Condition Assessment of Large Diameter Water Pipelines

Physical inspection of large diameter water mains has been carried out within the UK for at least 16 years following guidelines first published by the Water Research Centre. Both destructive and more commonly non-destructive inspections are  planned at  inspection sites either individually or as a zonal exercise, on strategically important water mains selected by simple combinations of either opportunistic maintenance, soil type, failure history, or frequency of coating defects.

Townley Brothers specialise in all survey and data collection techniques that allow a trunk main to be sub-divided based on asset life to failure point and resulting condition grade. To date we have carried out over 500 detailed water trunk main surveys.

Non destructive testing involves excavation (where buried) by the client’s approved contractor of a metre section of the pipeline all around its circumference, and involves removal of the external protective coating and any corrosion product prior to testing. External corrosion pit depth analysis and extensive ultrasonic measurement will then be carried out over the one metre section of exposed main, to determine the external corrosion and internal corrosion rate and the remaining pipe wall thickness. A detailed output map showing the remaining iron wall structure, often accurate to less than +/-0.2mm is produced allowing both remaining asset life and further calculations of failure likelihood to be provided. Digital photographs will also be taken to record condition of the main.

All survey parameters, digital photographs and spreadsheets containing service life calculations are supplied back to the client upon completion of works. A report is provided detailing the approximate distribution and variation of condition and remaining asset life along the length of the surveyed asset.

In many cases, failures associated with trunk mains result from poor condition where only a section of the asset is laid within aggressive external ground conditions. In most cases only a small proportion of the asset length may be at risk of further deterioration and supply interruption.