Wind Load on Tanks 2

[xema77]

When calculating Mf (moment about the shell to bottom joint from liquid) in section 5.11.2 of API 650, wl is the lesser of 0.9HD or 59*tb*(Fby*H)^.5. 0.9HD is significantly less than the other value and appears to have different units. Can anyone explain?

Thanks

 

[JStephen]

You might check the metric vs English unit equations to see if they are in line with each other. Also, this is based on the allowable annular plate uplift from App. E, and should be derivable from there.

The equations are not dimensionally consistent in the English units, and I assume not in the metric units. That is, I assume tb would be in millimeters, H in meters, etc., and the constant would have unshown units to make it all work. Check the definitions of the terms to confirm the units for them.

 

[JStephen]

See E.6.2.1.1. Putting in 0.7 specific gravity in Eq. E.6.2.1.1-1b gives you the 0.9HD equation in English units. The corresponding metric version should then be 201.1 x 0.7 HD.

 

[rikiraph2]

Thanks JStephen, I would have never known to look there but now you point it out it is clearly an omission in the code

 

[99491]

Does this now mean that "wl" merely replaces "wa" in the calculation from the earlier edition?

Does Mf = (wl)*(Diameter)*(Pi)*(Radius)