It is a well known fact that Thermal co-efficient of expansion is same for a particular material at the same temperatures.

Then Why Caesar II shows different thermal Co-efficient of expansion at same temperatures when I changed my Piping Code from ASME B31.3 to ASME B31.8 ?

The Codes list different values.
Ask the Code Committees why...please.

That's great>>>>..........!!!

Dear Dave Diehl,

To my knowledge,
Both the Codes gives same values for a specific temperature range. Please refer to ASME B31.3 and ASME B31.8.

Full disclosure: I have no experience with B31.8.

I just checked, both codes give different values. Close, but different.
I used an example of an expansion of Carbon Steel from 70°F to 200°F. Calculating the expansion manually using table C-3 of B31.3 got me 0.000829in/in. Using Table 832.2-1 of B31.8 got me 0.000854in/in. Those numbers match the ones calculated by CAESAR.

In fact, in B31.3, if you calculate the expansion manually using table C-1, you'd get a slightly different value than using table C-3.