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Engineering phase high-risk schedule, as there is also no possibility to

Since the bid phase, long before the certainty of perform other parallel activities on a convection
performing the job, Vergaengineering trooped a section (such as steelwork welding, supports
dedicated design task force with the mission of modification or refractory works) while the coil is in
seeking the best technical solutions for minimizing course of replacement.
realization risks, time and costs. Moreover, the 20 m tubes, even if of big diameter,
The tough requirements were faced through many are very flexible and generally lead to high
solutions, among which modularization had the leading installation time, which had to be added to the
role to bring decisive turning point in success. time required for all the site welds needed, with
Below the 3 parallel projects are described in details. consequent post weld heat treatment, hardness
I) The radiant sections revamping required many check, x-rays, magnetic and hydrostatic tests.
activities, but the big challenge was to completely In order to solve the matter, Vergaengineering
replace the connected six-passes coils in less- used a specifically designed device to save time
than-one-month turnaround. Difficulty-level was for such kind of jobs: a bundle puller, which
additionally increased, as the coils diameter had to allowed a quicker-than-usual installation of the coil
change, with the consequent variation of one hairpin at the time.
mechanical interfaces between the coils and the III) The highest-impact part of the project, with
structures. reference to weight and dimensions, was the
An uncommon solution solved the puzzle: since entire replacement of the visbreaker unit pre-
the coils in the vertical heaters were supported in heating system: an old ~250 tons structure to be
the top part of the radiant sections, the quickest demolished and a new ~250 tons structure (with
Fig. 3 - Insertion way to operate the replacement was to entirely different internal design to increase the plant
inside the old radiant replace the top parts of the radiant shells with the efficiency) to be erected at its place, always in the
section of the entire new coils hanged on them (figure 3). less-than-one-month time window.
completely II) The 20 m long convection section to be revamped
modularized coil Moreover, this replacement had to be performed
hanged on its top part could not be executed with the same approach of in the most crowded point of Vergaengineering
(arch) radiant sections, as the coil could not be entirely operation place: just between the radiant sections
assembled before installation. This brought to a and the convection section to be revamped.
Of course, modularization was an essential
expedient to cope with space and time
requirements. Consequently, the entire preheating
system was designed in several big modules to be
erected one after the other in a few days, being
the less-than-one-month of turnaround almost
entirely stolen by the demolition of the old system.
The biggest new module had ~100 tons weight.

Last but not least engineering act: in order to properly
check all interfaces and prevent any clash issue during
fabrication and erection, the whole project was
completely 3D designed (figures 1 and 2 show 3D
models for radiant modules of visbreaker and air pre-
heating system).

Planning phase
Since the context of a big revamping needed the
management of site works to be defined in detail
several months before turnaround, planning and
engineering development was strictly linked.
As a matter of fact, planning widely influenced
engineering, since the essential constraints were the
site yard space and mostly the less-than-one-month
turnaround.
A level-4 project schedule was developed almost one
year before the turnaround, and it was then used as an

IndustrIal Plants - May 2018
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