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Fitness Test for Old Pipes

Thames Water uses NDT to assess corrosion on large water mains

Published: Wednesday, November 18, 2015 - 15:56

Thames Water is the United Kingdom’s largest water and wastewater services provider with more than 15 million customers. As part of its business, Thames Water delivers an average of 2,600 million liters of drinking water every day. The company’s cast-iron water mains in many areas of London and the Thames Valley are among the oldest in the UK, and many of them are wearing out.

Thames Water employees have been working hard to replace the smaller distribution mains during the past 15 years, but now the larger trunk mains are of growing concern. A burst in just one of the these can leave thousands of customers without water, cause major flooding, and disrupt transport routes.

Tim Evans, water network innovation manager, explains how new technology is paving the way for a more sustainable replacement approach. “It’s costly to replace pipes, so we need to prioritize which are the riskiest ones,” he says. “A big challenge with cast iron is that it corrodes unevenly, and the corrosion is very hard to detect.”

“Traditionally, we’ve assessed the condition of a water main by cutting out a short length of pipe, sand-blasting it to remove the corrosion, then measuring the resulting craters by hand,” explains Evans. “But taking pipe cutouts is disruptive for customers and road users, and expensive for Thames Water. “To remove the need for pipe cutouts, we’ve started to use nondestructive testing (NDT) technology, such as ultrasound. The aim is to be able to send a device into a water main to gather NDT condition data all along it, not just in short excavations.”

Surface scanners help Thames Water understand what different NDT tools can measure, and a Konica-Minolta Vivid system had been used to map corrosion in small diameter (4–8 in.) pipes. However, such a system is inappropriate for pipes more than 18 in. in diameter. For large pipes a handheld scanner is needed, and Thames Water invited various suppliers to demonstrate their equipment.

Following up on a first demonstration, Patrick Thorn & Co., Thames Water’s local Artec specialist, worked with the company to scan a large pipe section so Thames Water could confirm that the Artec Eva delivered the essential performance required. They concluded the Eva would offer the most cost-effective option to meet their requirements. Following the purchase of an Eva, Thorn also trained Thames Water employees in the use of the scanning system, and acquired additional software for more detailed analysis of data from the Eva.

Since delivery of the Eva, Alex Rainer, working on a research project between Thames Water and the University of Surrey, has been developing an appropriate methodology that combines the Eva and its software, visual texture added to the pipe, and a motorized pipe rotator so that reliable 3D models of the pipes can be built.

Artec Studio 10.1, the recently updated system software, has increased the robustness of making the mesh by improved texture tracking while recording data. It also uses more of the multicore capability of Thames Water’s PC workstation so the raw data processing is completed in a significantly shorter time.

Comparing the models from before and after corrosion is removed from the pipe enables corrosion levels to be mapped to a good level of accuracy. The corrosion mapping provided by the Eva will be used as a baseline against which the effectiveness of different nondestructive approaches can be gauged.

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Artec 3D

Artec 3D develops and manufactures professional 3D scanning hardware and software, developed by a team of experts in the collection and processing of 3D surfaces and in biometric facial recognition. Fast and efficient, Artec scanners are used in many industries, including engineering, security, medicine, entertainment, design, fashion, heritage conservation, and other sectors. The company has subsidiaries in the United States, Moscow, and Luxembourg.