a bad experience descaling a brazed heat exchanger

[pardal]

Dear al HVAC people.

Last week I had a bad and sad experience.
I do a descaling process on a well recognized brand heat exchanger.
I use a descaling fuid supplyed by other well reputation brand.
After it I got the heat exchanger pinch or holed inside.
It was a 7.5 TR f22 condensator.
What could be happen, why it broke???
I do not know if the water at the tower is well treated.
Could a foul or scale damage the stainless steel??


Pardal

 

[imok2]

Dear sir, When ever you use an acid descaler you have to be careful that you don't increase the acidity content too much because the acid will not only attack the calcium deposits but it will always attack any exposed metal that doesn't have scale on it, this is not an unusual result In addition you should keep the brew in constant motion in order the maintain a constant concentration around all parts.

 

[TFurst]

I don't know what brand descaler you were using but if it is like most it contains hydrochloric acid. If this is the case then the cleaning solution is most likely what caused the heat exchanger to fail. For stainless steel heat exchangers never use anything other than sulfamic or phosphoric acid. I ahve succesfully cleaned numerous stainless steel heat exchangers with both of these types of acid with no problems whatsoever.

 

[ClydeMule]

Oxalic acid is also recommended by most BPHE manufacturers.

Clydemule

 

[kenvlach]

Possibly, corrosion existed under the scale, and descaling merely exposed it.
A name brand descaler likely contains inhibitors to protect bare metal.
Only when making your own uninhibited acid descaler is it necessary to use ‘safer’ acids such as citric, oxalic or sulfamic acids.

I have used Rodine inhibitors from Henkel in hydrochloric acid to descale carbon and stainless steels w/o attack of the metal. Of course, with a closed system with lots of flanges, one should avoid HCl since it is impossible to totally rinse crevices.

Check the corrosiveness of the water.
Please describe the type of corrosion.
Did the failure occur at a weld or at a stress concentration?