Overturning stability - Unanchored tanks
Overturning stability - Unanchored tanks
(OP)
Hello All,
I have the latest copy of API 650 11th Edition, June 2007, Addendum 1 Nov 2008.
I am designing a cone roof tank that is atmospheric and have a few queries with regards to the formula for working out MF and Liquid weight WL.
In the Code clause 5.11.2 states that unanchored tanks must satisfy equations:
1. 0.6Mw + Mpi < MDL/1.5
2. Mw + 0.4Mpi < (MDL+MF)/2
Mpi = 0 as tank is atmospheric.
With regards to finding the value for MF am i correct in saying that we use the formula:
WL = 59.tb x SQRT Fby.H (N/m)
This gives us the force from a band of liquid acting at the shell per meter....which we then multiply by the circumference of the tank to get the total force acting around the shell of the tank.
You then multiply this total force by the radius of the tank to get the value of MF which we use in equation 2?
Also the code states that WL shall be the lesser of 0.90HD or the mentioned above formula for WL.
Is this an error as if i use 0.90HD i get a figure that is completely out in comparison.
Many Thanks for your help
I have the latest copy of API 650 11th Edition, June 2007, Addendum 1 Nov 2008.
I am designing a cone roof tank that is atmospheric and have a few queries with regards to the formula for working out MF and Liquid weight WL.
In the Code clause 5.11.2 states that unanchored tanks must satisfy equations:
1. 0.6Mw + Mpi < MDL/1.5
2. Mw + 0.4Mpi < (MDL+MF)/2
Mpi = 0 as tank is atmospheric.
With regards to finding the value for MF am i correct in saying that we use the formula:
WL = 59.tb x SQRT Fby.H (N/m)
This gives us the force from a band of liquid acting at the shell per meter....which we then multiply by the circumference of the tank to get the total force acting around the shell of the tank.
You then multiply this total force by the radius of the tank to get the value of MF which we use in equation 2?
Also the code states that WL shall be the lesser of 0.90HD or the mentioned above formula for WL.
Is this an error as if i use 0.90HD i get a figure that is completely out in comparison.
Many Thanks for your help





RE: Overturning stability - Unanchored tanks
Usually the first equation is what determines if it is anchored.
RE: Overturning stability - Unanchored tanks
based on the equations in appendix E i have calculated that for SI units it should be 141HD
Im assuming that the equations in Appendix E do not apply in my case as i am not designing the tank for seismic conditions and that the formula for WL stated in my original post is the correct one to use.
Thanks again for your help :)
RE: Overturning stability - Unanchored tanks
RE: Overturning stability - Unanchored tanks
RE: Overturning stability - Unanchored tanks