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

2.B-110 API RECOMMENDED PRACTICE 581
2.B.13.6
Figures
Start
Yes
Is material
Carbon Steel or <13%
Cr?
No
No corrosion due to
Carbon Dioxide
Are liquid
HCs
present?
Yes Water
Yes Fluid Yes
Content
Velocity
< 20% ?
> 1 m/s ?
No corrosion due to
Carbon Dioxide
No
No
No
Calculate Dew Point
Temperature using
equation 2.B.25
No
Is the current temperature
less than the Dew Point
Temperature?
No liquid water
in steam
No corrosion due to
Carbon Dioxed
Yes
Calculate Base Corrosion Rate CR base
Equation 2.B.26
• Pressure
• Temperature
• pH
• Shear Stress
Is there
glycol or
inhibitor?
No
Corrosion Rate is equal to
Base Corrosion Rate
Yes
% weight glycol
Determine adjustment factors for
glycol and inhibitor using Paragraph
2.B.13.3.7.
Use Equation 2.B.23 to obtain Final
Corrosion Rate
Figure 2.B.13.1—CO 2 Corrosion—Determination of Corrosion Rate