Tuesday, January 20, 2009

API-650 11th Edition Addendum 1 - Part 3

Today we will look at the changes to the appendices. There have been some major additions.

1) Added Appendix AL - this is a complete section for the design, fabrication, erection and testing of aluminum tanks.
2) In Appendix B, they added section B.6 for tank foundations for tanks with elevated temperatures.
3) Added Appendix EC - a commentary on the seismic Appendix E including examples.
4) Revised Appendix F to use the yield strength of the material in formulas F.4.1 and F.5.1.
5) Appendix H added load combinations for floating roof supports.
6) Appendix M added a new paragraph M.3.3 to address the changes to to use Fy. This caused them to renumber everything below this. It appears that the new M.3.7 did not get changed to conform to the changes to Appendix F and will have to be modified.
7) Appendix S added that it is for a maximum of 200' diameter tank.
8) Appendix S added S.4.11.3 to allow the shop welding of narrow plate to form wider shell plate.
9) Added Appendix SC to allow mixed material (carbon steel and stainless steel) in the same tank.
10) Appendix V revised the maximum wind pressure formula, corrected various formulas, and added new formulas. The new formulas include the added stability factor. This sets the values for the stability factor and will require at least two different checks.
11) Added Appendix X to allow tanks built using Duplex Stainless Steel.

This covers most of the changes that are a part of Addendum 1. Some have minor affects. However, there are some major changes. We are working on incorporating these changes in our ITSdesign software and will keep you informed as to how that is going.

Thursday, January 15, 2009

API 650 11th Edition Addendum 1 - Part 2

Today we will continue with the review of the base code of API 650 11th Edition, Addendum 1.

1) In, they increased the maximum size of the outer peripheral weld on the repads in the SI units from 38 mm to 40 mm.
2) added that the reinforcing over the top of an opening shall be calculated for both the design and hydrotest condition.
3) A revision was made to both and to specify the basis for the thickness of the shell plate that can be used for the reinforcing calculations for flush type cleanouts and flush type fittings.
4) In 5.8.4 and, they added that the effect of loads other than normal personnel access applied at the roof manhole or rectangular roof opening and the supporting structure shall be considered and that the roof structure and the plate around the opening shall be reinforced as necessary.
5) revised the note for SI units to say that the minimum section modulus for the wind girder for tanks over 60m in diameter may be reduced but cannot be less than that required for a 61m diameter tank. (Seems like a bit of a problem here.)
6), frangible roofs, was revised. They also added requirements for 30' to 50' diameter tanks.
7), the requirement for rafter spacing was revised. They provided a formula to calculate the maximum spacing and set the maximum spacing to 84". This applies to all rafters.
8), the minimum thickness calculation now includes the the corrosion allowance for self supporting cone roof tanks similar to what was already in there for dome roof tanks. The one problem is that for dome roof tanks the formula has a >= sign while the cone roof tank has only a > sign. This will need to be addressed.
9) 5.11.2, they revised the calculation of MF for the wind overturning to include a formula for the maximum value equal to 0.90HD.
10) Tables 5-21a and 5-21b were revised. They will be revised again in the next addendum as these formulas have been corrected again.

These are the changes I have seen in the base code for design. Next time we will look at the various appendices including the new ones.

Monday, January 12, 2009

API 650 Addendum 1, Part 1

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, for minimum thickness of built up stiffening rings, and for minimum thickness of structural.

3) They revised sizes of angles in the SI units in such places as (minimum top angle sizes), (stiffener ring requirements), and (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 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.