Challenges and Opportunities for Innovation in the Public Works ...

materials were included in the bid packages to the prospective pipe
fabricators, along with the orthographic drawings.
When the Finest Hour construction schedule was completed, it was
downloaded to DXF format and uploaded into the modeling package.
The sequence model steps were placed around the schedule, matching
time frame and logic. The result is a document that provides all
of the logic and detail of the schedule and a 3-D graphic
representation of the project (Figure 4).
Three months prior to the start of the outage, the client delayed
the duct and scrubber modifications for approximately 18 months.
Business reasons were cited for the postponement, as well as
extensive boiler modifications scheduled during the same time
period and labor shortages in the area.
Prior to this announcement, Stone & Webster was awarded the boiler
modification construction work. This consisted of boiler water
wall panel replacement, asbestos removal, hot reheat pipeline
replacement, coal pulverizer refurbishment, and the replacement of
six feedwater heat exchangers.
Construction Specialists responded to this sudden change in scope
by again utilizing the 3-D modeling system. Facilities included in
the new contract were fully modeled using the owner's design
drawings, clarifying the scope of work and verifying preliminary
installation scenarios.
The model also proved to be invaluable when 3 weeks prior to the
start of the boiler modification outage, the owner requested that
the two existing precipitators be removed and replaced with duct
work. Using the design model, Stone & Webster's engineers were
able to select newly fabricated duct sections, previously designed
for use in the modified duct work arrangement, as transition pieces
in the precipitator area. Supports were designed as a combination
of the existing precipitator support steel and temporary support
modules. The ends of the transition pieces were modified to
connect the assembly to the existing boiler duct and the scrubber
duct. The temporary modification design was completed in only 4
weeks after notification.
These models also proved valuable on the jobsite in familiarizing
new construction personnel with the project. In the Spring of
1992, duct and scrubber outage planning and scheduling will begin
again.
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