Process Safety Blog

Reducing systematic failures

February 4, 2020

Systematic failures are the result of oversights, lapses, mistakes, and decisions of not only people, but of organizations. The UK HSE showed that most accidents involving control and safety system failures were due to incorrect and incomplete specifications, or design errors. This also includes the requirements for the application program (software implementation). If the requirements […]

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Part 2: the use of Bayesian networks in functional safety

January 28, 2020

Past performance is not an indicator of future performance, especially for rare events. Past performance would not have indicated (at least not to those involved at the time) what would happen at Bhopal, Texas City, or any other accident you can think of. So, what is the definition of a safe plant? Some have responded, […]

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The use of Bayesian Networks in Functional Safety

January 21, 2020

Functional safety engineers follow the ISA/IEC 61511 standard and perform calculations based on random hardware failures. These result in very low failure probabilities, which are then combined with similarly low failure probabilities for other safety layers, to show that the overall probability of an accident is extremely low (e.g., 1E-5/yr). Unfortunately, such numbers are based […]

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Reducing systematic failures reduces risk

January 9, 2020

[Updated 01/21/2020 to now include download of relevant whitepaper] Functional safety engineers are immersed in performance calculations involving failure rates, diagnostic coverage, proof test intervals, common cause and much more. It’s easy for engineers to focus on math. Yet such modeling only accounts for random hardware failures. But what percentage errors shown in the well-known […]

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EPA’s Risk Management Program (RMP) Reconsideration final rule

December 2, 2019

There were recently important changes made to the Environmental Protection Agency’s Risk Management Program (RMP).  On November 20, 2019, EPA Administrator Andrew Wheeler signed the Risk Management Program Reconsideration final rule to “better address potential security risks, regulatory consistency and reasonable consideration of costs.”   The EPA first proposed these changes to its RMP back in […]

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How about a stage zero functional safety assessment (FSA)?

November 3, 2019

Inspired by “Conducting an Effective Functional Safety Assessment” presented at 2019 ISA PIC 2019—Process Industry Conference.   The ISA/IEC 61511 standard defines a functional safety assessment as [an] “investigation, based on evidence, to judge the functional safety achieved by one or more safety instrumented systems and/or other protection layers.” The standard describes five stages where […]

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A problem (and solution) with estimating rare event frequencies

October 21, 2019

Industry uses many numbers in process safety associated with predicting the likelihood of rare, catastrophic events (e.g., failure rates, demand rates, incident rates, probability of failure, probability of ignition, etc.). Yet have you given serious thought to the accuracy and trustworthiness of those numbers? For example, layer of protection analysis (LOPA) often uses target numbers […]

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The top 5 reasons why people don’t want to evaluate human factors and barrier reliability… but should

July 29, 2019

The concept of barriers as discrete layers consisting of administrative controls, alarms, instruments, mechanical devices, and post‐release mitigation is highly idealized. It may in fact be misleading because it blinds us to the reality that all barriers rely on people. These groups of people consist of operations, maintenance, technical staff, contractors, and management. These groups […]

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