Decoding SIS: Are You Doing What’s Necessary to Prevent Disasters? | AIChE

Decoding SIS: Are You Doing What’s Necessary to Prevent Disasters?

When your facility is tasked with industry safety standard compliance, where do you start? What do all those SIS acronyms mean? For OSHA PSM-covered facilities, adherence to a functional safety lifecycle can be a critical step in overall SIS performance assurance.

What is hiding under the radar of a plant SIS? Risk assessments define hazard consequences with assumed initiating event frequencies. How do we prevent these consequences? By verifying the reliability and availability assumptions of SIL Verification design parameters. Without understanding the design parameters your SIS is based upon, or without proper maintenance of your SIS equipment, your risk assessment gap closure may be incomplete.

What factors into the assumptions of an SIS design?

Are your safety devices replaced at their specified asset life, tested at the interval, and tested with the necessary rigor to uncover dangerous failures as specified in your calculations?

What does following the Functional Safety Lifecycle entail?

Does your facility have a Functional Safety Management Plan, perform Functional Safety Assessments on your SIS Design, and keep records of device failures to evaluate field performance against assumed reliability?

This paper illustrates the real consequences of failing to uphold SIS design assumptions or follow the Functional Safety Lifecycle.

By Emily Henry, PE(SC), CFSE & Joel Ramírez


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