×
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

High Temperature

High Temperature

High Temperature

(OP)
I have a PV that must be designed for upset condition of 1200 deg. F. The code material for CS only goes to 1000 deg. F.

Any thoughts or ideas for getting allowable stresses at this temperature. Creep and distortion is not a concern.

RE: High Temperature

When reviewing the code allowable stress tables,  moving you finger down the page a bit past the carbon steel tubes, and pick out an alloy tube.

RE: High Temperature

Read the notes for the material in SecII D.

See SecVIII Div 1 UG-20 (c)

RE: High Temperature

Tankman650-

One word: REFRACTORY

As deanc pointed out, exceeding the max listed temperature is not permitted. To get a 1200°F hot wall design, you're looking at a 1¼Cr or higher material as davefitz referred to. Even then, it would be hugely uneconomical: Look at the allowable stresses at 1200°F compared to even 1000°F. You'll find a factor of roughly 6x. Sounds to me like you need to sharpen the pencil on the HAZOP (ie reduce the design contingency) or do what everyone else does and design a cold wall refractory lined carbon steel vessel. Although the design of a substantial vessel at 1200°F would be kind of fun... The vessel itself, internals, piping, L&P's...

jt

RE: High Temperature

(OP)
Thanks for the responses.

I am not trying to certify to 1200 F.  I want to verify that the structure will not colapse under PWHT conditions.  This is a non-code issue but an issue never the less.

I do have a large vessel under much dead load.


Thanks again.

RE: High Temperature

Be very careful here because creep (short term) will result in distortion, which will be a concern if you have too much static load while attempting to perform PWHT of fabrication or structural attachment welds.

Make sure the vessel structure is adequately supported and if necessary stagger your PWHT schedule to compensate for loss of strength of carbon steel during PWHT.

RE: High Temperature

You need to get the material properties from reference material such as ASTM Special Pub 180 (was available from UMI Out-of-Print Books on Demand) or API 579.

We would also consider creep buckling.

RE: High Temperature

Tankman650-

A field PWHT. Gotta love 'em! These can get difficult though. As pointed out above, you can consider a PWHT of circumferential segments while adjacent ones carry the load. For example, divide the circumference into eight 45° sections and PWHT alternating segments with a bit of overlap. Then go back and PWHT the segments which were cold the first time. Be careful here with potentially high thermal stresses. The other approach is to PWHT the entire band at once and consider creep buckling. The ASTM publication bvi referred to might be the same one I got from the ASTM which is ASTM Data Series DS 11S1 (Supplement to Publication DS 11, formerly STP 180). If you call the ASTM they won't find it in their listing on the 'puter but with further encouragement they did find it on some other list. API-579 appendix F will provide similar data.

jt

RE: High Temperature

tank,

Carbon steels can only be used to service temperatures about 775 to 800F. Above that temperature, they will degrade in a process known as graphitization.

Low chrome alloy and stainless steel materials have been developed to operate in the ~1200F range.

Try ASME SA335-P22 or P91 for your PV or ASME SA 240-type 316 or 321.

These materials all have been used in this temperature range....

My thoughts only.

MJC

  

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