Explain how the Ec/Eh ratio is applied for ASME B31.1?
It is there by default in ASME NB, but not B31.3, why?
Modulus ratio is (Ec/Eh) is optional for B31.3 under Model Result Option “Apply modulus ratio” and is unchecked by default. This option allows the calculated displacement stresses to be multiplied by the ratio of the cold elastic modulus to the hot elastic modulus per ASME B31.3 code para. 319.2.2(b)(4).
(4) variation of piping material or temperature in
a line. When differences in the elastic modulus within
a piping system will significantly affect the stress distribution,
the resulting displacement stresses shall be computed
based on the actual elastic moduli at the respective
operating temperatures for each segment in the system
and then multiplied by the ratio of the elastic modulus
at ambient temperature to the modulus used in the analysis
for each segment.
So this option becomes mandatory only when the condition “When differences in the elastic modulus within a piping system will significantly affect the stress distribution” becomes true for B31.3 piping. Therefore, sensible to keep this optional and unchecked by default for B31.3.
ASME B31.3 Piping Code Calculation Issues