If you would like to tailor your shutdown protocol, let me know:
Справочники | List of NACE in our library - Служба НТИ
If you are developing a specific maintenance or turnaround scope, let me know your equipment uses, the specific operating temperature range , and whether the unit will be opened for inspection so I can help tailor the correct chemical neutralizer or purging requirements for your procedure. Share public link
The standard NACE SP0170 (now managed by ) provides critical guidelines for protecting austenitic stainless steels and other austenitic alloys from Polythionic Acid Stress Corrosion Cracking (PTA SCC) nace sp0170 pdf 2021
Under normal operations, sulfide scales form on the inside of pipes and vessels.
SP0170 integrates corrosion science and probabilistic risk assessment. Important technical aspects include:
It is published by NACE International (now part of AMPP - Association for Materials Protection and Performance). The standard focuses on preventing SCC caused by polythionic acid, which forms when sulfide corrosion products (metal sulfides) react with water and oxygen during equipment shutdown. Why is 2021 Significant? If you would like to tailor your shutdown
provides detailed instructions on the required concentration of the solution, typically recommending a concentration of 0.5% to 1.0% Na₂CO₃ by weight, along with instructions on maintaining high pH levels during the neutralization process. How to Obtain the NACE SP0170 PDF (2021/Latest Revision)
The primary goal of this standard is to prevent the rapid cracking of sensitized austenitic alloys caused by polythionic acids, which form when sulfide scales on equipment surfaces react with moisture and oxygen during maintenance shutdowns. Core Recommendations Neutralization
"The 2021 version is only for new equipment." Truth: The PDF clearly states that existing equipment can remain in service if it was qualified under a previous revision. However, any repair, modification, or re-rating after the 2021 publication date must comply with the new rules. Important technical aspects include: It is published by
In summary, while NACE SP0170-2021 does not exist, the 2018 version is the current and crucial standard for anyone involved in the design, operation, maintenance, or inspection of refinery equipment containing austenitic stainless steels. The document provides the necessary framework to manage the severe risk of polythionic acid stress corrosion cracking during shutdowns. For engineers and asset managers, ensuring compliance with NACE SP0170 is not just about following a rule; it is an essential practice for ensuring safety, regulatory compliance, operational reliability, and the long-term economic viability of industrial assets.
The standard details several primary techniques to prevent the formation or impact of polythionic acids:
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