Why do industrial storage tanks fail earlier than expected?

Industrial storage tanks play an important role in many production processes. They are used to store chemicals, process water, food products, fuels, raw materials and other substances. They are generally expected to have a long and predictable service life.
In practice, however, that service life is not always as predictable as expected.
Over time, some tanks require increasing attention. Inspections reveal irregularities more frequently, minor repairs become recurring issues, and the condition of a tank may deteriorate faster than would be expected based on its age.
This raises an important question: why do some industrial storage tanks develop problems earlier than expected?
The answer can rarely be attributed to a single cause.

A storage tank can appear to be in good condition from the outside for years, while the material is gradually deteriorating internally.
This makes material degradation difficult to detect. Problems usually do not arise overnight, but develop over a longer period under the influence of the conditions in which a tank is operated.
Examples include moisture, temperature, the stored medium, contaminants and periods of downtime.
Individually, these factors do not necessarily lead to immediate problems. It is precisely their combined effect that can cause deterioration to progress faster than expected.

One of the most common causes of material degradation in industrial storage tanks is corrosion.
Corrosion occurs when a material reacts with its environment. The rate at which this process occurs can vary considerably depending on the specific conditions.
Moisture, oxygen, temperature, chemicals and contaminants can all influence the extent to which a tank wall is affected.
It is particularly important to note that corrosion does not always occur uniformly across the surface. In many areas, a tank wall may still have nearly its original thickness, while significant deterioration may already be present in one specific location.
As a result, the actual condition of a tank may be different from what might be expected at first glance.

An example of localized deterioration is pitting corrosion.

Pitting corrosion creates relatively small areas where the material is progressively attacked in depth, while the surrounding material may remain largely unaffected.

It is precisely this localized nature that makes pitting corrosion so insidious.

At the surface, the damage may appear limited, while the remaining wall thickness at one specific location may already have decreased significantly. As a result, a relatively small affected area can ultimately have a major impact on the integrity of a tank.

Conditions that may be associated with pitting corrosion include:

• water accumulating at the bottom of a tank;

• sediment and other deposits;

• stagnant zones;

• prolonged contact with aggressive substances;

• temperature fluctuations and condensation.

These conditions occur regularly in many industrial processes and can therefore easily become part of normal operating conditions.

When a storage tank shows signs of deterioration, attention often focuses first on the stored product.
This is understandable. The chemical properties of a medium can have a significant influence on the material.
However, the medium is only one part of the conditions to which a tank is exposed throughout its service life.
Factors such as temperature fluctuations, condensation, moisture exposure, cleaning cycles and periods of downtime can also affect the condition of the material.
In addition, conditions are not the same throughout a tank.
Around welds, connections, flanges, the tank bottom and other specific areas, conditions may differ from those on large, unobstructed surfaces. As a result, deterioration may develop more severely in certain locations.

An additional complication is that material degradation often progresses slowly.
Minor localized deterioration does not immediately have a noticeable impact on the production process. The tank continues to function, and there may be no visible signs of anything unusual on the outside.
Meanwhile, the material can continue to deteriorate.
Only when the deterioration reaches a certain threshold do the consequences become more apparent. For example, irregularities may be detected, the wall thickness may have decreased significantly in a localized area, or leakage may occur.
As a result, a problem that has developed over many years may ultimately be perceived as an unexpected failure.

Even tanks used for similar applications can exhibit very different degradation patterns.

This is because service life is not determined by a single factor.

Instead, it is influenced by the interaction between factors such as:

• the stored medium;

• moisture and condensation;

• temperature;

• contaminants and sediment;

• periods of downtime;

• cleaning cycles;

• local design details;

• mechanical and chemical loads;

• properties of the material used.

A change in one of these conditions can also affect other factors.

As a result, two tanks of the same age will not necessarily develop in the same way from a technical perspective.

When an industrial storage tank develops problems earlier than expected, it can sometimes appear to be a sudden technical failure.
In reality, however, a much longer process may have preceded it.
Corrosion, localized pitting, moisture, sediment, temperature fluctuations and other operating conditions can affect the material over many years without any immediately visible signs.
That is why the age of a storage tank alone does not provide a complete picture of its actual condition.
The more relevant question is which conditions cause material degradation and why this deterioration develops much faster in some areas than in others.
One specific form of corrosion illustrates this particularly well. Microorganisms can play a role in the localized deterioration of metals: MIC (Microbiologically Influenced Corrosion).
We will explore this in more detail in the next article.