Building upon pipe inspection techniques from other industries, WRc has developed a new condition assessment tool for sewer rising mains that can be used whilst the main is in service.
The tool gives information on the remaining wall thickness and can be used without affecting the mains operation. The technique also allows the line of the rising main to be marked and the location of specific features to be identified ensuring accurate excavation and hence minimising disruption.
The pipe inspection technique, “Gross Metal Loss”, was recently used to inspect a 4” rising main. The main surveyed had burst twice resulting in pollution incidents – the survey provided the water company with information that will be used to determine the extent of the replacement work that will be carried out to prevent further incidents.
The results obtained (see above) clearly show:
- the pipe joints - regularly spaced peaks at 5.5m intervals,
- previous repairs - at 68 and 89m (circled in red),
- the general variation in pipe thickness along the metallic section of pipe.
The pipe is thinner in the sections from 50 to 57m, 70 to 78m around 83m and at 102 to 105m. There is a critical point at 67m – adjacent to a previous burst and repair that is very thin and will require prompt action.
Development of the technique is continuing with the aim of providing absolute values for the wall thickness.
For further information contact Anthony Bond on 01793 865099 or firstname.lastname@example.org.
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