Total Installed Cost Considerations for Steel Fabrication on Large Projects
In many engineering companies, each individual discipline is usually challenged to work within the lowest possible budget – both for workhours and for material costs.
The lowest possible cost at the discipline or material level is not always the least expensive overall (both in terms of cost, but also in time in the fabrication shop and assembly in the field).
Smaller steel sections may have the lowest initial cost, but when the cost of added braces, stiffeners, gussets, etc. are included, they are not always the least expensive in terms of time in the fabrication shop and ease/number of workhours required for installation in the field. Keep in mind that direct construction hours are supported by indirect costs, so any reduction in the number of work hours can pay a double dividend in the field.
For a job with several large piperacks and/or equipment platforms it is worthwhile doing an exercise early in engineering to see if there are piperacks or other structures that can be constructed of the same size sections, even if some would be larger than the most efficient design would suggest.
Sections with less bracing are simpler and faster to produce. Fewer cutting and welding operations will mean faster production.
It is a good idea to work with the steel fabricator so that they understand the correct number and timing of detailers, as this will vary from the norm. A bulk order of steel section(s) is another possibility to explore. If the fabricator is responsible for shipping to the next location, this will help them plan the most cost efficient/effective transportation. Also, cleaner sections should (somewhat) reduce the number of review cycles.
Shop drawing reviews must also be assessed. If structures can be made with the same sections, there could be fewer erection drawings to review overall. Insufficient manpower to review these drawings can hold up a number of tonnes to advance to the shop floor. However, as always, it is a delicate balance between having enough manpower available to review the drawings at the earliest time, completing other civil/structural engineering tasks, and not overstaffing the job.
A significant portion of the time allotted for drawing review is used by document control to receive/distribute/return erection and piece drawings. It is worthwhile to spend time with them so they are aware of the number of documents that they will be required to process and the likely timeframe.
In the field or assembly yard, fabricated sections with fewer protrusions have less chance of being accidently damaged when being unloaded and marshalled. They are quicker to erect and they look cleaner.
The costs of the additional engineering hours to assess the situation and the initially higher costs of slightly larger steel sections should be compared against lower shop fabrication costs and lower assembly costs in the yard or at the job site. The potential for significant savings in total installed cost and assembly time is a prize worth pursuing.
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