Practice Test Geeks(SIL) Safety Integrity Level Certified Practice Test
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Safety Instrumented Systems Design & Validation Flashcards

7 cards from real SIL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the purpose of a 'Safety Integrity Level Verification' calculation?

    Answer: To confirm that the designed SIS achieves the required PFDavg or PFH

    SIL Verification calculations (using RBD, Markov, or simplified equations) confirm that the actual PFDavg (low demand) or PFH (high demand) of the as-designed SIS meets the SIL target.

  2. According to IEC 61511, who is responsible for ensuring that devices used in an SIS are suitable for the intended SIL?

    Answer: The SIS end user or asset owner

    IEC 61511 places responsibility on the end user (asset owner) to verify that devices are appropriate for the SIL, including reviewing manufacturer documentation and prior use justification.

  3. What distinguishes a 'High Demand' SIS from a 'Low Demand' SIS per IEC 61508?

    Answer: High demand mode has a demand rate greater than once per year or greater than twice the proof test frequency

    IEC 61508 defines high demand (or continuous) mode as a demand rate exceeding once per year or exceeding twice the proof test frequency; otherwise the system is low demand.

  4. In a Markov model used for SIL verification, what does the 'dangerous detected' (DD) state represent?

    Answer: A dangerous failure that is revealed by the automatic diagnostic function of the system

    The DD state in a Markov model represents dangerous failures that are automatically detected by built-in diagnostics, allowing the system to take a safe state or alert operators.

  5. What is the typical impact of increasing the proof test interval on PFDavg?

    Answer: PFDavg increases because dangerous undetected failures can accumulate longer

    Longer proof test intervals allow dangerous undetected failures to remain in the system for more time, which increases the average probability of failure on demand (PFDavg).

  6. Which type of failure is NOT typically revealed by automatic diagnostics in a SIS?

    Answer: Dangerous undetected (DU) failures

    Dangerous undetected (DU) failures are, by definition, those not revealed by automatic diagnostics and can only be found through periodic proof testing.

  7. In SIS validation, what is 'Factory Acceptance Testing' (FAT) primarily intended to confirm?

    Answer: That the assembled SIS system functions correctly per the SRS before shipment to site

    FAT verifies that the assembled SIS hardware and software perform as specified in the SRS under controlled conditions at the manufacturer's or system integrator's facility before site delivery.