The core value of NACE SP0170 lies in its mitigation strategies. When you download the standard, you will find detailed procedures for:
As the unit cools down, transition seamlessly to either the alkaline wash or the nitrogen blanket before internal metal temperatures reach the dew point.
If equipment does not require internal inspection or catalyst dumping, the most effective solution is to isolate it from oxygen entirely.
| Feature | NACE SP0170 | NACE MR0175/ISO 15156 | | :--- | :--- | :--- | | | Shutdown/Startup protection | Materials selection for sour service (H2S) | | Primary Threat | Polythionic acid SCC | Sulfide stress cracking (SSC) and HIC | | Applicability | During maintenance events | During normal operation | | Target Materials | Austenitic stainless steels | Carbon steels, low alloys, CRAs | | Key Measure | Neutralization washing | Hardness control, alloy composition | nace sp0170 pdf
Neutralizing acidic environments with solutions like soda ash. Nitrogen/Dry Air Purging: Eliminating water or oxygen from the internal atmosphere. Material Choice:
The NACE SP0170 PDF standard offers several benefits to the petroleum refining and petrochemical industries, including:
Will the equipment be or kept closed?
Protects external heater tube surfaces where reducing environments or fuel-rich combustion have built up external sulfide scales.
Residual stresses from welding, cold working, or thermal cycling during operational shutdown provide the mechanical driver needed to propagate the cracks along the sensitized grain boundaries.
: This could involve guidelines for designing, installing, and maintaining impressed current cathodic protection (ICCP) systems used to protect pipelines, storage tanks, and other metallic structures from corrosion. The core value of NACE SP0170 lies in
The alloy has been sensitized (typically through heat treatment or welding), causing chromium carbides to form at grain boundaries, which lowers local corrosion resistance. Sulfur Compounds: Metal sulfides (e.g., FeScap F e cap S
By keeping the system under a continuous positive pressure of dry nitrogen, oxygen and moisture are barred from entering. Without oxygen and water, sulfide scales cannot convert into polythionic acid.