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Functional safety – IEC 61508

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IEC 61508 applies to the functional safety of electrical, electronic and programmable electronic safety-related systems. This standard studies the use of programmable electronic systems in security features.

A fundamental part of the IEC 61508 is the Safety Integrity Level (SIL) for:

  • Ensuring that a safety related system adequately performs the required safety functions under all stated conditions within a defined period of time.
  • Assessing the risk reduction required for a tolerable level of risk.

Inappropriate SIL determination can affect the safety integrity of the asset protection envelope.  It may also, in some cases, place the asset integrity under threat. Unnecessary spending in capital and operational budgets can be incurred due to incorrect SIL determination.

Nemko uses a practical approach to adopting the standard to both new and existing systems through:

  • Realization of Safety Integrity Requirements (SIL levels)
  • Implementation of suitable protective measures
  • Ongoing managerial and maintenance requirements of such systems

Challenges in achieving appropriate functional safety:

  • Incorrect specification of the system (HW and/or SW)
  • Omissions in the safety requirements specification
  • Random hardware failure mechanisms
  • Systematic hardware failure mechanisms
  • Software errors
  • Common cause failures
  • Environmental influence
  • Human error