The potential exists for stress corrosion cracking (SCC) of carbon steel pipelines transporting fuel grade ethanol (FGE) and FGE- gasoline blends. The objectives of SCC 4-4 were to: 1. Develop data necessary to make engineering assessments of the feasibility of transporting FGE and FGE blends in existing pipelines, 2. Identify ethanol blends that can be transported in existing pipelines without significant modification of the system and operations (Case 1); blends that require significant modifications (Case 2) and blends that cannot be transported in existing pipelines, but could be moved in ...
The potential exists for stress corrosion cracking (SCC) of carbon steel pipelines transporting fuel grade ethanol (FGE) and FGE- gasoline blends. The objectives of SCC 4-4 were to: 1. Develop data necessary to make engineering assessments of the feasibility of transporting FGE and FGE blends in existing pipelines, 2. Identify ethanol blends that can be transported in existing pipelines without significant modification of the system and operations (Case 1); blends that require significant modifications (Case 2) and blends that cannot be transported in existing pipelines, but could be moved in specially designed systems (Case 3), and 3. Characterize the time to initiation of SCC in a range of potent ethanol environments and identify safe operating and or batching practices that prevent the initiation and growth of SCC. The results of the research (Phase 1 and Phase 2) demonstrated that: 1. Pipelines made of common line pipe steels (e.g., Grade B and X-42 to X-60) are likely to be susceptible to ethanol SCC and any differences in susceptibility are probably not relevant from an integrity perspective. 2. While differences in susceptibility were noted for some weld types, in general, the base metal, heat affected zone, and weld metal were all susceptible to SCC in SFGE. 3. For sharp cracks, SCC initiation times are short once the line pipe steel is exposed to FGE or FGE blends capable of promoting SCC. 4. Once cracks initiate, crack growth rates are high in comparison with other forms of pipeline SCC. 5. Batching does not appear to be a viable method for SCC mitigation. 6. The only blends that can be safely transported in existing pipelines without significant modification of the system or operations (Case 1) are those containing less than 15% ethanol. 7. All other blends require significant modifications of the system or operations (Case 2), or specially designed systems (Case 3). 8. Case 2 could include deaeration of the SFGE, or the addition of inhibitors. 9. Case 3 is the subject of ongoing research (SCC 4-5).