API Recommended Practice 579, Fitness-For-Service

By David R. Thornton, PE

The American Petroleum Institute has published the first edition of a new recommended practice, API RP 579 Fitness-For-Service. API RP 579 provides methods and procedures for evaluating the suitability for continued service of pressurized components of fixed equipment that contain flaws or damage. In addition to Fitness-For-Service (FFS) assessment procedures, API RP 579 provides guidance on determining component remaining life, remediation, and in-service monitoring of flaws. API RP 579 supplements the requirements in API 510, API 570, and API 653 for the evaluation of pressure vessels, piping systems, and storage tanks respectively.

The procedures in API RP 579 utilize the design and construction rules and methods in the ASME Boiler and Pressure Vessel Code, Section I and Section VIII, Divisions 1 and 2, the ASME B31.1 and B31.3 piping codes, and the API 650 and 620 storage tank standards. API RP 579 also provides guidance on adopting its procedures to equipment built to non ASME / API codes and standards. Individuals typically involved in a FFS assessment include:

While the size of API RP 579 may at first appear daunting, users should realize that approximately half of the contents consists of appendices containing equations, material information, and data required for conducting FFS assessments. API RP 579 contains eleven sections and ten appendices:

Section Contents

Appendix A Equations for determining MAWP, thickness, and stress in components
Appendix B Methods of stress analysis for Level 2 and Level 3 FFS assessments
Appendix C Compendium of stress intensity solutions (KI) for use with Section 9
Appendix D Compendium of reference stress solutions for use with Section 9
Appendix E Compendium of residual stress solutions for use with Section 9
Appendix F Guidance on material properties for use in conducting FFS assessments
Appendix G Guidance on failure modes and damage mechanisms
Appendix H Validation of assessment procedures
Appendix I Glossary of terms used in API RP 579
Appendix J Information on submitting technical inquiries to API regarding RP 579

Each of Sections 3 through 11 contains procedures for conducting three levels of FFS assessment:

Documentation of a FFS assessment should include sufficient information so that the assessment can be repeated at a later time. The documentation should reside in the equipment file with the inspection records. As a minimum, the following information should be included in the documentation:

Carmagen Engineering has resources available to conduct FFS assessments of plant equipment, assist plant personnel who may be unfamiliar with the FFS technology, or conduct FFS training courses.