Water Journal : Water Journal November 2013
WATER NOVEMBER 2013 44 Feature Article out a sample from a speci c pipeline, it is only proposed to recover samples from shards (off-cuts) arising from the work activity. An example of where it may be prudent to recover a sample is provided as follows: A failure of a ductile iron pipeline that is not due to damage from a third-party, has not been sampled in the same location over the past year, and in which greater than 1mm depth of corrosion/erosion has been observed after the hammer test. The purpose of the sample would be to allow further examination, after 'grit-blasting', to gain a better understanding of the pipe condition and remaining life. The recovery, transport and storage of pipe samples needs to be well managed to address associated safety risks (particularly with AC pipes), and ensure any results from further examination and testing can be readily correlated with and recorded against the relevant section of pipeline. Samples selected for dispatch to testing laboratories must be adequately labelled, stored and packaged to ensure safe storage and transport, and to ensure that hazardous materials such as AC pipe do not pose health risks to any person in the chain of the transport and delivery process. Labelling of all pipes must comply with current prescribed procedures for chain of custody of hazardous waste. Compliant labelling ensures that the receiving laboratory is noti ed of the contents of a package, and can safely handle and store a sample prior to laboratory testing. OFF-SITE SAMPLE EXAMINATION AND TESTING Whether to further examine and test a pipe sample needs to be decided on a case-by-case basis. Once again, the factors listed for in-situ testing need to be considered, in conjunction with the following: • The availability of adequate existing information on the subject pipeline or cohort; and • The cost of, and type of information that can be obtained from, further examination/testing. The general purpose of the examination/testing should be to con rm the mode of failure if the sample incorporates the part of the pipe that failed, assess the condition of the sample and provide an estimated remaining life of the pipe. The latter will require additional information, such as details on the operating environment (e.g. hydraulic head for pressure mains), and chemical data on (or a representative sample of) the surrounding ground and the uid being transferred through the pipeline. There are some relatively simple and low-cost methods, such as detailed examination of ferrous pipes after grit-blast cleaning (Figure 3), and the phenolphthalein indicator test for calcium-based and internal cement mortar lining. The types of more detailed examination and testing methods are numerous, varying based on the pipe material and class and the standard the pipe was constructed to. For this reason, and the improvements being made to pipe testing, the selection of method should be made in consultation with the service provider. CHALLENGES Some of the key challenges with an opportunistic pipeline assessment program are discussed as follows: Work Health and Safety All work needs to be completed in accordance with appropriate Work Health and Safety standards. There are signi cant risks associated with AC, high pressure and deep pipelines, and sections of pipelines on the side of, running parallel in, or across roads. Data Quality The quality of the outcomes from the assessment program is highly dependent on the quality of the data collected. Two key strategies to encourage the collection of good data are: • Demonstrate the reason for the assessment, and how the data collected is being used; and • Regularly provide summaries of data collected to those responsible for the assessments, and seek their input on trends etc. CONCLUSION Opportunistic assessment of buried pipelines can be a very ef cient and effective way to get a better understanding of the buried pipeline network, including the condition and risk of failure of various pipelines. A systematic process for the assessments needs to be developed and implemented to maximise the cost bene t. ACKNOWLEDGEMENTS The Authors would like to acknowledge the input of Unitywater staff, who not only helped with the development of the guide for Unitywater, but also informed some of the principles discussed in this article. WJ THE AUTHORS Alf Grigg (email: firstname.lastname@example.org) is Director of Alf Grigg & Associates, a regionally based consultancy rm that specialises in condition evaluation, failure analysis, and residual life predictions for water, sewer and stormwater assets. Geoff Hales (email: email@example.com) is Director of Barnewall Resources Pty Ltd, a small Queensland consultancy rm providing asset management services, particularly to the water industry. He has assisted several Queensland Water Utilities with the development of opportunistic asset assessment processes and guidelines. Figure 3. Recovered Ductile Iron pipe shard, displaying the effect of garnet-grit blasting that reveals the actual iron matrix surface and the extent of pipe wall loss.
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