Worked Example Trapezoidaldensity Method

Figure 3-28 illustrates a worked example of the trapezoidal density method for a Refinery FCC unit. As noted in the figure, a selected density level of 250 sq. ft./man, was too optimistic for such a complex unit as an FCC plant. The first step in the calculation process is to properly assess the manhour scope. As shown, allowances have been made for indirect labor working in the same area as direct labor and also, for an estimating allowance. An allowance for better subcontract productivity has been made.

Assessing the density/level is extremely important.

A 12% absenteeism allowance has been made.

The build-up duration was determined from a standard schedule that showed the peak labor period would be reached at 30% of the piping duration. This activity was preceded by foundation and equipment installation work (three months and two months, respectively). The total piping duration was fifteen months.

For the subcontract labor case, the manhours are reduced to reflect a better productivity than with the direct hire case (possibly a 10% improvement).

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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