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

2.B-68 API RECOMMENDED PRACTICE 581
2.B.8.6 Figures
Start
No
Is material of
construction
carbon steel or
low alloy?
Yes
No
Is material of
construction
Type 300
Series SS?
Yes
Determine Corrosion
Rate using Tables
2.B.8.2 and 2.B.8.3
• Acid gas loading
• HSAS
• Amine type and
Concentration
• Material
Consult with a
materials specialist.
Determine estimated corrosion
Rate from Table 2.B.8.5.
Determine multiplier from
Table 2.B.8.4.
Estimated
Corrosion Rate
Estimated Corrosion Rate X
multiplier.
Estimated
Corrosion Rate
Figure 2.B.8.1—Amine Corrosion—Determination of Corrosion Rate
2.B.9
2.B.9.1
High Temperature Oxidation
Description of Damage
Corrosion due to high temperature oxidation occurs at temperatures above about 482 °C (900 °F) for carbon
steel and increasing higher temperatures for alloys. The metal loss occurs as a result of the reaction of metal
with oxygen in the environment. Typically, at temperatures just above the temperature where oxidation
begins to occur, a dense comparatively protective oxide forms on the surface that reduces the metal loss
rate. The oxide scale tends to be significantly more protective as the chromium concentration in the metal
increases.
2.B.9.2
Basic Data
The data listed in Table 2.B.9.1 are required to determine the estimated corrosion rate for high temperature
oxidation service. If precise data have not been measured, a knowledgeable process specialist should be
consulted.
2.B.9.3
Determination of Corrosion Rate
The steps required to determine the corrosion rate are shown in Figure 2.B.9.1. The corrosion rate may be
determined using the basic data in Table 2.B.9.1 in conjunction with Tables 2.B.9.2 through 2.B.9.3.