Lead time

David,



I see that you posted the thread to the lead times website of Building Magazine. Readers of this forum might also like to know that the same information can be found at http://www.mace.co.uk/mace/approach/foresite.asp.



Mace have been creating the lead times chart in Building for many years now.



Hope you are well.



Gary France

Lead time is the time gap between the date when action to fulfill a current / future need starts, till the date the part / equipment / service is ready to fulfill the need. So abstract! Various scenarios - I just mention two!

(a) If you need a part readily available part in the market, assuming you can yourself place an order - leadtime is the time gap between placement of PO till you get the part in your lap.

(b)As mentioned in one of the posting, if you know the need but do not know what fulfils it, you may involve your engineering department to prepare a drawing which you will give to your known suppliers, manufacturing it, delivering it [installation, if required] till your need is fulfilled. Add activity for each with probablitstic time, sum of which is your lead time.



So you will have to define the lead time in real terms, though in general terms is given in the top.



Hope this would help a shade better.

Thanks

Venu K.

Daryl



I agree that the main ’construction’ programme may not be the best place to put the lead-in and procurement information. For a couple of reasons:



the procurement information is often needed by a primarily different team to the construction staff and it is often worthwhile to be able to print it out separately it , and



it can significantly increase the size of the construction programme and may make it a little unwieldy.



I advocate your approach of making a separate ‘lead-in’ or ‘procurement’ programme and cross-linking it to the construction programme. The method I use is to detail out the procurement/lead-in string, in most cases linear, finish-start, relationships will suffice and software such as Powerproject allows all these subtasks to be placed on one bar-line.



Generally the first task in the string, a ’milestone’ date, is the release of information of some type (dependent on the detail of the programme this could be, say, initial information for comment or final information for production). The last element in the string is a milestone date of ‘start on site’. This last milestone is then linked to the start of the activity on the construction programme to which it relates.



If the activities on the procurement programme are rescheduled ‘as late as possible’ the dates indicated will show the latest dates for, for instance, release of information. This is useful for putting together information release schedules and for determining the possible effects of late issue of information.



Scheduling the procurement information at latest dates may, however, not be the best option when considering procurement in general. There are often other constraints that mean that the information and lead-in tasks should be carried out earlier than the latest dates (for instance; to provide a regular flow of work for estimating/procurement staff, to provide release of information in a logical sequence, to reduce risks associated with JIT deliveries).



After the initial as late as possible reschedule I then suggest that all tasks, except for the start on site milestone, are reset to ‘as soon as possible’, earliest, dates. The initial milestone then, at least, should be held in the optimal position by use of an imposed ‘start on or after flag’. Other activities in the string can also be artificially held in position by start flags, if required, to optimise workload and to create buffer between procurement activities.



Using this method, if the procurement programme is also monitored and updated as it is dynamically linked to the construction programme any effects of delays in the procurement string will have a causal effect on the construction programme (late information for instance). If the construction programme alone is delayed the start on site milestone on the procurement programme will move thus showing increased float on the procurement programme. Conversely, if the construction gets ahead of programme then the start 0n site milestone will be forced earlier and, if there is insufficient float in the procurement string will produce ‘negative float’ or force the string and consequently information release dates earlier.



The techniques I have described, multiple tasks on one bar line and mixed earliest/latest start time reschedules are possible in Asta Powerproject – I am not aware if this can be done in any other software but I am sure there will be ‘work arounds’ to achieve the same result.



David

dbordoli@burofour.co.uk



Visit Buro Four on the web.

Lead time is dependant on the activity descriptions. Lead could be manufacturing, design, supply, delivery or a combination of all. I would look at the nature of the project and the schedule before deciding how to define lead.



Interesting debate below about whether to show lead times on a schedule. It is sometimes better to link to a separate procurement schdedule that defines latest start dates in the construction programme and subsequently provides the lead times.

Hi Anil,



Lead time is the time taken from issuence of a PO and to the delivery of that stuff to site.

This usually shown as

prepration for manufacturing

Manufacturing

Shipping and delivery to site.

These things can be taken as a lag period between PO and installation or as activities.it is better to show it as activities as you can also monitor the each activities better.



I hope this information useful.



Dinesh

Anil and Mktse



This may not help you too much but Building Magazine in the UK produces a quarterly review of lead times (produced by our good friends at Mace and Gardiner & Theobald). The last review can be found on-line at Lead Times although you may need to subscribe to the site (free) to get access.



David

dbordoli@burofour.co.uk



Visit Buro Four on the web.

Having an activity for ’Lead Time’ is much better when you progress the network/programme, as any delay will show on updates.

Depend how to use this function. Your assumption can be applied.

However, I prefer not to use lead time, instead, use an activity to respresent it. The advantage is let others easy to understand what will happen in that period rather have a gap between activities.