What steps can be taken to avoid stress corrosion cracking (SCC) in steel vessels used for storing anhydrous ammonia?

Submitted by: Administrator
The U.S. National Board of Pressure Vessel Inspectors recommends the following in one of their classic articles:

1. Pressure vessels should be fully stress relieved or fabricated with heads that are hot-formed or stress relieved.

2. Extreme care should be used to eliminate air from the ammonia systems; new vessels must be thoroughly purged to eliminate air contamination.

3. Ammonia should contain at least 0.2 percent water to inhibit SCC. Source: National Board of Pressure Vessel Inspectors
Submitted by: Administrator

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