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36” Caisson Repair

 

Overview

Following a survey on a North Sea installation, the weld joining a 16” seawater return line to a 36” caisson had failed, resulting in a circumferential crack. A fully engineered Technowrap 2K™ design was to be installed to bring back the integrity of the line.

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Scope

The scope of work was to provide a Technowrap 2K composite wrap to the complete 16” bend up to the nearest flange, and around the complete circumference of the 36” caisson with a 2 year design lifetime.

Challenges

The main challenge was getting access to the area where the repair required installation. Scaffolding was erected around the pipe to allow access around the full area requiring wrapped.

Solution

Surface preparation to Sa2.5 was carried out by the client to ensure best bond of repair after the caisson had been fully isolated. The Technowrap™ repair was then installed according to Walker Technical Installation Guidelines.

The open crack around the weld was filled with an epoxy putty prior to being wrapped. Although it was expected that application of the repair would stop the stress corrosion cracking it could not be guaranteed that the cracks underlying the repair would stop growing due to the applied pressure loads.