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DNV GL, the technical advisor to the oil and gas industry has introduced a new methodology designed to address the major safety threat and multi-billion-dollar cost posed by corrosion under insulation (CUI), according to a statement by the company

CUI risk leaking pipeCUI risk-leaking pipe. (Image source: DNV GL)

CUI, a type of corrosion which arises when water becomes trapped between the insulation and the piping and vessels it is designed to protect, has contributed to more than 20 per cent of all major oil and gas accidents in the EU alone over the past 35 years.

DNV GL’s methodology helps integrity engineers and plant managers to identify the areas of a plant with the greatest current and future risk of CUI and take action to prevent failures.

Recommended Practice (RP) DNVGL­-RP­-G109 was developed in collaboration with several regulatory bodies, international oil and gas operators and major players in the supply chain to deliver a practical and cost-effective methodology for managing the threat of CUI and is setting a new standard for managing CUI risk.

CUI can take the form of localised external corrosion in carbon and low-alloy steels, external stress corrosion cracking (ESCC) or pitting in austenitic and duplex stainless steel. Despite the risks that CUI exposes, the oil and gas industry has never adopted a standard approach for identifying and managing the threat.

Operators currently employ a variety of methods to identify the presence of CUI on their assets. These range from using diverse inspection methods that can lead to undetected defects to the expensive process of systematically removing and renewing all insulation and coating with a limited upfront assessment of the risk of CUI presence. DNV GL’s RP provides a systematic approach to assessing, mitigating and updating CUI risk.

Koheila Molazemi, technology and innovation director, DNV GL - Oil & Gas, said, “Corrosion under insulation is recognised as the single most expensive corrosion issue in the oil and gas and petrochemical industries. Our Recommended Practice has been developed as a guide to the most effective and efficient way to assess, mitigate and systematically manage the risk.

“With its hidden and pervasive threat to life, property and the environment, and the cost of accidents and mitigation being staggeringly high - the combination of the new Recommended Practice and the CUI Manager, digital tool enables the industry to control CUI risk significantly more cost-efficiently.

“The new Recommended Practice is a great example of DNV GL’s approach to exploring and identifying problems with our partners, to ultimately establish industry benchmarks for safely and effectively manage these issues.”

DNV GL has also developed a digital tool to support the implementation and use of its methodology. CUI Manager applies machine learning to CUI data gathered from operators with the methodology from DNV GL’s Recommended Practice, to continuously assess and calculate the risk of CUI in process plants.