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Safety System Bad Actor Identification – Time in Bypass

Your company has started the journey for compliance to the IEC 61511 safety lifecycle.  But, it’s a long and 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?

Here’s your simple steps to success:

  1. Review bypass logs for the past “X” years for several high consequence unit operations that has had a LOPA completed along with initial SIL Calculations for the associated SIFs.
  2. Lookup instruments bypassed in your bypass logs versus protection layers used in your LOPA. This includes SIFs, Alarms with Operator Action, BPCS Control Loop, BPCS Interlocks, etc.
  3. Document total time in bypass for past “X” years and number of times the device has been bypassed, consequence severity, mitigated event likelihood with fully functional protection layers.
  4. Present a report to management that shows excessive time in bypass bad actors.
  5. Document the assumed risk ranking from the LOPA versus the actual risk ranking based upon your bypass review.
  6. Calculate assumed and actual increased financial risk based upon the excessive time in bypass bad actors.

Below is a sample of what one might find. 

I assume operations will not run a pressure vessel that only has a single Pressure Relief Valve (PSV) with the PSV out of service.  However, I’ve seen numerous end users that will readily bypass a SIL 2 high pressure Safety Instrumented Function (SIF).  What they are not realizing is that mathematically from a risk perspective often a PSV and SIL 2 SIF provide the identical amount of risk reduction.

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 time in bypass bad actors and reviewing how this financially impacts the business, one can start to get management alignment and better understanding on your IEC 61511 compliance efforts.



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