LifeAssessment of Large Cast Iron Watermains

ReportNo WSAA 146

December 1998




Issues affectingthe condition assessment of large cast iron watermains are discussed in detailand the need for soil evaluation as a cost effective condition assessmentoption is explained. The limitations of using traditional soil parameters as aquantitative condition assessment method are outlined, and the potential of theLinear Polarisation Resistance (LPR) technique discussed.


The project isfocussed on comparing the predictions of corrosivity obtained from various LPRtechniques against actual pitting measurements made on exhumed pipe sampleswith a known history and condition.


One technique(referred to as the ‘manual CIE method’) proved to be both reproducible andstatistically significant in establishing a quantitative relationship betweenthe soil test and corrosion rate of buried iron pipe. The automated techniqueswere disappointing in their results and possible reasons for these poorcorrelations are discussed.


However, it siclearly established that the basic LPR technique is capable of better assetlife predictions than the chemical test regimes it replaces, and themethodology should be developed. Although the Remote Field Tool (RFT) technologyhas proven excellent for detailed investigations of relatively small diametercritical pipelines, there are economic and size limitations on widespread use.The development of an in-situ probebased on LPR methodology would be a worthwhile goal for the industry.


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