Best material for alkaline & acidic services?

[kkp3456]

We have a neutralisation basin which supplies fresh caustic (20% conc.) to gas scrubber & the return line comes to basin. Now within one year the return pipeline failed 3 times at different locations near to basin & the failure was not on the joints but in pipe itself. Failure is in form of pinhole in pipeline. The process study shows the pH value for the return service is 4 (which is acidic). The whole pipeline is A53 GrB designed for 20 % NaOH @ 0 degC.

Kindly suggest any solution?

 

[EdStainless]

sounds like a job for a non-metallic.
whoever selected steel in the first place should be paying for all of this. It had zero chance of survival.

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Plymouth Tube

 

[patprimmer]

Could HDPE do it. It is good to acid and alkali so long as there are not also strong oxidizing agents present. Even then it seems to work although it may be with reduced life.

Regards
Pat
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[Ron]

Agree with Ed....composite or plastic (many formulations available...) would be correct.

 

[kkp3456]

There is one correction for the design temp. It should be 70 degC.

What bout FRP?

 

[patprimmer]

Should be OK but it depends on the resin. Strong hot caustic gets into polyesters and eats them away. I don't about caustic and epoxy. Strong hot caustic can also get into some glass.

I still say HDPE or PP, depending on physical load and support.

Regards
Pat
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[EdStainless]

I was thinking fibergalss with selected resin inner layer. This would allow you to select the liner resin separate from the strength member.

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Plymouth Tube