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Functional Safety Principles & Standards 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.

Read the first 7 Functional Safety Principles & Standards flashcards as text

  1. Which international standard provides guidance specifically for the application of functional safety in the machinery sector?

    Answer: IEC 62061

    IEC 62061 is the IEC 61508-derived standard for safety-related control systems in the machinery sector, defining SILCL requirements.

  2. A functional safety plan (FSP) required by IEC 61511 must document which of the following?

    Answer: The functional safety activities, responsibilities, and resources for all lifecycle phases

    The FSP defines the overall approach to managing functional safety, covering activities, responsibilities, resources, and schedules across all lifecycle phases.

  3. When applying the risk graph method for SIL determination, which parameter accounts for the ability of people to avoid the hazard after it has been initiated?

    Answer: Probability of avoiding the hazard parameter (P)

    The avoidance parameter (P) in the risk graph reflects whether people can avoid the hazard after initiation, such as through warning or escape routes.

  4. Under IEC 61508, what does 'hardware fault tolerance (HFT)' of 1 mean?

    Answer: The system requires redundancy such that one fault does not cause loss of the safety function

    HFT = 1 means the subsystem can tolerate one dangerous hardware fault without losing its ability to perform the safety function, typically requiring redundancy.

  5. What is the significance of the 'ALARP' (As Low As Reasonably Practicable) principle in functional safety risk assessment?

    Answer: It requires that residual risk be reduced further if the cost of doing so is not grossly disproportionate to the benefit gained

    ALARP requires demonstrating that residual risk has been reduced to the lowest level practicable, with further reduction only waived if costs are grossly disproportionate to safety benefit.

  6. Which of the following lifecycle activities is associated with the term 'pre-startup safety review (PSSR)' within the IEC 61511 framework?

    Answer: Verifying that the installed SIS meets the SRS before placing it into service

    A PSSR verifies that the installed SIS has been built, commissioned, and tested in accordance with the SRS before being placed into operation.

  7. According to IEC 61511, what is the recommended maximum SIL for a single safety instrumented function using off-the-shelf non-PE (non-programmable) safety instrumented equipment?

    Answer: SIL 3

    IEC 61511 limits a single SIF to SIL 3 maximum, as SIL 4 requires extraordinary justification and is rarely applied in the process industry.