API 620, R3?

[Pato12]

Hi guys,

Just wondering if someone could shit some light regarding R3 and with respect to R2.

As I understand it R2 is a function of a(horizontal semi axis),b(vertical semiaxis) and x. (elliptical function mentioned in the standard 620)
and
R3 is R2/cos(half-apex-angle).

I was trying to get figure a function of changing R2 to get the R3 value at the point. At the moment I made my a=radius of tank(as it is a cylinder sidewall), now with 'b' I made it the cone height(not sure if this is right).

So I put the numbers in the R1 and R2 functions are working as expected at varying values of x but R3 isn't working as expected. I was thinking at x=0, R3 should be Zero(which correspond to the cone's top point and at x=radius of tank, R3 should also be the radius of the tank at that point as it would correspond to the base of the cone.

Unless my understanding of what R3 re-presents is wrong I don't really understand what value of R3 should I use to size the cone roof of my tank.

any help would be appreciated.

regards,

Pato

 

[JStephen]

See 5.10.2.5(b). R3 is the horizontal radius at the point in question, R1 and R2 are not needed to figure T1 and T2.

 

[Pato12]

I understand that but how they came to the T1 and T2 equations for a cone plate is by saying R1=infinity and R2=R3/cos(alpha) and putting them in the general equation of T1 and T2.

What I don't understand is how is R2 varying with R3. I guess ill just form my own equation for the slant of cone with a linear line using the apex angle as my gradient and radius and height for x and y intercepts.


Shame really wanted to have a complete understanding of this standard, ive been working pretty hard to understand it all.