API 650 : 2013/ADD3 :2018

The limiting piping loads are as follows: In SI units: FRmax = 310,000 N (tension at A controls) MCmax = 6.37 × 108 N-mm (tension at C′ controls) MLmax = 1.95 × 108 N-mm (tension at A controls)
In USC units: FRmax = 70,900 lbf (tension at A controls) MCmax = 5.73 × 106 in.-lbf (tension at C′ controls) MLmax = 1.75 × 106 in.-lbf (tension at A controls)

A.1.1 This Annex provides requirements for field-erected tanks of relatively small capacity in which the stressed components have a nominal thickness of no more than 13 mm (1/2 in.). The stressed components include the shell and reinforcing plates, shell reinforcing plates for flush-type cleanout fittings and flush-type shell connections, and bottom plates that are welded to the shell. The nominal thickness limit of 13 mm (1/2 in.) does not apply to: 1) bottom plates not welded to the shell; 2) the bottom reinforcing plate of flush-type cleanouts and flush-type shell connections; 3) flanges and cover plates of flush-type cleanouts; 4) flush-type shell connection necks attached to shell and flanges and cover plates of flush-type shell connections; 5) nozzle and manhole necks, their flanges and cover plates; 6) anchor bolt chair components and shell compression ring. A.1.2 This Annex is applicable only when specified by the Purchaser and is limited to design metal temperatures above –30 °C (–20 °F) [above –40 °C (–40 °F) when killed, fine-grain material is used]. A.1.3 This Annex is applicable to any of the Section 4 materials, although the single allowable stress does not provide any advantage to higher strength steels. A.1.4 This Annex states only the requirements that differ from the basic rules in this standard. When differing requirements are not stated, the basic rules must be followed; however, the overturning effect of a wind load should be considered. A.1.5 Typical sizes, capacities, and shell-plate thicknesses are listed in Tables A.1a through A.4b for a design in accordance with A.4 (joint efficiency = 0.85; design specific gravity = 1.0; and corrosion allowance = 0). A.2 Materials A.2.1 Shell-plate materials shall not be more than 13 mm (1/2 in.) thick, as stated in A.1.1. A.2.2 For stressed components, the Group-I and Group-II materials listed in Table 4.3a and Table 4.3b may be used at a design metal temperature of –30 °C (–20 °F) or warmer but need not conform to the toughness requirements of 4.2.9, Figure 4.1, and 9.2.2. Group-III and Group-IIIA materials may be used at a design metal temperature of –40 °C (–40 °F) or warmer and shall conform to impact requirements of 9.2.2.
A.2.3 Material used for shell nozzle and manhole necks and flanges shall conform to 4.5, 4.6, and Table 4.3a and Table 4.3b but need not conform to the toughness requirements of 4.2.9, 4.5.5, and Figure 4.1.