tube bend design criteria

[chrisMac]

i have several questons...

1) what is the standard for a tube bend radius?...is it three times the tube OD?

2) if you were to deviate from a standard bend radius, does it affect the tube wall thickness and how?...will there be an affect on pressure or temperature if it is a fuel line for a liquid propellant?

3) besides routing concerns, what should i be aware of for a good tube design?

chrismac

 

[JohnWegkamp]

1)The standard for bend radius is 1.5D, but other size are also used, like 5D, or 3D.
D stands for the nominal size in inches (not the outside diameter).

Example 10" pipe, then bend radius 1.5*10=15"

3) The larger the bend radius, the more flexibilty is put into the system. This is important when you design systems for high temperature en large diameters (<4&quot.

 

[butelja]

Forged fittings are typically either D, 1.5D, or 3D. If you are cold bending straight tubing, I believe that either 3D or 5D are common radiuses. Bending to a shorter radius than 3D can cause wrinkling of the inside of the bend, excessive thinning at the outside of the bend, cracking the tubing, or a combination of these effects depending upon the material.