Wind and Overturning in API 650
Wind and Overturning in API 650
(OP)
I've been out of API for some time and things have changed. I need some help.
Used to be you looked at overturning like this;
Pressure * Area (height * Diameter) * (height /2) (for shell)
plus
(Pressure * Area ((diameter * height of roof) /2) * (Centroid of roof + height of tank)
We then converted the moment found above to uplift to evaluate anchorage.
Now the wind pressure on the roof is in uplift but the overturning calculations are still in moment.
Can I just disregard the term uplift and calculate overturning moment like I used to? If not, what is expected now?
Any help is appreciated.
Used to be you looked at overturning like this;
Pressure * Area (height * Diameter) * (height /2) (for shell)
plus
(Pressure * Area ((diameter * height of roof) /2) * (Centroid of roof + height of tank)
We then converted the moment found above to uplift to evaluate anchorage.
Now the wind pressure on the roof is in uplift but the overturning calculations are still in moment.
Can I just disregard the term uplift and calculate overturning moment like I used to? If not, what is expected now?
Any help is appreciated.





RE: Wind and Overturning in API 650
You calculate moment about one edge of the tank, including the uplift force on the roof, and neglecting lateral load on the roof. So you have horizontal pressure x projected shell area x half the shell height plus vertical pressure x cross-sectional area x radius. Then use the indicated equations to check for overturning.
For the overturning check, this works okay. However, when you use this wind moment moment to figure anchorage, it is overly conservative. The practical difference is not usually that large, though.
RE: Wind and Overturning in API 650
RE: Wind and Overturning in API 650
RE: Wind and Overturning in API 650
RE: Wind and Overturning in API 650
You should have started another thread with your question. However, since I was interested in this thread, I have read your question and will respond.
In API 650, tanks built with group 1, 2, or 3 materials that exceed 1" in thickness are required to have nozzles 12" in diameter or greater installed into insert plates and stress relieved prior to installation into the tank. Additionally, if the tank us made using group 4 or higher materials and the thickness exceeds 1/2", all nozzles that require reinforcement are required to be installed into an insert and stress relieved prior to installation into the tank. In additiona to these nozzles, all clean-out doors, regardless of materials used are required to be stress relieved prior to installation into the tank. There may also be a requirement to stress relieve flush-type nozzles but I would have to look that one up to confirm.
Hope this helps
LeonEarle
RE: Wind and Overturning in API 650
In your reply, you indicated that the uplift was to be multiplied by the cross-sectional area. In API, they indicate that it is to be multiplied by the "horizontal projected area". I have searched and searched and can not find how to calculate "horizontal projected area". The projected area of a cone is diameter * height of cone / 2. Is this the same as "horizontal projected area"?
Thanks
RE: Wind and Overturning in API 650
RE: Wind and Overturning in API 650