In all of the years that I have been performed LOPA (16 now…), I am still shocked at the lack of use of templates for this activity.  Especially for common pieces of equipment where the operation, and hazards are very consistent from unit to unit.  With respect to selecting SIL targets for SIS equipment, I would speculate that about 80-90% of safety functions fall into this category.

For instance, fired heaters used in refineries and chemical process plants are all very similar.  They usually have roughly the same set of safeguards, operate in very similar process conditions and environments, and are operated by organizations that are also very similar.  While I don’t think that every process heater should be designed the same way, I do think that there is a great opportunity to decrease the amount of analysis time while increasing the consistency and quality of the risk analysis process by using templates for these equipment types.  In addition to fired heaters, a similar approach could be employed for compressors, and high head pump systems.

A streamlined approach would begin with a template of all of the safety instrumented functions that are typically deployed on that piece of equipment.  For each function, the hazard that is being prevented would be listed along with either a constant consequence category, or rules for determining the consequence category based on conditions of the equipment (such as operating temperature/pressure, processed material phase, and location/occupancy considerations).  Each of the potential initiating events would then be listed out along with rules for determining whether or not the initiating event is valid for a particular device.  For each initiating event, a list of typical safeguards would be listed.  Each of the safeguards could either be credited if it is present and valid, or recommended if it is not.

I think it is easy to see a huge benefit of this type of approach.  It is easy for me to see as I know a lot of “failed” LOPA studies that did things like omit important initiating events, fail to take credit for obvious safeguards, and set non-credible consequence categories.  The reason for these failures is that the team – who are usually tired and bored (and even more so if the LOPA occurs along with the HAZOP) – are required to creatively dream up things that they may have never experienced.  Starting with a good template should be able to greatly improve quality with the benefit of streamlining the process because the template can be used with a smaller team, who can cover ground more quickly because there is less of a requirement for brainstorming.

I think that the ultimate end result of this thought process would be for SIL selection software tools to include “wizards” for common pieces of equipment (e.g., fired heaters) that ask questions about the design and operating conditions of these pieces of equipment, and then automatically create and pre-populate the LOPA scenarios that result in the selection of SIL targets. Keep your eyes on the development of the Kenexis Instrumented Safeguarding Suite (KISS), as this capability may be ready for commercialization soon!