The pipeline repair system, named ARCOS, is based on the connector technology developed by SNAM SpA (the Eni company that operates in the supply, transmission and distribution of natural gas) and on a suite of intervention tools designed and fabricated by Sonsub to install and actuate those underwater connectors required to re-establish the pipe functionality. The ARCOS intervention tools have been conceived in a view of limiting the tool sizes, so avoiding use of massive structures and minimizing offshore operations by using standard made ROVs fitted with specific work packages. These are able to cut and remove the damaged pipe section, install the connectors into the pipe ends and replace the pipe length with a spool piece. ARCOS is based on the cold forging and "low force" modular concepts, which have been developed and successfully proven whit a testing program by SNAM and Sonsub. A great advantage of this repair system is that it does not require a strict tolerance between pipe and connector, clearance between them is about 20mm; moreover, it requires no pipe preparation, such as removal of the polyethylene corrosion protection coating and beveling: thus allowing significant simplification of intervention tasks. The second special system feature is that it is designed to accommodate rather large tolerances and angular misalignments between the facing pipe-ends of the pipeline to be repaired. Hereby are described the repair system modules with their merits and the main ARCOS concepts that induced SNAM to adopt the system for the 20" and 26" TRANSMED pipelines.
As pipe-laying operation moved toward deep waters a need was recognized for diverless repair systems, in the event severe damages to the pipelines. Since the early eighties several Oil Companies started to develop diverless pipeline repair systems, pursuing different philosophies both for the connection technology and for the system installation.