Dear Srs.,

Which allowable must be used in a heater tube (coil) stress analysis?

Considering the material A106 Gr.B and a temperature equal to 950ºF, we have the following allowables:

API 530: 89MPa (figure F.2 - curve 5)
ASME B31.3: 31MPa

Why is there a large difference between the codes?

Thank you.