Water Journal : Water Journal November 2013
WATER NOVEMBER 2013 38 Feature Article Melbourne Water Corporation's Eastern Treatment Plant (ETP) comprises a vast number of buried metallic assets that require an effective corrosion mitigation strategy. Previous strategic decisions on providing cathodic protection of selected buried assets were made without assessing the full impact on the plant or nearby foreign assets. Melbourne Water identi ed the need for a plant-wide strategy to protect all metallic underground assets from corrosion and stray current effects. This culminated in the development of a Corrosion Management Manual, jointly developed by Melbourne Water and Aurecon. The objective was to provide a step-wise guidance methodology for operators and engineers to make decisions on future corrosion mitigation for existing and new assets. The steps involved were: 1. Identify key existing buried metallic assets; 2. Outline issues to be considered when identifying corrosion mitigation strategies based on risks, asset type and process criticality; 3. Summarise existing cathodic protection systems and discuss lessons learned; 4. Summarise and explain applicable codes, standards and regulations; 5. Give guidance on the application of existing Melbourne Water standards; 6. Develop process ow charts to assist with decision-making processes. The Manual was developed to be fully applicable to all buried metallic assets including pipes, steel tanks, earthing systems, steel piling and lead shielded cables. Of all the infrastructure types, arguably that relating to water is the most fundamental to life and liveability. Water utilities are facing signi cant challenges, with ageing infrastructure, population growth, higher community expectations and severe economic pressures in trying to balance water security, quality and customer affordability. Melbourne Water's Eastern Treatment Plant (ETP) is located in Carrum Downs and was opened in 1975 to treat a large proportion of Melbourne's sewage (Figure 1). The plant covers more than 1,100 hectares and treats approximately 330 million litres per day or about 40 per cent of Melbourne's total sewage load. The ETP is, therefore, a vital part of Melbourne's critical infrastructure, and is required to maintain a high level of service at all times. The plant comprises a large number of buried metallic assets including pipelines and ttings, steel tanks, earthing systems, steel piling and cables. Most of these assets are crucial to maintaining ef cient operation of process systems at the ETP. Key assets include a two- metre diameter south-eastern outfall (SEO) steel pipeline, natural gas distribution steel pipelines and 1.8 metre diameter grit and coarse screenings mild steel pipelines. Failure of these assets could lead to potentially serious consequences, due to long lead times required to access, repair and reinstate buried sections of failed pipe. Potential consequences can include prolonged service outages, environmental spills and an inability to maintain ef uent discharge limits. Previously, Melbourne Water made strategic decisions to provide cathodic protection to selected individual critical assets, such as the SEO pipeline. These decisions were often made reactively after an incident, without individuals appreciating possible effects upon the plant as a whole and upon nearby surrounding foreign assets. This resulted, on occasion, in costly consequences where newly installed cathodic protection (CP) systems had to be removed from service. In 2012 Melbourne Water, in partnership with Aurecon's Materials Technology team, embarked on a project to develop a plant-wide A UNIFIED APPROACH TO MONITORING AND MANAGING CORROSION OF ASSETS AT EASTERN TREATMENT PLANT The development of a Corrosion Management Manual for buried metallic assets at the ETP. By Ulf Kreher, Ike Solomon, David Solomon and Robert Callant. Figure 1. Aerial plan of the Eastern Treatment Plant.
Water Journal September 2013
Water Journal December 2013