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FF Relationship with minus lag

6 replies [Last post]
Fri, 2014-10-10 00:26
Jason LI
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Groups: Petro-Chem / Oil & Gas

Dears,

When you are using FF relationship, Do you use the minus Lag or not, like Activity B FF after Activity A Minus 10 days, if using minus log, will it working correct or not?

Thanks for your reply

Jason

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Replies

Sun, 2014-10-12 08:12
#1
Vladimir Liberzon
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Hi Jason,

we do not advise to use negative lags but FF relationships are not rare in construction, especially in linear projects like road, pipeline and similar objects construction. Usually FF is used together with SS link (plus lag) with the same activities. These links usually reflect the requirement to keep certain distance between the crews that are doing consequent works.

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Fri, 2014-10-10 13:31
#2
Mike Testro
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Groups: Building Information Modelling, Content Moderators, GPCCAR Editors

Hi Jason

Because software developers have never worked in construction.

SS - FF links do have a place in manufacturing on a production line where a "ladder" system works well.

Early MSP systems blocked FF links but they changed it in the latest versions.

Best regards

Mike Testro

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Mon, 2014-11-03 12:27
#3
Zoltan Palffy
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agree never use a negative lag. A lot of time scheduling specifications prohibits the use of negative lags. 

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Fri, 2014-10-10 08:48
#4
Jerome Odeh
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Joined: 19 Jan 2004
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Groups: Petro-Chem / Oil & Gas

Hi Jason,

 

Like Mike said, never use FF relationships in a construction, installation or a working schedule. FS is the way to go.

I'll only recommend use of FF & SS relationships when building a high-level schedule for

  1. Management reporting
  2. Integrating different contractors schedule
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Fri, 2014-10-10 07:22
#5
Jason LI
User offline. Last seen 4 years 25 weeks ago. Offline
Joined: 1 Jan 2008
Posts: 37
Groups: Petro-Chem / Oil & Gas

Thanks Mike,

If only think it from the soft wise, and not consider the construction step, why P6 Provide the FF relation, and when we can use the FF relation actually.

 

Best regards,

Jason.

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Fri, 2014-10-10 06:32
#6
Mike Testro
User offline. Last seen 4 weeks 9 hours ago. Offline
Joined: 14 Dec 2005
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Groups: Building Information Modelling, Content Moderators, GPCCAR Editors

Hi Jason

Never ever use a FF Lag in a construction programme

Just because the software allows you to do it there is no situation in the construction process that is represented by a FF Link.

Only ever use FS links.

If you a putting in a SS link with a lag you are really using a FS link except that you are guessing where the finish point is.

Best regards

Mike Testro

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