SA 179 in a 21% CaCl2 brine solution 3

[mssweene]

Typically steel in a brine solution is not a good mixture, but I am looking at a chiller that was installed for an ice rink and they used SA179 for the tubes in the chiller and a 21%CaCl2 solution. The refrigerant is R-717(ammonia). Is this as obvious of a mistake as I think it is?
Thanks

 

[EdStainless]

If it is a closed system maybe not.
The oxygen will deplete rapidly and then corrosion will be very slow.
Being cold slows it down also.
How old is it?


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P.E. Metallurgy, consulting work welcomed

 

[mssweene]

5 years. Plus they have automatic makeup which would be adding more oxygen. There were several tubes that exhibited pin holes and there was corrosion throughout the pipes. Regardless this was a long term occurrence and not something sudden, which for my current scope is all I need. I assume you are correct. If this is typical there would be much better control on the oxygen within the system. Thanks for your help

 

[MJCronin]

EdStainless, what would be the best material choice to resist corrosion in this application ?

MJCronin
Sr. Process Engineer

 

[EdStainless]

I would consider a ferritic stainless, maybe even one of the 13% Cr grades would be enough.
They could also install a system to de-gas the incoming makeup water.
Not only does the water bring in oxygen, but CO3 also which lowers the pH.
And both are bad over the long term.
Do they add any inhibitors? There are many made for this kind of service.
With the right chemicals carbon steel may be a good option.
But then treatment becomes critical.
And you can't go back and do that in a rusty system, you need bare metal.

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P.E. Metallurgy, consulting work welcomed

 

[Guest102023]

5 years is not very long term.

If there are one or two pinhole leakers I expect there are many other tubes with well progressed pitting.

I have to think that industry standard equipment and materials of construction were used, meaning this was the result of a process control problem.

Ammonia is a hazardous chemical, so don’t dice with it. Maintenance workers have died in ice rinks.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"