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!

*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.

Jobs

Load Case - Displacement Stress Range

Load Case - Displacement Stress Range

(OP)
I have the following load cases:

L1: W+D1+T1+P1 OPE ( THE HOT OPERATION LOAD SET )
L2: W+D2+T2+P1 OPE ( THE COLD OPERATION LOAD SET )
L3: W+P1 SUS ( SUSTAIN LOAD )
L4: L1-L3 EXP ( EXPANSION IN HOT OPERATION )
L5: L2-L3 EXP ( EXPANSION IN COLD OPERATION )
L6: L1-L2 EXP (DISPLACEMENT STRESS RANGE FOR EXPANSION STRESS CALCULATION)

So, I have some doubts.

In the standard B31.3 says that I have to calculate the "displacement stress range" to ensure that the stresses are not above the acceptable 0.8 SA.

- First: The Case 6 represent correctly the case for the displacement stress range?
- Second: If so, how caesar calculate this? I have to put something in case 6 to CAESAR understand that in this case the stresses cannot exceed permissible 0.8 SA?

Thank you very much my friends.

Regards,

Saulo Cunha

RE: Load Case - Displacement Stress Range

Why are you quoting 0.8SA as a B31.3 allowable stress ??

The usual allowable is SA = f(1.25Sc + 0.25Sh)

To get the full stress range you could combine L4 and L5.

RE: Load Case - Displacement Stress Range

(OP)
We need to check the Severe Cyclic Conditions. I work in WHITE MARTINS, It's a Praxair's Company and we have a standard that say something like that:

Use L6: L1-L2 EXP (DISPLACEMENT STRESS RANGE FOR EXPANSION STRESS CALCULATION) for severe cyclic service, because severe cyclic service requires special considerations for pipe material, weld X-rays and construction procedures. Therefore to allow use of the standard pipe specifications and welding standars, limit the maximum stress to less than (0.8 SA).

ASME B31.3

Severe Cyclic Conditions: conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5), and the equivalent number of cycles (N in para. 302.3.5) exceeds 7000; or other conditions
that the designer determines will produce an equivalent
effect.


So, what do you about it?

Thank you very much for your answer.

Regards,

Eng. Saulo Cunha


RE: Load Case - Displacement Stress Range

It' a company standard, not part of B31.3 which does not retrict stresses to 0.8SA, merely requires some additional work.

Get someone in the company responsible to sort it out.

RE: Load Case - Displacement Stress Range

(OP)
I know, but B31.3 say this:

"Severe Cyclic Conditions: conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5), and the equivalent number of cycles (N in para. 302.3.5) exceeds 7000; or other conditions
that the designer determines will produce an equivalent
effect."

So, I understand that we have to keep the stresses below the permissible 08SA. What do you think about ? And how can I use this information in CAESAR to ensure this assumption ?

Thank you again.

Regards,

Eng. Saulo Cunha

RE: Load Case - Displacement Stress Range

See Dave Deihl's reply in the Caesar II (Intergraph) forum.

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


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