Subsea & Offshore Service Magazine May'16

Page 24


roVs & AuVs

How ROVs Can Improve Potable Water Management Strategies and Processes Julie Hart, Water Hygiene Technical Manager and Andrew Russell, Senior Microbiologist at Intertek Production and Integrity Assurance, consider the advantages of Remotely Operated Vehicles (ROVs) to assure the quality and safety of potable water systems. Managing the potable water supplies of offshore facilities, such as oil rigs, FPSOs, flotels and industrial vessels, is a vital undertaking in oil and gas and other industries. Maintaining a thorough water management strategy tailored to the needs of a facility comes with no small amount of accountability. Potable water is heavily relied upon during all stages of day to day routines offshore, from personal use such as showering and drinking to food preparation, cooking, cleaning and laundry. It is also required for industrial processes such as utilities, cooling systems and other technical uses. The Dangers of Poor Potable Water Quality Legislation varies between regions, but typically an installation’s water management strategy will be the responsibility of an appointed individual. In the UK, this is the duty holder, as stipulated by the Health and Safety Executive.

Neglecting water hygiene practices on an offshore facility could have catastrophic consequences for those working and operating on board. In terms of operational continuity and cost, it could also have major repercussions if an unplanned shutdown is required. A water tank that hasn’t undergone inspection within the timeframes recommended could harbour a number of contaminants, including microbial, chemical, hydrocarbon based and excessive debris and or sediment. These can then pose a risk to human health and the integrity of the tank. The worst case scenario widely acknowledged across all industries is the breeding of Legionella. As is generally known from high profile cases in the past, Legionella can result in serious widespread illness and death through the inhalation of airborne bacteria. Another problem the microbiology team at Intertek encounters in the case of water storage tanks is corrosion. The development of corrosion is serious as it poses a risk to water quality and the integrity of the tank itself. It is also known that iron is a vital food source for Legionella and in turn, corroded tanks have a higher incidence of positive Legionella results. Below: Legionella bacteria, a potentially deadly bug that uses iron as a food source.

Above: An Intertek Production Chemist examining a corrosion damaged component. An annual inspection schedule should be put in place to monitor the need for re-lining, re-coating and cleaning, a costly and time consuming process that will require the tank to be kept out of service while the process is completed. Alternatively, an inspection can satisfy the legislative requirement and demonstrate that tanks are in a good and hygienic condition. The Challenges of Potable Water Tank Cleaning Cleaning a water storage tank is no small task, especially when dealing with large volume capacities that can range from tens to hundreds of thousands of litres or more. Traditionally, water tank cleaning requires taking the tank out of service, draining, cleaning and re-filling before bringing the tank back into service. This process typically lasts for around three days if straightforward, but can easily be longer if corrosion and other more significant problems are identified. The Use of ROVs for Tank Inspection ROVs have the potential to improve upon the traditional approaches taken to water tank inspection. A crucial factor in deploying an ROV for potable water tank inspection is that the method statement and process must ensure that no new toxins or bacteria are introduced into the water supply.

p24 | | May 2016