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Posted by Vern on January 07, 2002 at 22:11:41:
In Reply to: Sodium Sulfite depletion posted by Gern Blanston on January 07, 2002 at 09:43:18:
: I have a small 150# Bryan water-tube boiler that has developed localized pitting in several tubes resulting in leaks. The boiler was regularly treated by a professional chemical consultant. He says that by leaving the water in the boiler overnight & weekends, the oxygen scavenging sulfite is depleted and loses its effectiveness. The boiler typically operated 40 hrs per week.
: The boiler has been replaced. Does sodium sulfite evaporate or leak out or otherwise disappear overnight? Is there a way that the operators can maintain the required levels of sodium sulfite in the boiler? Most of the condensate is returned in this system.
: Thanks.
I believe oxygen pitting to be more common in boilers that are shutdown
overnight and weekends than in boilers that are left in operation. Are you
certain the localized pitting is caused by O2 corrosioon and not something else?
If it is O2 corrosion, you should start running sulfite levels about 50-100
ppm to compensate for any oxygen introduced into the water on intermittent shutdowns.
Also check your condensate for oxygen, this is a common way for it to get back to
the boiler. You may have to use an oxygen scavenger in your condensate system.
Check with your chemical vendor, he should be able to test for it. Email me if you have
further questions.