corrosion reason

[wwtp2014]

Dear Sirs

We are facing many corrosion in our Stainless steel network pipe and PHE. we are dairy factory, our water from RO. Kindly i am asking the possible reasons for that and what shall we do to stop it.


Thanks

 

[cloa]

RO- reverse osmosis? PHE- Plate Heat Exchanger made from what? Put more details of the corrosion to increase chances of good answer.

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[wwtp2014]

Stainless steel 316 and 304
the problem that we are facing always there is leak in the pipe and PHE

 

[wwtp2014]

what is suitable water characteristics for Stainless steel 316 and 304 to avoid corrosion

 

[EdStainless]

What are you using as cleaning chemicals?
Are the leaks at welds? Are they usually in the bottoms of tubes?
Does this plant run at full capacity 24 hrs/day?

Many food product plants run with all 316 tubing for 40 years without any leaks.
It requires high quality tubing (not just ASTM), proper installation and commissioning, and proper operations and maintenance.

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P.E. Metallurgy, Plymouth Tube

 

[wwtp2014]

What are you using as cleaning chemicals? Nitric acid 68% and NaOH 40-45%
Are the leaks at welds? Are they usually in the bottoms of tubes? the leaks at welds and at the pipe itself and the leaks everywhere bottom, top and sides
Does this plant run at full capacity 24 hrs/day? Yes

What about water specification and what is the suitable Total Hardness for Stainless steel 316 and 304

 

[EdStainless]

There are only a few things that will attack 316.
The chief among them in chlorides. What is the chloride (as in salts, not chlorine) content of your water?
What temperatures do you run?
Once pitting and crevice corrosion have started there is no stopping them. You will need to replace the system.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

You might want to review the attached publication regarding diary piping design and installation. It sounds to me like original problems with welding issues and handling of the pipe itself during installation.

http://www.staalcentrum.dk/files/pdf/dokumenter/00152.pdf

 

[NBrink]

Other than the water question Ed asked above, I would note that depending on the source, NaOH can easily be contaminated with a significant amount of chlorides.

Something to check.

 

[wwtp2014]

Please What are the most important water parameters to monitor and its limits ?

 

[EdStainless]

pH and Cl are the most critical.
But if the tubing was not well shielded when welded, and thoroughly cleaned (nitric acid passivated) before being put into service then you will have problems for sure.

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P.E. Metallurgy, Plymouth Tube