New tools for an old battle

Industrial insulation systems, typically meant to last 20 years or longer, can be very difficult to maintain while simultaneously ensuring quality service. Part of the maintenance process regarding insulation systems is focused on the prevention and treatment of corrosion under insulation (CUI). CUI is any corrosion that occurs due to moisture build-up on insulated pipes and equipment beneath the insulation or the protective metal jacket over the insulation. Prevention is the best method to combat CUI because once it occurs, it is costly and time consuming to fix. Preventative methods for CUI can include the use of products imbued with corrosion-inhibiting chemistry and/or providing a pathway through the metal jacket for water that may enter an insulation system to rapidly escape.

Many industrial insulation products have features to prevent water from migrating through the insulation to the metal substrate beneath. Most experts agree that no matter what precautions are taken, water will eventually enter any insulation system. Therefore, it makes sense to focus on how to remove the water as quickly and thoroughly as possible. If the amount of time that water is present in the insulated system can be reduced, the chances of CUI occurring are dramatically reduced.

While many insulation system designers and specifiers recognise the importance of water egress from an industrial insulated pipe system, insulation products themselves often do not create pathways for water to escape. Once moisture does enter an insulation system, it will travel from the exterior jacketing through the insulation underneath to the metal pipe or equipment, where CUI will then occur. If the pipe system in question is hot enough, the heat will evaporate the moisture and drive the resulting steam away from the pipe, back through the insulation to the inside of the exterior jacketing. Because the temperature of the outer portion of the insulation and jacket will be well below the dew point, the steam will recondense on the surface of the insulation/jacket. This process is then repeated until the insulation in the system is rendered waterlogged and inefficient.

To help combat this issue, Johns Manville introduced a metal jacketing product, Cross-Flo^®, designed specifically to help mitigate the occurrence of CUI in industrial insulation systems. When used in conjunction with weep holes positioned at the low points of the system, the embossed design creates a pathway for water to quickly flow between the jacketing and insulation to exit through the weep holes. As compared to typical stucco embossed and smooth metal jacketing, the pattern allows water to exit the system quickly and completely, and the Cross-Flo pattern allows water to effectively drain in any orientation (horizontal, vertical, etc.). This is not the case for corrugated jacketing, another metal jacketing option, which is only effective at aiding in water egress when installed vertically. When installed horizontally, water will instead pool in the cross-crimped jacketing patterning, trapping more water between the jacketing and insulation beneath it.

Sign up to read the full article and many more in the latest issue of Tanks & Terminals.

Read the article online at: https://www.tanksterminals.com/special-reports/08092025/new-tools-for-an-old-battle/