Oil and gas service involving water and H2S at a partial pressure high enough to cause sulfide stress cracking, set at 0.05 psia (0.3 kPa) under NACE MR0175/ISO 15156. A sour designation drives material choice, hardness limits, welding procedures and HIC and SSC testing. Sweet service, by contrast, is dominated by CO2, where the threat is carbonic acid corrosion and mesa attack rather than cracking.
Line goes into sour service once the new wells tie in, so every flange and fitting needs MR0175 paperwork.
Sour is not about corrosion rate. A sour line can show almost no wall loss and still crack, so hardness and material certs matter as much as inspection.
Also heard as
- sour
- H2S service
- sour gas service
Related terms
Sulfide stress cracking
Cracking of hard steel under tension in wet hydrogen sulfide service, a form of hydrogen embrittlement.
Hydrogen embrittlement
Loss of ductility when atomic hydrogen gets into steel, leading to sudden cracking under stress.
Black powder
Fine black dust of iron sulfides and oxides that forms inside gas pipelines and fouls filters, meters and valves.
Corrosion inhibitor
Chemical added in small doses to a fluid to slow corrosion of the metal it touches.