Appendix E of API 650 11th Edition 2007

[dharmeshajoshi]

As per Add4 in the formula for calculating Impulsive natural period (Ti) the term E(elastic modulus for the tank material) is in the denominator.

But as per API 650 11th Edition 2007 the term E is in the numerator. If we use E in the numerator then the Impulsive time period comes in days.
If we use E in the denominator then the Impulsive time period comes in seconds ( say 0.028 sec ).

I think there is a problem in the formula given in API 650 11th Edition 2007.
Should the term E in the numerator be shifted to the denominator ?


Also the units of the following :
E(Elastic modulus for the tank material)
Fc(Allowable longitudinal shell membrane compression stress)
Fy(Minimum specified yield strength of bottom annulus)
were given as lbs/in^2 in Add 4 but in 11 th Edition they are changed to kPa.

Should the units of these parameters be changed to lbs/in^2 ?

 

[IFRs]

The 11th edition has several typographical errors in Appendix E. There should be an Addendum coming out with the corrections. In the meantime some folks have been using the 10th Edition Addendum 4. Also, the units should be consistent - either Imperial or Metric - do not mix units in one equation.

 

[jehan17718]

dharmesh,

welcome to eng-tips.

API 650 tenth ed Add 4 and eleventh edition have many inconsistensies and typo errors. the formulas you are refering to on careful inspection will not be dimensionally correct and will yeild different answers if performed in SI and US customary units (as specified in Apeendix E).

If you see IS-1893 Part 2 DRAFT with commentary then that formula is similar to the one in API but again it will yeild an altogether a different result.

regards,

Jehan Noras

 

[DSB123]

dharmesh,
I concur with others there are several typo's listed in 11th Edition. Looks like it was rushed out without a comprehensive proof reading.

 

[jaydees]

Yes, there are errors in Appendix E of the 11th Edition. It will be corrected when Addendum 1 comes (still waiting to see the final proof copy) sometime "soon". API issued the wrong version of the appendix and decided to wait until Addendum 1 to correct it. In the meantime it has led to a lot of confusion.