Project crashing full example (part 1/2)

alright in this video we are doing a full comprehensive example on project crashing so in the last video you'll see you learn what project Russian is and how to do it this video we will be actually going through this example and in working your way through and seeing what this is all about so first of all we need to draw our PBM network diagram for this project so let's go ahead and do that here so we can first do our forward pass and then we can do a backwards pass and then we can go and we can write all of our total floats on the top here so we'll have 0 0 1 0 0 right just subtracting these two numbers from each other all right so the next thing that we want to do then is we can just fill out all of our information here for the on the table for initial so our normal duration you can see we'd have 2 5 7 6 etc we are crash duration we'd have 2 4 4 etc the cost per day we would be easy we've been considering the additional cost per day to crash and then the total flow it's TF here we're going to read right off this table then for the rest of the information here this cost of savings is per iteration so at the beginning initial we we're not going to put anything there we can't figure out the initial project cost though so the initial project cost is the cost of all of the activities added together including also the overhead cost of the per day times the number of days so first of all if you add up all of these the normal costs you will find a number that is a yeah the number is actually eight thousand one hundred dollars if you have this if you have six hundred dollars per day times our project duration which is eighteen days so 600 times eighteen we're going to get a value there which is ten thousand eight hundred okay so if you add ten thousand eight hundred plus eighty one hundred let's even write that we'll have ten thousand eight hundred plus eighty one hundred that number that you get is eighteen thousand nine hundred dollars and that is your initial total project cost without crashing or anything that's like what you would normally expect to pay for this so project cost we'll write that down here we'll have 18900 and our initial project duration before we crash will be 18 days right or early finish late finish there as 18 so we'll go ahead and write that there all right so let's go ahead and let's do this let's do our first project crashing run so what we need to do if you remember from the last video we find we identify the critical path so we have a B D e then what we want to do is we want to find activity that has the it's the cheapest to crash we want to crash it and then reassess so will because one day at a time so let's look at this well activity a we can't crash it because it's already reached its crash duration activity B D and E are left over so B would be 600 D would be 700 and a would be 500 so the cheapest thing that we can do right now is crash activity by one day so that would cost us 500 dollars to crash compared to 700 or 600 so that's the most desirable thing to do we always wanna get the cheapest ones of the way first so for that said we will be crashing activity by one day so we were going to find here day save will be one from activity e will put for the duration column here will update that so the guys will stay the same so we'll have 2 5 6 7 but we are reducing the normal duration by 1 2 3 and you'll notice we have reached the crash duration so we can only actually crash activity e once anyway so this will affect our total floats now so we have to do is have to go up to the PDM Network diagram and assess what's happening so we have actually changed the duration from 4 we've changed that to 3 now we're going to update all of the values that this is going to change so if we have 14 plus 3 now we'll actually get an early finish of 17 which means our late finish of 17 will also be there and then we'll have 17 minus 3 is 14 so we don't need to update that right that's already it still stays the same because we're only changing the duration we're not changing the start date of activity E so let's go ahead and let's let's fill out the rest of our information here on a per iteration basis so our cost to do this it cost us five hundred dollars to do that so we're going to write in here it cost us five hundred but we did reduce the project duration by one day so with that said we have to pay $600 a day regardless of all the activities this is like a management equipment rental fee or something like that it's just part of the question so every day we say if we actually save $600 so we spend $500 but we're saving 600 because we're saving one day of that project overhead cost all right so then we have eighteen thousand nine hundred and what we do is we'll basically add our costs we'll add five hundred subtract or savings and then we will find that we're actually going to end up with a difference we've actually saved our whole project one hundred dollars so we'll have eighteen thousand eight hundred dollars and then a duration will now be seventeen days so that's our first crash that we've done to this project the other thing I didn't mention is you also have to check the total float here in this case 17-17 the total float is also still zero this could change especially when you have branches at war if you're doing what crashing projects later back in the schedule so anyways that checks out so we actually don't need to change anything all right but we do need to write down actually we do need to record all of our total floats here so we're still getting zero zero one zero zero just like that all right so let's go ahead and let's do run number two let's look at this also so we've already reduced this to three we can even write that in here if we want just to keep track of things or we can cross it out because we've reached our crash duration we can't crash anymore so that's out of the question even though it still has a total float of zero we physically cannot crash it anymore that's the definition of the crash duration so also let's look at activity a we can't crash activity day so let's not look at that so our left over options for anything that we're going to crash now is only B C or D all right you can't crash anything if it's already at this crash duration so with that said now we have to figure out which one of these is on the the critical path so we have B C or D well B C or D it's not C because it has a total float of one so our options to crash because so if we crashed activity C the the project duration actually won't change and you can you can easily work through that anyways what we need to do is we need to graduate B or D because they are on the critical path and if we change their duration it will affect the duration of the whole project so between B or D it looks like the cheapest one is going to be right we could pay $600 or we can pay $700 so let's pay $600 so we're going to find B we're going to save one day from it when you cut a day from it so our durations here we'll still have to we're going to drop or duration down here to four and then the rest should all stay the same because we're only saving a day from activity B so then we'll get where every six seven and then three all right so let's go back to our PDM Network diagram and let's update it and maybe let's just keep using keep switching out the colors and you might be able to track keep track of what's going on here a little bit clearer for each iteration that we're doing so activity B we're cutting one day so that's going down to a four so now we're gonna have to update everything else kind of go around come back but we were not changing anything before B right so two plus four well that will now be six so we're going to bring that six into both of these positions and then six plus six this guide becomes a 12 six plus seven this becomes a 13 and we're gonna have to bring in this is now oops now this guy will be a 13 13 plus three sixteen you see there we've knocked off one day from the duration of the project bring that 16 down sixteen minus three so we get 13 I usually fast-forward this put you have to really have to see what's going on here so now we're going to bring back about 13 into each of these positions 13 minus seven six so we'll cross that out 13 minus six seven so we'll put that in there and then we'll pick the winner here so we'll have we're going to bring in the smaller one so we'll bring in six versus bringing in seven and then 6 minus 4 is 2 so we're not actually changing that okay so let's look and what double check to see if any of our total floats have changed so we have 6 minus 6 is 0 13 minus 12 that one is still acceptable 16 minus 16 0 and 13 minus 13 is 0 so those are all still okay so when we're going to come back down here and our total floats will actually all remain the same so we'll still have 0 1 0 0 0 just like that alright so our cost because we crashed activity B for one day our cost will be 600 our savings will be 600 because we have reduced our project duration by another day saving the other $600 per day that we have to pay regardless and so if we do that well look at that actually our total project cost will stay completely the same 18800 but we have managed to reduce the the the duration of the project again by one day so now we're at sixteen days so we'll write in our little 16 down there all right but it looks like we're running out of time so I'm going to split this lesson into two videos you can find the second half of the video right here

Channel: Engineer4Free

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Keywords: free, engineer, engineering, math, university, science, tutor, tutorial, lesson, online, learning, mathematics, engineer4free, worked, example, project, management, Project Management (Industry), PDM, CPM, network diagram, gantt, chart, crash, crashing, project crashing, activity, task, plan, planning, schedule, scheduling, control, controlling, duration, cost, what is, how to, construction, agile, PMP, PMI, PM, software

Id: ZOW2QU_sbJ4

Length: 9min 35sec (575 seconds)

Published: Mon Feb 16 2015