Materials Selection – Design Life
The design life typically used for pressure vessels is 20 years. Exceptions are:
1. Small vessels less than about 400 cubic feet. If the vessels are easily accessible, a design life of 10 years may be appropriate.
2. Large heavy walled vessels, thicker than 2 inches. A 30-year design life is recommended.
Corrosion allowances are specified to achieve the design life and are based on the expected corrosion rate. Corrosion allowances are discussed in more detail in the Corrosion Prevention and Metallurgy Manual, but recommendations for pressure vessels are summarized in Figure 500-1. If the corrosion allowance required to achieve the design life is greater than ¼ inch, then a more corrosion-resistant alloy or a clad vessel is generally economical.
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