R1 value, negative?

[Pato12]

Hi Guys,


Just wondering if someone could help explain what is meant by the R1 value of elliptical tank wall can be negative?

regards,

Pato

 

[fegenbush]

The positive R1 value would represent a shape like a sphere. If you were to dent the sphere such that the plate in the region of the dent curved in the opposite direction, that dent would have a negative R1 value since it curves in the opposite direction.

Said another way, if the center of the radius of curvature is on the product side, R1 is positive. If the center is on the opposite side, R1 is negative.

 

[Pato12]

Oh I see so this negative value of R1 only applies for double curvature type tanks.

So with basic shapes like cylinders, domes and sphere without dents R1 is always positive?

is that right?

thanks in advance.

 

[JStephen]

Assuming you're using API-620- R1 is defined for cyclinders, for spheres, domes, cones.

For the negative R1, I think it would be something like a curved transition between a cone and cylinder, where the cylinder is at the small end of the cone.