Nace Sp0170 Pdf 2021 !full! Jun 2026

Note: Always ensure you are accessing standards through official NACE/AMPP channels to guarantee you have the most accurate and authorized version.

Hydroprocessing loops operate under deeply reducing conditions with high hydrogen sulfide (

) precipitate along the grain boundaries. This depletes the adjacent areas of chromium—dropping it below the 12% threshold required for passive corrosion protection. This microstructural change is known as sensitization. The Three-Part Reaction Matrix nace sp0170 pdf 2021

To lower this risk, engineers often utilize stabilized grades like (stabilized with titanium) or Grade 347 (stabilized with niobium), which undergo specialized Stabilization Post-Weld Heat Treatment (PWHT) to tie up free carbon. However, even stabilized alloys can exhibit vulnerability if operations run continuously at extreme temperatures, making the shutdown procedures in NACE SP0170 critical regardless of the exact austenitic alloy variant used. Key Shutdown Mitigation Methods

AMPP - The Association for Materials Protection and Performance Key Mitigation Strategies Note: Always ensure you are accessing standards through

AMPP - The Association for Materials Protection and Performance Overview of NACE SP0170

), which can accidentally be triggered if the wash water contains trace chlorides. This microstructural change is known as sensitization

Existing metal sulfides deposited inside the equipment during operation. Moisture ( H2Ocap H sub 2 cap O

Uncertainty Quantification: SP0170 recognizes measurement uncertainties and variability in soil and coating properties. It encourages conservative thresholds for prioritizing excavations when data quality is poor and advocates sensitivity analysis in ranking outputs.

The most effective method is to prevent air from entering the equipment until it is completely clean and dry.

[ Sulfur in Hydrocarbons ] │ (High Temps during Operation) ▼ [ Metal Sulfide Scale (FeS, NiS) ] │ ┌──────────────┴──────────────┐ (During Shutdown) ▼ ▼ [ Oxygen (O2) ] [ Moisture (H2O) ] │ │ └──────────────┬──────────────┘ ▼ [ Polythionic Acid Formation ] │ ▼ (On Sensitized Austenitic Alloys) [ Polythionic Acid SCC (Cracking) ] Material Vulnerability and Sensitization