Even though this Human Factors model is going on 30 years old, it is still the most widely used and recognizable today. In my process safety career, Human Factors were intended to be part of all Process Hazard(s) analyses; and although the chemical industry adopted some really good checklists to aid in these analyze’s, they never really drove HF engineering as I had hoped. Having graduated with my BS in OSH in the early 90’s, James Reasons was just getting recognized in his HF work, including his Human Failure model. By the time I completed my MS in SE in 1996, his work was ingrained in much of the curriculum. So yes, I am “old school” when it comes to HF as, this model just makes too much sense and has been proven time and time again to be an accurate view of how our workers make their decisions AND how we can best affect that decision making.
Here is an updated view of this model, provided by The Energy Institute. If you are not familiar with this organization – you should get to know them and their materials. Absolutely the best source for advanced safety management, leadership, and technical SE matters such as HF.
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Error Type |
Description | Examples | Potential error recovery mechanisms |
| Slip | When a person does something but not what they meant to do |
The plant operator pressed the start button for ‘pump A’ instead of ‘pump B’
Petroleum blender keyed in the wrong proportion of benzene to produce a batch of fuel
Welder ground off too much material when finishing a weld |
Alarms would sound in response to the wrong pump being started; other plant indications would alert the operator to the error, and other plant operators might notice that the expected flow is absent In checking the progress of the blending process, the blender may notice their error; laboratory samples taken at intervals should identify the error The welder should check the quality of the weld; for high-integrity welds, a senior supervisor should check; final testing of the system before putting it into service may show flaws in the weld |
| Lapse | When a person forgets to do something due to a failure of attention/concentration or memory |
A tanker driver forgets to set the blend indicator on their tanker and fills the compartment intended for LRP with unleaded
The control room operator misses a step in a plant start-up sequence after taking a phone call mid-task |
The driver may check their docket before starting the delivery and realize their error: this is an example of an error where recovery may not occur
Normal alarms are likely to be disabled for start-up and the error may be unrecovered; plant indications or colleague/supervisor checks (if planned into the start-up) may act as a cue to the operator that they are at the wrong stage in the start-up process; interlocks may stop the process from proceeding further following the error |
| Mistake |
When a person does what they meant to do, but should have done something else. This is not necessarily a “violation” (see below) but part of the action taken could involve rule-breaking or similar non-compliances |
A busy fitter investigating a leaking water pipe ‘nips up’ the flange and notices that the leak stops. He thus diagnoses the problem as an incorrectly tightened flange but the real problem is a poorly fitting seal (the leak worsens later)
A power-operated relief valve has stuck open; the operator does not know this since the panel shows that power is off to that valve; believing the valve is closed leads to the conclusion that the pressure and level drop is due to a pipe break |
This may not be recovered before a more serious failure occurs as a result of damaging the seal further or over-tightening the flange studs
Difficult to recover from quickly as people have a tendency to make the evidence fit their existing conclusion; it may be recovered by plant operators noticing materials venting to the atmosphere or monitoring other plant variables such as pressure controller valve opening |
| Violation | When a person decided to act without complying with a known rule, procedure, or good practice |
The first mate of a tank barge crew reports for duty knowing that he has already exceeded his working hours for the day Plant operators open a by-pass valve to speed up the filling of a tank but forget to close it again |
Violations are difficult to recover from; fitness for duty procedures (if in place and enforced) may pick up the mate’s fatigued state
Alarms fitted to the tank may indicate that the tank is unexpectedly filling (or emptying) |