Nace Sp0170 Pdf Here
When refinery equipment is shut down, the materials inside are exposed to air and moisture, which can trigger a highly destructive phenomenon: Polythionic Acid Stress Corrosion Cracking (PTA SCC). (now updated as NACE SP0170-2018) is the industry-standard practice designed to mitigate this risk.
What is Polythionic Acid Stress Corrosion Cracking (PTA-SCC)?
Grades 321 (titanium-stabilized) and 347 (niobium-stabilized) contain elements that tie up carbon before it can react with chromium, drastically reducing sensitization at operating temperatures.
In the high-stakes world of oil and gas processing, corrosion is the silent enemy. While much attention is given to the corrosion of the pipe wall itself, a more vulnerable area often determines the lifespan of a facility: the and the underlying steel. nace sp0170 pdf
Typically utilizes a solution of sodium carbonate ( , soda ash).
This standard provides critical mitigation methods to prevent , which often occurs during refinery shutdowns. Key sections include:
The specific standard SP0170 likely deals with a detailed methodology or protocol for a particular aspect of corrosion management. As an example, standards might cover: When refinery equipment is shut down, the materials
Because PTA SCC can cause extensive, through-wall cracking within hours of exposure to air, refineries must strictly enforce the procedures found in the NACE SP0170 PDF. Core Mitigation Methods Outlined in NACE SP0170
The standard (Standard Practice) is titled "Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During a Shutdown of Refinery Equipment" . Maintained by Task Group (TG) 173 under the Association for Materials Protection and Performance (AMPP) (formerly NACE International), this document outlines critical operational mitigation methods to prevent catastrophic structural failure from polythionic acid stress corrosion cracking (PTA SCC) when refinery process units undergo maintenance or turnarounds.
For asset integrity managers and corrosion engineers, owning an authorized copy of the is necessary for compiling standard operating procedures (SOPs) for turnarounds. Typically utilizes a solution of sodium carbonate (
| Standard | Focus | Key Difference from SP0170 | | :--- | :--- | :--- | | | Weld protection (sulfidation) & polythionic acid SCC | For welds on carbon steel in high-temp sulfur service. | | NACE MR0175/ISO 15156 | Materials resistant to H₂S (sour service) cracking | For wet H₂S (low temp), not hot sulfidation. | | NACE MR0103 | Materials for sour refining environments | For general refinery sour service, not specifically weld overlay. | | API RP 939-C | Sulfidation corrosion in refinery components | A broader guideline; SP0170 is more prescriptive for weld protection. |
Desulfurizing, hydrocracking, hydrotreating, FCCUs, and crude/lube distillation units Polythionic Acid Stress Corrosion Cracking (PTA SCC) Where to Purchase/Download ANSI Webstore , AMPP Store, or authorized standards vendors. Understanding the Threat: What is PTA SCC?
PTA-SCC is a rapid, intergranular cracking mechanism that occurs when three specific conditions are met simultaneously:
Refinery engineers and organizations can acquire a fully authorized copy through several main channels: NACE SP0170-2018
In a refinery environment, equipment made from austenitic stainless steels (like 300-series alloys) often develops sulfide scales on internal surfaces during operation. When the unit is shut down and opened, these sulfides react with moisture and oxygen in the air to form . These acids can cause rapid, catastrophic cracking in sensitized metals—sometimes within hours of exposure. Key Mitigation Strategies in SP0170