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Case Study: Risk-based Operability Assessment of a Fire Protection System

Updated: Apr 19, 2023


A fire risk analysis on a fuel loading facility resulting in identifying the fire protection systems improvement to ensure an appropriate level of fire risk in the facility.


It was a rainy day in the country's northwest region when the water got in the fire and alarm system of a fuel loading terminal. This terminal has been considered one of the busiest gasoline and aviation fuel terminal in the region.

The water suddenly caused a short-circuit in the electrical system generating an accidental activation of the foam-based fire protection system, releasing the foam, and filling the loading racks with the foam solution.

This situation affected the operations, causing process downtime. This undesired event was enough to call the manager's attention, who thought that he needed to get rid of the foam but was unsure about the terminal's fire safety implications on that decision.

The analysis team recommended performing a risk-based operability assessment to understand the relation between the terminal's fire risk and the fire protection philosophy. The fire protection philosophy should be aligned with the facility's risk, ensuring proper risk control.

This operability assessment included a performance-based fire protection engineering assessment, a reliability engineering assessment, and a fire risk analysis.

CFD Fire Modeling

During the fire protection engineering phase, the evaluation started by identifying the fire hazard, followed by defining and modeling a design fire scenario. This activity followed a fire protection system design evaluation against its performance to control the identified scenarios. For this case, a transfer hose's failure during the transfer operation causing a pool fire was considered the main design fire scenario.

The analysis team evaluated the fire detection system performance by comparing the temperature profiles and heat flux against the system set temperature and locations. The temperature profile shows higher temperatures in the loading rack's ceiling, indicating that the detection system would detect the fire.

Hydraulic Analysis Software

This system was set up so that once the detection system detected the fire, the deluge system is automatically activated by opening the deluge valve and let the water mixed with the foam concentration leading to an AFFF foam solution discharge. As the fire detection was considered adequate, the team reviewed the deluge system. A hydraulic analysis shows that most of the nozzles did not deliver the required foam rate required by NFPA 16, which is the design standard that covers foam-based deluge systems.

Additionally, the entire system's discharge was considered excessive by comparing the location of the flames in the fire model.

Fault Tree Analysis (FTA)

Reliability engineering considers the potential system failure and estimates the probability of failure on demand (PFD) given the current arrangement.

The team performed a fault tree analysis (FTA) to estimate the PFD of the system. This type of analysis uses "AND" & "OR" logic gates to define potential failure paths that allow estimating de probabilities.

Two FTA were developed, one for activation on-demand and another for accidental activation, comparing the environmental and safety cases.

Additionally, the study considered the impact of the current inspection, testing, and maintenance (ITM) philosophy. The ITM activities frequencies impacted the probabilities estimated by the FTAs.

As the definition of risk involved the severity and frequency. The fire risk assessment combined the fire protection and reliability engineering assessments in a semi-quantitative analysis by completing the FTA with the fire frequency and comparing the results against the organization's risk tolerability criteria for safety and environmental risks.

The risk analysis indicated that the environmental and fire safety risks were above the organization's tolerable risk, indicating that modifications were needed to reduce the risk to acceptable levels.

The exercise shows that the fire safety risk contributed to 60% of the combined risk, indicating that it should take precedent. Nevertheless, the analysis evaluated diverse recommendations to reduce the fire safety and environmental risk to acceptable levels. Additionally, the analysis performed a cost-benefit analysis to identify the best solutions to implement. The risk-based approach allows making sound and intelligent decisions consistent with the level of risk present in the installation.

Contact Surety Consultants if you want to know more about this case or if you want to apply a similar approach to evaluate your fire protection system.


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