UK breaks record for longest hydraulically-inserted pipeline

19 November 2020

UK energy company National Grid has completed what has been hailed as the world’s longest hydraulically-inserted pipeline, now officially recognised by Guinness World Records.

Handed over last week, the 4.96km-long River Humber Gas Pipeline project involved a new 3.65m internal diameter tunnel to house an important section of gas pipeline beneath the estuary of the River Humber in North East England. National Grid achieved the feat working in conjunction with the Porr Skanska A.Hak joint venture.

Replacing the existing pipeline was necessary due to a shifting river bed over the years which resulted in exposing sections of the pipeline to the mercy of the tides. The £100m (US$131m) project was undertaken in two stages. First, a tunnel of 4.38m excavation diameter was bored 30m beneath the river in chalk geology by a Herrenknecht mixshield (M-2141) TBM installing a segmental lining as it advanced. The machine broke through into a reception shaft at Paull on the river’s north bank after an 18-month operation.

Once completed, the tunnel was flooded with specially-treated water to aid installation of the steel pipe push-through and ensure no adverse reaction occurred with the steel.

In spring 2020, two hydraulic thrust machines pushed through giant 620m pre-welded sections of steel pipe from the south side of the river at a rate of around one metre per minute; each new pipe section was welded to the one in front.

Excavated material from the first stage was graded and reprocessed before being used to help restore a nearby quarry. The pipeline is now being connected to the UK network with gas expected to start flowing in December 2020. During the winter months, it will convey around 25% of Britain’s gas.