Stay ahead of corrosion

Water is a major challenge in many process-intensive industries, and LNG is no exception. In most plant operations, the ingress of water through the insulation system and onto the metal surfaces of pipes and other equipment can cause aggressive corrosion under insulation (CUI). If left unchecked, CUI can lead to unanticipated heat loss, unplanned downtime, and leaks and spills that create hazards for plant personnel and may hurt the plant’s standing as a responsible environmental steward.

While many LNG processes require insulation for low-temperature applications, some critical areas in the plant operate at elevated temperatures where CUI poses a higher risk. The severity of CUI is related to the temperature of the pipe or equipment, with higher temperatures translating to more aggressive corrosion at higher rates. For cyclic plant operations running between cold and hot temperatures, the risk of CUI is considered ‘extreme’, with dangerous and expensive consequences. During cycling, water vapour gets into the system at cold temperatures and the system is susceptible to higher CUI risks as it cycles through the water dew point. During each temperature cycle, the chloride salts in the water concentrate on the surface of the metal (and possibly in the insulation) when the water evaporates during the higher temperatures. By some estimates, CUI accounts for 10% of a plant’s overall maintenance costs and up to 60% of pipeline maintenance costs.^1,2

In addition, a growing number of LNG facilities are being built along the US Gulf Coast and in India and Pakistan – high-humidity regions prone to increased rainfall and seasonal weather events such as hurricanes and monsoons. The warm, moisture-laden climate of these regions makes corrosion resistance a critical need for the vast network of pipelines and other equipment in an LNG facility.

Traditional materials like coatings are considered the best line of defence against CUI, but are not always a singular corrosion mitigation solution in these regions. These coatings often need to be reapplied every few years, which adds maintenance costs and may require non-productive downtime in some parts of the LNG plant. With the rapid and common onset of flash rusting in some high-humidity environments, this means that the coatings cannot always be effectively applied.

Mitigating CUI with water-repellency technology

ROCKWOOL Technical Insulation is a global leader in stone wool insulation solutions, with more than 85 years of history in providing innovative products that help meet required design criteria and help solve the most critical industry challenges – including enhanced water repellency and proven corrosion mitigation. Leveraging the natural power of stone, the company’s ProRox insulation materials provide proven, effective thermal and sound resistance in industrial applications. These materials are manufactured by melting natural rock, spinning it into long fibre strands, and then weaving the strands into high-density mats or sectional forms that easily conform to the outside of piping systems and other LNG equipment.

ROCKWOOL has built on the proven thermal and acoustics insulation performance of its ProRox stone wool solutions, to now mitigate against CUI with a water-repellent additive called WR-Tech (‘Water Repellency Technology’). This binder technology coats each individual fibre of the stone wool insulation with an inorganic, hydrophobic additive during the manufacturing process. This imparts the stone wool with superior water repellency, even at elevated operating temperatures, while preserving the insulation’s thermal and acoustics performance.

WR-Tech substantially lowers CUI and extends the piping network’s operating life in several ways.

Water repellency for long-lasting corrosion protection

In third-party tests conducted to the EN 13472 standard (the European standard for determining short-term water absorption in pipe insulation), insulation treated with WR-Tech has a water absorption five times lower than the next-closest insulation material. The treated insulation also very importantly maintains this water repellency even after being subjected to pre-heat stress tests of 250°C (482°F) for 24 hours.

The insulation also contains less than 10 ppm water-soluble chloride content, making it compliant with industry standards such as ASTM C795 and EN 13468, ensuring its safe application over steel. Additionally, in testing per the ASTM C1763 standard (test method for water absorption by full immersion in liquid water), the insulation’s fibrous, vapour-open structure shortens drying times, even over long periods of time in applications with cycles of heating and cooling.

Wide performance versatility beyond corrosion mitigation

ProRox insulation with WR-Tech maintains a stable and durable thermal performance to minimise heat losses in hot pipes, save on energy consumption, and reduce greenhouse gas emissions for the plant. On average, stone wool insulation saves 20 000 times more carbon dioxide over its operating life than what is emitted during its manufacturing process.³

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Read the article online at: https://www.lngindustry.com/special-reports/23112023/stay-ahead-of-corrosion/