One critical defect in the SIL standards (and technical reports from ANSI/ISA 84 committees) to remember is they do NOT account for specific human errors of mis-calibration (especially critical for SIFs with multiple sensor) and or leaving in bypass. So, the PFD to use for the IPL is the PFD(avg) from the SIL verification calc [...]
There is data in the new book, Guidelines for Initiating Events and Independent Protection Layers, 2015, CCPS/AIChE. (It is finally published as of January 8, 2015.) The failure rate is presented in probability of failure (due to damage mechanism such as corrosion) per meter of pipe. Two different values (for different diameter ranges) are presented [...]
We have not seen a drop in quality of the HAZOP (risk reviews) in projects lately. BUT, we saw a dramatic drop about 25 years ago; this occurred when lots of new folks (EPC companies especially) starting saying "Sure, we can provide that HAZOP for you." There was (and still is) little control of competency [...]
On the issues of blame: It is important to differentiate when the blame and discipline (positive and negative forms) are appropriate. If you find a worker doing something wrong (in the lower part of the safety iceberg), then blame and discipline may be appropriate once you figure out why the mistake is made. However, if [...]
There is considerable science in the field of human error, and the human factors that make them more or less probable. And there are decades of experience from implementing management systems to control these human factors or to determine when compensating layers of protection are necessary when the human error rate is already as low [...]
