Condition Assessment Methods for 1920s Lock-Bar Steel Pipe

摘要

This paper presents a case study for the examination of one of the City of San Diego's oldest and most critical water transmission pipelines, a 36-inch (900 mm), 7-mile (11.3 km) long lock-bar steel pipe. A history of the original installation and subsequent maintenance improvements (addition of cathodic protection and re-lining with cement mortar) is discussed, and the results of recent field examinations are presented, along with conclusions. The paper also discusses a number of condition assessment methods and techniques that were utilized on this pipe, including internal video inspection and leak detection; external broadband electromagnetic scanning, guided wave testing, and ultrasonic thickness testing; corrosion testing; transient monitoring; and assessment of valves and appurtenances. Additionally, the paper briefly covers the methodology and results of a risk analysis that was conducted for prioritizing potentially required repair and rehabilitation improvements. The finding of this case study is of direct benefit to other agencies that own and maintain this unique type of steel pipe.