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 5.7.2.7, they increased the maximum size of the outer peripheral weld on the repads in the SI units from 38 mm to 40 mm.
2) 5.7.7.4 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 5.7.7.5(b) and 5.7.8.4(e) 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 5.8.6.1, 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) 5.9.6.1 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) 5.10.2.6, frangible roofs, was revised. They also added requirements for 30' to 50' diameter tanks.
7) 5.10.4.4, 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) 5.10.5.1, 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.