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Safety System Bad Actor Identification – Demands

Your company has started the journey for compliance to the IEC 61511 safety lifecycle. But, it’s a long an arduous path to get organizational alignment around the benefits of the safety lifecycle. So what’s a relatively quick win you could get that will help demonstrate to management some of the end game benefits of the safety lifecycle?

So here’s your simple steps to success:

  1. Select a unit operation that has multiple Safety Instrumented Functions (SIFs) installed. Note the higher the SIL targets the better for this initial review.
  2. Confirm that the sensor(s) for the SIF are transmitters (or a BPCS transmitter in the same service exists) which has been configured to record data in a historian.
  3. Review the facilities Safe Operating Limits Table (SOLT) for process variable(s) being researched. The SOLT will provide you the following:
                 • Normal Operating Envelope – Green Zone
                 • Troubleshooting Zone – Yellow Zone
                 • Buffer Zone – Red Zone


  4. Review of historical data for the past “X” years for the transmitter(s) in question. Record # of times and total aggregated duration operating in yellow / red portions of the SOLT.
  5. Document the assumed risk ranking from the LOPA versus the actual risk ranking based upon your protection layer demand review.
  6. Calculate assumed and actual financial risk based upon the excessive demands bad actors.

Below is a sample of what one might find.

In theory, the process variables reviewed should stay within the “green zone” for the majority of the time. Operating excessively in the “yellow” and / or “red” indicates you are relying on your Independent Protection Layers to prevent a potential loss of containment event more frequently than the initial risk analysis assumed.

Every time we’ve been involved with the above review process, some eye opening items are discovered which help focus awareness on the benefits of the safety lifecycle. By highlighting some potential excessive demands bad actors and showing how this financially impacts the business, one can start to get management alignment and understanding of your IEC 61511 compliance efforts.