• Why are we doing it?


    Across Great Britain, gas distribution networks have been systematically replacing metallic gas mains with plastic pipe, but the country still has over 80,000km of metallic gas distribution mains.

    Metallic mains are subject to ageing and deterioration, are costly to maintain and require continuous inspection, repair or replacement.


    There are three reasons why we would need to intervene in relation to metallic mains.




    Leaking joints on metallic gas mains are responsible for the largest share of leaks on the GB distribution networks. This also impacts negatively on the environment.

    Leakage is cause by fractures and joint failures. The larger the diameter, the thicker the pipe wall, and the fewer fractures per kilometre.

    Conversely, larger diameter pipes experience a higher incidence of joint failure per kilometre, as shown below.

    The diagram on the left shows that as the diameter of cast iron (CI) pipes increases, there are fewer fractures per km. The thickness of larger pipes increases with diameter which makes more robust pipes.   The diagram on the right shows that these larger pipes are much more likely to fail at the joints.


    At the moment, we have to excavate around every joint to detect and repair leaks. It’s costly and disruptive to the public. New robotic techniques will remove the need for most of these excavations, as the joints will be repaired from inside the pipe.


    Risk management


    We need to manage risk associated with our mains assets. This enables us to plan our interventions e.g. by understanding where weaknesses and corrosion exist, and where leaks are most likely to occur. A planned approach is less costly and disruptive than emergency intervention.

    At the moment, we deal with risks to smaller diameter pipes by replacing them, but larger diameter mains are subject to a programme of maintenance and repair.

    Our project presents an opportunity to explore alternative methods of reducing risk for these larger pipes e.g. by developing robotic techniques to measure stress and strain in pipe walls from inside the pipe.


    Third party damage


    Robotics can open up new ways to map gas pipes accurately. Distribution networks will be able to share this information with other utilities and authorities who are excavating the roads, reducing the risk of accidental damage.