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Relief Valves: "What Can Go Wrong" Scenarios - Part 1

Nov 08 2010 01:30 PM | pleckner in Safety and Pressure Relief -----

Final Say for this Installment

Always analyze the system as a whole. Don't get tunnel vision on one area of the process. Of course you will consider individual "what can go wrong" scenarios but remember the example I used when discussing Double Jeopardy. I considered two actual failures that combined into one. I found these two by considering the system as a whole.

"What can go wrong" scenario analysis is a very important but complex process. I do not intend to cover every nuance associated with it (simply because it will be impossible). I also don't expect everyone to agree with my analysis for every API RP521 Item number (Table 1 above). That's the fun and scary part of doing this type of work. Some of it can be highly subjective as to what constitutes a credible scenario. I strongly suggest you get a copy of API 5203 and 5212 and the ASME Boiler and Pressure Vessel Code, Section VIII, Division 14 and try to read through them (the operative word here is "try").

I welcome and encourage your feedback. Feel free to E-Mail me at the Internet address below. All correspondences that include a name will be published in this column. Better yet, I encourage discussion of any topic I cover utilizing The Chemical Engineers' Resource Message Board. This will enable the entire Internet community to join and learn. And, don't forget to check back for future installments on this series.


  1. "Boiler and Pressure Vessel Accidents Soar," Chem. Eng. Progress, p 13 (August 2000)
  2. API (www.api.org) Recommended Practice 521, "Guide for Pressure-Relieving and Depressuring Systems", 4th Edition (March 1997)
  3. API (www.api.org) Recommended Practice 520, "Sizing, Selection, and Installation of Pressure-Relieving Device in Refineries, Part 1-Sizing and Selection", 7th Edition (January 2000)
  4. ASME (www.asme.org) "Boiler and Pressure Vessel Code, Section VIII, Division 1" (1998)

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