What is the permissible maximum percentage of flattening for tubing in bends?

What is the permissible maximum percentage of flattening for tubing in bends?

• A. 20%
• B. 25%
• C. 30%
• D. 40%

Answer: (B)

Bending tubing makes the cross-section oval rather than perfectly round. There’s a practical limit to how much flattening (ovalization) can be tolerated without narrowing the inner passage too much or causing excessive stress on the material. About a quarter of the original diameter is the commonly accepted maximum because it keeps the flow area adequate and maintains structural integrity in service. Values larger than this risk significant constriction and potential problems, while a smaller limit would be unnecessarily restrictive for many applications.

Bending tubing makes the cross-section oval rather than perfectly round. There’s a practical limit to how much flattening (ovalization) can be tolerated without narrowing the inner passage too much or causing excessive stress on the material. About a quarter of the original diameter is the commonly accepted maximum because it keeps the flow area adequate and maintains structural integrity in service. Values larger than this risk significant constriction and potential problems, while a smaller limit would be unnecessarily restrictive for many applications.