Corrosion Issues in Gas Boilers 

With high operating temperatures and water treatment during operation, corrosion is prevented from occurring. During shut down for repairs or on standby, the system starts to cool down and high relative humidity in the air starts to become a problem, creating corrosion. 

Water vapour circuit 

Relative humidity must be kept at a low 30%. The sizing of units depend on variations in absolute humidity with respect to the exterior temperature difference.  It works as an open system(all exterior air). Pumping air to the areas most sensitive to humidity. Air conditions must be measured in the outlets. 

Gas circuit

Corrosion is the result of the presence of sulphuric acid. This is less aggressive when its concentration increases: and the concentration increases when the environment is dehumidified. According to the graphs, the relative humidity  required is 5%. We have however learned from experience that 20% is enough.

The Results

When the dry air method is used, excellent results are achieved:

• It is easy to check whether there are corrosion risks, by simply evaluating the humidity in the air outlets. 

• It enables access to the parts conserved, while they are being protected. 

• Less energy is required than in the heating method, and no dangerous and expensive chemical compounds are required as for humid conservation. 

All the above mentioned points of a technical and economic nature mean the dry air conservation method is preferable to all other possible methods.