Importance of installation practices for corrosion protection of ductile iron pipe

Abstract

Loose polyethylene encasement is a widely used corrosion protection measure for buried ductile iron pipes. Polyethylene encasement functions as a physical barrier between the pipe and surrounding soil environment. Findings from an international industry survey strongly suggest that performance of polyethylene encasement is governed by installation and repair practices. Common problems reported were inappropriate repairs at tapping connections, pre-installation damage, failure to overlap encasement at joints and improper excavation to accommodate encased joints during installation. To quantify the benefits of improved installation practice, physical and economic models were developed. The physical model predicts corrosion related failures and the economic model calculates the benefits accrued through their avoidance. The model indicates that pipelines in moderate to extremely corrosive soils, better installation practices were beneficial. Extrapolating to the network scale, a moderate 5% reduction in installation damage through improved practice created a benefit of approximately $1M/year benefit after 30 years in-service.

Keywords:

• PE encasement
• ductile iron pipe
• field assessment
• modelling
• economic
• survey
• damage

Acknowledgements

The authors would like to acknowledge the support of the Water Research Foundation project 4098.