Using a non-destructive technique for evaluating water mains conditions

UK Water Utilities have on average 25 bursts per 100km per year. Failure in water pipelines have serious consequences for the UK Water Industry and its ability to maintain an effective water supply. Furthermore the 1991 New Roads and Street Works Act, increase the responsibility and consequential costs. In addition, enhanced regulatory, customer and stakeholder pressures require the need for Water Utilities to ensure proper management of their pipeline systems. Therefore an effective monitoring and inspection technique for pipelines is essential in order to properly plan for system maintenance, rehabilitation and replacement plans. Justification for such schemes should be based on sound assessment methodologies and proven inspection techniques with adequate condition assessment. It is important that the technique used is cost effective and result in the minimum interference to the pipeline and subsequently to customer supplies. There are many Non-Destructive Techniques (NDT) proposed for pipe condition assessment. A review study on NDT technologies by the American Water Works Association Research Foundation indicated that the Remote Field Eddy Current inspection technique by Russell Technologies was one of the most successful NDT methods evaluated. The results of the technique indicated that the relative compact and transportable system revealed the extend of graphitisation of the pipe wall. In order to corroborate the claims of the AWWARF study, an experimental trial was set up for a 0.5km length and 6 inch diameter ductile iron pipe located within the Thames Water Utility boundary. The Russell Technologies equipment was transported from Canada to the UK. The trials were carried by Russell Technologies technical staff in co-operation with Thames Water Group R&D. The results obtained form the Russell Technologies technique were compared with visual inspection and measurements made on pipe samples from the 0.5 km long pipe. The comparison concluded that the method adequately described the condition of the pipe so that decisions could be made on the type of pipe rehabilitation method needed. Furthermore it also indicated the location of pipe joints and some pipe fittings. However, further work is required to (a) improve the practicability of the method (b) reduce the effective cost of inspection (c) minimise the need for expert data interpretation and (d) address water quality issues during on-line use arising from possible disturbance of solid deposits.