US: new pipes for old

The US pipeline system is in need of maintenance. But inspecting and repairing pipelines is no easy task

Natural gas flows from the US' producing regions to residential, industrial and commercial customers through a network of 2.3m miles of pipelines. But the system is ageing; according to the National Energy Technology Laboratory (NETL), over two-thirds of these pipes are more than 40 years old – manufactured well before construction materials and technology were introduced to help keep corrosion and cracks from causing them to fail. Distribution mains and service lines, which connect customers to the large-diameter, high-pressure transmission lines that crisscross the country, comprise about 2m miles of the grid. Unlike transmission lines, which generally traverse rural areas, distribution pi