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Which type of Float to Use?

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Edniel Recamadas
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All,

What are the advantages/disadvantages of using these two type of floats in managing Critical Paths:

- Longest path
- Total float is equal to 0

I am from the Contractor side, and the Engineer wants to use the longest path.

Regards,
Edniel

Replies

Rafael Davila
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Looking for more info in this matter I just found that Spider Project provides for Resource Critical Float. While P6 is still lagging P3 by over 10 years, P3 being a 20+ old software, Spider Project seems to be ahead of the pack. To me it is incredible that for a so obvious issue, a 40 years plus issue, no USA software developer have been able to address the issue as of today. Definitively Primavera got to be Doomed! No good anymore. Just into the surface, nothing of substance.

Seems like a common practice to look at the critical path to recover your schedule. If you miss a few activities you are misled.

Sorry solution(s) seems like into the difficult to understand.
http://faculty.kfupm.edu.sa/CEM/jannadi/Resource-Activity.pdf

Rafael Davila
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Edniel

OOPS!!!! CORRECTION.

SEE MY EDITED PREVIOUS REPLY. THE DEFINITION I USED WAS ERRONEOUS IT WAS MY WISH.

Seems like Resource Critical Float was defined long ago.

http://books.google.com/books?id=0JOgSQBzUdkC&pg=PA210&lpg=PA210&dq=cpm+...

To me, P6 in addition to its bugs is already obsolete.

SORRY ONCE AGAIN.
Rafael Davila
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Joined: 1 Mar 2004
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Edniel
OOPS!!!! CORRECTION.

LONGEST PATH IS TO BE USED TO SHOW ALSO ACTIVITIES WITH A TOTAL FLOAT NOT EQUAL TO 0 BECAUSE OF MULTIPLE CALENDARS BUT WHO DRIVE THE SCHEDULE DURATION. IT IS ON YOUR BENEFIT.

I HAD ISSUES WITH OWNERS WHO PRETEND NOT TO GRANT DELAY TIME WHEN THEIR ACTIONS DELAY ACTIVITIES THAT DRIVE THE SCHEDULE DURATION AFTER RESOURCE LEVELING BUT NOT IDENTIFIED AS CRITICAL UNDER ANY OF THE PREVIOUS DEFINITIONS I CREATED MY OWN.

THE FOLLOWING IS MY WISH:

Suppose your job consist on the construction of 3 separate Buildings, none related by logic but the actual construction driven by limited resources.
Let say:
Building 1 takes 100 calendar days and requires a crew of 30 people
Building 2 takes 80 calendar days and require a crew of 30 people
Building 3 takes 80 calendar days and require a crew of 30 people

With unlimited resources your schedule would be:
Building 1 xxxxxxxxxx
Building 2 xxxxxxxx......
Building 3 xxxxxxxx......
Here Building 1 would be your critical path.

With limited resources set to a maximum of 60 people after resource leveling your schedule would be:
Building 1 xxxxxxxxxx...............
Building 2 xxxxxxxx
Building 3 ________xxxxxxxx
Here under the first definition of Critical Path only Building 3 would be shown as critical, yes you would see a non continuous path, under MY OWN THIRD DEFINITION Buildings 2 and 3 would be shown as Critical. Here under either definition your schedule would remain the same.
SORRY
Edniel Recamadas
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Rafael,

Thanks to the links, broad explanations about scheduling process.

But honestly I found it difficult to understand the contents of it (newbie though!).

Can somebody explain it in simple way which one is beneficial to use for Contractors, and why?

Thanks in advance.

Edniel
Rafael Davila
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Joined: 1 Mar 2004
Posts: 5000
In managing Critical Path total float = 0 does not take into consideration that your schedule duration might be driven by limited resources. Schedule duration will be the same whether you use or not the total float = o or longest path definition for Critical Path.

The advantage of using longest path is that if after resource leveling your schedule is driven by resource availability it is shown. It is good for you the Engineer realizes this, is not against either party. I would call it a good scheduling practice.

The "old" definition of Critical Path to be when total float = 0 I believe it to be misleading as it is missing the issue of limited resources. Follow the link for further discussion on The Theory behind LONGEST PATH Software:

http://scheduleanalyzer.com/sa_long_theory.htm

I am not surprised of your suspicion at all as some specifications take the schedule away from the Contractor. I would suggest the following readings without further comments as not to divert the discussion away from the main Subject: Which type of Float to Use?

http://www.lorman.com/newsletters/article.php?article_id=573&newsletter_...

http://www.lorman.com/newsletters/article.php?article_id=579&newsletter_...

http://www.lorman.com/newsletters/article.php?article_id=584&newsletter_...


Arnold Puy
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