B31.1 design code 1

[lahane1443]

I am not that much familier with 31.1 design code.
My design temp is 750 F and design pressure is 4.1 bar.
line size is 10 inch and only 1.5" branch connection at 45 deg is to be provided. i have chosen A 106 Gr B for pipe and A105 for nozzle material.there are no circumferential or longitudinal joints.

per allowable stress in table A, stress value for A105 is in itallic form which means creep and rupture strength will govern the stress value.

What is the meaning of above, can any body guide me to find the stress value to be considered for design. I stuck up at this stage as i have no idea about design per creep and rupture strength.


A quick reply is highly apprciated.

 

[stanweld]

The design allowable stress listed in the Table for the materials at 750 F are to be used. They have already taken Creep into account.

 

[StevenHPerry]

ASME Section II Appendix 2 gives some insight.

In a nut shell, these time dependent stress values do not give you the same margin of safety found in the non-italicized values. The Committee has included them because, in their judgment, those values will lead to a sufficiently safe design.

The usual caveats apply. (I.e. don't blame the Committee.)

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[CRG]

1443,

You referenced A105 with regards to a nozzle. Do you mean that you are planning to install a 1.5" A105 lateral-o-let on the 10 A106 line?

 

[lahane1443]

yes CRG