NACE International Task Group T-8-16 on Cracking in Wet H2S Environments was formed in 1988 to conduct an organized study on the incidence and mechanisms of cracking in pressure vessels operating in refinery wet hydrogen sulfide (H2S) environments. Specific objectives were to (a) define the nature and extent of the problem by means of an industry survey; (b) define mechanisms for the type of cracking found, to be accomplished primarily through a literature survey; (c) establish inspection guidelines for existing vessels; and (d) develop repair and mitigation guidelines for cracked vessels. Four work groups were formed to address these tasks. In 1990, a fifth work group was formed with a fifth objective, (e) to investigate material specifications and fabrication practices for new pressure vessels.

This standard recommended practice summarizes objectives (a), (c), and (d) listed above. A technical committee report (NACE Publication 8X294), "Review of Published Literature on Wet H2S Cracking of Steels Through 1989," 1 has been issued to address objective (b). Finally, objective (e) has been handled by another technical committee report (NACE Publication 8X194), "Materials and Fabrication Practices for New Pressure Vessels Used in Wet H2S Refinery Service."

This standard is intended for use primarily by refinery corrosion and materials engineers and inspection, operations, and maintenance personnel. Information and guidance presented in this standard reflect the work of many individuals representing numerous companies worldwide.

The titles and source information of the codes, specifications, and standards referred to or discussed in this standard are provided in Appendix A rather than listed in footnotes throughout the standard. Confining this important source document information to one appendix should help readers who have any interest in further research.

This standard was originally prepared in 1996 by Task Group T-8-16 on Cracking in Wet H2S Environments. It was reaffirmed in 2000 by Specific Technology Group (STG) 34 on Petroleum Refining and Gas Production and is issued by NACE International under the auspices of STG 34.

1.1 This standard is intended to be a primary source of information on cracking in wet H2S petroleum refinery environments and provides guidelines on the detection, repair, and mitigation of cracking of existing carbon steel refinery pressure vessels in wet H2S environments. Refinery pressure vessels include items such as, but not limited to, columns, heat exchangers, drums, reboilers, and separators. Piping is not included in the scope of this standard; inspection requirements for new pressure vessels (never in service) are also beyond the scope of this standard.

 Historical Document 2000