Tips on using this forum..

(1) Explain your problem as best as you can. Don't simply post "XYZ Isn't working". What is it you expected or wanted? 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.

Example in turnarounds for 4 basic relationships.

5 replies [Last post]
floris gering
User offline. Last seen 3 weeks 2 hours ago. Offline
Joined: 30 Jul 2014
Posts: 23

Hi guys,

I'm new to the scheduling world (coming from a computer science track) now working as a consultant.

As I understand it there are 4 basic relationships between activities and they are central to the concept of network analysis.

1) FS finish to start

2) FF finish to finish

3) SS start to start

4) SF start to start.

 

Number 4 is especially difficult to grasp for me, in a practical sense.

Could someone please explain these 4 relationships with commonly used activities in a turnaround ?

Replies

Thomas Hinckley
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Joined: 12 Jun 2014
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FS should be your most used relationship.  You should never use SF relationships.  In my opinion they should be removed from the program. 

SS and FF are useful in certain circumstances but especially in a TAR schedule will be very limited. 

Mike Testro
User offline. Last seen 5 days 1 hour ago. Offline
Joined: 14 Dec 2005
Posts: 4366

Hi Floris

This forum is predominantly used by construction professionals.

You have to remember that the people who develop programming software are geeks not builders.

Programming software is used for many industries as well as construction but the programmers are not pharmacists or industrialists either.

In manufacturing for instance with a production flow line the SS plus lag combined with FF creates a "ladder" chart which replicates the production method.

This method has no place in construction although my sparring partner Vladimir will disagree when planning linear projects such as pipelines.

The fact that a SF link is available is an example of the software writers complete ignorance of practical usage - at least Vladimir and I agree on that point.

Best regards

Mike Testro

Floris,

I don't recommend to use SF relationship. In most cases it is used by an error. Other three reflect real life constraints and may be used. But usually SS+Lag shall be used together with FF+Lag, if an activity can start after another activity it usually shall not finish before succeding activity. So both dependencies shall be used in parallel.

floris gering
User offline. Last seen 3 weeks 2 hours ago. Offline
Joined: 30 Jul 2014
Posts: 23

Why ?

Why are there 3 other types (which also make sense, except the Start to finish for my understanding ?) when only the Finish Start relation could deal with everything ?

Mike Testro
User offline. Last seen 5 days 1 hour ago. Offline
Joined: 14 Dec 2005
Posts: 4366

Hi Floris

The simple answer is only use FS links in any form of programming.

Best regards

Mike Testro