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

2-58 API RECOMMENDED PRACTICE 581
Table 8.2—Environmental Severity—SSC
pH of Water
Environmental Severity as a Function of H 2 S Content of Water
<50 ppm 50 to 1,000 ppm 1,000 to 10,000 ppm >10,000 ppm
<5.5 Low Moderate High High
5.5 to 7.5 Low Low Low Moderate
7.6 to 8.3 Low Moderate Moderate Moderate
8.4 to 8.9 Low Moderate Moderate a High a
>9.0 Low Moderate High a High a
a
If cyanides are present, increase the susceptibility to SSC one category for pH > 8.3 and H 2 S concentrations greater than 1,000
ppm.
Table 8.3—Susceptibility to SSC—SSC
Susceptibility to SSC as a Function of Heat Treatment
Environmental
Severity
As-welded
Max Brinnell Hardness a
PWHT
Max Brinnell Hardness a
<200 200 to 237 >237 <200 200 to 237 >237
High Low Medium High Not Low Medium
Moderate Low Medium High Not Not Low
Low Low Low Medium Not Not Not
a
Actually tested as Brinnell, not converted from finer techniques, e.g. Vickers, Knoop, etc.
Table 8.4—Determination of Severity Index—SSC
Susceptibility
Severity Index—S VI
High 100
Medium 10
Low 1
None 0