Safety Considerations Guide for Triconex General ... - ICEWeb
Safety Considerations Guide for Triconex General ... - ICEWeb
Safety Considerations Guide for Triconex General ... - ICEWeb
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4 Chapter 1 <strong>Safety</strong> Concepts<br />
SIS Factors<br />
According to the ANSI/ISA S84.01 and IEC 61508 standards, the scope of an SIS is restricted to<br />
the instrumentation or controls that are responsible <strong>for</strong> bringing a process to a safe state in the<br />
event of a failure. The availability of an SIS is dependent upon:<br />
• Failure rates and modes of components<br />
• Installed instrumentation<br />
• Redundancy<br />
• Voting<br />
• Diagnostic coverage<br />
• Testing frequency<br />
SIL Factors<br />
An SIL can be considered a statistical representation of the availability of an SIS at the time of a<br />
process demand. A process demand is defined as the occurrence of a process deviation that causes<br />
an SIS to transition a process to a safe state.<br />
An SIL is the litmus test of acceptable SIS design and includes the following factors:<br />
• Device integrity<br />
• Diagnostics<br />
• Systematic and common cause failures<br />
• Testing<br />
• Operation<br />
• Maintenance<br />
In modern applications, a programmable electronic system (PES) is used as the core of an SIS.<br />
The Tri-GP controller is a state-of-the-art PES optimized <strong>for</strong> safety-critical applications.<br />
<strong>Safety</strong> <strong>Considerations</strong> <strong>Guide</strong> <strong>for</strong> <strong>Triconex</strong> <strong>General</strong> Purpose v2 Systems