Sustained Stress:
As per ASME B31.3 paragraph 302.3.5(c), the stresses due to sustained loads, SL, in any component in a piping system, shall not exceed the basic allowable stress, Sh.
SL < Sh
Expansion Stress:
As per ASME B31.3 paragraph 302.3.5(d), the computed displacement stress range, SE, in a piping system shall not exceed the allowable displacement stress range, SA.
SE < SA
Where:
SA = allowable displacement stress range
SA = f(1.25Sc + 0.25Sh)
when Sh is greater than SL, the difference between them may be added to the term 0.25Sh
SA = f [1.25(Sc + Sh) - SL]
Sc = basic allowable stress at minimum metal temperature
Sh = basic allowable stress at maximum metal temperature
SL = stress due to sustained loads
SE = computed displacement stress range
f = stress range reduction factor
Occasional Stress:
As per ASME B31.3 paragraph 302.3.6, the sum of the stresses due to sustained loads, such as pressure and weight, SL, and of the stresses produced by occasional loads, such as wind and earthquake, shall not exceed 1.33 times the basic allowable stress.
SOL < 1.33Sh
