there.
Therefore the earliest start time that we can start activity, I will be when F G and H are finished, we have to wait the longest for G, therefore the answer is for node 4, early start time 15, there are no other activities apart, go from node 4.
Therefore, it’s simply a question of going from node 4 to node 5 and adding in the duration for activity I which must mean that the project completion time today at all 9 activities completed is 18.
In this case, 18 weeks most diagrams relatively straightforward, when you work out the latest finishing time, you work backwards always taking the lowest calculated figure and sometimes these diagrams are more complicated than this.
It will work out to be the same as the earliest start time, as you work your way back to that data, that’s the completed original diagram for the network with the assumptions about the nine activities and their duration.
It tells us that the overall project will take 18 weeks to complete and spot the critical path, don’t forget that the critical paths are the activities that are on the longest path through the project, these are activities which they are delayed.
They will add to the delay for the overall project, so we can work it out, therefore, it must be activity B, that’s the longest in that series, activity D, activity G, we normally highlight those on the critical path with a little double dotted line B D G I.
As the critical path the project completion time 18 weeks, so there’s our original project, but what happens if that project completion time is affected or potentially affected by a couple of delays to the project? What happens if activity A and activity F are both delayed by two weeks?
Does this change the project completion time? Does it change the critical path, both being delayed by two weeks, you might think that’s a four-week delay, but it may not necessarily impact the completion time, it depends on whether there are other activities.
That are on the critical path, so let’s have a look at that revised chart and we can see here that we were told activity A two weeks longer and therefore that does have an effect at the start, previously, it was three weeks, therefore activity A takes longer than activity B.
Therefore we can’t start C D and E until five weeks have passed when previously it was four, so that’s built in some extra delay into the project C D and E are the same no change there, so we can’t start F G and H until those three have been finished.
Therefore, it must be five plus the longest activity which is 6 5 plus 6 is 11, the earliest start time for F G and H is 11, but we’ve also been told that F has been delayed by two weeks, F was previously 4, therefore F now becomes the the activity requiring the longest time.
Before we get to node 4, where previously, it was G, so using our earliest start time, it’s 11 plus, the highest calculated figure 6 n plus 6 17, we then add on I three more to get to a total project completion time of 20.
So the effect of this has been to firstly make A a longer activity than B, therefore S on the critical path and F are longer activity than G, therefore F becomes part of the critical path,so the critical path is now a D F.
Overall, effect on the network is that whilst both were delayed by two weeks, overall, the effect on the project completion time is an extra two weeks, not to lots of two weeks, it’s two weeks and that’s because of the way that those two activities were treated the first time round on the critical path.
That’s a typical way that the examiner might test network analysis to give you either a pass or completed network and then ask you to consider the effect on the project completion time of a delay in one or more of the activities.
The key thing is to remember and work out whether that delayed activity was on the critical path in the first place, could the business respond to these delays well? It could be that, there are activities that have, which is known as float, but they can be completed without delaying the critical path, without extending the critical path.
It may be that some resources that are devoted to those activities which could be redirected to the activities which have been delayed in order to help them achieve their target more quickly to be completed, that’s the beauty of float, what you tried to do is to allocate flows or spare resources to activities that are on the critical path to try to make them shorter, therefore potentially reduce the project completion time, so that’s an overview of an example of how you make changes to networks which affect the critical path.