PROJECT OUTLINE

The Corrib Gas Pipeline Project is one of the most significant engineering projects ever undertaken in Ireland and Murphy International Ltd was awarded the final phase of its construction – the laying of the onshore pipeline from the landfall site at Glengad to the Bellanaboy Bridge Gas Terminal.

The client was Shell E and P Ireland Ltd (SEPIL). The works were awarded in 2 stages – the first came in January 2013 for the 3.2km land section from Aghoose to Bellanboy in collaboration with Roadbridge who prepared the spread, backfilled and reinstated. Murphy were employed as specialist pipeline contractors to weld, NDT and ditch the pipeline.

The second stage, negotiated with BAM / Wayss Freytag JV the tunneling contractor, was tendered in May 2013 and following an international competition provisionally awarded in November 2013 under a LOI. The award was for the installation of the 500mm dia X 5km long gas pipeline, together with a number of service and umbilical control lines into the tunnel, through the pits to the tie in locations.

Completion had to be by mid- January 2015. MIL undertook the design of the pipeline and services within the tunnel and landing areas and employed the services of the Murphy Land and Marine specialist design team ProTech to approve the pipeline support and restraint systems. The pipeline was designed to operate at MAOP of 100bar with a test pressure in excess of 500bar so colossal forces had to be designed for.

KEY CHALLENGES

The designed and approved installation method of the main pipelines involved welding them into 72m long strings and stockpiling them in the yard in Aghoose before delivery and lifting onto the working platform in the drive pit and subsequent travel and installation into the tunnel. The compound in Aghoose was designed and constructed to minimise environmental impacts particularly as the site stood in a dedicated conservation area – a candidate Special Area of Conservation SAC and proposed Special Protection Area SPA.

PROJECT DELIVERY AND INNOVATIONS

The main challenge of the tunnel fit out was how to install the gas pipe, water pipes, grout pipes, umbilical’s, fibre optic and signal cables and ventilation ducting into the tunnel in a set sequence to satisfy the planning layout requirements. Extensive early engineering and design was required by the Murphy team to propose, test and approve the various systems required to install the pipework. This process took 4 months to satisfy all the parties and involved the construction of a life sized tunnel mock up to prove the installation methodology. In the final scheme the tunnel locos were utilised to pull a working platform mounted on tunnel bogeys up and back through the tunnel.

KEY FACTS

  • Tunnel possession 5 months
  • of men employed at peak – 70 workers and 15 staff / supervisors. 200,000 Murphy man hours worked accident free
  • 6200 brackets installed in 2 weeks
  • 4900 m of 750mm dia PE ventilation pipe installed in 1 week
  • 18,000m of 250mm dia PE water outfall + grout pipe installed in 3 weeks 4900 m of 500mm dia welded steel gas pipe installed in 7 weeks 30,000m signal and fibre optic cable installed in 3
  • 20,000m of umbilical cable installed in 10.5 weeks.

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