RE: MIC on Potable Water Piping.

From: <SARE>
Date: Thu May 31 2001 - 03:00:00 EDT

our spec calls for a max of 50 ppm chloride for ss306L/316L piping. this is the same requirement we used to spec out our insulation/coating - max of 50 ppm leachable chloride.

our demin water is 304L and generally applies as well on process water. yet no mic. the only other type of failure we experienced with our 304L is the SCC on our ethylene oxide system since a big amoutn of edc (ethlyelen di-cholirde) was injected. Lab analysis od deposit indicated an amount of over 1000 ppm.

a new potable line will be installed parallel to existing one. more leaks was observed in the past few weeks (all at or near the weld joint).

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com] Sent: 30 May, 2001 7:35 PM
To: ?
Subject: RE: [PipingDesign] MIC on Potable Water Piping.

>To quote nalco " the most likely cause
>for this perforation is microbiologically influenced corrosion involving
>acid producing bacteria". sample of the potable water indicated a 15 ppm
>choloride.

That much chloride will really do a number on stainless, regardless of whether it was micro-biological or other contamination contamination. The HAZ cracking you describe also sounds very much like sensitization--chromium carbide precipitation due to weld heat. You might want to check the carbon levels in the steel you're using. If it is sensitization, you're in deep sauce if you have a relatively high carbon content. Some years ago there were some nuke plants here in the US that had to have large quantities of pipe replaced because the weld HAZ material was simply disappearing. Re-welding didn't help much because the heat just tied up more chromium. I've seen this is some hard ballast tanks made of stainless steel used in nothing more corrosive than sea water.

Christopher Wright P.E. |"They couldn't hit an elephant from <a href="/group/PipingDesign/post?postID=o7w2XKWiekK59Ah4cLPXzZRwlUxxa_7ltmQ3rp6-5o255im_e6AATrpD8S9GVe64fUuQrnijcrk9nIb5">chrisw@skypoint.com</a> | this distance" (last words of Gen.

___________________________| John Sedgwick, Spotsylvania 1864)

<a href="http://www.skypoint.com/~chrisw">http://www.skypoint.com/~chrisw</a>

---

Piping Design Central
[ http://www.PipingDesign.com ]

---

We hope you find this newsletter useful. If not, you can unsubscribe at:
<a href="/group/PipingDesign/post?postID=AuFbAvI1zVqlgOlF3rzt5j5nQZvfsOgINJvTLm1NcsulJr3IbSzLDfGLNN9u13zAsLM1tTZ2loZrSvebu0AyaBjgM-mPQFWhEKHVPGBAR04fqA0">PipingDesign-unsubscribe@yahoogroups.com</a> Post message: <a href="/group/PipingDesign/post?postID=m3-4kKgIFiCtV1m4HDz_baXYECpASmiJ-BQYxyCrnJufvxD4zxp0etnNhqSyJu_H5DzNYYYqKBoECXbMlJ2yZrf24nZn-kE">PipingDesign@yahoogroups.com</a> Subscribe: <a href="/group/PipingDesign/post?postID=bPuv9QqxeleM99xHeAKBKZ0DD8XZOZTnwO3-4HraBykwCHZHZSfR7eZQLdMr7bOcMuxVj9zJ4HAJz8rkWofaqzuie8iiPJQCWGVyu48P3w">PipingDesign-subscribe@yahoogroups.com</a>

Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Thu May 31 03:00:00 2001