×
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

internal coatings,potable water tanks

internal coatings,potable water tanks

internal coatings,potable water tanks

(OP)
good day, great site, I have been reading the postings for some time and finally have a query to post

I need to find a epoxy type coating for the inside of a stainless steel potable water tank 30US gallon capacity.
the tanks are welded, passivated and then flushed before being stored to air dry.

at this stage I need to apply the coating, unfortunatly access for spraying the caoting is extremly limited. There is only a "fill" hole approximatley 1.50 dia and two exit holes bothe 0.50 dia

thanks


 

RE: internal coatings,potable water tanks

britcan...

A few questions to clarify the tank construction...

Was this tank made "per" a drawing with "spec requirements" [MIl, MS, AS, Etc]... or just a drawing [with notes]?

What alloy/temper is the tank construction??

What welding process was used?? What NDI process??

Please confirm that the finish-welded tank interior was passivated ... if so, per what spec??

Are the interior surfaces completely "smooth"... or are there "bits" of weld-thru [flash or other sharp edges] and/or possible "open" metal seams??? IE: inspection [by borescope] of interior show any significant roughness or fluid-traps???

Regards, Wil Taylor

RE: internal coatings,potable water tanks

(OP)
Thank you for the response

The tank is welded in accordance with Learjet specs LES 1026 and LES 1014 to a specification control dwg.

The material is 304 stainless annealed per AMS 5513. The NDT tests are called in the welding process(s)

The tank is passivated per LES 1323 and ASTMA967  then cleaned in accordance with ASTM A380 using distilled water.
 Upon completion of the cleaning there is a water purity test per ISO 14951-10.

The tank is then hot air dried and sealed "to prevent moisture buildup"

The interior is fairly smooth although Visual evaluation shows several areas of open seams where interior baffles meet the tank walls with welded areas (weld -thrus) at intervals along the baffle's length


regards

Britcan

RE: internal coatings,potable water tanks

You could make your own spray nozzle, say a "J" shaped extension for the sprayer you normally would use for priming.  Something you could feed into the hole, go half-way down, and spray a narrow, tall pattern.  Rotate the nozzle 360°.  You might need to cut open a prototype to see how well the process works.  It would also aid in the certification to have done so.

      ___ <in
__ / __________  top of tank
 \ |                   |
  \J                   |
  / spray           |
 /                     |
/____________|

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

RE: internal coatings,potable water tanks

I suggest britcan repost this question under the "steel coatings engineering" and/or "corrosion engineering" forums,  they have many readers that will provide knowledgable responses.  

My input is this:
1.  The most important aspect of any coating application is SURFACE PREPARATION.  Your design, from the very start, hinders surface preparation and it is doubtful you'll get good performance from an epoxy in this application  (for example,  the small, mostly closed tank;  a smooth passivated CRES surface, both work against good performance of coating systems).
2.  Many epoxy paint companies have epoxy coatings the meet NSF requirements for potable water applications.
3.  If the container is CRES 304, annealed and passivated,  WHY PAINT IT?

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