Process plant and process piping life

[1piping1]

I came across few projects which were mentioning 25 years as the design life of the plant. Recently I came across a project which mentions the design life as 25 years for the plant equipment and 20 years for the piping. Can anyone please mention the relevance of the same in design?? I understand that the corrosion allowance in both the cases will be different. But after all what is the meaning in taking different design life for equipment and piping?? Effectively the lowest is the plant design life??

 

[weldstan]

Initial pricing (owners capital costs) for the most part dictated differences in piping design life and equipment design life (at least back in the '70's and '80s).

 

[bimr]

Would suspect that there is not much thought put into either the 20 or 25 years.