(190a) Risk Abatement Provided by Safety Instrumented Systems May Cause Remote Hazards with Higher Risks

A basic law of physics states that for every action there is an equal and opposite reaction. Translating that law into the world of risk analysis, we might state that for every action (even a risk mitigation action) there are consequences?and not all of those consequences are 1) clearly identified, 2) fully understood, and/or 3) good. Even when the initial actions are an effort to mitigate a perceived risk, the range of consequences (i.e. reactions) can sometimes create another set of hazards and possibly larger risks than initially addressed.

The complexity of instrumented systems also facilitates the creation of unanticipated and sometimes unwanted consequences at seemingly remote locations. Because of interactions with other control components, instrumented systems can easily create several layers of risk abatement actions cascading from the initiating event making it virtually impossible for operations personnel to trouble shoot and correct the original anomaly in a timely manner?adding another hazard to the operations.

This paper addresses the potential of creating ?downstream? or remote hazards by the installation of safety instrumented systems and then discusses how the initial consequence analysis should be expanded to identify these potential new hazards. This is done using the life cycle approach for the design and maintenance of safety instrumented systems discussed in the newly published CCPS book, ?Guidelines for Safe and Reliable Instrumented Protective Systems.?