Contact US

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!

*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

Low carbon steel and caustic service

Low carbon steel and caustic service

Low carbon steel and caustic service

I have a steam jacketed pressure vessel made up of SA 516 GR 70 low carbon steel. It is rated at MAWP 72 psi, 350 F.and built to ASME,Section viii, Division 1. Year of manufacture was 1995. The manufacturer is now out of business.

I am thinking of changing its use and derating it to operate at 212 F, ambient pressure with 10 % NaOH by weight solution in  city water and animal tissue.

I would appreciate knowing:
1.If the welds and bends were stress relieved when the vessel was manufactured.
2. Will the mild steel be compatible with caustic soda service at the conditions mentioned.
3. What type of corrosion can be expected? Is SCC an issue here?

RE: Low carbon steel and caustic service

First question: To know if pressure vessel was stress relived you have to check drawings, if thickness is bigger than 1 1/2 in, then it was stress realived since it is a code requirement.

Second question: To know if it has to be stress relived for sodha caustic services, the rule is it is going to be working a temperature above 60ºC (128ºF), which it si not the case, stress realive it is not necessary.

Third question: Yes, the risk with this product it is caustic embritlement.

RE: Low carbon steel and caustic service


Consider asking the caustic soda suppliers (PPG, DOW and others) about the requirements for caustic soda piping and storage tanks.

Information can be found at:




I believe you will find that carbon steel becomes a bad material choice for caustic duty above abou 150F

Also see:


Good luck....

Let us know what your final selection is and please complete this thread with that information


RE: Low carbon steel and caustic service

RE: 1.If the welds and bends were stress relieved when the vessel was manufactured?

Look at the Data Plate on the vessel, and the data rport it will state if it received any postweld heta treatment.

If you do not have the data report contact the Nation Board of Boiler & Pressure Vessel Inspectors http://www.nationalboard.org/ to get a copy of it (if it is registered)

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! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close