scope:

Foreword

This technical committee report describes the state of the art regarding alkaline carbonate stress corrosion cracking (ACSCC) experiences in certain sour waters found in petroleum refining plants. This report outlines where ACSCC has occurred in process equipment in petroleum refining service, the refining community's current theory(ies) on the conditions and mitigation techniques that may have an impact on this type of damage, and analytical and inspection techniques that have been used to address the issue. The main focus of this report is on fluidized catalytic cracking units (FCCUs) and light ends recovery systems and associated sour water processing equipment where the majority of the damage has been reported. The technical committee has also chosen to include ACSCC in sour water stripper (SWS) units. This report is intended to provide the refining industry with a resource for current information that is available on ACSCC.

The main sections of this report include:

What Is Alkaline Carbonate Stress Corrosion Cracking?

Where Has ACSCC Occurred?

What Conditions Are Observed When ACSCC Occurs?

Literature-Proposed Regions for ACSCC Susceptibility

Chemical Analysis in ACSCC Likelihood Assessment

Inspection for ACSCC

Mitigation of ACSCC

Supplemental information is provided in the following appendixes:

Appendix A: Examples of ACSCC

Appendix B: Graphs of TG 347 Survey Data

Appendix C: Proposed Guidelines for ACSCC Susceptibility

Appendix D: Examples of CO₂/Bicarbonate/Carbonate Equilibrium Curves