Nace Sp0170 Pdf 2021 «DIRECT ⇒»
The is a critical document for materials, corrosion, and inspection engineers in the refining and petrochemical industries. Its primary focus is the prevention of Polythionic Acid Stress Corrosion Cracking (PTA SCC) in austenitic stainless steels and other high-alloy materials during shutdowns and maintenance.
NACE SP0170 (2021) strengthens industry guidance for External Corrosion Direct Assessment by emphasizing data quality, multi-method indirect inspection, probabilistic ranking, uncertainty quantification, and feedback from direct examinations. While ECDA is a powerful tool—especially for locations where direct inline tools are impractical—its effectiveness depends heavily on the quality of input data, appropriate selection and combination of indirect techniques, and disciplined verification. Operators should treat SP0170 as part of an integrated integrity-management strategy that includes CP optimization, targeted excavations, and, where feasible, complementary inspection technologies.
NACE SP0170-2018 remains the active standard for protecting austenitic stainless steels from polythionic acid stress corrosion cracking (PTA SCC) during refinery shutdowns as of 2021, focusing on nitrogen purging and alkaline washing to mitigate risks. The standard, now managed by AMPP, outlines critical procedures for preventing corrosion in sensitized austenitic alloys common in hydrotreating and cracking units. Access the standard through the ANSI Webstore . nace sp0170 pdf 2021
This method prevents PTA formation by excluding oxygen, a key ingredient in the formation reaction. Equipment is filled and pressurized with an inert gas, typically nitrogen, after it has been properly purged.
| Test | Frequency | Acceptance | |------|-----------|-------------| | Pull-off bond | 1 per 100 m² | ≥ 1.5 MPa | | Thickness (magnetic) | 5 per 10 m² | 80–120% of spec | | Porosity (ferroxyl) | 1 per 50 m² | ≤ 3 blue spots per 100 cm² | | Continuity | 100% of anode segments | ≤ 2 ohms | The is a critical document for materials, corrosion,
The standard's full title is .
). If the alloy is under tensile stress (either residual weld stress or operational load), the acid causes severe, rapid intergranular cracking within a matter of hours. Key Mitigation Strategies Mandated by NACE SP0170 While ECDA is a powerful tool—especially for locations
When equipment must be opened for maintenance or catalyst dumping, nitrogen blanketing is impossible. Workers must wash the internal surfaces with an to neutralize any polythionic acid as it forms.
) in the presence of sulfur compounds, iron sulfides form on the surfaces of stainless steel.