: Covers the entire shutdown process, including downtime and the periods immediately preceding and following it (start-up). Target Materials : Focuses on common refinery alloys like UNS S30400 (304 SS) S31600 (316 SS) , and stabilized grades like
: Maintaining low relative humidity to prevent the condensation necessary for acid formation.
Keeping the internal relative humidity low enough to prevent liquid water from condensing on the metal surfaces, blocking the acid formation chain. Summary of Mitigation Methods Primary Mechanism Best Used For Key Consideration Nitrogen Blanket Excludes Oxygen ( O2cap O sub 2 Vessels not requiring internal inspection Requires strict confined space safety monitoring. Soda Ash Wash Neutralizes Acids ( H2SxO6cap H sub 2 cap S sub x cap O sub 6 Equipment opened for physical inspection/cleaning Must dry completely; chloride content must be minimized. Dehumidification Excludes Water ( H2Ocap H sub 2 cap O Piping and large vessels during prolonged turnarounds Requires continuous power and monitoring equipment. Critical Operational Best Practices nace sp0170 pdf 2021
The standard outlines several strategies to prevent the formation of polythionic acid or to neutralize it before damage occurs: NACE SP0170-2018
Displacing air with dry nitrogen to keep oxygen out so the acid can never form. : Covers the entire shutdown process, including downtime
You need three parameters:
If you are looking for the specific 2021 "narrative" or technical updates, you should focus on: Summary of Mitigation Methods Primary Mechanism Best Used
Understanding and applying NACE SP0170 is critical for corrosion engineers, inspection personnel, and refinery maintenance managers during turnarounds.
: The full designation is AMPP SP0170-2021 (Revised 2021-12-10).
For detailed technical specifications, application guidelines, and any updates or revisions, referring directly to the NACE documentation or reaching out to NACE experts is recommended.
As of 2021, NACE International merged with SSPC to form AMPP. The standard is available for purchase and download through: (formerly NACE Store) ANSI Webstore GlobalSpec/Accuris