API-650 Table 5-21b

[richay]

Comparing 11th Edition Addendum 2 to Addendum 1:

In Addendum 2 the equations in Table 5-21b for "design pressue + wind", "design pressure + seismic", and "frangibility pressure" all have a constant of "0.08" as the mulitiplier for "th". However, the same equations in Addendum 1 use a constant of "8". The 0.08 constant is used in the SI version, Table 5-21a. I presume this is a mistake in Addendum 2, and the constant in Table 5-21b should still be "8" ?

For the frangibility pressure, I also assume the loss of the "4.08" multiplier is a mistake ?

Richard Ay
COADE, Inc.

 

[TankDude]

If memory serves, these changes were due to mistakes discovered in the S.I. table. The calculated values were not consistent with those calculated using the formulas in the Imperial table. You may be able to verify this by performing some sample calcs from the two addenda.

 

[JStephen]

The "8" is 490/62.4 with roundoff.
The 4.08 is pi/4 x 62.4/12.
I think your assumptions are correct.

 

[xema77]

I was confused with the units in table 5-21a Add 1.

The pressure P and 0.08th in kPa mutliplied by diameter in meters result in units of kN. The wind and seismic moments are in N-m and W1, W2 and W3 are in kN and the resulting uplift loads are in N?
Believe Ms & Mw should be in kN-m and the uplift forces are in kN. Can anyone confirm.

Add 2 does not do much to help clarify these as the units all remained the same, however a factor of 785 was added. Where does this factor come from?