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SUPER-MODULES.
Traditional
designs Why super modules
? Super module design
Advantages Previous
page
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The traditional platforms and modules:
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- The traditional platform design is normally made up of the
following:
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- - A platform support. ( A steel jacket, concrete or
floating).
- - A cellar deck. (A module support frame).
- - A platform topsides (A collection of modules containing various
process and utility systems).
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- The reason for designing the platforms like this, probably has to
do with the offshore lifting capacity, i.e. the fact that the offshore
cranes could not lift more than the module weight.
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- The disadvantages are easy to comprehend:
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- - Too much steel in the cellar deck in order to make a stiff bridge
for the modules.
- - Too much structural steel in the modules since they are made as
separate units.
- - Too many interface areas between modules.
- - Too much offshore hook-up work. Expensive maintenance and
re-building.
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Why Super-modules ?
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- The floating crane lifting capacity has been steadily increasing from some 300 ton
to 12000 ton, and this has made it more attractive to design platforms
with "super-modules". This means that the systems are
contained in bigger modules in order to save steel weight and offshore
hook-up work.
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Most super-module platforms still have got a cellar deck, but often 4-5
large modules are used to contain the systems. This also provides a
better and more planned weight distribution, which in turn
makes it possible to save weight also in the cellar deck.
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- However, one problem remains to be solved, the fabrication of the
super-modules.
- These building blocks are some 30 m high, 30 m long and 15-19 m
wide with a load-out weight of between 4000 and 6000 ton. The number of
fabricators will be limited because of the size and load-out
facilities. In addition, the
productivity suffers, the project risk is increased and the modules
becomes more expensive than one should anticipate, despite the saving in
structural steel and reduced hook-up work.
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The reason for this problem is mainly due to the traditional fabrication
method, the so-called "stacking method" or the
"steel-first then the outfitting" type of schedule.
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- The stacking method shown on the picture above was for a period the most popular
fabrication method. This method was however not suited for the new
module size, and the yards got into problems, especially with decreased productivity, complicated project schedules, dramatic
effects of late arriving equipment and changes, long delivery times
and rigid project execution plans.
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 Now take a look at the typical fabrication schedule above
by clicking on the picture. It is easy to see that the series type of schedule is a direct
function of the module fabrication method. Note that most of the
activities are on the so-called critical path, meaning that any delay
in the activity will effect the project finish date. ( A more
comprehensive schedule is found on the TRC demo disk version 1.2.)
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- Yet an other problem is the receipt of long-lead items. As you
know, the long lead items are normally equipment like gas turbines,
separators, water treatment systems, etc. that pertain to the main
deck areas. This means that either the equipment has to be installed
early in the building process, or one has to find a way to get them in
at a later stage.
- The super- module also imposes problems on the detail planning
level, as there will be conflicts between the activities of different
trades. Typical problem areas are; sand blasting, fire proofing,
painting, instrumentation etc.
- The productivity is also reduced due to the fact that lifting, handling
and transport becomes more and more difficult as the module is being
built and closed.
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The optimized super-module design and fabrication
method.
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- To overcome all these problems, TRC has developed and patented a
new and very efficient super-module design and fabrication method
called the LMEF method. The method takes advantage of quite a
different fabrication schedule, a parallel activities schedule. This
makes the project much more flexible to manage, since most of the
activities are not on the critical path. The schedule opens up for
changes and late arriving equipment without extra cost or delay, and
may therefore shorten the total fabrication time.
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- The module design and fabrication method is the
following:
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- The module truss systems is fabricated as one complete unit. This
may be performed in different ways, but TRC favor the roll-up method
shown on the picture below if a huge shed with overhead cranes is not
available.
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- At the same time, all the module system decks are fabricated with
mezzanines etc. The equipment, spools, HVAC, instrumentation etc. is
installed on the system decks, which has full open access from above
and from all sides.
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- The systems are then tested out and commissioned, and brought to
the finished module frame.
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- The installation of the system decks takes only one day by lifting
the decks up from the ground level and fitting them inside the main
frame. Then the vertical hook-up and testing remains before the module
may be shipped to the platform.
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- The LMEF method is also paving the way to the fully integrated
topsides platform, IPEF, which may be even more efficient and cost
saving.
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Advantages:
 | Significant saving in structural steel |
| Parallel fabrication schedule |
| Shortened fabrication time |
| Flexible in receiving late arriving equipment |
| Flexible if changes are needed |
| Full open access to the system decks at all times during fabrication and
installation |
| Accepts a very high worker density without loss of productivity |
| Deck fabrication may take place in small yards / buildings |
| Module trusses may be erected in the open without the use of cranes. |
| Fabrication productivity is improved by 35% |
| May be used for sequential development in that decks may be introduced
offshore. |
| Very cost-effective. |
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TR Consulting 
