Howell and Ballard characterize common practice for
moving pipe spools from engineering through off-site
fabrication to erection. "When engineering falls behind
schedule, fabrication will be delayed, thereby also delaying
installation work." "The order in which drawings are provided
to the fabricator and the sequencing in which spools are output
by the fabrication process may bear little relationship to site
needs, therefore requiring re-sequencing for site delivery
provided that priority information be available." "Time delays
and out-of-sequence work make the supply of materials to the
job site unpredictable. This leads to inefficiencies because work
cannot be adequately planned and executed, and thus results in
low productivity.