Hello,

I have question regarding load case L2-L4 (T1-T2)
Do we have to use this load case because i have
Temp 1 -300 Deg F
Temp 2 350 Deg F

Using the above load case the system fail. The Delta T is 650 Deg F
Is it possible that the system will see such a high change in temperature.

Does B31.3 states that we have to use the L2-L4 case to satisfy the code

Thank you for your help.

From my reading of the Code, I'd say yes. Even if the system won't ever heat up from -300F to 350F in one shot each time, the "range" is still that big. Say it goes from 70F down to -300F and back to 70F. 10 days later it starts going from 70F to 350F and back to 70F. Your range remains the same (-300F to 350F).

You have a system that varies from -300 to +350F? You need to be careful with material selection and ensure all components are also acceptable for that wide range.

This is indeed an atypical temperature range.

If these temperatures are based on some pipe spec, it may not be the actual design temperatures of the line in question. Consult the process engineer.

If, however, these are actual design temperatures of the line, yes, the "full expansion" range is required.

If so, I would caution you to understand where you're lifting off supports, if anywhere, and see about fixing that. Otherwise, expect to treat it as a 650 degree line.