Measuring a number of failure mechanisms in exit assessments

A lot of money is involved in the distribution pipe replacement programme and the choices made in this regard must be justified. This is done with prediction models and condition determinations. In a condition determination the condition of the pipe is first measured, using one or more measuring methods. To determine the condition of the pipe, the measured condition is then compared with the standard. The results can, on the one hand, be used as confirmation of decisions taken and on the other to improve the justification of the future replacement programmes, by broadening the information basis of the prediction models.

Condition determination by knowing the degradation

The condition measurements currently carried out are aimed exclusively at the degradation mechanisms of ‘leaching’ and ‘leading’. These degradation mechanisms lead to a reduction in pipe wall thickness, so that stresses in the pipe wall increase at equal load, possibly resulting in the wall cracking. Knowing the degradation in the pipe wall is therefore important for a condition determination.

It is also interesting to see whether other measuring techniques can be used in an exit assessment to analyse whether or not other failure mechanisms occur. As time and resources for exit assessments are limited, the practical feasibility of techniques will be explicitly considered in this regard.

Quantitative foundation improves decisions

Additional information from the more detailed exit assessments allows water companies to improve decisions with better quantitative underpinning. Decisions taken as part of the replacement programme can, therefore, be better evaluated and future choices better considered. Ultimately, this increases the impact of the spending on the replacement programme and confidence in it.

The additional information obtained from the more detailed exit assessments can also be used to better validate prediction models, which again contributes to the above.