Nace Sp0170 Pdf |work| Jun 2026
Certain process units are more susceptible to PTA SCC and thus require strict adherence to NACE SP0170. These are typically units in the 'sulfur train' of a refinery, including:
By following the guidelines outlined in NACE SP0170 PDF, industries can prevent corrosion and ensure safety, environmental protection, and cost savings.
The standard outlines several primary strategies to prevent the formation or impact of these acids: Alkaline Washing
While you will not find a free, legal PDF, the document is available for purchase from several legitimate sources. nace sp0170 pdf
If liquid washing is impractical, keeping the internal environment completely dry is an alternative. By introducing dehumidified air with a relative humidity (RH) below 20%, moisture is eliminated from the equation, preventing the chemical reaction that yields polythionic acid. Evolving Material Selection to Complement SP0170
PTA SCC can lead to rapid, catastrophic equipment failure, making the guidance within the NACE SP0170 standard essential. Core Components of NACE SP0170
Without moisture, the sulfur compounds cannot form corrosive acids. Key Considerations for Refinery Shutdowns Certain process units are more susceptible to PTA
NACE SP0170, titled "Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During Shutdown of Refinery Equipment," provides industry-vetted procedures to prevent environmental cracking.
) reacts with the iron and chromium in equipment walls to create a protective, dark . While the unit remains hot and running, this scale is relatively stable. However, the moment the system is breached for inspection, maintenance, or catalyst replacement, a hazardous chemical chain reaction initiates:
For precise solution concentrations, holding times, and chemical formulations, engineers should always consult the complete, official standard document provided via AMPP or authorized standards distributors. If liquid washing is impractical, keeping the internal
When exposed to sulfide corrosion products (formed during operation) + oxygen + water, these sensitized materials form polythionic acid ( H2SxO6cap H sub 2 cap S sub x cap O sub 6
NACE SP0170 is a standard practice that provides essential mitigation methods to protect austenitic stainless steels and other austenitic alloys from polythionic acid (PTA) stress corrosion cracking (SCC). Importantly, the standard's scope covers the entire shutdown period, including the downtime as well as the contiguous periods required to shut down and start up the equipment.
While NACE SP0170 focuses on operational mitigation, it highlights how material selection alters shutdown protocols. Alloy Type Sensitivity to PTA-SCC NACE SP0170 Requirement High (if exposed to design temps) Full neutralization or nitrogen blanket mandatory. Stabilized Alloys Moderate (resistant but can sensitize over long durations) Often requires safeguarding depending on service severity. Low-Carbon Alloys 304L, 316L Low (delayed sensitization)
A wetting agent or surfactant is often added to help the solution penetrate heavy oil or coke films covering the sulfide scale. Inhibitors: Sodium nitrate ( NaNO3cap N a cap N cap O sub 3
