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in recent years there has been a growing diffusion of stainless steel flue pipes. but the use of this material is becoming more and more frequent in plant design for the evacuation of fumes. why? for its excellent specific characteristics. in fact, the aisi 316l austenitic stainless steel:
is resistant to the corrosive effects of acid condensation
offers inadequate resistance to flow of the fumes
reaches (and exceeds) in a short time the “dew point” that is the value of temperature which gives rise to the phenomenon of condensation
thanks to their linear form, the flues can:
easily be insulated
maintain an adequate temperature of the inner insides.
the effects of corrosion and residual heat.
what are the effects due to the heat and corrosion?
heat effects: the temperature value is extremely variable in relation to the type of heat generator used. in fact, the interval:
for wall-mounted condensing boilers is about 50 °c
for the fireplaces and wood stoves is about 300 °c
the use of stainless steel prevents deterioration due to the effects of heat and all of thermo-mechanical stresses.
corrosion effects: the nitric and sulfuric acid presence (together with the presence of chlorine or other corrosive substances in the air combustion) aggravates the aggressive action, causing serious damages of the insides that comes in contact with the fumes. an example? the acids (with high concentrations of chlorine) used in environments such as industrial laundries, dry cleaners and hairdressers if dissolved in air are highly corrosive. therefore, the use of aisi 316 stainless steel makes the flue suitable for use with various types of fuel and various weather conditions.
the gas and condensation resistance of stainless steel.
the gas and condensation impermeability is one of the basic requirements, especially for security. in fact, the fumes have a high toxicity due mainly by the presence of sulfur and carbon oxides. the increasing diffusion of installations with exhaust of forced draft fumes makes more frequent cases of chimneys running in positive pressure. finally, the use of external junction cable ties ensures the stability of the connections by the mechanical character of stresses.
