Updating failure rates and test intervals in the operational phase: A practical implementation of IEC 61511 and IEC 61508

Safety instrumented systems (SIS) are frequently used in the oil and gas industry to detect the onsets of hazardous events (e.g., gas leakages and high pressures) and to mitigate their consequences to humans, the environment, and material assets. Failure to do so can lead to major accidents and it is therefore of vital importance to monitor the performance of the SIS in the operational phase.