Is our industry addressing the problems facing it today? We idealize infinitesimally small event rates for highly catastrophic hazards, yet are we any safer? Have we solved the world’s problems? Layers of protection analysis (LOPA) drives hazardous event rates to 10-4 per year or less, yet industry is still experiencing several disastrous events per year.
If one estimates 3,000 operating units worldwide and industry experiences approximately 3 major incidents per year, the true industry accident rate is a staggering 3 / 3,000 per year (i.e. 10-3). All the while our LOPA calculations are assuring us we have achieved an event rate of 10-6. Something is not adding up! Rather than fussing over an unobtainable numbers game; wouldn’t it be wiser to address protection layers which are operating below requirements? We are (hopefully) performing audits and assessments on our protection layers and generating findings. Why are we not focusing our efforts on the results of these findings? Instead we demand more bandages (protect layers) for amputated limbs (LOPA scenarios) instead of upgrading those bandages to tourniquets. Perhaps the dilemma is we cannot effectively prioritize our corrective actions based on findings. Likely we have too much information and the real problems are lost in the chaos. What if there was a way to decipher the information overload and visualize the impact of our short comings? Enter Bayes rule to provide a means to visualize findings through a protection layer health meter approach; to prioritize action items and staunch the bleeding.
by Keith Brumbaugh
Keywords: Bayes, Bayes rule, Bayes theory, LOPA, IPL, SIS, SIF, SIL Calculations, systematic failure, human factors, human reliability, operations, maintenance, IEC 61511, ANSI/ISA 61511, hardware reliability, proven in use, confidence interval, credible range, safety lifecycle, functional safety assessment, FSA stage 4, health meter.