On the May Article by Earl Glenwright on the Subject of Ladder Feed - PDM

14 May 2011

Dear Editor,

Earl and Vladimir’s discussion in the May edition of PM World Today on managing linear projects using PDM networks is a classic example of Abraham Maslow’s quote “If the only tool you have is a hammer, you tend to see every problem as a nail.” Master craftsmen use the right tool for the right job!

Whilst it is possible to manage linear projects in the ways described, surely the most effective option would be to use a methodology and tool set designed for the job.  Chainage Charts (or Line-of-Balance) have been around for far longer than the various derivatives of CPM and are specifically designed for planning and monitoring this type of linear project.

Of course, Chainage Charts also have their limitations, but why only use one tool for the project?  What is wrong with setting up the overall project master schedule as a PDM network using appropriate Schedule Levels to plan out the overall project.  Include one long task for the ‘Lay pipe-line’ work and manage that task efficiently with a L-o-B tool.  The L-o-B statusing provides accurate feedback on work accomplished, progress rates and predicted performance outcomes that can be used to update the summary activity in the overall master schedule.

Regards,

Patrick Weaver
Mosaic Project Services Pty Ltd
Melbourne, Australia
patw@mosaicprojects.com.au
http://www.mosaicprojects.com.au

 

Earl Glenwright Answers:

Dear Editor:

Pat Weaver is spot-on.

The column prefaced the pipeline discussion with Vladimir with “Let’s agree that whatever works for the planner and schedulers is the answer for them. We all have our ways which each of us believes is the better way because we like to do it that way.”  So be it. 

But that is not really the question.

Pat asks, “Why only use one tool for the project”?  Neither Vladimir nor I would only use ‘one tool’.

What Pat is suggesting is step 2 of the scheduling process, and that is ‘Line-of-Balance’. {aka Linear Scheduling ?}.  The first step was the development of the logic diagram as discussed in my May column. 

I am probably the greatest proponent of Line-of-Balance and applying the Line-of-Balance common sense to linear projects.  It is how the real world will plan and schedule linear projects as well as repetitive work such as in high rise buildings or multiple building campuses.

So, it is not either one tool or the other, but an integration of all applicable tools.

I will explain my understanding of construction Line-of-Balance in the June issue.

Thanks to Pat Weaver for his comment on the scheduling process of linear projects.

Earl Glenwright, PE, PSP
Colorado, USA

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