×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Stainless Steel in Potable Water System

Stainless Steel in Potable Water System

Stainless Steel in Potable Water System

(OP)
Hi!

We are looking at putting in some new piping and filters in our new potable water system and have a few questions on material selection (our galvanized carbon steel is very corroded and we need this section replaced).  The water will have a pH between 7.5 and 9.1.  The project manager was originally going to use PVC but has since decided to use 316L SS because the amount for the PVC with the extra support it would require was the same price as the 316L SS.  In a few years this system will not be used all the time anymore and would only be a backup.  My question is, is it ok to use 316LSS in this application?  There are some chlorides in the water (probably 2-4 ppm) and when a shock treatment is done more chlorides would be injected into the system as required by the AWWA.

I'm thinking the 316SS should be fine with this amount of chlorides but I am concerned that leaving it out of service may cause problems if any stagnant water/moisture gets into the pipe.

Please help!!

RE: Stainless Steel in Potable Water System

I assume that this would all be butt welded tubing, no threaded joints.
Make sure that the welds are inspected for heat tint on the inside.  Light yellow is fine but anything darker either needs to pickled or cut out.
Your concern is well placed.  If the line is stagnant then microbial corrosion is very probable.  Continuous circulation is the safest.  Either that or drained and dried.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Stainless Steel in Potable Water System

(OP)
Hi Ed,

Thanks for the info.

Do you think the amount of Chlorides are fairly negligible in this case?   

RE: Stainless Steel in Potable Water System

Don't worry about this chloride level.
316 is fairly safe up to 100 ppm in warm water (125F) and as high as 500 ppm in cold water (45F).
Fouling and microbial growth are what will kill you.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Stainless Steel in Potable Water System

(OP)
Hi Ed,

I'm not too familiar with microbial growth/corrosion and had a question.  I'm assuming microbiological corrosion is harmful for either stainless or PVC right?  Or would PVC be more resistant to this type of corrosion?

RE: Stainless Steel in Potable Water System

as Ed said SS316 can handle water with 500-1000 ppm depending on the operating temperature so in your case i'll see no problem regarding the chloride content.

SS in stagnant water can loose its passive layer and corrode.. and microbiological corrosion is a possibility..

Stainless Steel for Potable Water Treatment Plants
http://www.nickelinstitute.org/index.cfm/ci_id/15786/la_id/1/ci_doc_id/3104/search_keyword/Potable%20water/method/1.html

Application of Stainless Steel in the Water Industry
http://stainlessconstruction.com/Fabrication/General/Application_of_SS_in_Water_Industry.htm


http://www.ssina.com/publications/sswhd.html

hope this help

S

Corrosion Prevention & Corrosion Control
 

RE: Stainless Steel in Potable Water System

http://www.s-p-l-a-s-h.org/index.cfm/ci_id/13650/la_id/1.htm

here is a site dealing with SS in potable water systems.

Your PVC would be resistant to MIC, but it will need a lot of support and don't let the sun shine on it.

Build the SS system so that it drains well, use lots of slope.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources