In most situations we relate the stress range to thermal expansion stress range (min to max temperature), but in ASME B31.3 302.3.5 (d) in discussion about allowable stress range, stress range factor f and computed stress range it is said: “When the computed stress range varies, whether from thermal expansion OR OTHER CONDITIONS, Se is defined as the greatest computed displacement stress range.

I need an assurance from the ASME gurus! What are these “other conditions”? Are they only thermal and displacements driven loads?

What about change in weight and pressure pulsing? Weight and pressure are causing primary stresses, but can their “pulsation” be considered as part of stress range? The pressure pulsation has already been discussed on this forum and consensus was that it should be included in fatigue calcs…but not as a part of the stress range. So, the weight changes should be treated the same way.

If my understanding of ASME requirements about delta P and delta W are correct, then cases for different operating regimes on my job should be as follows:

L1. W1+T1+P1+D1 (T1=5degC, SG1.5, P1 =2000kPa - OPE1) – Caesar file no1
L2. W1+P1 (SUS) – Caesar file no1
L3. W2+T2+P2+D2 (T2=200degC, SG0.5, P2=1000kPa - OPE2 ) – Caesar file no2
L4. W2+P2 (SUS) – Caesar file no2
L5. WNC (line is drained on regular bases SUS) same for both Caesar files

Combination cases are:

L6. L1-L2 (accounts for delta T1+D1) EXP – Caesar file no1
L7. L3-L4 (accounts for delta T2+D2) EXP – Caesar file no2
L8. L6+L7 (ABS) should be the greatest displacement stress range – EXP combination of results from two Caesar files
L9. L2-L5 (accounts for max delta W and max delta P in FAT analysis, 20,000cycles) – Caesar file no1

All comments will be appreciated