Sodium Hypochlorite with Alloy 20

sandorfla · Dec 22, 2008

I checked the Compass handbook & found that Carpenter 20Cb-3 is rated "A to 16% to 80 F". The application is at a drinking water treatment facility where 12.5% sodium hypochlorite is dosed into drinking water at ambient temperature. We used some 1/2" threaded fittings designated "ASP USA B473 IM A-20 H7G SP114 OA3436C" which I thought would be compatible. The fittings were on an injector system and they failed in 4 weeks. Can anyone offer an explanation for this? Thanks.

EdStainless · Dec 22, 2008

The ref at the Outokumpu web site says at 5% no chance with any SS grade. I can't imagine handling 12% hypo with alloys below 6% Mo. You might even need to consider a "G" type Ni based alloy for this service.

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Plymouth Tube

metengr · Dec 22, 2008

Yes. The concentration of hypochlorite locally exceeded 15% in the threads (natural crevices), which is the useability limit for Alloy 20 at 75 deg F.

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Sodium Hypochlorite with Alloy 20

sandorfla

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metengr

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