STHE minimum radius for bend part of U tubes.

[jbesson]

Hy everybody,
My concern is about the minimum radius for bend part of U tubes.

STHE is in destination of a nuclear plant project, grade of tubes is 316L and according to the speakers the minimum radius fluctuates between 1.5 to 2 times the external dia of tube.

Does anyone know if a precise limitations is mentioned in ASME or TEMA or CODAP ?

Thank in advance

 

[TJOrlowski]

TEMA RCB-2.3 discusses U-tubes. Minimum radius can be inferred from the max allowable tube wall thinning, and max allowable flattening of the OD in the bend.

The smaller your bend radius, the greater your fiber elongation, which may require stress relieving, as required by ASME.

-TJ Orlowski

 

[Duwe6]

Concurr with TJO. ASME wants you to figure fiber elongation, wall thinning and ovality into your calc's. That is where Code bend radius limits properly come from.

 

[DG72]

Generally, for most materials, a bend diameter 3 X tube o.d. is acceptable. As stated above, you will need to compute minimum tube thickness per ASME and apply TEMA rules to calculate thinning at u-bends. Beyond TEMA and ASME, you should contact tube supplier. Some materials present different challenges at small bend diameter.