Safety instrumented functions and safety integrity levels (SIL)

Area of Science:

• Industrial Safety Engineering
• Risk Management in Process Industries

Background:

• Performance-based standards like ANSI/ISA S84.01 and IEC 61508 are crucial for managing risks in systems.
• User companies must adhere to stringent requirements for electrical, electronic, and programmable electronic safety-related systems (E/E/PE SRS).

Purpose of the Study:

• To detail the requirements imposed by ANSI/ISA S84.01 and IEC 61508 on companies using Safety Instrumented Systems (SIS).
• To provide a framework for achieving compliance with these critical safety standards.

Main Methods:

• The study outlines a multi-step process for compliance, including identifying safety targets, evaluating hazards, and determining necessary safety functions.
• It discusses various risk analysis techniques applicable to meeting these requirements.
• A simple example illustrates the application and trade-offs of these techniques.

Main Results:

• Compliance involves a systematic approach from risk identification to verification of risk reduction.
• The paper emphasizes the importance of implementing SIS to achieve target safety levels.
• Risk analysis techniques are presented as tools for effective hazard evaluation.

Conclusions:

• Adherence to standards like ANSI/ISA S84.01 and IEC 61508 is essential for ensuring process safety through SIS.
• A structured methodology ensures that SIS effectively reduces process risks to acceptable levels.
• The paper provides a clear roadmap for companies to implement and verify safety systems.