API-650, 11th Edition, Addendum 1

I am continuing to review Addendum 1 to the 11th Edition of API-650. Here are some comments on what I have found so far.

1) There are many slight modifications in the values used for SI units. Places that used to specify 12.5 mm now use 13 mm. In the table for 5.1.5.9(e), they have revised the angle size slightly. In 5.5.1 they changed 172 MPa to be 171 MPa. In 5.6.3.1 they changed the limit for using the 1-foot method for shell design to 61 m. Revised the angle size in 5.9.3.1 and 5.9.3.2.
2) In 5.2.1 (loadings) they revised the external pressures so that tanks with internal floating roofs with circulation vents do not require a minimum external pressure.
3) In 5.2.1 they also added loading requirements for internal floating roofs.
4) In 5.6.1.3 they added additional rules when using a lower allowable stress material in the upper courses. You now can do an elastic analysis or the lower course must be no thinner than the required thickness for product design or hydrotest design of the upper course.
5) They have revised some of the tables for manway neck thicknesses, nozzle reinforcement, cover plate thicknesses, and flush cleanouts.
6) For intermediate wind girders, the shell course thickness is now to be based on the thinnest shell course which may not be the top shell course.
7) An expanded design for frangible roofs has been added.
8) 5.10.2.9 now states that the purchaser can specify that lateral loads be imposed on the roof supporting columns.
9) 5.10.3.2 has been revised to reduce the minimum thickness for roof support columns from 0.25" to 0.236".
10) 5.10.4.4 has been revised to provide calculations for the maximum spacing of the roof rafters. It also set the maximum spacing at 84". These limits apply to both inner and outer rafters.
11) 5.11.2 has been revised to add a limit on the value of wL for the wind condition. It also now specifies that tb is in the corroded condition. A calculation of the minimum annular ring width for wind has been added.

This covers most of the changes I see in the design section (Section 5). Next time I will give you information on the changes to the various appendices and which new appendices have been added.

To keep our software, ITSdesign, current, we are already working on the revisions to incorporated these changes into ITSdesign.