IMG develop flat surface composite repair method
Posted: 04 February 2004
Operators can now look to solve problems caused by reduced wall
plate thickness or leaks on vessels and tanks with a recently developed
flat surface IMG composite repair method.
Composite repairs have already been extensively used on pressurized
pipe work where the material is wrapped around the affected pipe
to form a permanent repair and the same techniques have been adapted
and developed by IMG Offshore to be applied onto flat surfaces.
Internal working pressures however, need to be carefully controlled,
and preferably reduced to zero wherever possible especially for
work involving flat plate surfaces. IMG shall separately qualify
the actual procedures to be implemented, in each case!
Basically this is a composite of Kevlar sheeting and epoxy which
is applied onto the prepared surface and built up in layers to reinstate
the integrity of the tank wall or pipe wall. The design pressure
will determine the number of layers of re-enforcement Kevlar sheets
and amount of epoxy to be applied.
The final repair will have great strength but be very light and
crucially will have greater flexibility than the steel vessel so
will be able to flex as the vessel expands and contracts.
These composite repairs can be applied either internally or externally
on vessels and either onto flat plate surfaces or applied onto the
radius of any sized vessel or pipe.
The repair can be applied in a patch of say half a metre by half
a metre to solve localized problems or can be used to seal and reinforce
larger areas of say 10 metres by 20 metres. There is no limit to
the size of repairs as the sheets can be overlapped and cut to shape
on site and also any interruptions to the vessel surface such as
off takes or welded pipe supports can be incorporated into the repair.
The major advantage to the operator is that these repairs can be
undertaken whilst the system or pressure containment vessel is still
‘live’. Using traditional methods the operator would
have to decant product from the vessel, prior to gas freeing and
then purging out all before welding on re-enforcement plates internally
or externally.
Using this new IMG Composite Repair procedure, there is minimal
disruption as there is no hot-work involved. Once completed, the
reinforced area can be painted over to blend back into the rest
of the paint system used.
Crescent Petroleum Company of Sharjah operate the offshore Mubaraka
oilfield and were interested in finding a permanent solution for
the corroded deck plate areas on their “FSU”-Floating
Oil Storage Unit main top deck. The FSU Mubaraka is a 250,000 ton
converted tanker which has been specially converted to store the
field oil production.
Traditional methods of welding steel plates onto the affected area
had been considered, however, there were two (2) distinct disadvantages.
Firstly, an additional weight problem from the 15mm thick plates
required, which would have added significant loads onto the existing
substructure and Secondly, the preparation for cutting and welding
additional re-enforcement plates, would have necessitated that all
the affected storage tanks be drained, gas freed, then purged, -
a time consuming and costly procedure. Traditional methods would
have also reduced storage capacity and have inhibited field production
during the repair duration.
Crescent Petroleum contacted the IMG composite repair specialists,
who, after an initial site survey, were able to design a repair
which would be lightweight and could be applied without emptying
the tanks. The ability of the composite reinforcement to move and
flex with the tanker deck and the structural strength provided by
such a repair method was also a crucial factor in Crescents Petroleum’s
decision.
A 25 square metre top plate deck area was reinforced and took 4
days to install without any disruption to operations.
Crescent Petroleum commented that: “The repair method selected
proved to be innovative, and has enabled CPC to continue normal
un-interrupted operations without impacting safety, production or
the total storage capacity.
The final “Composite” repair has also proven to be
simple, strong, and durable, and will provide a permanent solution
to an otherwise difficult and complex problem, when compared to
repair using traditional methods. Traditional methods would have
undoubtedly have been more expensive, time consuming, and could
have severely impacted field crude oil production and reduced oil
storage capacity during any repair outage”.
Posted by Richard Price,
Editor Pipeline Magazine
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