Question: "...it
was noted that some values of SA exceeded the yield strength of the material,
for example: For A335P5, the allowable stress SA according to CAEPIPE
is 39500 psi at 400 deg.C, while the min. yield strength of this material
acc. to ANSI B31.3 code is 23800 psi at 400 deg. C and 30000 psi at standard
condition. Can you please explain?"
Reply: S(A) is the allowable displacement
stress range and, using B31.3 Eqn. (1b), will approach 1.6 times the yield
stress, if S(L) values are negligible. This is correct and is based on
the assumption of "shakedown" or "self-springing"
of the piping which is assumed to be ductile. (See B31.3 para. 319.2.3).
Note: We strive to provide accurate data for the
material properties. Sometimes, typographical errors do creep in. It is
recommended that you verify the properties before using them.
Author: Mr. Ron Haupt, P. E., of Pressure Piping Engineering (www.ppea.net) is a member of several piping code committees (B31, B31.1, B31.3, BPTCS, and others). He consults with us in the capacity of Nuclear QA Manager.
Tip for the Month (May 2001)See technical article on a quicker method for evaluating piping vibration by Dr. R. T. Hartlen (under Tech Articles).
Tip for the Month (Jun 2001)See technical article on a quicker method for evaluating piping vibration by Dr. R. T. Hartlen (under Tech Articles).
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