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    Compliance with the Process Safety Management (PSM) Standard is challenging for even the most sophisticated operators because of the broad scope and highly technical nature of the 14 PSM elements. This paper provides guidance on how to comply with the three elements
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    The process industries are primarily concerned with the reliability, availability, auditability, and maintainability of relief and flare systems data. These data are critical component of process safety information and its lifecycle must be properly managed to ensure sound process safety management and loss prevention programs.
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    A detailed risk-based approach is proposed for addressing flammable and toxic dispersions impacting occupied buildings.
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    QRA as a technique for managing and understanding risks dates back to the 1970s, initially applied in the aerospace, electronics, and nuclear power industries.
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    Detailed dynamics. Challenges associated with PRV stability issues for existing installations are not unique to any particular segment of the chemical process industry. This is an industry wide problem that has received a lot of attention from both OSHA and industry associations such as API, ACC, and AFPM. A consistent definition of what constitutes an Engineering Analysis is currently being proposed by API/ACC/AFPM for inclusion in the upcoming revision to API 520.
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    Screening. In part I of this paper we established a detailed dynamics methodology for the modeling of PRV stability. We demonstrated that (a) the irrecoverable inlet pressure loss due to friction has essentially no impact on PRV stability (also see [3]), (b) PRV instability is caused by the coupling of PRV disk motion with the pressure wave caused by excessive acoustic pressure drop (1/4 wave) during PRV opening/closing, (c) the instability does not amplify, and (d) liquid systems are the most likely to cause damage to piping and piping components..
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    How to avoid the singing PRV problem. Excitation of acoustic standing waves in a main process flow line closed side branch, such as the inlet line of a pressure relief valve (PRV), can occur due to vortex shedding generated by increased flow in the main process line. The flow velocity for process lines where pressure relief devices are mounted via a side branch should be limited to where ce is the effective isentropic speed of sound of the main process flow pipe fluid system, u is the maximum allowable fluid flow velocity in the main process line, and d/L is the pressure relief device inlet line diameter to length ratio. This limit can be very restrictive for flashing two phase flow.
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    On the estimation of speed of sound and thermodynamic properties for fluid flow and PRV stability. An independent and accurate estimation of the speed of sound can provide an important quality check for a multitude of single and multi-phase flow applications. More recently, proposed screening methods for the calculation of PRV stability require an accurate estimate of the speed of sound for the fluid/piping system. This paper outlines proper methods for the calculation of thermodynamic properties and speed of sound for single and multi-phase systems. Comparisons with actual measurements indicate that credible values can be obtained for single and multi-phase systems.
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    Get a handle on PRV stability. There is general agreement that the 3% inlet pressure loss rule (IPL3) is not sufficient to guarantee PRV stability and does not work all the time. This is confirmed by recent findings from actual PRV stability measurements and dynamic modeling. IPL3 only considers irrecoverable pressure loss. IPL3 assumes that the fluid dynamic pressure is ultimately recovered at the disk surface as the PRV is closing. This recovery of fluid dynamic pressure can keep the PRV open, even at reduced lift. But this is only possible if the inlet line length is less than the ”critical length”. In other words, the returning pressure wave can keep the PRV open before the PRV reaches full closure only if it can get there before the PRV closes. One might even argue that as long as the ”total” wave/dynamic pressure drop in the inlet line is less then PRV blowdown, the PRV can operate in a stable manner, even at reduced lift. The pressure wave travel time depends on the speed of sound of the fluid/pipe system and the presence of any acoustic barriers.
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    Even before the adoption of ISA-S84.01 as a national standard, safety instrumented systems (SIS) were used to mitigate the risks of process hazards. With the establishment of the standard, there is now a framework for defining Safety Integrity Levels (SIL) for such systems and the associated reliability requirements. However, the standard does not address the topic of how to determine what SIL category is needed to fill the independent layers of protection (IPL) gap. It assumes (section 4.4.2) that this analysis is performed prior to applying the principles of the standard.
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    Asset Integrity (also referred to as Mechanical Integrity) findings remain on top of OSHA’s citation list during PSM inspections. Violations most frequently found include failure to address equipment deficiencies, lack of AI written procedures, and failure to perform internal AI inspection(s) and test performance.
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    Ever since OSHA implemented their National Emphasis Program in 2007, facility’s pressure relief systems design basis have come under increasing scrutiny. Recognizing that they may not be fully compliant, many companies are conducting audits of their relief systems design basis to determine their current state, identify gaps, and establish a path forward for compliance.
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    Properly conducted interviews of witnesses following an incident is as important to understanding what occurred, as is saving data and information following an incident (presented in the first paper of this series).
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    Significant critical information is often lost following an accident/ incident due to poor data and information gathering procedures. As a result, should litigation occur, information that could be useful in determining the cause of the incident and later in building a defense is not collected.
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    Traditional pressure relief sizing calculations have typically used steady state equations to determine both the required relief rate and the pressure relief system capacity, for every applicable overpressure scenario. These equations are well accepted and understood and are available in API Standards 520 and 521.
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