Hidden Threats Beneath the Surface: Why Your Ammonia Tank’s Greatest Enemy May Be Its Own Insulation

In industrial facilities across the globe, CUI is insidious and costly because it often isn’t caught until the damage is done. Deep pitting and corrosion could compromise the pipe’s integrity, and if left unchecked, it could lead to system failures and safety risks. For ammonia storage systems, this hidden menace poses particularly severe consequences due to the toxic and volatile nature of the stored substance. Understanding modern detection methods and protective coatings is crucial for preventing catastrophic failures and maintaining operational safety.

Understanding Corrosion Under Insulation in Ammonia Systems

Corrosion Under Insulation (CUI) is a severe form of corrosion that affects metallic equipment such as piping systems, pressure vessels, and tanks, which are encapsulated with thermal insulation. This type of corrosion occurs when water or moisture infiltrates the insulation and makes contact with the underlying metal surface, leading to external corrosion beneath the insulation. In ammonia storage applications, it most often affects carbon steel and stainless steel systems that operate between -12°C (10°F) and 175°C (350°F).

The challenge with ammonia systems is particularly acute because CUI is difficult to find because the insulation covers the corrosion problem until it is too late. Removing insulation, inspecting, and then reinstating the insulation after inspection is an expensive process. CUI is responsible for up to 60% of corrosion related incidents and the direct damage done by CUI is estimated to be $276 billion per year as of 2005.

Modern Detection Methods for Ammonia Tank CUI

Today’s industrial professionals have access to sophisticated non-destructive testing (NDT) methods that can detect CUI without removing insulation. The challenge to find CUI is difficult and one single NDE technique cannot be used to identify it. This remains the case today as we combine NDE techniques to perform CUI assessments.

Advanced Detection Technologies

Corrosion Under Insulation can be detected using various non-destructive testing (NDT) methods such as Pulsed Eddy Current (PEC), real-time radiography (RTR), profile radiography, computed radiography, and digital detector arrays. Each method offers unique advantages:

• Pulsed Eddy Current (PEC): Pulsed Eddy Current (PEC) is an NDT technique that measures wall thickness loss by emitting an eddy current from an excitation coil towards the object. A time-varying magnetic field is reflected back to a receiver coil, with changes in the magnetic field indicating the presence of defects or flaws. PEC can inspect through insulation without removal and is effective for detecting general wall loss.
• Real-Time Radiography (RTR): Real-time radiography (RTR) produces imaging of a pipe’s outer diameter profile through the insulation. Changes in the profile may indicate areas of corrosion. This technique can pinpoint areas of concern for further analysis. RTR is a safer and faster CUI testing method than traditional radiography methods.
• Neutron Backscatter: Neutron backscatter operates by emitting neutrons into the equipment being tested. The higher energy neutrons are moderated by collision with hydrogen atoms in trapped moisture within the insulation/fireproofing. Wet insulation will produce a higher count per unit of time than dry insulation. So, while this technique does not indicate the presence of active CUI, it does indicate the presence of moisture, and therefore is a good indicator that CUI may be present.

Technicians quantitatively determine corrosion severity by utilizing a combination real-time radiography (RTR), neutron backscatter, phased array (PAUT) and conventional ultrasonic (UT) inspection techniques. This multi-technique approach provides comprehensive assessment capabilities for ammonia storage systems.

Protective Coatings: The First Line of Defense

A primary way to combat the hidden threat of CUI is to apply protective coatings on the surfaces of assets that will be covered with insulation. The coatings create a barrier between the metal substrate below and the chlorides, moisture and other exposures on the surface. They are an essential part of an insulation system, serving to mitigate the corrosion process for as long as possible so assets can operate longer before maintenance is needed.

Advanced Coating Technologies

Modern protective coatings have evolved significantly beyond traditional paint systems. The new generation of ceramic designed coatings provide insulation without being affected by moisture and air flow. They can contain the heat at the surface level and therefore resist heat loss from the surface and holding more heat on the interior of the pipe or tank. The closed film can help prevent moisture and air to enter the coating film and therefore provide for a dramatic decrease in corrosion under insulation which is a major cause of corrosion problems in the field.

For ammonia-specific applications, specialized products like VaporGuard™ Butyl Tape provides excellent cold temperature flexibility at -20º F and is designed to seal vapor stops, expansion joints, and terminations on ammonia systems, preventing moisture from infiltrating the insulation system. These specialized solutions address the unique challenges of ammonia storage environments.

Thermacon’s Expertise in Ammonia Tank Protection

Companies like Thermacon understand the critical importance of proper ammonia tank insulation systems. For over forty years, Thermacon has designed, engineered, manufactured and installed storage tank insulation products throughout the world. Thermacon provides a safe solution to insulate and maintain the operating temperature required for ammonia, propane and butane tank applications. For ammonia and butane tanks, Thermacon offers cold storage systems that allow for cooling as low as minus 50 degrees. This operating temperature is maintained for proper system function.

Thermacon is one the most experienced and professional tank insulation companies and we have been a leading provider of tank insulation systems since 1971. We service companies of every size all over the United States as well as internationally. Their comprehensive approach includes isocyanurate foam lamination to outer aluminum sheathing panels in a variety of thicknesses. Insulation panels are installed in multiple layers and the result is a design with a double vapor barrier system. The external banding system allows them to meet the most demanding wind load requirements.

Prevention Strategies and Best Practices

Effective CUI prevention requires a multi-layered approach. Material Selection: Using insulation materials with low water retention and high thermal efficiency can reduce the risk of Corrosion Under Insulation. Protective Coatings: Applying high-quality coatings to the metal surface before insulating can provide an additional barrier against moisture. Design Improvements: Ensuring proper design and installation of insulated systems to minimize water ingress and facilitate drainage.

Regular inspection programs are essential. It has been found that on-going and regular inspection surveys using a combination of inspection methods can reduce the risk of CUI going unnoticed and can minimise the potential for catastrophic or unplanned outages and failures. Create a CUI inspection plan based on risk zones. Address any jacket damage, reseal problem areas, and regularly test coating integrity.

The Future of Ammonia Tank Protection

As industrial facilities continue to prioritize safety and operational efficiency, the combination of advanced detection methods and protective coatings represents the most effective approach to CUI prevention. The common lifespan of traditional organic coatings used in CUI service ranges from only 5 to 13 years before facilities must engage in costly recoating efforts. However, that time frame is expected to extend significantly as advanced coating technologies come to market. Such solutions are designed to better address a variety of common coating failure mechanisms, thereby enhancing performance and extending the life of coated assets.

For ammonia storage systems, where safety is paramount and downtime is costly, investing in modern CUI prevention technologies is not just prudent—it’s essential. The hidden enemy beneath your insulation doesn’t have to remain invisible when you have the right detection tools and protective strategies in place.