Estimation of average hazardous-event-frequency for allocation of safety-integrity levels

Reliability assessment of safety instrumented systems subject to different demand modes

“…The SIS reliability may be analyzed by approximation formulas (IEC 61508, 1997), fault tree analysis (Misumi & Sato, 1999), reliability block diagrams (Guo & Yang, 2007;Rausand & Høyland, 2004), Markov models (Bukowski, 2006;Langeron, Barros, Grall, & Berenguer, 2008), and Bayesian methods (Yun, Rogers, & Mannan, 2009). More recently, Petri nets have also been introduced to model the SIS reliability (Dutuit, Innal, Rauzy, & Signoret, 2008).…”

“…Here, the duration means the time the system is in a demand state when a demand occurs. Misumi and Sato (1999) classify SISs according to both demand rate and demand duration. They consider situations with high, medium, and low-demand rates as well as long, medium, and short duration.…”

New PFH-formulas for k-out-of-n:F-systems

“…It is noted that when l DD is disregarded, such that l D ¼ l DU , the new approximation formula (20) is identical to (19) as well as (10) in Section 4.…”

“…Since tbt 1 , the terms containing t 1 in the sum in (19) will be significantly smaller than the term without t 1 . We may therefore use the following approximation formula for PFH:…”

“…Some researchers prefer not to distinguish the SIS operational modes and use a common reliability measure with basis in Markov modeling [3,[13][14][15]17,19,23]. Despite the limitations in modeling capacity, the simplified formulas are still preferred by most practitioners, due to their simplicity.…”