API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology

5-22 API RECOMMENDED PRACTICE 581
A
rt
Table 4.3⎯Thinning Damage Factors for Storage Tank Bottom Components
E
Inspection Effectiveness
1 Inspection
D C B A
0.00 0.1 0.1 0.1 0.1 0.1
0.05 4 1 0.5 0.4 0.3
0.10 14 3 1 0.7 0.5
0.15 32 8 2 1 0.7
0.20 56 18 6 2 1
0.25 87 32 11 4 3
0.30 125 53 21 9 6
0.35 170 80 36 16 12
0.40 222 115 57 29 21
0.45 281 158 86 47 36
0.50 347 211 124 73 58
0.55 420 273 173 109 89
0.60 500 346 234 158 133
0.65 587 430 309 222 192
0.70 681 527 401 305 270
0.75 782 635 510 409 370
0.80 890 757 638 538 498
0.85 1,005 893 789 696 658
0.90 1,126 1,044 963 888 856
0.95 1,255 1,209 1,163 1,118 1,098
1.00 1,390 1,390 1,390 1,390 1,390
Release Hole
Number
Table 4.4⎯Release Hole Sizes and Areas⎯Storage Tank Courses
Release Hole Size
Range of Hole
Diameters
(inch)
Release Hole Diameter
(inch)
1 Small 0 – 1/8 d
1
= 0.125
2 Medium > 1/8 – ¼ d
2
= 0.25
3 Large > ¼ – 2 d
3
= 2
⎛ ⎞
4 Rupture > 2 d4 = 12⎜ ⎟
⎝ 4 ⎠
D tank