Amine cracking is a common term applied to cracking of steels under the combined action of tensile stress and corrosion in aqueous amine systems used to remove/absorb H2S, CO2 and their mixtures. Amine cracking is a form of alkaline stress corrosion.
Amine Cracking | Materials And Corrosion Control
| Damage Mechanism | Amine Cracking |
| Damage Description | · Amine cracking is a common term applied to cracking of steels under the combined action of tensile stress and corrosion in aqueous amine systems used to remove/absorb H2S, CO2 and their mixtures. Amine cracking is a form of alkaline stress corrosion
· It is most often found at or adjacent to non-PWHT’d carbon steel weldments, or in highly cold worked part · Cracking severity is related to amine type (see SAES-W-011) |
| Affected Materials | Carbon steel, low alloy steels |
| Control Methodology | · The critical factors are stress, amine type, concentration and temperature.
· All equipments subject to amine carryover are likely to suffer this damage. · PWHT all carbon steel welds in piping and equipment in accordance with API RP 945. The same requirement applies to repair welds and to internal and external attachment welds. · PWHT all piping and equipment in DGA service operating above 190°F. · Use solid or clad stainless steel, Alloy 400 or other corrosion resistant alloys in lieu of carbon steel. · Water wash non-PWHT’d piping and equipment prior to welding, heat treatment or steamout. |
| Monitoring Techniques | · Focus inspection on all DGA solutions above 190°F metal temperature.
· Although cracks may be seen visually, crack detection is best performed with WFMT, EC, RT or ACFM techniques. · PT is usually not effective in finding tight and/or scale filled cracks and should not be used. · If the cracks have minimum branching, crack depths can be measured with a suitable UT technique including external SWUT. · AET can also be used for monitoring crack growth and locating growing cracks. |
| Inspection Frequency | As determined by OSI |
| KPIs | · Insure velocities less than 1.5 m/s for CS. · If amine carryover is expected, PWHT any piping and equipment when operating temperatures exceed 190°F. · Number of inspections performed for amine SCC. |
| Reference Resources (Standards/GIs/BPs) | · API RP 571 (DM #22)
· API RP 945 |
Wet H2S Cracking | Materials and Corrosion Control
Carbonate Stress Corrosion Cracking | Materials And Corrosion Control