Power Management

Prepare for the Winter Corrosion Speedup

How does the condensation process affect electrical and electronic equipment during winter?

On one hand, automation and control facilities with critical functions and processes are always exposed to changing environments in both thermal and environmental terms. On the other hand, when winter arrives, there can be an acceleration of the phenomenon of corrosion.

With winters approach enters the two most important variables that affect corrosion:

  • Low or very low temperatures (<5 ° C)
  • High relative humidity (> 70%)

No matter the time of year, surface condensation will occur in areas if – and when – the temperature drops below the dew point. Add that to industrial environments, and you get corrosion rates that rise nearly to the maximum, as indicated in Table 1.

The (uniform) corrosion rate of steel in different atmospheres

Table 1: The (uniform) corrosion rate of steel in different atmospheres. Source: American Galvanizers Association https://www.galvanizeit.org/corrosion/corrosion-process/corrosion-rate

Now, just why does the dew point exist at all? What sets the onset of condensation?

Technically, condensation is due to the combination of two physical quantities of the air: the ambient temperature (Ta) and the relative humidity (RH). Condensation occurs when the water vapor in the air contacts a surface below the dew point temperature (Tr).

This happens everywhere, but particularly on the ceilings of electrical cabinets or metal surfaces such as connectors, busbars, connection terminals and so on, as shown in image 1. These components do not dissipate heat well during times of high humidity. Depending on the values of Ta and RH, these surfaces will end up wet as the water in the air ends up on them.

Condensation

Image 1: Condensation

Reflection: we may not identify the problem of condensation because it is not visible (it can occur at night and disappear).

It is typical of many installations, whether indoor or outdoor, to not operate at night. If they do stop and there is a temperature drop with high concentration of water vapor, we will find condensation – especially in metal parts and lower parts of the cabinets. If so, there will be direct risk of water contacting the electronic equipment.

It can be an invisible phenomenon, as condensation can appear and disappear. Those in charge of maintenance may not be aware that it is going on, but condensation accelerates the process of corrosion as can be seen in Image 2.

Corrosion

Although the basic cabinet is protected by selecting a good material (such as polyester, corrosion protected or stainless steel), the air inside may not be protected.

Consequently, it is very important to know the process or cycle of temperature and humidity that can occur both outdoors and in the design process of electrical panels.

The most effective solution is to effectively and quickly reduce the value of relative humidity. This can be done with a control element (Hygrostat / Hygrotherm and / or thermostat) combined with a heating resistor. This can ensure the RH is controlled below 60%.

An important recommendation is to properly seal the cabinet to minimize moisture entry (for example by adding cable entry plates to the bottom of the cabinets).

Different heating architectures can be proposed depending on the kind of installation or customer needs. For more information on solutions, you can download the guide: How to protect electrical equipment from condensation.

But also the use of new diagnostic tools, such us ClimaSys DT, will allow you to study the evolution of the humidity variable on the time axis. You can then spot problem areas and times.

Software can help determine the correct dimensioning of resistances. For instance, ProClima thermal software (available for a free download) offers reliable thermal calculation.

For more info about the complete ClimaSys thermal management family, please visit this page.


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