O2 pitting locations 1

[mjpetrag]

"The most severe damage occurs at the economizer inlet and, when present, at the tube weld seams. Where economizers are installed, effective deaerating heater operation is absolutely essential. The application of a fast-acting oxygen scavenger, such as catalyzed sodium sulfite, also helps protect this vital part of the boiler."

This is from GE water.

Why is oxygen pitting most prevalent in the economizer inlet and not the rest of the economizer. I realize that it boils out of solution at this point, but wouldn't the oxygen still eat away at the tops of the tubes throughout?

-Mike

 

[MJCronin]

Well,.... I disagree..

I have always found oxygen induced pitting in the DA storage tank, on the tank heads, below the water line.

This pitting is especially prevalent in systems that are shut down frequently and with ancient, partially functioning Deaerators.

Ohhhh.....There is also usually a brand-new, 23 year old boiler plant operator standing in the corner......holding a schematic drawing upside down.

-MJC

 

[adamuk]

Wherever conditions are right for O2 pitting it'll occur but you need to have oxygen.. Once the oxygen is used up the pitting won't occur anymore. So the heat from the flue gas in the economiser will just heat it up enough to initiate pitting. If you had lots and lots of oxygen then it'd occur more extensively than the inlet.

Simples!

Adam Potter MEng CEng MIMechE

http://www.ax-ea.co.uk

 

[mjpetrag]

Ahhhh...thank you adamuk. That makes complete sense.

-Mike