The potential for pressure relief valve instability (chattering) is a known hazard. Because of this, relief systems design basis documentation must demonstrate expected stable pressure relief valve (PRV) operation and performance for a multitude of credible scenarios. Historically, expected stable pressure relief valve performance has been demonstrated by showing that the irrecoverable inlet line pressure loss is less than or equal to 3% of the pressure relief valve set pressure (the 3% rule).
It is now widely known and recognized that the 3% rule is not sufficient to guarantee pressure relief valve stability. Through measurement, incidents, and modeling it has been shown that some installations with an irrecoverable inlet pressure loss of less than 3% can be unstable, while some installations with irrecoverable inlet pressure loss greater than 3% can be stable. Published research by Chiyoda, Pentair, and ioMosaic show that pressure relief valve instability leading to flutter and/or chatter is due to the coupling of the PRV disk motion with the quarter-wave pipe/fluid mode frequency without resonance.
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The American Petroleum Institute and the Petroleum Environmental Research Forum have co-sponsored two major studies on PRV stability. The results of those studies have been incorporated into recent editions of the API 520 standard. Recent editions of API 520 allow the user to perform an engineering analysis to demonstrate expected stable PRV performance for installations where the irrecoverable inlet pressure loss exceeds 3%. One engineering analysis method described by API 520 is the force balance, recommended by ioMosaic. The force balance is a simple method and ioMosaic recommends it be used in conjunction with an estimate of the critical line length. This simple method is most applicable to simple piping geometries. Where complex piping geometries are encountered and/or inlet line lengths exceed the critical line length, ioMosaic recommends 1D dynamics to demonstrate expected stable performance.
Register now and don’t miss this 60-minute ioMosaic webinar. Attendees will leave this webinar learning how the 3% rule came about, its shortcomings, and how to ensure that new installations and modifications to existing installations can be designed and evaluated. Dr. Melhem will demonstrate this by showing how to bridge the 3% rule with new methods including force balance and critical line length.
Earn 1 PDHs / 0.1 CEUs Online
Monday, September 13, 2021
2:00 PM – 3:00 PM EDT
This webinar is designed for chemical engineers and safety-related professionals in the oil & gas, chemical, petrochemical, pharmaceutical, food, agricultural, wood pulp/paper, plastics/polymers, cosmetic, and metals/or manufacturing industries.
President & CEO
The founder of ioMosaic and internationally renowned expert in the areas of pressure relief and flare systems design, chemical reaction systems, process safety and risk analysis.
Top instructors with extensive global, industry, technical and litigation experience. You will receive clear, practical and real world recommendations on how to get and stay compliant with local and worldwide regulations.