“The Process Industry has an established practice of identifying barriers to credit as IPLs (Independent protection layers) through the use of methods such as PHA (Process Hazard Analysis) and LOPA (Layer of Protection Analysis) type studies. However, the validation of IPLs and barriers to ensure their effectiveness especially related to human and organizational factors is lagging.
The concept of barriers as discrete onion layers comprised of administrative controls, alarms, instruments, mechanical devices, and post-release mitigation is highly idealized. The focus has been primarily on hardware reliability over human reliability. This model is misleading because it blinds us to the reality that all barriers are fundamentally human. This human influence is made up of small groups of people, comprised of operations, maintenance, and technical staff, with a management layer. Many catastrophic incidents arise in industry due to human and organizational failures related to barriers. The methods of PHA and LOPA as currently practiced are not addressing this issue. There is not even awareness of this issue, because tools such as LOPA depend on assumptions (for example, independence) that creates over confidence in the results….”