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AutoQuiz: Failures of Complex Systems in SIS Design and SIL Selection

The post AutoQuiz: Failures of Complex Systems in SIS Design and SIL Selection first appeared on the ISA Interchange blog site.

AutoQuiz is edited by Joel Don, ISA’s social media community manager.


Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.



In safety instrumented system design and safety integrity level selection, what is the most common top-down approach for describing the failures of complex systems?

a) Fault Tree Analysis
b) HAZOP Analysis
c) Root-Cause Analysis
d) Markov Analysis
e) none of the above

<span class="collapseomatic " id="id388" tabindex="0" title="Click Here to Reveal the Answer” >Click Here to Reveal the Answer


A fault tree analysis begins with the “top event,” which is the result of a number of basic events that contribute to, or initiate, the system failure.  The logic of a fault tree is displayed by the symbols that represent the basic events and gates that logically relate those events.

The correct answer is A, Fault Tree Analysis.

Reference: Edward M. Marszal, P.E., C.F.S.E and Dr. Eric W. Scharpf, MIPENZ; Safety Integrity Level Selection: Systematic Methods Including Layer of Protection Analysis, ISA Press.

Source: ISA News