Functional and Failure Rate Analysis of High Integrity Pressure Protection Systems (HIPPS) for Safety Integrity Level (SIL) Determination in Oil and Gas Production Facilities

Abstract

Process industries rely on High Integrity Pressure Protection Systems (HIPPS) as primary safety barriers to avoid hazardous overpressure situations. Using a detailed framework of functional-performance modelling, this work investigates the suitability of HIPPS functional behavior and degradation characteristics as well as Safety Integrity Level (SIL) suitability. Continuous-time simulation was used to evaluate various performance measures, including the Functional Performance Index (FPI), System Performance Indices (SPI) and Probability of Detection (PODs). Other important metrics include false alarm rate; coverage probability; and average Probability of Failure on Demand (PFDavg). HIPPS is found to operate with high functional integrity at its inception, with FPI values nearing 1.0 and diagnostic responsiveness being the key factors. Despite this, functional performance gradually declines as undetected failures accumulate and diagnostic efficiency decreases. Over time, the SPI trend indicates an increasing divergence between projected and actual performance. A proof test interval of five years leads to a PFDavg of 2.5, which means that the system is not compliant with IEC 61508. Ensuring compliance with SIL thresholds and verifying the impact of longer test intervals on safety standards. Robustness of the system is bolstered by low false alarm rates and strong coverage probability, but close alignment between simulated and real-world SPI values supports confidence in the model. The results highlight the need for shorter test intervals and improved diagnostics to sustain SIL performance.