Sulfuric Acid 3

[MKA4281]

I am facing a big problem in our Alloy 20 piping in the sulfuric acid system ( 98%).
This is a new system commissioned few months ago , I am experiencing many leaks due to erosion . The max velocity as per design is 0.2 mt/sec. so what do you think is the problem

 

[mfgenggear]

Hire a failure analysis engineer.

 

[IRstuff]

Where are these leaks occurring on the piping? Pictures?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[MJCronin]

More details .... Pipe size, schedule, temperature pressure and Country of manufacture ?

What is the flowrate and diameter at the point of erosion ?

Please post Pictures of the point of erosion ? is erosion occuring just after a control valve ?

Was the piping hydrotested ?...... Was your piping positively identified ?

Substitutions of defective or inferior materials is a way of life in the third world ... especially for Alloy 20

Expensive, Alloy 20 is pretty good stuff .... if indeed that is what you have... Convince us

Alloy 20 (UNS N08020)is a chromium-iron-nickel-based, austenitic alloy that comes with excellent corrosion resistance in chemical environments. It contains sulfuric acid and many aggressive media well. The alloy is stabilized with niobium that helps it to resist intergranular corrosion. Alloy 20 can help provide potential cost savings compared to the higher nickel-based alloys as it outperforms standard stainless steel.

https://en.wikipedia.org/wiki/Alloy_20

You are not using that cheap-ass Schedule 5S piping from China, are you ?

Tell us more

MJCronin
Sr. Process Engineer

 

[dik]

Alloy 20 or Carpenter 20? The situation with that alloy has been a bit fraught. Nevertheless it is specialized for sulphuric acid, so something has gone wrong.

Start by picking up a free copy of the Nickel Development Institute's publication on Sulphuric Acid.
Then follow mfgenggear's advice.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

20Cb3 being the common name for the stabilized version of the alloy, If you are welding anyplace then you need this version.
Was everything clean and pickled to start with?
Had it been hydro tested with clean water and then quickly dried out?
There are a lot of ways to screw this up.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

there are so many failure possibilities, that it would be prudent for the op to hire an experienced guy. starting with the raw material fabrication of it, to the final stages of manufacturing the pipe, then the assembly. welding procedures, proper non destructive and destructive testing through out the entire manufacturing process as well as proper procedures. this is not a guessing game. an entire audit is required, of all procedures.

 

[Stallionbreed]

Alloy 20 failing in 3 months with 98% sulfuric acid? I'm not saying you are lying but that is very hard to believe. Is it a different material?

 

[MJCronin]

Strongly agree with Stallionbreed ... Do we have positive material Identification here ?

... or was "Alloy 20" hand written with Sharpe on the side of the piece ?

... No pictures, no more details, no more information ... just another Third World Scam ... Why do we bother ?

It has been two weeks, MKA4281 has given up on this thread and has gone on to harass others on eng-tips ....

MJCronin
Sr. Process Engineer