analysis at minus temp. by B 31.8 code

Dear frnds

I m doing stress analysis for gas pipeline, which is designed acc. to the code B 31.8, and system design temperature is -20 degree celsius. But when i run the system with B 31.8 it is showing an error but when i run the system with B 31.3 it runs satisfactorily. may i know the reson for this cause. Help me ASAP.

With Regards

I don't know what material you are using but I guess some parameter (coefficient of expansion?) is not defined for below ambient temperatures in B31.8. The job won't run without it.

I'll assume its that alpha that's missing. instead of temperature, you can type in the coefficient of expansion. (Press F1 while focused on that cell for Help.) Keep an eye on the other material parameter fields (SYMS) to make sure they are not confused by this change.