I'm sure you have heard of Independent Safety Layers, alarm management and operator intervention being one of them. Operators are the fist line of defense when alarms activate so they are a safety layer, however, just because you rationalized your alarms does not mean the operator will respond in time. What about, fatigue, distractions, data overload, confusion, procedure issues, etc...
In the past 18 years, I have helped over 500 companies achieve their alarm management goals; because we all know that alarms are one of the most valuable tools that operators use when abnormal situations occur in the process. Unfortunately not as much effort has been invested in "operator intervention" the human side of this safety layer, the operator, and their ability to detect and intervene when their is a problem. James Reason points out in the image of above, when you have weaknesses or holes in a safety layer, eventually you will have an incident. You have likely seen these holes at your own site, in your graphics, training, procedures, etc.
Operator intervention requires much more than good alarm management, so why stop there? The console design, number and size of screens and what is actually on the screens should be designed based on human factors with one goal, to achieve Situation Awareness. Other issues that have to be addressed are: The control room design (lighting, acoustics, traffic flow, layout) communication standards, procedures, training, workload, and supervision all have holes or weaknesses.
If your operators fail to respond to a situation quick enough you may be complacent with and rely on your SIS to stop a major incident from occurring but have you ever considered the costs and consequences associated when operators are operating in alarm for several minutes? Specifically looking at "Time in Alarm". If you set your alarms to support your operating boundaries (operating limits), and your operating in alarm for several minutes, what negative impacts does that have on your assets and what safety risks are you taking?
Email me for the paper on this subject:
firstname.lastname@example.org and I will send you the PDF.