Section II, Part D Theramal expansion values 2

[ruthi]

Thermal expansion coefficient for 90Cu-10Ni in section II Part D, Table TE-3 has a value of 9.5 at 550 F. The table doesn’t show values at other temperatures and neither does TEMA. How do we evaluate differential expansion of tubes at different temperatures other than 550 F? Any help is appreciated.

 

[TGS4]

Does B31.3 have any values?

 

[ruthi]

Not available in B31.3. I am working on a fixed tubesheet shell & tube heat exchanger with carbon steel shell and 90Cu-10Ni tubes. Existing unit has no expansion joint and the customer has complained that there is a tube failure. Our program shows that the unit does not need an expansion jt as it is using 9.5 for all temperature conditions which is incorrect. I wanted to double check it by manually calculating the differential expansion using thermal coeff values(which is not available in code or tema)

 

[SnTMan]

Looked for any industry published values yet?

Regards,

Mike

 

[TJOrlowski]

You should contact a reputable manufacturer of expansion joints to confirm, but it's my understanding that's it's pretty common to use a single value for the coefficient of thermal expansion from room temperature (70F) up to the temperature listed in Section II (550F) for 90/10. You might also check with a manufacturer of the tube.

Be advised, even if you are confident that the HX does not indeed require an expansion joint, improper start-up, shut-down, or operating practices can cause failures at the tube-tubesheet joint on a well-designed, well-fabricated unit.

Have you confirmed that the HX has failed at the tube-tubesheet joint, and not in the tube(s) themselves?

-TJ Orlowski

 

[gr2vessels]

ruthi,
The definition of the coefficient B in the 'General Notes' below the Table TE-3 appears to me quite comprehensive, that is 9.5 applied between 70F and 550F. The tube material is anyway limited to 600F application. Is it the 50F difference between 550F of Table TE-3 and 600F on Table 1B that bothers you? It is indeed a bit of inconsistency of the code, but I'm sure you can use the same figure up to 600F and the IA won't complain.

 

[ruthi]

Thank you all for your response.
No,I have not looked for the industry publised values yet.
Yeah,according to the definition 9.5 can be applied from 70F to 550F but I was not quite sure if that was correct.