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Float Float Float How many are there......?

10 replies [Last post]
Tue, 2009-05-26 06:28
SHAJI MOHAMED
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Dear Sirs,

I have come across a word of "Interrupting Float" while reading regarding Float.

Now i have more interest to know how many types of floats are available in the project management studies except Total and free float which are more familiar to planners.

Awaiting for your response....]

& Many Thanks in advance

Regards,
S.SHAJI MOHAMED
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Replies

Sun, 2009-06-14 21:59
#1
Trevor Rabey
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I think you are right that this part of the definition is just a mistake due to sloppy language, since "Brought Forward" appears to mean earlier but float is only about how much delay, ie later.
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Sun, 2009-06-14 19:36
#2
Greg Stacey
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Not sure about the definitions for float in the “Planning Engineers Organistaion – Glossary of Terms”.
As float is calculated using the early dates, I don’t understand how the activity can be ‘brought forward’. Can anyone explain the basis for the ‘brought forward’ part of the explanation.
In relation to Free Float – I believe it is how long the activity in question can be delayed before it affects the start of the earliest successor activity.
The definition as I understand it is ES earliest successor – (ES+duration) of activity being calculated.
Greg
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Sun, 2009-06-14 08:13
#3
Adekunle Arisilejoye
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just following

cheers

Kunle
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Tue, 2009-06-02 06:16
#4
Anoon Iimos
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Chris,

"Free Float"

"The period by which an activity, or group of activities, can be delayed, brought forward or extended without affecting any other tasks, or the Programme End Date."

I’m not sure with this one, but for me, "free float" is the amount of time an activity or group of activities can be delayed, brought forward or extended without affecting the "successor activity" (not any other task or activity) and/or the Programme End Date.?

The other "Float" I may know is the "Total Float", all others, I have no idea how it works.

cheers!
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Tue, 2009-06-02 02:11
#5
Chris Oggham
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Hi Guys,

I’ve had a bit of a dig around in the Planning Engineers Organisation - Glossary of Terms and they seem to have plenty of information there.

As a quick reference I’ve reproduced what I found here, but dont take it as definitive, I may have missed something.


Float</dt>
The period by which a task can be delayed, brought forward or extended without affecting the Programme End Date

Finish Float

The period by which the finish of an activity, or group of activities, can be delayed, brought forward or extended without affecting the Programme End Date.  For an activity with finish float only the start of the activity cannot be delayed, brought forward or extended without affecting the Programme End Date.

Free Float

The period by which an activity, or group of activities, can be delayed, brought forward or extended without affecting any other tasks, or the Programme End Date.

Interrupting Float

The period by which an activity can be delayed, brought forward or extended without affecting the Programme End Date but will affect successor activities.

Negative Float

Time that an activity must make up to stay on schedule. An activity with negative float is said to be Super-Critical.  Negative float is usually caused by conflicting Constraints on activities.

Start Float

The period by which the start of an activity, or group of activities, can be delayed, brought forward or extended without affecting the project end date.  For an activity with start float only the finish of the activity cannot be delayed, brought forward or extended without affecting the project end date.

Total Float

The period by which an activity can be delayed, brought forward or extended without affecting the project end date.  Total Float comprises Free Float and Interrupting Float.


Hope this is useful

Chris Oggham
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Mon, 2009-06-01 09:32
#6
SHAJI MOHAMED
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Dear Mr.Greg,

Many Thanks for your valuable reply. I tried some problems with your explanations. hope i have got good result for the problems.Really good to learn some unknown terminologies from experienced persons like you...

Again telling thanks for the reply....

Regards,

S.Shaji
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Mon, 2009-06-01 06:28
#7
Greg Stacey
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Shaji,
From my understanding there are 5 terms applied to float. In my experience only total and free float are used by planners.
There is Interfering float:- that is the difference in time between total and free float for that activity.
Independent float:-the difference between the earliest start time of earliest succeeding activity, less the latest activity start date of the selected preceding activity plus the duration. The independent float cannot be shared with any other activity.
These last two definitions were obtained from a construction planning text book - sorry can’t remember which. I also remember the author said both were esoteric calculations and never used by planners.
Terminal Float; to my understand, is as Gary Whitehead explained it in his posting, but I don’t think it is yet recognised by PMBOK. I have found the Client PM uses this time to refute any builder claims for delay if the builder is ahead of time, and then delayed by the client. In this case the client claims to ‘own the float’. This is the only explanation I have been able to find that relates to float ownership that makes sense.
Hope this helps,

Greg
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Wed, 2009-05-27 23:18
#8
A D
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Hi Shaji,

Just related with Floats, there are two constraints available within P3, called ZERO TOTAL FLOAT and ZERO FREE FLOAT Constraint.

Zero total float constraint is used to make activity into critical whereas, zero free float constraint allows an activity to start as late as possible.

Cheers,
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Wed, 2009-05-27 00:56
#9
SHAJI MOHAMED
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Mr. Gary

Thanks once again.... Interrupting Float is mentioned in our Planning planet wiki only under Planning Term---->Total Float. Pls check this...


Regards,

S.Shaji Mohamed

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Tue, 2009-05-26 06:48
#10
Gary Whitehead
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In some contract forms there is the concept of "Terminal Float". This is the difference between contractors forecast completion and contractualy mandated completion date, and is available for use solely by the contractor.

Though nto strictly float, there is also in some contracts a "Time Risk Allowance". This again is for use only by the contractor and is there to mitigate against possibility of overrun on activities with a high (schedule) risk.

If Stephen D sees this topic, I’m sure he’ll give you a breakdown of "DRAG" which is not float but in the same ballpark.

Affraid I’ve not come across "Interrupting Float" before.

Cheers,

G
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