We have entered 2009 and I am finally getting around to talking about the changes in API 650 Addendum 1. There will be a series of posts to talk about the different changes, so come back and see what else is changed.
We will start with the basic code section.
1) There are many places where they simple changed the thickness specifed in the SI portion from 12.5mm to 13 mm. You will find this mainly in places where 1/2" maximum thicknesses is specifed such as for self-supporting roofs and in Appendix A.
2) The minimum thickness in many places was revised from 1/4" to 0.236" for conform to 6mm thickness conversions and from 5mm to 4.8mm for 3/16" thickness conversions. This is specified in 5.3.5. This includes such places as 5.4.1 for minimum bottom thicknesses, Table 5-1 for annular bottom plate thicknesses, 18.104.22.168 for minimum thickness of built up stiffening rings, and 22.214.171.124 for minimum thickness of structural.
3) They revised sizes of angles in the SI units in such places as 126.96.36.199 (minimum top angle sizes), 188.8.131.52 (stiffener ring requirements), and 184.108.40.206 (top angle size required for open top tanks).
4) 5.2.1 b was revised to say that external pressure can be zero for tanks with circulation vents per Appendix H.
5) 5.2.1 also added loadings for internal floating roofs. Of course they could not add it to the end of the list, but had to add it near the beginning so they could renumber all of the items below it.
6) Revised 220.127.116.11 to specify that if you use lower strength material for a upper course, the lower course must be at least as thick as the required thickness of the upper course for product or hydrotest or you must do an elastic analysis.
7) They revised most of the tables to separate the SI from the US and made them table a and b.
8) In Table 5-4, shell manhole thickness, they revised some of the thicknesses required for the higher shell course thicknesses and added for up to 45mm (1 3/4") shell plate.
9) In various tables it appears that they revised SI dimensions to conform to the US dimension conversions. This includes Figure 5-7a (shell manhole gasket and bolt hole dimensions), Table 5-5a (shell manhole bolt circle and cover plate dimensions), Table 5-7a (shell nozzles), Table 5-8a (shell nozzle flanges), and Table 5-9a (flush cleanouts).
10) Table 5-10a was revised to change the maximum design liquid level for flush cleanout flanges in SI units. They also revised the bottom plate thickness for the largest flush cleanout at the maximum liquid level for the SI units.
Next time we will finish up the changes to the base code.