For an organic waste pulp pipes a t

[Rachbay]

For an organic waste pulp pipes a temperature of 65°C and a chloride concentration around 1100 ppm is alloy 20 a good choice? If there is any reference showing the chloride limits according to temperature? My first choice is the duplex 2205 and according to the supplier the Alloy 20 can be considered especially because of the cost difference between duplex 2205 and alloy 20.

 

[Dhurjati Sen]

https://www.eng-tips.com/viewthread.cfm?qid=12180

You can have a look at the above thread.

DHURJATI SEN

 

[Rachbay]

@ Dhurjati Sen, thank you interesting thread.
What about the alloy 20? do you have any reference showing his chloride limits according to temperature?

 

[SJones]

@Rachbay. Have a look at ISO 15156-3, you will see temperature and chloride limits in the presence of H2S; not unknown in organic waste systems. The standard is aimed at SSC/SCC but it's a reasonable first pass.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

alloy 20 is a common choice in H2SO4, but its Cl resistance is not so great.
I think what he means by cost difference is that he would rather sell you 20 because it so much more expensive. The alloys have similar Cr and Mo content, but 2205 5% Ni and 20 is 33% Ni. That does not come cheep.
And consider that because of its high strength you can use lighter walls in 2205.
What is the pH of hte service? That is the key to me.

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P.E. Metallurgy, consulting work welcomed

 

[Rachbay]

@ EdStainless: we expect 65°C, pH between 4 to 7 and 1100 mg/L of chloride.

 

[EdStainless]

I don't think that a superduplex or superaustenitic can handle 150F, pH=4, >1000ppm Cl.
You are looking at Ni alloys if you really have this pH.

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

 

[Rachbay]

@EdStainless: according to the provided information, the pH varies over a fairly wide range (4 to 7), I am not sure if it will be really 4 or less acid. Do you have any feed back about pH from organic waste treatment plants (organic waste pulp)? can we really expect a pH of 4.

 

[EdStainless]

That info you are going to need to get from your process people. An SASS or SDSS would work down to a pH of about 6 or so. But be careful about crevices and welds, the design will need to be good at preventing localized corrosion.

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

 

[Rachbay]

So even with pH 6 the duplex 2205 will not handle it?