Water Journal : Water Journal November 2013
WATER NOVEMBER 2013 42 Feature Article Opportunistically assessing buried pipelines during pipeline maintenance and minor works activities is an ef cient and effective means of sourcing information on the pipelines to assist with risk management and renewal and maintenance programming. This article provides an overview of the key principles in establishing an ef cient and effective opportunistic assessment process for buried water and wastewater pipelines. Effective management of assets relies on a good understanding of those assets, including their condition and risk of failure. Due to their inaccessibility, obtaining such information for buried pipelines can be signi cantly dif cult and costly. An opportunity to ef ciently source such information for buried pipelines presents itself at the time the pipelines have been exposed and isolated for maintenance and minor works purposes (Figure 1). To ensure that the most important information is collected and the effort and resources used in collecting this are not in vain, a systematic process is required to be implemented. The authors have recently developed an Opportunistic Pipeline Condition Assessment and Data Collection Guide for Unitywater. The guide identi es the type of information to collect, including the use of simple in-situ tests, and sampling for further off-site examination and laboratory testing. BACKGROUND DISCUSSION Every pipeline failure, except where solely due to damage by a third party, represents a statement of the condition of a pipeline. All failures demand a maintenance response, even if the pipeline asset requires no more than the installation of a sealing band to stop a leak from a perforation or circumferential crack. Evaluation of the failure, and the condition of the exposed section of intact pipe, adds to the knowledge base of the particular pipeline asset. Many failures follow well-documented patterns. The failure, therefore, adds to that pattern and strengthens the case for replacement. Failures of pipeline assets with no prior history of failures represents an opportunity to assess a potentially emerging failure mechanism, some of which are slow and others of which represent the leading edge of a systemic failure pattern. Maintenance and construction crews often yield pipe shards from site activities. Such shards provide a snapshot in time of the condition of the particular pipeline. That knowledge, when added to a dataset that has been progressively accumulated over time, may yield a timely warning that the pipeline is approaching the end of its useful life. An example is a 300 AC pipeline constructed in coastal conditions in the early 1960s, which is the subject of planned cut-in works. A simple phenolphthalein indicator test on the recovered shard can reveal the extent of the progressive external pipe wall section loss from acidic groundwater conditions (Figure 2). A gouge test would reveal a similar story to the phenolphthalein test. Given a pipe length of 15km, advanced knowledge of the residual life remaining will be vital for advanced nancial planning. Sourcing information from eld crews is very valuable. Often they are quite familiar with the pipeline and environment and can provide good insight into the issues, so decisions can often be made without the need for further investigation. Providing a systematic process to communicate their observations and recommendations is important. OPPORTUNISTIC ASSESSMENT OF BURIED PIPELINES Information to guide the assessment and data collection of buried pipelines as part of a water utility's maintenance and minor works program. By Alf Grigg and Geoff Hales. Figure 1. An opportunity for pipe assessment. A 300mm DN MSCL pipeline, ready for repair using repair bands. The exposed section of pipe displayed externally corroded sockets. Figure 2. The result of phenolphthalein being applied to the ends of an AC pipe shard. The pink colour indicates the presence of calcium in the pipe wall media.
Water Journal September 2013
Water Journal December 2013