Water Main Breaks - High Time to Learn from Mistakes and Avoid Further Breaks

摘要

Water main failures are very expensive for municipalities because they typically result in expenses associated with repair costs, flood damage, and loss of revenue to affected businesses. Water main failures also interrupt the operation of vital services, such as medical care and fire-fighting operations. Currently, millions of dollars are spent annually by the water utility industry and by municipalities on the repair of failed components of the water distribution infrastructure, such as components that are made from gray cast iron or "gray iron" pipe and ductile cast iron or "ductile iron" pipe. The rate of municipal water main failures is expected to increase as the existing cast iron infrastructure continues to age. The cost of repairing damages caused by broken water mains (and subsequent flooding damage) may become an important item in many municipal budgets. It is important to develop a corrosion program to prevent catastrophic failures of water mains. This paper presents a plan consisting of several phases including preassessment, indirect assessment, direct assessment, and integrity assessment of failed water mains. We will elaborate on the failure mechanisms, failure analysis protocols, and corrosion mitigation strategies for water mains that experience breaks. Water main breaks are mainly due to corrosive soil, pipe material, galvanic action, stray current corrosion, or microbiological induced corrosion (MIC). This paper provides an overview of corrosion issues commonly experienced by water main pipes, presents specific case histories involving graphitic corrosion, galvanic corrosion, stray current corrosion, and MIC. In this paper, we will introduce a graphitization sensor for condition assessment of water mains. This sensor can identify the location and extent of graphitization on water main.