Material and fuel

The selection of suitable materials should ensure that the condensate created will not cause the boiler to suffer corrosion damage. During combustion, constituents of the fuel (fuel oil or natural gas) and of the combustion air create compounds which shift the pH value (degrees of alkalinity or acidity) of the condensate up to acid levels

Carbon dioxide can form from the CO2 created during combustion, and the nitrogen N2 contained within the air reacts to become nitric acid. Using standard fuel oil for combustion can create particularly aggressive condensate, as the sulphur content of fuel oil creates sulphurous and sulphuric acid. Therefore, all heat exchanger surfaces which come into contact with condensate must be made from materials which remain unaffected by the chemical attack of the condensate constituents.

For some years now, stainless steel has proved to be the ideal material for this purpose. For fuel oil and natural gas, different stainless-steel alloys are available (alloying elements are, amongst others, chromium, nickel, molybdenum, titanium), which have been matched to the characteristics of condensate. This enables these materials to withstand the corrosive attack of condensate without further treatment.