Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
(OP)
I have searched past threads on this topic, but my situation is as follows. It is proposed to use CSA Z662 Clause 14 to design some steam distribution pipelines (Canada). Clause 14 directs the designer to ASME B31.3, in which some "Funk & Wagnalls" mental gyrations leads the designer to 302.3.2(d) and ASME Section II Part D Table Y-1 to obtain the required allowable stress value at temperature. The only trouble is, I cannot locate allowable stress values above 400 F for CSA Z245.1 Grade 448 (API 5LX-65) or CSA Z245.1 Grade 550 (API 5LX-80) to enter into CSA Z662 Appendix I Equation I.2.1.1.
That equation is: t = (0.5)(D-2Co)[1-exp(-1.55P/S)], where S is the allowable stress at the elevated temperature in question.
Can anyone advise where I can get "S"? I feel profoundly dumb and frustrated.
That equation is: t = (0.5)(D-2Co)[1-exp(-1.55P/S)], where S is the allowable stress at the elevated temperature in question.
Can anyone advise where I can get "S"? I feel profoundly dumb and frustrated.





RE: Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
Yes, that [and then presumably ASME B31.3 323.2.4 (a) & (b)(1)&(2)&(3)] is understood. I ultimately end up at verifying the material through testing. However, Grades 448 and 550 are commonly used at temperatures much higher than 400 F up here (SAGD), so somebody, somewhere, must have already demonstrated the validity of stress levels at elevated temperatures for these materials. I can't imagine that the material has to be requalified over and over again...
RE: Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
My client and I were able to obtain the manufacturing specification for the material in question. The answer was surprisingly simple: they just guarantee to meet or exceed room temperature yield and tensile strength at elevated temperatures up to 354 C, and have the test results on record to prove it. Application of Code rules falls out from that.
RE: Allowable stress values for API 5LX Grade (xx) pipe above 400 F?
Surprising what a little communication can achieve sometimes.
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek