Flue Gas Stack and Breeching Lining
AAS rebuilt and lined a flue gas stack and breeching that had thinned where acidic condensate attacked the steel below the dew point.
What was failing
The flue gas stack and the breeching feeding it had corroded where flue gas cooled below its dew point and acidic condensate formed on the wall. The attack concentrated along the seams and at the cold spots, and the steel there had thinned to the point that pinholes were starting to open. Once a stack or breeching starts to perforate at the cold spots, the gas finds the path of least resistance, the holes grow, and the unit can no longer carry the flue gas safely. Patching over the thin metal does nothing if the condensate keeps reaching bare steel, so the wall had to be both rebuilt and protected from the acid that caused the loss in the first place.
How AAS approaches it
We treated this as one continuous repair, not a series of patches, because the condensate does not respect a patch edge. First we got the affected internals back to clean, sound metal so the composite and the coating had something to grip. Where the plate and the seams had thinned, we rebuilt the lost section with composite so the wall carried its load again. Then we put down a coating chosen for the operating temperature and for the acidic condensate it would sit in, taking it across the rebuilt steel and the surrounding sound steel as one film. The rebuilt metal carries the structure and the film keeps the condensate off the wall, so the acid no longer reaches the steel at the cold spots where it had been eating through.
Assess the loss
We surveyed the stack and breeching internals to map where the steel had thinned along the seams and at the cold spots below the dew point.
Blast to clean metal
We abrasive blasted the affected internals back to clean, sound steel with the profile the rebuild and coating needed.
Rebuild the wall
We rebuilt the thinned plate and seams with a metal repair composite from the 1000 Series so the wall regained its section.
Line for temperature and acid
We applied a high temperature coating rated for the operating temperature and the acidic condensate across the rebuilt and sound steel as one continuous film.
Return to service
We confirmed the rebuild and the coating cured to spec before the breeching and stack were put back into flue gas service.
The result
From the job
Repair and protection work of this kind, performed by AAS crews across Louisiana.
Capabilities used here
Where this work happens
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