PRODUCTION • PROCESSING • HANDLING
W
ith an estimated US$2.2 trillion spent repairing, replacing and maintaining equipment and materials affected by corrosion,1
it is
a major concern for organisations across a huge range of sectors. From oil and gas companies, through process, marine and automotive businesses, to the nuclear industry – all need to take action to combat corrosion. But although rust can provide a clear signal of external corrosion, identifying corrosion under insulation (CUI) is more difficult. A test on one area of pipework may come back negative for CUI, while the trigger factors that cause it may be occurring just a few metres away. Te potential for extensive structural damage to pipelines makes CUI a major worry for the oil and gas industry. Companies are facing a huge challenge in identifying the electrochemical changes under pipeline lagging, as there are more than 2.5 million kms of pipework in the USA and the UK2
alone. Logistically, the schedule for
checking pipework may have to factor in complex issues including remote locations, access problems, shutdown requirements and the risk of damaging the insulation – making it expensive and time-consuming. Even the lagging material itself may
The potential for extensive
structural damage to pipelines makes CUI a major worry for the oil & gas industry
promote CUI, through its free chloride chemical content. Coatings are often promoted as a solution to protect against corrosion – the application of ceramic, polyurethane or enamel, for example – as they can suppress the corrosion-forming electrochemical reactions, or form a seal against air and water incursion. Cathodic or anodic protection, using an external power supply, is also used to protect pipework, as is metal plating. But there are problems associated with each approach: whether poor abrasion resistance or strength of adhesion of coatings; environmental concerns around the chemicals used; or the complex and costly requirements for their application. Furthermore, even pipework
that has had a protective layer applied will still need regular checks, and this may require a shut down of equipment that impacts upon production.
A SENSOR-BASED APPROACH Non-intrusive sensors, which monitor the environment under lagging for changes in chemical composition, and provide an indication that corrosion may be developing, are an ideal solution. Frazer- Nash Consultancy, working with the University of Southampton, has developed a new approach that uses innovative sensor and logging technologies, supported by degradation and probabilistic corrosion models, to identify the condition of a metal asset under insulation. Te sensors are installed across the network and deliver continuous monitoring and detection remotely, minimising external access and disturbance. Using a microelectrode array that detects and monitors the metal ions present in a microenvironment, the boron-doped diamond sensor can identify multiple potential corrosion factors. It can measure the chemical environment, including the pH balance and presence of oxygen; the types of cations that are being removed from
The sensor data could mean that remedial action such as welding repairs can be made before failure occurs
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