Chloride content guidelines in the water of a 2100 psi pressure boiler

[wayuu1981]

Hello,

I'm trying to look for limits and guidelines about chloride content in the water for high pressure coal fired boiler (meassured in make-up water and boiler drum).

I have foung some information but it's so dispersive, I've seen limits from 12 PPB to 50 PPM (more than 4000 times difference).

The boiler has been in operation for more than 30 years, and information from original manufacturer's manual is not clear (manual are written in two languages and in each language stablish a different limit).

During my research I've seen many articles refering to "EPRI interim consensus guidelines" but I don't have acces to that document where they stablish limits for continuous normal operation (N), potential corrosion that should be correctect within a week (1), contamination that should be corrected within 24 h (2), rapid corrosion with suggested shut down (3), and inmediate shut down (4).

Does anyone have any reference chloride content limits for a 2100 psi boiler? I'll really appreciate your help.

Javier Guevara E.
Projects, Mechanical Engineer

 

[kclim]

It will depend on the chemistry regime you choose but generally for make-up, chloride limits tend to be around the single digit ppb mark. Drum measurements for units with reheat do vary as you have found, generally from 10-100 ppb.

EPRI suggests conductivities rather than chloride levels are a better indicator of boiler impurities.

 

[wayuu1981]

The boiler protection is AVT with filming amine, and the boiler is natural circulation with drum and reheat.

Condenser is cooled with seawater, so we constantly measure chloride levels in condensate and boiler water with ion selective electrode method and we get values around <0.2 ppm in condensate and < 1 ppm in boiler water.

The situation is that recently we have had many tube failures due to hydrogen embrittlement (window type explosion), but according to manufacturer recommendations, unit can continuously operate given than chloride levels remain below 5 PPM (This is the limit parameter that I want to check).

Recently we found that chloride levels measured by ion selective electrode method may be altered by filming amine (anodamine) and supposedly the only reliable way to measure it with no interference is chromatography, so we did additional tests and chloride values were near this limit (4.5 ppm).

I would like to know reference values of critical high chloride content in condenser and boiler water, when in becomes dangerous for boiler tubes and turbine.

Thanks again for your help



Javier Guevara E.
Projects, Mechanical Engineer

 

[EdStainless]

You should be measuring Cl (and Na) in ppb range. I would agree with the previous post.
What is your measured conductivity?
Danger to the turbine will depend on how much carry over you get.
Try looking at these:

http://www.epri.com/search/Pages/re...ts on Power Plant Steam-Cycle Water Chemistry

http://www.iapws.org/techguide.html

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P.E. Metallurgy, Plymouth Tube