Tips on using this forum..

(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?

(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.

Total Float

12 replies [Last post]
Dayanidhi Dhandapany
User offline. Last seen 1 year 41 weeks ago. Offline
Joined: 18 Mar 2003
Posts: 472
Groups: None
Is there any duration limit to have a total float for an activity?.
or in other words, what is the maximum duration allowed as total float in a activity for any standard project.

Replies

Sunil Babu
User offline. Last seen 5 weeks 4 days ago. Offline
Joined: 8 Nov 2010
Posts: 156

Hi Sandip,

First of all you have to make these analysis.

1. List out all delay events

2. Create a seperate WBS

3. Add the delay activities with durations

4. Link to the corresponding delayed activites and Schedule

If the delay occured from client side, you are entitled for EOT claim.

Best Regards,

Sunil.

Rafael Davila
User offline. Last seen 1 hour 29 min ago. Offline
Joined: 1 Mar 2004
Posts: 4780

The rule to avoid splitting an activity just to make it shorter applies to all related activities to the pipe installation deliverable; excavation, bedding, pipe alignment & lamination or bell & spigot, partial backfilling, hydrotest, complete backfill etc. are all separate activities related to the same deliverable. Each of these activities shall not be split if are to be modeled as contiguous. This is understood by even a rookie scheduler, especially by those who resource load their schedules. If the schedule is long then the activities will all have long durations when there is concurrency logic.  It is important to understand how differently a CPM model might schedule a set of activities versus a single contiguous activity.

If you separate each activity under many activities using only FS sequential logic it would be a fatal flaw of logic that will result in inefficient schedules.

http://www.me.utexas.edu/~jensen/network_02/topic_pages/kanegaronkar/opinions.htm

Even the fanatics that insist on very strict rules can accept the use of SS and FF with lag as an acceptable method to model some concurrency, it is not perfect but better than FS only.

Linear diagrams are good at this and usually a few lines are enough to represent all works in a very simple way.  To my knowledge no one ever suggested putting some time limit to the lines.

I do not use P6 but for users of P6 Ron Winter provides software to analyze P6. Ron Winter does not advocate for inflexible rules, he advocates for some guidance to be used wisely.

http://www.ronwinterconsulting.com/DCMA_14-Point_Assessment.pdf

Another reason not to literally interpret guidelines happens when the schedule is used as a tool for payment purposes. The following link provides some reasons why cost loading for payment purpose is not a good idea and what to do if you have no other option because it is on the specifications. 

http://www.nflaace.org/index_files/john_orr_cost_loaded_schedule_updatin...

Another common exception to general guidelines is when the specifications require to keep under separate activities the resources that do some portion of the activity but who report to a separate contractor or subcontractor.  If they are required to do the job at the same time all other crews you shall keep all crews working as a group within the same activity or the resources might be assigned at different time when in reality they must work the activity at the same time. 

In my jobs a common case is when working on elevated slabs where we have electrical, plumbing and civil contractors working on the same slab during the same time period. If you assigned them under separate activities the resource leveling might schedule them working at different periods.

Kannan CP
User offline. Last seen 3 weeks 1 hour ago. Offline
Joined: 12 Jun 2008
Posts: 278
Groups: None

Hi Rafael,

Take for example the installation of a water main 40 km long and a project duration of 36 months.  Why dividing it into 36 activities when a single activity is enough?

Related to your above statement, the Underground pipeline laying includes different category of works like excavation, bedding, pipe alignment & lamination or bell & spigot, partial backfilling, hydrotest, complete backfill etc. These will be doing by different group of resources or even could be different sub contractors. In addition the 40km length could be divided into 4 sections because of access reasons and not possible to excavate the full trench in one go and handover it to the pipe laying group.

In my understanding, there is importance to divide the activities as per the possible site sequence. More over with only one activity it will be difficult to understand which group or which section of the whole pipe laying activity is behind progress. It will be easy to control and explain the logic and critical path in the work.

Best Regards

Kannan

Rafael Davila
User offline. Last seen 1 hour 29 min ago. Offline
Joined: 1 Mar 2004
Posts: 4780

Total Float is a calculated value it is what it is based on your model.

Activities usually represent deliverables or related tasks necessary to make the deliverables to happen.  Activity durations are whatever they need to be.  

We use resources to make them happen, for us not taking into consideration the resources is senseless.  We make use of resource constraining even if all resources are infinite, well this is hard to believe.  Good resource planning requires planning for low idle resources as you cannot hire and fire resources on a daily basis.  For this you use what-if models in your search of a plan that minimizes idle resources. One approach is to artificially limit non critical resources and see if idle resource time is reduced without impacting the schedule total duration or contractual milestones.  

Sorry but there are no fixed rules and some forensic analyst want you to believe scheduling is an exact science, otherwise why experts from both sides cannot agree?

Take for example an equipment or materials delivery activity that takes 6 months.  Why not? What is the purpose of subdividing it into six monthly activities.  What if delayed, to which activity will you apply the delay?  It does not require much brain to figure out remaining duration based on expected delivery date as per most recent available information.

Take for example the installation of a water main 40 km long and a project duration of 36 months.  Why dividing it into 36 activities when a single activity is enough?  Is it that you bill by the activity count?  Is it that more but unnecessary activities make it look better and you sell your schedules by the look? Is it that you need more activities to know how much work have been performed?

By dividing a contiguous activity into several activities the resource leveling might spread apart several segments, especially if some resources such as equipment is shared with other activities. This is not what you want if the activity is to be performed in a continuous way.

To determine progress of an activity only intermediate school math is required.  Most construction activities have a volume of work related to it and percentage complete equals actual volume of work divided by total volume of work, it is very easy, this is not kindergarten. 

We believe scheduling specifications shall always be Performance based specifications that allow the contractors to bring their own expertise to the schedule process without restricting them in any way to predetermined methods.  If the contractor is responsible for the means and methods why restraining him to yours. If you want to keep control of the means and methods why hiring a contractor, better do it yourself. 

No matter what the scale of the project at home we find such rules senseless and and childish. 

Sandip Chakraborty
User offline. Last seen 4 years 18 weeks ago. Offline
Joined: 9 Oct 2006
Posts: 9
Groups: GPC Qatar

Hi Guys,

Need to have your views....

Can it be concluded that the Total Negetive Float in any project update represents the maximum entitlement a contractor can have if it can be proved that the entire delay is client imposed ?

or while doing apportioning should the total -ve float be considered as the basis to apportion client & contractor delay ?

 

Regards,

 

Sandip

 

 

Zoltan Palffy
User offline. Last seen 34 min 27 sec ago. Offline
Joined: 13 Jul 2009
Posts: 2404
Groups: None

The DCMA (Defense Contract Management Agency) uses float as one of it's key indicators when assessing the health of a cpm schedule. The DMCA sets this parameter for testing high float values at 44 days. The DCMA has set the total number of activities with float values at 44 days. The threshold is set at 5% or less. This means that of the total number of activities with float values of 44 days should be less than 5% of the total number of activities in the schedule.

As a side note the DCMA also suggests that individual projects may wish to expand or contract that threshold based on the length of the project and the type of project being scheduled; however, any changes in thresholds should be coordinated with the customer first to confirm the viability of the alternate measurement.

I have revised my threshold to 80 days and I do not consider long lead time times in my analysis. 

I see a lot of answers about the length of the duration when it is really a matter of logic. Duration is also another DCMA test with high durations this is al so set at 44 days and the threshold is also at 5%. This maybe in conflict with tighter scheduling specifications which limit the durations to 20 or 21 working days. Which as previously mentioned is a monthly updating period.

JOEL OSORIO
User offline. Last seen 4 years 1 week ago. Offline
Joined: 25 Apr 2005
Posts: 5

Guys,

 Whats the pros & cons if I impose a limit for each Total Floats of each Activities to a 5% on the Contract Duration.

Example:

Project Durations= 300 days

my max. allowed TF for each activities is 5% of 300 days= 15 Days.

the purposes is to keep my sched tight..

Or whats the standard practice for this ?

 

Thanks,

Joel

 

 

Ronald Winter
User offline. Last seen 5 years 21 weeks ago. Offline
Joined: 4 Jan 2003
Posts: 928
Groups: None
A ‘rule of thumb’ for activity durations is that the maximum duration of an activity (excluding summary activities) should never be greater then the update period. You do not want activities that begin in one update period and do not terminate in the next (or earlier) as the determination of status in these cases is very error-prone.
Bernard Ertl
User offline. Last seen 4 years 40 weeks ago. Offline
Joined: 20 Nov 2002
Posts: 757
Oh, I see.

The level of detail in a schedule is usually something that must be specified in the contract (or agreed to by involved parties). I dont think there is a generic answer to this question.

It is a good idea to ensure that task durations are less than or equal to the progress reporting periods, but this is not necessarily possible for all cases. Planning to a higher degree of detail allows for better progress reporting as there is less guesswork involved. However, it can lead to more overhead in managing the schedule as it expands (in # of tasks).

I have never heard of anyone concerning themselves with tasks that have too much float. As long as it is not an indication that the task(s) are not properly tied into the logic network (ie. that proper successors have been specified), I do not see where it is a problem.

Bernard Ertl
InterPlan Systems Inc. - Project Management Software, Project Planning Software
Forum Guest
User offline. Last seen 9 years 19 weeks ago. Offline
Joined: 28 Jan 2009
Posts: 0
Groups: None
[duplicate post deleted]
Bernard Ertl
User offline. Last seen 4 years 40 weeks ago. Offline
Joined: 20 Nov 2002
Posts: 757
See definitions for total float and total slack:

Wideman Comparative Glossary of Project Management Terms

Duration <= Late Finish - Early Start

Bernard Ertl
InterPlan Systems Inc. - Project Management Software, Project Planning Software
Dayanidhi Dhandapany
User offline. Last seen 1 year 41 weeks ago. Offline
Joined: 18 Mar 2003
Posts: 472
Groups: None
Dear Bernard,

Thanks for your reply, i mean to say that usually in a turnkey project the activity durations will not be allowed to exceed 24 days(3 weeks) just for an example, we need to break down the activity into further and limit the duration into 14 days(2 weeks) or so in order to have better grip over sub-cons schedule, in the same way i did want to ask whether the total float in an activity has been restricted and should not exceed 100 days or so for example. i hope that now i could have clarified my intention of the question. or still i mis something?

Regards
daya