: Dehumidified, dry air with an exceptionally low dew point is circulated through the equipment.
Equipment is purged and kept under a continuous positive pressure blanket of dry, high-purity nitrogen ( N2cap N sub 2
This standard was first published in 1970 as a recommended practice (RP), designated as . It has since been updated several times, evolving to its current form as a standard practice (SP) numbered SP0170. Today, the standard is owned and maintained by Task Group 173 of the Association for Materials Protection and Performance (AMPP) . nace sp0170 pdf
Adherence to is a cornerstone of mechanical integrity management in modern refining environments. Polythionic Acid Stress Corrosion Cracking is a rapid and unforgiving failure mode, but it is entirely preventable. By rigorously applying nitrogen blankets, executing precise alkaline carbonate washes, and managing humidity, operators can protect their austenitic stainless steel assets, ensuring safe turnarounds and reliable subsequent production cycles.
To understand the importance of NACE SP0170, one must first understand the mechanism it seeks to prevent. PTA SCC is a phenomenon that can cause rapid, catastrophic cracking in susceptible materials. : Dehumidified, dry air with an exceptionally low
Using alloys like 304L or 316L restricts the carbon content to a maximum of 0.03%. With less carbon available, chromium carbide precipitation is significantly delayed, reducing sensitization during short-term thermal exposures (like welding). However, prolonged exposure at high operating temperatures can still cause sensitization in L-grades.
A corrosion inhibitor (typically a nitrate-based compound) is added to the solution to prevent chloride stress corrosion cracking, as soda ash solutions can sometimes concentrate chlorides. Today, the standard is owned and maintained by
The most reliable way to obtain the correct and most current version is through NACE/AMPP's authorized distribution network. Several online standards retailers, such as Accuris (formerly Techstreet), ANSI Webstore, and GlobalSpec, are official partners.