×
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

Low temperature issue

Low temperature issue

Low temperature issue

(OP)
Friends,

We've a scenario in one of our gas plants:  A106B 14" piping sch 80, WT 0.75" (no PWHT) is installed for design pressure 15MPa.  Normal operating 3.5MPa, max pressure the system will see is 10MPa.  As per curve B, the min temp it can go is -10degC without impact test.  In winter months, the pipe can see temp below -15degC becoz of some J-T effect across the throttling valve.  Is this permissible to operate below -10deg without impact test.  Can we apply temp reduction factor in Fig 323.2.2B?

RE: Low temperature issue

As I recall you cannot use the pipe without the Charpy test.  The temperature reduction is applied, if you do the testing.

From "BigInch's Extremely simple theory of everything."

RE: Low temperature issue

Sorry BI, this is piping to 31.3!  The minimum temperature without Charpy testing ajustment can indeed be applied, but you have to be very certain of the stress level.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04
 

RE: Low temperature issue

In addition to the hoop stress (from internal pressure) that is coincident with the lower temperature excursion, you also have to calculate the longitudinal stress, and compare that against the allowable, as well.  Not a particularly complicated task.

RE: Low temperature issue

I think it is also further complicated by the fact that the intent of 322.2.2 appears to be to calculate the forces and moments developed assuming non-corroded pipe but with the  corresponding stresses evaluated in the corroded condition.

Regards,

SNORGY.

RE: Low temperature issue

B31.3 it is. Sorry.

Stress is not evaluated in the corroded state?  Forces and moments would be higher, but resulting stresses would be lower.  I'd have to take issue with that procedure.

From "BigInch's Extremely simple theory of everything."

RE: Low temperature issue

BigInch...
Maybe I was ambiguous, but what I meant to say is that by my interpretation, you assume strong uncorroded pipe to compute the forces and moments, and then take those forces and moments to evaluate the stress levels in corroded pipe.  So thick wall pipe force divided by thin wall pipe area makes for higher stress.  By my interpretation of 323.2.2 anyway.

Regards,

SNORGY.

RE: Low temperature issue

That makes more sense.  At least it should be the conservative method.

From "BigInch's Extremely simple theory of everything."

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