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

RISK-BASED INSPECTION METHODOLOGY, PART 5—SPECIAL EQUIPMENT 5-27
Table 4.9⎯Number of Release Holes as a Function of Storage Tank Diameter
Storage Tank Diameter
(m (ft))
Number of Release Holes with or Without a Release Prevention Barrier
Small Medium Large
30.5 (100) 1 0 0
61.0 (200) 4 0 0
91.4 (300) 9 0 0
NOTE For intermediate storage tank diameters, the number of small release holes may be calculated using the
following equation where the function nint() is defined as the nearest integer. For example, nint(3.2)=3, nint(3.5)=4,
and nint(3.7)=4.
n rh ,1
2
⎡ ⎡⎛
D ⎞ ⎤ ⎤
= max ⎢nint ⎢⎜ ⎟ ⎥, 1⎥
⎢ ⎢ C
⎣⎝
36 ⎠ ⎥
⎦
⎥
⎣
⎦
Figures
1
Dike Area
6
Tank
Surface Water
2
Onsite
Offsite
3
Subsurface Soil
4
Ground Water
5
Figure 4.1⎯Storage Tank Consequence