Recertification of Pressure Vessels and Pressure Systems

Abstract

There are strong economic and safety incentives to recertify pressure vessels, pressure components, and piping for continued service after their nominal original design life has been exhausted. No specific rules, and certainly no national consensus standards exist for doing this. Therefore, methods have been developed to rank vessels as to urgency for recertification, and a five-step recertification process has been devised. The five steps are: 1) gathering design and operating information, 2) performing basic analysis to establish maximum allowable working pressure (MAWP) and to identify high-stress areas, 3) performing visual and nondestructive examination, concentrating NDT in high stress areas, 4) performing detailed stress analysis to confirm MAWP, and 5) performing flaw-growth analysis to establish the interval between inspections. Experience has shown that recertification costs are between 10 and 15 percent of replacement costs and that recertification adds greatly to confidence in the safety and availability of equipment.