Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

B31.3 Allowable Stress for High Pressure Piping

Status
Not open for further replies.

TXLSUCHE

Chemical
Mar 13, 2006
8
I am calculating the W.T. for 7" OD 10,000# prssure piping using 4130 mechanical tubing. Unless I am misunderstanding B31.3, Section K302.3.2, it appears that it is acceptable to use 2/3 the SMYS for the allowable stress. However, everyone I have conferred with uses 2/3 the SMYS or 1/3 the tensile, whichever is less. Am I missing something in B31.3 that says I have to use the lower of the two? Even most of the allowable stress values given for the materials in Table K-1 use 2/3 SMYS. The piping system I am designing will be operating at about 75 F. Please help.
 
Replies continue below

Recommended for you

Normal piping per B31.3 use lower of 2/3Yield and 1/3 of the tensile , as per par. 302.3.2.
High pressure piping is per par. K302.3.2 , the lower of 2/3 Sy and 2/3Syt.
 
Thanks for the response ijzer. But what worries me about that is for higher pressures, the safety factor is actually decreasing because 2/3 yield is greater than 1/3 tensile.

The pipe I am considering (I have the MTR's) is 7" OD x .9375 W.T., 4130, 104,600 TS, 80,900 YS. As you can see, which of the two allowable stresses you choose can make a significant difference in determining if the tubing will be "rated" for 10,000#.
 
TXLSUCHE,
Suggest you post this in the "Piping and Fluid Mechanics engineering" Forum or the "ASME(Mechanical) Code Issues" forum.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor