What NDT technique works best for cast iron trunk main testing?

Corrosion Mapping / Phased Array

Our Victorian forefathers were true innovators when it came to the development of their utility infrastructure. They built enormous underground sewage systems, such as that in London, to remove waste and long chains of reservoirs and aqueducts to carry water into urban areas. Manchester benefited enormously from the Longdendale Valley and Thirlmere Aqueduct project, which brought fresh water into the city, and allowed it to develop into a centre of industry.

The Victorian development of the sewage and water supply systems in the UK still forms the basis of much of our current system. In modern times, we have extended, improved and renovated the existing infrastructure. But elements of the original construction remain and can be the cause of significant problems.

NDT for the Water Utility Sector

It was one such Victorian era object that caused a water utility company in south Wales to get in contact with NDT Group this month. A 19th century 18-inch cast-iron trunk main in South Wales had previously catastrophically burst and the company wanted to ensure the integrity of the element.

NDT Group has a professional partnership with Water Research Centre Infrastructure (WRc), which uses innovative technologies to inspect and manage water pipeline systems. The Water Utilities company had been in contact with WRc and they had recommended the use of NDT Group to perform the non-destructive testing services that were required.

Condition Assessment of Cast Iron Trunk Mains

The Water Company wanted to include a condition assessment of the pipe on either side of the burst location to confirm the condition and likelihood of further bursts. We responded quickly to the request and were able to send a team to the site in a short space of time.

As the asset was over a hundred years old, we decided to try a range of inspection techniques to determine which could give the best report, the quickest, for the client. Our team utilised RMS corrosion mapping and Phased Array, using a wheel probe which was supplied for the trial by one of our suppliers Sonatest to perform the cast iron trunk main testing.

The Result

It was a good opportunity for our team to upskill in the techniques required for inspecting 19th-century pipes. Trialling the different techniques allowed us to determine which inspection worked best for the Victorian cast iron material. The combination of the two tests provided a high-quality result on the condition of the pipe.

We should now have a better idea of which inspection methods will work ‘in practice’ on cast iron trunk mains for any future inspections. This will reduce operational disruption and minimise costs for our clients in the water utility sector in the future.


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