by Dave Grattan
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 maintain and manage the barriers and can be the most critical factor for ensuring their performance. However, process hazard analysis (PHA) and layer of protection analysis (LOPA) methods as currently practiced are not addressing this issue. In fact, there is generally not even awareness of a potential problem.
Here are the top 5 reasons why people don’t want to evaluate human factors and barrier reliability in the process industry.
The ISA/IEC 61511 standard says you don’t have to consider systematic failure (i.e., human error) in the calculations. True, but simply following all the procedural requirements in the standard has proven to not be enough. Can we at least acknowledge that an error rate attached to the SIL calculation would be appropriate, and that this error rate is primarily a function of the human factors?
Human reliability is used in the nuclear industry, it’s not for the process industries. True, but human reliability analysis methods are catching on in the process industry. In fact, a recently published method, “Petro-HRA” was developed specifically for the Oil and Gas Industry.
We already evaluate human factors in our process hazard analyses, human factors checklists, and independent protection layer validation programs. These tools look at states and conditions, not behavior. You must look at how people behave (and more importantly why) for human factors to work.
The process industry isn’t ready for it yet. See #2 above.
There’s no money to do it. True, but it’s a matter of establishing priorities based on what’s important, and human factors are
Evaluating human factors and making good recommendations to reduce human error is not easy. It’s a skill that comes with practice and a broad knowledge of human factors. Simply recommending better procedures or more training is not going to get us where we need to be, because all procedures could be improved, and everyone could use more training.
To learn more about how to evaluate human factors in analyzing independent protection layer effectiveness, read the full paper “Improving barrier effectiveness using human factors methods” .