creating a program

Sorry Guys

I keep forgetting that you are stuck with P6.

Last week I was giving a training session on planning a 120km pipeline - 30 inch coated and buried.

Using only FS links and setting the spreads to convenient lengths and seperating Auto welding crews from Semi auto crews I did the whole programme in 90 miniutes including all crossings - rock breaking - valves and structures.

The pipeline section only took 20 minutes and the welding crews were fully resourced.

But then I waqs using Asta powerproject in Task-per-line mode where I can copy paste chainages directly from the spreadsheet.

The whole programme fitted comfortably into an A4 lanscape sheet of paper.

Progress up dates are again a copy paste excercise and takes 5 minutes maximum.

Now we will know precisely what will be the delay effect if the 10.3mm Free Issue Pipes fail to arrive when required.

Best regards

Mike T.

David Copperfield and Houdini,



Let say you are installing a new 90 cm sewer trunk along an existing highway that cannot be closed.



If at the start of the day you have daily mobilization, setup road barricades; 1st segment excavation, pipe laying, backfill; 2nd segment excavation, pipe laying, backfill; ...; nth Segment  excavation, pipe laying, backfill ...., remove traffic barricades and demobilization of daily operations all in sequence. How can you predict how many segments are to be installed each day? What is going to be first and last segment of the day?



Unless you can predict the volume of work for each segment on a daily basis you will end up in hundreds of activities out of phase with reality.



As you suggest, a compromise between two imprecise models is in order, I go for the option that will keep me closer to reality.  It is not that one is correct and the other is not, neither are precise and depending on each particular case one option might be the better choice.



About modeling continuous feed, use of either time of volume lag is not enough as neither of the lag definitions are implemented as a fixed link. Continuous feed modeling means a change in the start or finish of any continuous feed activity will move the others as they got to be linked by fixed links. You got to model continuous feed using some kind of laddering that will keep the fixed links. For this I use hammock activities linked to a single driving activity so as to drive changes on the ladder rungs width by either the driving activity duration or ladder lags.



Remember that under continuous feed logic governs and resource usage is determined without considering resource leveling, these two are technically incompatible, if you got unlimited resources good for you, if not just make sure they are available. Fortunately hammock activities are not resource leveled and therefore they can be used to model continuous feed.



The following is an example of a simple continuous feed ladder (Activities 1, 2 and 3), can be expanded to hundreds activities that belong to a same continuous feed operation.







Best regards,

Rafael

Gary

Indeed you are right, you would break the job down further in to chainage sections, manhole to manhole in sewer work or perhaps junction to junction in cleanwater cases ..... but in a lot of cases the distance is still too long to alllow only FS links, especially in some cases where you may only be achieving 7.5m/day on a 50m+ run ..... you could plan it to the far end of a fart and FS link excavate, bed, lay, backfill, reinstate for each tiny section as Mike would like but that would be one hell of a programme and your boss isn't going to be too impressed when the programme cost more than the job ;-), especially when profitability can be so tight on such work.  That's not even mentioning the update time when you may have 15 similar jobs onsite at one time all requiring the same treatment!

I'm as pro FS (0) as the next man, but in some cases you have to tailor the level of detail you plan to based on the requirements, timing and value of the project .... you learn that sometimes working on the smaller value high volume type works!

Andy

If you wanted to do this using only FS(0) links, you'd have to break the job down into a cascade of multiple short chainage sections.

The plus side to doing this is you have a schedule which responds much more acurately when things start changing mid-job

The down side is you greatly increase the number of activities, which as well as increasing the maintenance time/cost of the schedule, can also make it harder to read at a glance.

Mike's a bit of a purist when it comes to FS(0) links, but personally I'm a tad more flexible -especially on tender schedules which often are there purely to communicate timings rather than for any analysis or pipeline projects which typically do consist of a number of long duration activities occuring in staggered parallels. If you're looking at a pipeline tender, I'd have no problem at all in the example given.

This actually sounds like a classic example of where software with a volume lag function such as Spider really scores big over things like P6. But since I've never used such software, I'll leave the resident experts such as Vladimir or Rafael to comment further.

Mike

If you read activity names on the programme James attached you will notice it mentions 'lay pipe'!!

In some cases you are totally right, you will string out the pipe, weld, test and lower in to the trench, but in other cases you don't!  You don't weld concrete sewer pipe for instance, you lower each section of pipe and butt it against the last section of pipe and with some types of PE plastic water/sewer pipe you can actually lower and then electro couple the pipe in situ in the trench ..... Obviously it depends on what type of pipe it is on James' job as to which method will be used.

I agree that FS links are the best form of link and they are what I endeavor to use, but in certain cases on long pipe runs in a utility works environment the SS with a small lag between each activity can work ..... you could perhaps be stripping back the topsoil for any easement, excavating, bedding, laying pipe, backfilling and reinstating all at the same time, you could use a single activity for the whole works (not particularly descriptive), use multiple activities all SS at the same time (doesn't reflect reality as at the start and end you won't be doing all of these works at the same time), or SS with a small lag to show you will start each activity in phase but will be carrying on doing the same sequence of works as you move along the run until you get the end where you finish topsoil strip first, then staop excavating, then stop bedding etc .....  You can't really show that using FS, unless you use a massive negative lag.  On smaller pipe runs of course you would use FS as you would do one task at a time in sequence.

Hi Andy

I did not see anything in James text that talks about pipelines.

But even if they did your assertion that laying a pipeline is one continuous process is wrong.

You have to string out the pipes before you can weld them.

Then test and joint the required length.

After that you can excavate and lower the pipe which can be continuous but rarely is in practice.

After lowering there is usually a fibre optic cable to be ducted in.

Then backfill and then reinstate.

A true SS link requires that both tasks start at the same time - as soon as you put in a lead lag then you have created a FS link that has no relation to reality.

Even in pipelines I use only FS links.

To answer James question as to why his superior uses such techniques it is because he is a sloppy lazy planner who does not understand how to do his job properly.

Best regards

Mike Testro

Not quite clear on what your query is? 

This looks like a reasonably 'normal' programme for linear pipelaying type works.  Everything overlaps because you will be excavating, bedding, laying, backfilling continously as you move along the pipe run.  It's not like other types of works where you finish one task and then have a FS link to the next task, you will be continuing to excavate the next section as you lay pipe in the fist etc ...

Over time you will get an idea for how long this type of linear/pipe laying works takes which in the future allows you to use you experience to put durations on the work based on length of run, pipe size, ground type, depth etc ...