New Modeling Approach for Predicting Corrosion Under Insulation

The downside to regular physical inspections is that there are millions of miles of oil, gas, and chemical piping in the U.S. alone, much of which needs insulation.

Commercial piping is all around us, and that means the threat of pipe corrosion and ensuing problems are also pervasive. Fortunately, there is insulation to protect pipes from some damage, but that also comes with a risk. Sometimes, insulation on the pipes themselves creates an environment that encourages corrosion.

Building information modeling (BIM) and BIM software can help predict when those conditions are more likely to occur, as well as the risk posed to the integrity of piping. Here is how.

Why Predicting Corrosion Matters

Several industries utilize insulation to protect piping. In addition to fireproofing, piping insulation is a primary weapon oil, gas, food, and chemical corporations use to ward off corrosion from moisture, exposure to the elements, and other environmental risks.

If corrosion of a pipe starts, the walls of the pipe weaken. Several environmental factors increase that risk. For example, a gas pipeline that goes through saltwater is vulnerable to rapid corrosion from salt as well as oxidation.

Insulation protects piping, but unfortunately, it can also create an environment conducive to creating or aiding pipe corrosion. Left untreated, corrosion can:

Rupture piping
Create soft spots in the piping
Contaminate whatever is in the piping
Spread corrosion along the piping

While no breach of piping is good, some breaches are more impactful. A ruptured oil or gas line can pose an explosion and fire hazard and destroy entire ecosystems. If the rupture is to piping transferring food, food poisoning could get into the public food supply. Corrosion on sewage pipes can cause contamination of water tables.

Corrosion Under Insulation

Corrosion under insulation (CUI) can occur if the environment under insulation is conducive to creating or allowing corrosion to occur. The situation most associated with this risk is when wetness gets under the insulation and oxidation occurs.

Because of the nature of the insulation, the moisture does not easily dry, perpetuating oxidation. The corrosion speeds up if a corrosive chemical like salt is present.

To address the corrosion risk, the insulation must be stripped away, the piping dried, and, if necessary, repaired or replaced. The piping will then need new insulation.

Because of the nature of CUI, it is challenging to detect, pinpoint and address environments conducive to pipe corrosion. The insulation hides any evidence of moisture, particularly if the moisture is under the insulation. Hiding corrosion leads to its spread.

Unfortunately, there are only two ways to detect CUI.

Regular, Physical Inspections

The downside to regular physical inspections is that there are millions of miles of oil, gas, and chemical piping in the U.S. alone, much of which needs insulation. When you add to that other forms of piping, the miles of insulation needing inspection jump dramatically.

Even with the best intentions, it is physically impossible to look at every square inch of insulation in the country and determine if it is compromised, harboring conditions friendly to corrosion, or helping corrosion spread.

In addition, insulation that harbors conditions conducive to corrosion is not always evident. In many cases, corrosion results from moisture seeping under the insulation and settling. The moisture and corrosion are invisible unless the insulation bursts or gets cut. Given the sheer volume of pipe insulation, physically cutting it all is impossible and prohibitively expensive.

Predictive Analysis

Fortunately, the ingredients needed for the environment under insulation that would encourage corrosion are well documented. Additionally, the type of external environmental factors that must be present is well known. A pipe in a sub-tropical location and exposed to salt and other chemicals is more prone to corrode than one buried in the desert, for example.

While it is impossible to physically inspect every inch of piping for corrosion, projections that consider several factors are possible. Those include, but are not limited to:

Exposure to water
Relative humidity of the location of the insulation
Temperature and temperature ranges
Characteristics of the physical location of piping (buried, exposed, enclosed, etc.)
Exposure to corrosives such as salt

When all of these factors get considered and what we know about corrosives and how they interact with environmental factors is added, projective analysis is possible. Additionally, areas more susceptible to corrosive influence can be flagged, and those areas are inspected more closely than areas with only one or two risk factors for corrosion.

The predictive approach lets inspectors prioritize inspection processes, locations, and how closely they need to inspect to determine if corrosion is under insulation (whether to cut the insulation). The streamlined approach saves time and money and narrows inspection focus to high-risk areas rather than wasting time on areas that do not need much attention.

The Role of BIM

That explanation is needed to understand how BIM can help insulation inspection processes. By adding environmental and location data, plus any other influencing factors, into a BIM system, a “map” of pipelines and insulation locations can be formed. Additionally, markers for areas that are higher risk can be affixed to the location of areas needing inspection.

Those areas can be color-coded based on the severity of the risk. Using this model, insulation on a pipe next to the ocean and exposed to weather or occasionally submerged by water will be coded red. In contrast, insulation inside a factory in a dry but humid location might be coded as orange. Insulation at little risk of corrosion would be colored blue or green.

In this scenario, red and orange take priority over green or blue-coded areas.

Using BIM to map out pipeline insulation and possible corrosion points helps inspectors narrow where they want to inspect. Furthermore, it helps inspectors determine if they are only looking for signs of corrosion or if they need to look deeper, underneath the insulation for corrosion, or the environment that can promote corrosion.

Final Thoughts

BIM streamlines the inspection of piping insulation. Identifying and flagging high-risk areas narrows the physical inspection work needed. Inspectors can use the analysis to cover more ground while increasing the likelihood of finding corrosion if it exists. BIM analysis saves time, money, and effort while focusing on areas that most need attention.

Source: Microsol, www.microsolresources.com.

Editor’s note: This article, by Jack Barrett, Microsol Resources, first appeared on MaterialsPerformance.com 5/1/2023. Reprinted with permission.

More CUI Resources

Corrosion Under Insulation Course and Micro-Credential

CUI Community of Interest

CorrCompilation: Corrosion Under Insulation (E-book)