Wet H2S environments at ambient temperatures can do nasty, nasty things to the wrong kinds of steels and alloys. Microfracturing and
intense corrosion of certain alloys was noted early in the history of the oilpatch. Rules-of-thumb about what NOT to use quickly
evolved, but those did not address causes or systematic preventative measures. A history of NACE MR0175 can be found
here.
The Standard has its origins in the group efforts of Western Canadian Sedimentary Basin oilfield engineers who pooled their knowledge about successful
sour gas handling, organized themselves as a NACE commitee and began issuing recommendations and documents as early as 1963.
Today, NACE MR0175/ISO 15156 is a standard evolved and maintained by the National Association of
Corrosion Engineers (NACE) International. It deals with how to manufacture and maintain
equipment in such a way that it has good resistance to sulfide stress cracking
(SSC). API 6A deals with specifications for wellhead and Christmas tree
equipment. Together, both specs lay out how to inspect maintain and
certify equipment like flanges and drilling spools for use in wet sour service
environments. We can test items for unacceptable materials, test for
unacceptable hardness, and test for the presence of SSC and certify compliance.
We can be part of a team that does everything already mentioned, and have
the dimensional verification and pressure test for API
6A completed as part the whole certification operation.
